On 2022 March 4, the object known as WE0913A crashed into the Moon after several close flybys of the Earth and
the Moon in the previous three months. Leading up to impact, the identity of the lunar impactor was up for debate,
with two possibilities: the Falcon 9 from the DSCOVR mission or the Long March 3C from the Chang’e 5-T1
mission. In this paper, we present a trajectory and spectroscopic analysis using ground-based telescope
observations to show conclusively that WE0913A is the Long March 3C rocket body (R/B) from the Chang’e
5-T1 mission. Analysis of photometric light curves collected before impact give a spin period of 185.221 ± 6.540 s
before the first close Earth flyby on 2022 January 20 and a period of 177.754 ± 0.779 s, both at a 1σ confidence
level, before the second close Earth flyby on 2022 February 8. Using Markov Chain Monte Carlo sampling and a
predictive light curve simulation based on an anisotropic Phong reflection model, we estimate both physical and
dynamical properties of the Chang’e 5-T1 R/B at the start of an observation epoch. The results from the Bayesian
analysis imply that there may have been additional mass on the front of the rocket body. Using our predicted
impact location, the Lunar Reconnaissance Orbiter was able to image the crater site approximately 7.5 km from the
prediction. Comparing the pre- and post-impact images of the location shows two distinct craters that were made,
supporting the hypothesis that there was additional mass on the rocket body
The Possible Tidal Demise of Kepler’s First Planetary SystemSérgio Sacani
We present evidence of tidally-driven inspiral in the Kepler-1658 (KOI-4) system, which consists of a giant planet
(1.1RJ, 5.9MJ) orbiting an evolved host star (2.9Re, 1.5Me). Using transit timing measurements from Kepler,
Palomar/WIRC, and TESS, we show that the orbital period of Kepler-1658b appears to be decreasing at a rate = -
+ P 131 22
20 ms yr−1
, corresponding to an infall timescale P P » 2.5 Myr. We consider other explanations for the
data including line-of-sight acceleration and orbital precession, but find them to be implausible. The observed
period derivative implies a tidal quality factor
¢ = ´ -
+ Q 2.50 10 0.62
0.85 4, in good agreement with theoretical
predictions for inertial wave dissipation in subgiant stars. Additionally, while it probably cannot explain the entire
inspiral rate, a small amount of planetary dissipation could naturally explain the deep optical eclipse observed for
the planet via enhanced thermal emission. As the first evolved system with detected inspiral, Kepler-1658 is a new
benchmark for understanding tidal physics at the end of the planetary life cycle
X-rays from a Central “Exhaust Vent” of the Galactic Center ChimneySérgio Sacani
Using deep archival observations from the Chandra X-ray Observatory, we present an analysis of
linear X-ray-emitting features located within the southern portion of the Galactic center chimney,
and oriented orthogonal to the Galactic plane, centered at coordinates l = 0.08◦
, b = −1.42◦
. The
surface brightness and hardness ratio patterns are suggestive of a cylindrical morphology which may
have been produced by a plasma outflow channel extending from the Galactic center. Our fits of the
feature’s spectra favor a complex two-component model consisting of thermal and recombining plasma
components, possibly a sign of shock compression or heating of the interstellar medium by outflowing
material. Assuming a recombining plasma scenario, we further estimate the cooling timescale of this
plasma to be on the order of a few hundred to thousands of years, leading us to speculate that a
sequence of accretion events onto the Galactic Black Hole may be a plausible quasi-continuous energy
source to sustain the observed morphology
Hubble Asteroid Hunter III. Physical properties of newly found asteroidsSérgio Sacani
Context. Determining the size distribution of asteroids is key to understanding the collisional history and evolution of the inner Solar System. Aims. We aim to improve our knowledge of the size distribution of small asteroids in the main belt by determining the parallaxes of newly detected asteroids in the Hubble Space Telescope (HST) archive and subsequently their absolute magnitudes and sizes. Methods. Asteroids appear as curved trails in HST images because of the parallax induced by the fast orbital motion of the spacecraft. Taking into account the trajectory of this latter, the parallax effect can be computed to obtain the distance to the asteroids by fitting simulated trajectories to the observed trails. Using distance, we can obtain the absolute magnitude of an object and an estimation of its size assuming an albedo value, along with some boundaries for its orbital parameters. Results. In this work, we analyse a set of 632 serendipitously imaged asteroids found in the ESA HST archive. Images were captured with the ACS/WFC and WFC3/UVIS instruments. A machine learning algorithm (trained with the results of a citizen science project) was used to detect objects in these images as part of a previous study. Our raw data consist of 1031 asteroid trails from unknown objects, not matching any entries in the Minor Planet Center (MPC) database using their coordinates and imaging time. We also found 670 trails from known objects (objects featuring matching entries in the MPC). After an accuracy assessment and filtering process, our analysed HST asteroid set consists of 454 unknown objects and 178 known objects. We obtain a sample dominated by potential main belt objects featuring absolute magnitudes (H) mostly between 15 and 22 mag. The absolute magnitude cumulative distribution logN(H > H0) ∝ αlog(H0) confirms the previously reported slope change for 15 < H < 18, from α ≈ 0.56 to α ≈ 0.26, maintained in our case down to absolute magnitudes of around H ≈ 20, and therefore expanding the previous result by approximately two magnitudes. Conclusions. HST archival observations can be used as an asteroid survey because the telescope pointings are statistically randomly oriented in the sky and cover long periods of time. They allow us to expand the current best samples of astronomical objects at no extra cost in regard to telescope time.
Visible spectra of (474640) 2004 VN112–2013 RF98 with OSIRIS at the 10.4 m GT...Sérgio Sacani
The existence of significant anisotropies in the distributions of the directions of perihelia and
orbital poles of the known extreme trans-Neptunian objects (ETNOs) has been used to claim
that trans-Plutonian planets may exist. Among the known ETNOs, the pair (474640) 2004
VN112–2013 RF98 stands out. Their orbital poles and the directions of their perihelia and their
velocities at perihelion/aphelion are separated by a few degrees, but orbital similarity does
not necessarily imply common physical origin. In an attempt to unravel their physical nature,
visible spectroscopy of both targets was obtained using the OSIRIS camera-spectrograph at the
10.4 m Gran Telescopio Canarias (GTC). From the spectral analysis, we find that 474640–2013
RF98 have similar spectral slopes (12 versus 15 per cent/0.1 µm), very different from Sedna’s
but compatible with those of (148209) 2000 CR105 and 2012 VP113. These five ETNOs belong
to the group of seven linked to the Planet Nine hypothesis. A dynamical pathway consistent
with these findings is dissociation of a binary asteroid during a close encounter with a planet
and we confirm its plausibility using N-body simulations. We thus conclude that both the
dynamical and spectroscopic properties of 474640–2013 RF98 favour a genetic link and their
current orbits suggest that the pair was kicked by a perturber near aphelion
The hazardous km-sized NEOs of the next thousands of yearsSérgio Sacani
This document discusses methods for assessing the long-term impact risk of km-sized near-Earth objects (NEOs) over thousands of years. It analyzes the evolution of the Minimum Orbit Intersection Distance (MOID) between NEOs and Earth to identify objects that remain in close proximity for extended periods. It then estimates the probability of a deep Earth encounter during these low-MOID periods based on the growth of orbital uncertainties over time. This allows the authors to rank km-sized NEOs by their long-term impact hazard and identify targets that warrant further observation and analysis.
Spirals and clumps in V960 Mon: signs of planet formation via gravitational i...Sérgio Sacani
The formation of giant planets has traditionally been divided into two pathways: core accretion and gravitational instability. However, in recent years, gravitational instability has become less favored, primarily due
to the scarcity of observations of fragmented protoplanetary disks around young stars and low occurrence rate
of massive planets on very wide orbits. In this study, we present a SPHERE/IRDIS polarized light observation
of the young outbursting object V960 Mon. The image reveals a vast structure of intricately shaped scattered
light with several spiral arms. This finding motivated a re-analysis of archival ALMA 1.3 mm data acquired
just two years after the onset of the outburst of V960 Mon. In these data, we discover several clumps of continuum emission aligned along a spiral arm that coincides with the scattered light structure. We interpret the
localized emission as fragments formed from a spiral arm under gravitational collapse. Estimating the mass of
solids within these clumps to be of several Earth masses, we suggest this observation to be the first evidence of
gravitational instability occurring on planetary scales. This study discusses the significance of this finding for
planet formation and its potential connection with the outbursting state of V960 Mon.
Refined parameters of the HD 22946 planetary system and the true orbital peri...Sérgio Sacani
Multi-planet systems are important sources of information regarding the evolution of planets. However, the long-period
planets in these systems often escape detection. These objects in particular may retain more of their primordial characteristics compared
to close-in counterparts because of their increased distance from the host star. HD 22946 is a bright (G = 8.13 mag) late F-type star
around which three transiting planets were identified via Transiting Exoplanet Survey Satellite (TESS) photometry, but the true orbital
period of the outermost planet d was unknown until now.
Aims. We aim to use the Characterising Exoplanet Satellite (CHEOPS) space telescope to uncover the true orbital period of HD 22946d
and to refine the orbital and planetary properties of the system, especially the radii of the planets.
Methods. We used the available TESS photometry of HD 22946 and observed several transits of the planets b, c, and d using CHEOPS.
We identified two transits of planet d in the TESS photometry, calculated the most probable period aliases based on these data, and
then scheduled CHEOPS observations. The photometric data were supplemented with ESPRESSO (Echelle SPectrograph for Rocky
Exoplanets and Stable Spectroscopic Observations) radial velocity data. Finally, a combined model was fitted to the entire dataset in
order to obtain final planetary and system parameters.
Results. Based on the combined TESS and CHEOPS observations, we successfully determined the true orbital period of the planet d
to be 47.42489 ± 0.00011 days, and derived precise radii of the planets in the system, namely 1.362 ± 0.040 R⊕, 2.328 ± 0.039 R⊕, and
2.607 ± 0.060 R⊕ for planets b, c, and d, respectively. Due to the low number of radial velocities, we were only able to determine 3σ
upper limits for these respective planet masses, which are 13.71 M⊕, 9.72 M⊕, and 26.57 M⊕. We estimated that another 48 ESPRESSO
radial velocities are needed to measure the predicted masses of all planets in HD 22946. We also derived stellar parameters for the host
star.
Conclusions. Planet c around HD 22946 appears to be a promising target for future atmospheric characterisation via transmission
spectroscopy. We can also conclude that planet d, as a warm sub-Neptune, is very interesting because there are only a few similar
confirmed exoplanets to date. Such objects are worth investigating in the near future, for example in terms of their composition and
internal structure.
The ExoplanetSat Mission to Detect Transiting Exoplanets with a CShawn Murphy
1) ExoplanetSat is a CubeSat mission that aims to detect Earth-sized exoplanets transiting nearby bright stars using ultra-precise photometry.
2) It will monitor individual target stars to detect the characteristic dip in light level caused by a transiting exoplanet. Any planets detected could then be studied by larger telescopes to characterize their atmospheres.
3) ExoplanetSat's design incorporates a 6cm telescope combined with a fine image stabilization system to achieve near shot-noise limited photometry, allowing detection of Earth-sized planets transiting stars as bright as magnitude 6.
The Possible Tidal Demise of Kepler’s First Planetary SystemSérgio Sacani
We present evidence of tidally-driven inspiral in the Kepler-1658 (KOI-4) system, which consists of a giant planet
(1.1RJ, 5.9MJ) orbiting an evolved host star (2.9Re, 1.5Me). Using transit timing measurements from Kepler,
Palomar/WIRC, and TESS, we show that the orbital period of Kepler-1658b appears to be decreasing at a rate = -
+ P 131 22
20 ms yr−1
, corresponding to an infall timescale P P » 2.5 Myr. We consider other explanations for the
data including line-of-sight acceleration and orbital precession, but find them to be implausible. The observed
period derivative implies a tidal quality factor
¢ = ´ -
+ Q 2.50 10 0.62
0.85 4, in good agreement with theoretical
predictions for inertial wave dissipation in subgiant stars. Additionally, while it probably cannot explain the entire
inspiral rate, a small amount of planetary dissipation could naturally explain the deep optical eclipse observed for
the planet via enhanced thermal emission. As the first evolved system with detected inspiral, Kepler-1658 is a new
benchmark for understanding tidal physics at the end of the planetary life cycle
X-rays from a Central “Exhaust Vent” of the Galactic Center ChimneySérgio Sacani
Using deep archival observations from the Chandra X-ray Observatory, we present an analysis of
linear X-ray-emitting features located within the southern portion of the Galactic center chimney,
and oriented orthogonal to the Galactic plane, centered at coordinates l = 0.08◦
, b = −1.42◦
. The
surface brightness and hardness ratio patterns are suggestive of a cylindrical morphology which may
have been produced by a plasma outflow channel extending from the Galactic center. Our fits of the
feature’s spectra favor a complex two-component model consisting of thermal and recombining plasma
components, possibly a sign of shock compression or heating of the interstellar medium by outflowing
material. Assuming a recombining plasma scenario, we further estimate the cooling timescale of this
plasma to be on the order of a few hundred to thousands of years, leading us to speculate that a
sequence of accretion events onto the Galactic Black Hole may be a plausible quasi-continuous energy
source to sustain the observed morphology
Hubble Asteroid Hunter III. Physical properties of newly found asteroidsSérgio Sacani
Context. Determining the size distribution of asteroids is key to understanding the collisional history and evolution of the inner Solar System. Aims. We aim to improve our knowledge of the size distribution of small asteroids in the main belt by determining the parallaxes of newly detected asteroids in the Hubble Space Telescope (HST) archive and subsequently their absolute magnitudes and sizes. Methods. Asteroids appear as curved trails in HST images because of the parallax induced by the fast orbital motion of the spacecraft. Taking into account the trajectory of this latter, the parallax effect can be computed to obtain the distance to the asteroids by fitting simulated trajectories to the observed trails. Using distance, we can obtain the absolute magnitude of an object and an estimation of its size assuming an albedo value, along with some boundaries for its orbital parameters. Results. In this work, we analyse a set of 632 serendipitously imaged asteroids found in the ESA HST archive. Images were captured with the ACS/WFC and WFC3/UVIS instruments. A machine learning algorithm (trained with the results of a citizen science project) was used to detect objects in these images as part of a previous study. Our raw data consist of 1031 asteroid trails from unknown objects, not matching any entries in the Minor Planet Center (MPC) database using their coordinates and imaging time. We also found 670 trails from known objects (objects featuring matching entries in the MPC). After an accuracy assessment and filtering process, our analysed HST asteroid set consists of 454 unknown objects and 178 known objects. We obtain a sample dominated by potential main belt objects featuring absolute magnitudes (H) mostly between 15 and 22 mag. The absolute magnitude cumulative distribution logN(H > H0) ∝ αlog(H0) confirms the previously reported slope change for 15 < H < 18, from α ≈ 0.56 to α ≈ 0.26, maintained in our case down to absolute magnitudes of around H ≈ 20, and therefore expanding the previous result by approximately two magnitudes. Conclusions. HST archival observations can be used as an asteroid survey because the telescope pointings are statistically randomly oriented in the sky and cover long periods of time. They allow us to expand the current best samples of astronomical objects at no extra cost in regard to telescope time.
Visible spectra of (474640) 2004 VN112–2013 RF98 with OSIRIS at the 10.4 m GT...Sérgio Sacani
The existence of significant anisotropies in the distributions of the directions of perihelia and
orbital poles of the known extreme trans-Neptunian objects (ETNOs) has been used to claim
that trans-Plutonian planets may exist. Among the known ETNOs, the pair (474640) 2004
VN112–2013 RF98 stands out. Their orbital poles and the directions of their perihelia and their
velocities at perihelion/aphelion are separated by a few degrees, but orbital similarity does
not necessarily imply common physical origin. In an attempt to unravel their physical nature,
visible spectroscopy of both targets was obtained using the OSIRIS camera-spectrograph at the
10.4 m Gran Telescopio Canarias (GTC). From the spectral analysis, we find that 474640–2013
RF98 have similar spectral slopes (12 versus 15 per cent/0.1 µm), very different from Sedna’s
but compatible with those of (148209) 2000 CR105 and 2012 VP113. These five ETNOs belong
to the group of seven linked to the Planet Nine hypothesis. A dynamical pathway consistent
with these findings is dissociation of a binary asteroid during a close encounter with a planet
and we confirm its plausibility using N-body simulations. We thus conclude that both the
dynamical and spectroscopic properties of 474640–2013 RF98 favour a genetic link and their
current orbits suggest that the pair was kicked by a perturber near aphelion
The hazardous km-sized NEOs of the next thousands of yearsSérgio Sacani
This document discusses methods for assessing the long-term impact risk of km-sized near-Earth objects (NEOs) over thousands of years. It analyzes the evolution of the Minimum Orbit Intersection Distance (MOID) between NEOs and Earth to identify objects that remain in close proximity for extended periods. It then estimates the probability of a deep Earth encounter during these low-MOID periods based on the growth of orbital uncertainties over time. This allows the authors to rank km-sized NEOs by their long-term impact hazard and identify targets that warrant further observation and analysis.
Spirals and clumps in V960 Mon: signs of planet formation via gravitational i...Sérgio Sacani
The formation of giant planets has traditionally been divided into two pathways: core accretion and gravitational instability. However, in recent years, gravitational instability has become less favored, primarily due
to the scarcity of observations of fragmented protoplanetary disks around young stars and low occurrence rate
of massive planets on very wide orbits. In this study, we present a SPHERE/IRDIS polarized light observation
of the young outbursting object V960 Mon. The image reveals a vast structure of intricately shaped scattered
light with several spiral arms. This finding motivated a re-analysis of archival ALMA 1.3 mm data acquired
just two years after the onset of the outburst of V960 Mon. In these data, we discover several clumps of continuum emission aligned along a spiral arm that coincides with the scattered light structure. We interpret the
localized emission as fragments formed from a spiral arm under gravitational collapse. Estimating the mass of
solids within these clumps to be of several Earth masses, we suggest this observation to be the first evidence of
gravitational instability occurring on planetary scales. This study discusses the significance of this finding for
planet formation and its potential connection with the outbursting state of V960 Mon.
Refined parameters of the HD 22946 planetary system and the true orbital peri...Sérgio Sacani
Multi-planet systems are important sources of information regarding the evolution of planets. However, the long-period
planets in these systems often escape detection. These objects in particular may retain more of their primordial characteristics compared
to close-in counterparts because of their increased distance from the host star. HD 22946 is a bright (G = 8.13 mag) late F-type star
around which three transiting planets were identified via Transiting Exoplanet Survey Satellite (TESS) photometry, but the true orbital
period of the outermost planet d was unknown until now.
Aims. We aim to use the Characterising Exoplanet Satellite (CHEOPS) space telescope to uncover the true orbital period of HD 22946d
and to refine the orbital and planetary properties of the system, especially the radii of the planets.
Methods. We used the available TESS photometry of HD 22946 and observed several transits of the planets b, c, and d using CHEOPS.
We identified two transits of planet d in the TESS photometry, calculated the most probable period aliases based on these data, and
then scheduled CHEOPS observations. The photometric data were supplemented with ESPRESSO (Echelle SPectrograph for Rocky
Exoplanets and Stable Spectroscopic Observations) radial velocity data. Finally, a combined model was fitted to the entire dataset in
order to obtain final planetary and system parameters.
Results. Based on the combined TESS and CHEOPS observations, we successfully determined the true orbital period of the planet d
to be 47.42489 ± 0.00011 days, and derived precise radii of the planets in the system, namely 1.362 ± 0.040 R⊕, 2.328 ± 0.039 R⊕, and
2.607 ± 0.060 R⊕ for planets b, c, and d, respectively. Due to the low number of radial velocities, we were only able to determine 3σ
upper limits for these respective planet masses, which are 13.71 M⊕, 9.72 M⊕, and 26.57 M⊕. We estimated that another 48 ESPRESSO
radial velocities are needed to measure the predicted masses of all planets in HD 22946. We also derived stellar parameters for the host
star.
Conclusions. Planet c around HD 22946 appears to be a promising target for future atmospheric characterisation via transmission
spectroscopy. We can also conclude that planet d, as a warm sub-Neptune, is very interesting because there are only a few similar
confirmed exoplanets to date. Such objects are worth investigating in the near future, for example in terms of their composition and
internal structure.
The ExoplanetSat Mission to Detect Transiting Exoplanets with a CShawn Murphy
1) ExoplanetSat is a CubeSat mission that aims to detect Earth-sized exoplanets transiting nearby bright stars using ultra-precise photometry.
2) It will monitor individual target stars to detect the characteristic dip in light level caused by a transiting exoplanet. Any planets detected could then be studied by larger telescopes to characterize their atmospheres.
3) ExoplanetSat's design incorporates a 6cm telescope combined with a fine image stabilization system to achieve near shot-noise limited photometry, allowing detection of Earth-sized planets transiting stars as bright as magnitude 6.
The Internal Structure of Asteroid (25143) Itokawa as Revealed by Detection o...WellingtonRodrigues2014
- The authors detected an acceleration in the rotation rate of asteroid (25143) Itokawa through photometric observations spanning 2001 to 2013.
- By measuring rotational phase offsets between observed and modeled lightcurves, they found a YORP acceleration of 3.54 ± 0.38 × 10−8 rad day−2, equivalent to a decrease in the asteroid's rotation period of about 45 ms per year.
- Thermophysical modeling of the detailed shape model from the Hayabusa spacecraft could not reconcile the observed YORP strength unless the asteroid's center of mass is shifted by about 21 m along its long axis. This suggests Itokawa has two components with different densities that merged, either from a
The internal structure_of_asteroid_itokawa_as_revealed_by_detection_of_yorp_s...Sérgio Sacani
The study detected an acceleration in the rotation rate of asteroid (25143) Itokawa through long-term photometric monitoring between 2001-2013. By measuring rotational phase offsets between observed and modeled lightcurves, a YORP acceleration of 3.54 ± 0.38 × 10−8 rad day−2 was measured, equivalent to a decrease in the asteroid's rotation period of about 45 ms per year. Thermophysical analysis of the detailed shape model from the Hayabusa spacecraft found that the center-of-mass must be offset by about 21 m along the long axis to reconcile the observed and theoretical YORP strengths, suggesting Itokawa is composed of two separate bodies with densities of 1750 ± 110 kg m
Evidence for reflected_lightfrom_the_most_eccentric_exoplanet_knownSérgio Sacani
Planets in highly eccentric orbits form a class of objects not seen within our Solar System. The most extreme case known amongst these objects is the planet orbiting HD 20782, with an orbital period of 597 days and an eccentricity of 0.96. Here we present new data and analysis for this system as part of the Transit Ephemeris Refinement and Monitoring Survey (TERMS). We obtained CHIRON spectra to perform an independent estimation of the fundamental stellar parameters. New radial velocities from AAT and PARAS observations during periastron passage greatly improve our knowledge of the eccentric nature of the orbit. The combined analysis of our Keplerian orbital and Hipparcos astrometry show that the inclination of the planetary orbit is > 1.22◦, ruling out stellar masses for the companion. Our long-term robotic photometry show that the star is extremely stable over long timescales. Photometric monitoring of the star during predicted transit and periastron times using MOST rule out a transit of the planet and reveal evidence of phase variations during periastron. These possible photometric phase variations may be caused by reflected light from the planet’s atmosphere and the dramatic change in star–planet separation surrounding the periastron passage.
This document presents an analysis of transit spectroscopy observations of three exoplanets - WASP-12 b, WASP-17 b, and WASP-19 b - using the Wide Field Camera 3 instrument on the Hubble Space Telescope. The observations achieved almost photon-limited precision but uncertainties in the transit depths were increased by the uneven sampling of the light curves. The final transit spectra for all three planets are consistent with the presence of a water absorption feature at 1.4 microns, though the amplitude is smaller than expected from previous Spitzer observations possibly due to hazes. Due to degeneracies between models, the data cannot unambiguously constrain the atmospheric compositions without additional observations.
Kepler’s last planet discoveries: two new planets and one single-transit cand...Sérgio Sacani
The Kepler space telescope was responsible for the discovery of over 2700 confirmed exoplanets, more than half of the total
number of exoplanets known today. These discoveries took place during both Kepler’s primary mission, when it spent 4 yr
staring at the same part of the sky, and its extended K2 mission, when a mechanical failure forced it to observe different parts of
the sky along the ecliptic. At the very end of the mission, when Kepler was exhausting the last of its fuel reserves, it collected
a short set of observations known as K2 Campaign 19. So far, no planets have been discovered in this data set because it only
yielded about a week of high-quality data. Here, we report some of the last planet discoveries made by Kepler in the Campaign
19 dataset. We conducted a visual search of the week of high-quality Campaign 19 data and identified three possible planet
transits. Each planet candidate was originally identified with only one recorded transit, from which we were able to estimate
the planets’ radii and estimate the semimajor axes and orbital periods. Analysis of lower-quality data collected after low fuel
pressure caused the telescope’s pointing precision to suffer revealed additional transits for two of these candidates, allowing
us to statistically validate them as genuine exoplanets. We also tentatively confirm the transits of one planet with TESS. These
discoveries demonstrate Kepler’s exoplanet detection power, even when it was literally running on fumes.
High-resolution UV/Optical/IR Imaging of Jupiter in 2016–2019Sérgio Sacani
Imaging observations of Jupiter with high spatial resolution were acquired beginning in 2016, with a cadence of 53
days to coincide with atmospheric observations of the Juno spacecraft during each perijove pass. The Wide Field
Camera 3 (WFC3) aboard the Hubble Space Telescope (HST) collected Jupiter images from 236 to 925 nm in 14
filters. The Near-Infrared Imager (NIRI) at Gemini North imaged Jovian thermal emission using a lucky-imaging
approach (co-adding the sharpest frames taken from a sequence of short exposures), using the M′ filter at 4.7 μm.
We discuss the data acquisition and processing and an archive collection that contains the processed WFC3 and
NIRI data (doi:10.17909/T94T1H). Zonal winds remain steady over time at most latitudes, but significant
evolution of the wind profile near 24°N in 2016 and near 15°S in 2017 was linked with convective superstorm
eruptions. Persistent mesoscale waves were seen throughout the 2016–2019 period. We link groups of lightning
flashes observed by the Juno team with water clouds in a large convective plume near 15°S and in cyclones near
35°N–55°N. Thermal infrared maps at the 10.8 micron wavelength obtained at the Very Large Telescope show
consistent high brightness temperature anomalies, despite a diversity of aerosol properties seen in the HST data.
Both WFC3 and NIRI imaging reveal depleted aerosols consistent with downwelling around the periphery of the
15°S storm, which was also observed by the Atacama Large Millimeter/submillimeter Array. NIRI imaging of
the Great Red Spot shows that locally reduced cloud opacity is responsible for dark features within the vortex. The
HST data maps multiple concentric polar hoods of high-latitude hazes.
The closest known_flyby_of_a_star_to_the_solar_systemSérgio Sacani
The closest known flyby of a star to the solar system was a low-mass binary star system called WISE J072003.20-084651.2, also known as "Scholz's star". By integrating the orbits of this 0.15 solar mass binary system and the Sun, astronomers found that it passed within 0.25 parsecs (52,000 AU) of the Sun about 70,000 years ago, within the outer bounds of the Oort Cloud. This is the closest encounter with a star to the solar system that has been well-constrained in distance and velocity. While the flyby likely had a negligible impact on long-period comets from the Oort Cloud, it highlights the possibility
Direct Measure of Radiative And Dynamical Properties Of An Exoplanet AtmosphereSérgio Sacani
Two decades after the discovery of 51Pegb, the formation processes and atmospheres of short-period gas giants
remain poorly understood. Observations of eccentric systems provide key insights on those topics as they can
illuminate how a planet’s atmosphere responds to changes in incident flux. We report here the analysis of multi-day
multi-channel photometry of the eccentric (e ~ 0.93) hot Jupiter HD80606b obtained with the Spitzer Space
Telescope. The planet’s extreme eccentricity combined with the long coverage and exquisite precision of new
periastron-passage observations allow us to break the degeneracy between the radiative and dynamical timescales
of HD80606b’s atmosphere and constrain its global thermal response. Our analysis reveals that the atmospheric
layers probed heat rapidly (∼4 hr radiative timescale) from<500 to 1400 K as they absorb ~20% of the incoming
stellar flux during the periastron passage, while the planet’s rotation period is 93 35
85
-
+ hr, which exceeds the predicted
pseudo-synchronous period (40 hr).
Key words: methods: numerical – planet–star interactions – planets and satellites: atmospheres – planets and
satellites: dynamical evolution and stability – planets and satellites: individual (HD 80606 b) – techniques:
photometric
ASTRONOMICAL OBJECTS DETECTION IN CELESTIAL BODIES USING COMPUTER VISION ALGO...csandit
Computer vision, astronomy, and astrophysics function quite productively together to the point where they are completely logical for each other. Out of computer vision algorithms the
progress of astronomy and astrophysics would have slowed down to reasonably a deadlock. The new researches and calculations can lead to more information as well as higher quality of data. Consequently, an organized view on planetary surfaces can change all in the long run. A new
discovery would be a puzzling complexity or a possible branching of paths, yet the quest to know more about the celestial bodies by dint of computer vision algorithms will continue. The detection of astronomical objects in celestial bodies is a challenging task. This paper presents
an implementation of how to detect astronomical objects in celestial bodies using computer vision algorithm with satisfactory performance. It also puts forward some observations linked
among computer vision, astronomy, and astrophysics.
WASP-69b’s Escaping Envelope Is Confined to a Tail Extending at Least 7 RpSérgio Sacani
Studying the escaping atmospheres of highly irradiated exoplanets is critical for understanding the physical
mechanisms that shape the demographics of close-in planets. A number of planetary outflows have been observed
as excess H/He absorption during/after transit. Such an outflow has been observed for WASP-69b by multiple
groups that disagree on the geometry and velocity structure of the outflow. Here, we report the detection of this
planet’s outflow using Keck/NIRSPEC for the first time. We observed the outflow 1.28 hr after egress until the
target set, demonstrating the outflow extends at least 5.8 × 105 km or 7.5 Rp This detection is significantly longer
than previous observations, which report an outflow extending ∼2.2 planet radii just 1 yr prior. The outflow is
blueshifted by −23 km s−1 in the planetary rest frame. We estimate a current mass-loss rate of 1 M⊕ Gyr−1
. Our
observations are most consistent with an outflow that is strongly sculpted by ram pressure from the stellar wind.
However, potential variability in the outflow could be due to time-varying interactions with the stellar wind or
differences in instrumental precision.
Studies of ngc_6720_with_calibrated_hst_wfc3_emission_line_filter_imagesSérgio Sacani
This study uses calibrated Hubble Space Telescope images of the Ring Nebula (NGC 6720) taken 12.925 years apart to measure tangential motions within the nebula. Individual features were measured in nitrogen emission line images as well as dark knots seen against oxygen emission. The results indicate that the nebula is expanding homologously, but at a faster rate along its major axis. Dark knots were found to expand more slowly than the nebular gas. The tangential motion measurements allow estimates of the nebula's distance and dynamic age to be about 720 pc and 4000 years, respectively.
Confirmation of the_ogle_planet_signature_and_its_characteristics_with_lens_s...Sérgio Sacani
O Telescópio Espacial Hubble e o Observatório W. M. Keck, no Havaí, fizeram confirmações independentes de um exoplaneta orbitando sua estrela central de uma distância bem grande. O planeta foi descoberto através de uma técnica chamada de microlente gravitacional.
Essa descoberta traz uma nova peça para o processo de caçada de exoplanetas: para descobrir planetas longe de suas estrelas, como Júpiter e Saturno estão do Sol. Os resultados obtidos pelo Hubble e pelo Keck apareceram em dois artigos da edição de 30 de Julho de 2015 do The Astrophysical Journal.
A grande maioria dos exoplanetas catalogados são aqueles localizados bem perto de suas estrelas, isso acontece porque as técnicas atuais de se caçar exoplanetas favorecem a descoberta de planetas com curtos períodos orbitais. Mas esse não é o caso da técnica de microlente gravitacional, que pode encontrar planetas mais frios e mais distantes com órbitas de longo período que outros métodos não são capazes de detectar.
A surge of light at the birth of a supernovaSérgio Sacani
It is difficult to establish the properties of massive stars that explode
as supernovae1,2
. The electromagnetic emission during the first
minutes to hours after the emergence of the shock from the stellar
surface conveys important information about the final evolution
and structure of the exploding star3–6. However, the unpredictable
nature of supernova events hinders the detection of this brief initial
phase7–9. Here we report the serendipitous discovery of a newly
born, normal type IIb supernova (SN 2016gkg)10, which reveals a
rapid brightening at optical wavelengths of about 40 magnitudes
per day. The very frequent sampling of the observations allowed
us to study in detail the outermost structure of the progenitor of
the supernova and the physics of the emergence of the shock. We
develop hydrodynamical models of the explosion that naturally
account for the complete evolution of the supernova over distinct
phases regulated by different physical processes. This result
suggests that it is appropriate to decouple the treatment of the
shock propagation from the unknown mechanism that triggers
the explosion.
Confirmation of the_planetary_microlensing_signal_and_star_and_planet_mass_de...Sérgio Sacani
This document summarizes follow-up Hubble Space Telescope observations of the planetary microlensing event OGLE-2005-BLG-169. The HST observations confirm the relative proper motion between the source and lens stars predicted by the planetary signal in the original light curve. This provides the first confirmation of a planetary microlensing signal. The HST observations also measure the brightness of the planetary host star, allowing a precise determination of the planet and host star masses as well as their projected separation. Combined with measurements from Keck adaptive optics, the HST observations confirm the identification of the lens star and characterization of the planetary system.
LHS 475 b: A Venus-sized Planet Orbiting a Nearby M DwarfSérgio Sacani
Based on photometric observations by TESS, we present the discovery of a Venussized planet transiting LHS 475, an M3 dwarf located 12.5 pc from the Sun. The mass
of the star is 0.274 ± 0.015 M. The planet, originally reported as TOI 910.01, has an
orbital period of 2.0291025 ± 0.0000020 days and an estimated radius of 0.955 ± 0.053
R⊕. We confirm the validity and source of the transit signal with MEarth ground-based
follow-up photometry of five individual transits. We present radial velocity data from
CHIRON that rule out massive companions. In accordance with the observed massradius distribution of exoplanets as well as planet formation theory, we expect this
Venus-sized companion to be terrestrial, with an estimated RV semi-amplitude close to
1.0 m/s. LHS 475 b is likely too hot to be habitable but is a suitable candidate for
emission and transmission spectroscopy.
An energetic stellar_outburst_accompanied_by_circumstellar_light_echoesSérgio Sacani
1) V838 Monocerotis (V838 Mon) underwent an energetic stellar outburst in early 2002, temporarily becoming the brightest star in the Milky Way. 2) Hubble Space Telescope images revealed expanding light echoes in the circumstellar dust surrounding V838 Mon, allowing astronomers to set a minimum distance of over 6 kiloparsecs. 3) The light echoes, combined with the object's high luminosity and evidence that it resides in a binary system, indicate that V838 Mon represents a new class of stellar outburst not fully explained by current models.
Planeta 9 - A Pan-STARRS1 Search for Planet NineSérgio Sacani
We present a search for Planet Nine using the second data release of the PanSTARRS1 survey. We rule out the existence of a Planet Nine with the characteristics
of that predicted in Brown & Batygin (2021) to a 50% completion depth of V = 21.5.
This survey, along with previous analyses of the Zwicky Transient Facility (ZTF) and
Dark Energy Survey (DES) data, rules out 78% of the Brown & Batygin parameter
space. Much of the remaining parameter space is at V > 21 in regions near and in the
area where the northern galactic plane crosses the ecliptic.
TOI-4600 b and c: Two Long-period Giant Planets Orbiting an Early K DwarfSérgio Sacani
We report the discovery and validation of two long-period giant exoplanets orbiting the early K dwarf TOI-4600
(V = 12.6, T = 11.9), first detected using observations from the Transiting Exoplanet Survey Satellite (TESS) by
the TESS Single Transit Planet Candidate Working Group. The inner planet, TOI-4600 b, has a radius of
6.80 ± 0.31 R⊕ and an orbital period of 82.69 days. The outer planet, TOI-4600 c, has a radius of 9.42 ± 0.42 R⊕
and an orbital period of 482.82 days, making it the longest-period confirmed or validated planet discovered by
TESS to date. We combine TESS photometry and ground-based spectroscopy, photometry, and high-resolution
imaging to validate the two planets. With equilibrium temperatures of 347 K and 191 K, respectively, TOI-4600 b
and c add to the small but growing population of temperate giant exoplanets that bridge the gap between hot/warm
Jupiters and the solar system’s gas giants. TOI-4600 is a promising target for further transit and precise RV
observations to measure the masses and orbits of the planets as well as search for additional nontransiting planets.
Additionally, with Transit Spectroscopy Metric values of ∼30, both planets are amenable for atmospheric
characterization with JWST. Together, these will lend insight into the formation and evolution of planet systems
with multiple giant exoplanets.
Observational constraints on mergers creating magnetism in massive starsSérgio Sacani
Massive stars (those ≥8 solar masses at birth) have radiative envelopes that cannot sustain the dynamos that produce magnetic fields in lower mass stars. Despite this, ∼7% of massive stars have observed magnetic fields. We use multi-epoch interferometric and spectroscopic observations to characterise a magnetic binary system formed of two massive stars. We find that only one star of the binary is magnetic. Using the non-magnetic star as an independent reference clock to estimate the age of the system, we show that the magnetic star appears younger than its companion. The system properties, and a surrounding bipolar nebula, can be reproduced by a model in which this system was originally a triple within which two of the stars merged, producing the magnetic massive star. Thus, our results provide observational evidence that magnetic fields form in at least some massive stars through stellar mergers.
Initial characterization of interstellar comet 2I/BorisovSérgio Sacani
Interstellar comets penetrating through the Solar System had
been anticipated for decades1,2
. The discovery of asteroidallooking ‘Oumuamua3,4 was thus a huge surprise and a puzzle.
Furthermore, the physical properties of the ‘first scout’ turned
out to be impossible to reconcile with Solar System objects4–6,
challenging our view of interstellar minor bodies7,8. Here, we
report the identification and early characterization of a new
interstellar object, which has an evidently cometary appearance. The body was discovered by Gennady Borisov on 30
August 2019 ut and subsequently identified as hyperbolic by
our data mining code in publicly available astrometric data.
The initial orbital solution implies a very high hyperbolic excess
speed of ~32 km s−1
, consistent with ‘Oumuamua9 and theoretical predictions2,7
. Images taken on 10 and 13 September
2019 ut with the William Herschel Telescope and Gemini
North Telescope show an extended coma and a faint, broad
tail. We measure a slightly reddish colour with a g′–r′ colour
index of 0.66 ± 0.01 mag, compatible with Solar System comets. The observed morphology is also unremarkable and best
explained by dust with a power-law size-distribution index
of –3.7 ± 1.8 and a low ejection speed (44 ± 14 m s−1
for β= 1
particles, where β is the ratio of the solar gravitational attraction to the solar radiation pressure). The nucleus is probably
~1 km in radius, again a common value among Solar System
comets, and has a negligible chance of experiencing rotational
disruption. Based on these early characteristics, and putting
its hyperbolic orbit aside, 2I/Borisov appears indistinguishable from the native Solar System comets.
The binding of cosmological structures by massless topological defectsSérgio Sacani
Assuming spherical symmetry and weak field, it is shown that if one solves the Poisson equation or the Einstein field
equations sourced by a topological defect, i.e. a singularity of a very specific form, the result is a localized gravitational
field capable of driving flat rotation (i.e. Keplerian circular orbits at a constant speed for all radii) of test masses on a thin
spherical shell without any underlying mass. Moreover, a large-scale structure which exploits this solution by assembling
concentrically a number of such topological defects can establish a flat stellar or galactic rotation curve, and can also deflect
light in the same manner as an equipotential (isothermal) sphere. Thus, the need for dark matter or modified gravity theory is
mitigated, at least in part.
EWOCS-I: The catalog of X-ray sources in Westerlund 1 from the Extended Weste...Sérgio Sacani
Context. With a mass exceeding several 104 M⊙ and a rich and dense population of massive stars, supermassive young star clusters
represent the most massive star-forming environment that is dominated by the feedback from massive stars and gravitational interactions
among stars.
Aims. In this paper we present the Extended Westerlund 1 and 2 Open Clusters Survey (EWOCS) project, which aims to investigate
the influence of the starburst environment on the formation of stars and planets, and on the evolution of both low and high mass stars.
The primary targets of this project are Westerlund 1 and 2, the closest supermassive star clusters to the Sun.
Methods. The project is based primarily on recent observations conducted with the Chandra and JWST observatories. Specifically,
the Chandra survey of Westerlund 1 consists of 36 new ACIS-I observations, nearly co-pointed, for a total exposure time of 1 Msec.
Additionally, we included 8 archival Chandra/ACIS-S observations. This paper presents the resulting catalog of X-ray sources within
and around Westerlund 1. Sources were detected by combining various existing methods, and photon extraction and source validation
were carried out using the ACIS-Extract software.
Results. The EWOCS X-ray catalog comprises 5963 validated sources out of the 9420 initially provided to ACIS-Extract, reaching a
photon flux threshold of approximately 2 × 10−8 photons cm−2
s
−1
. The X-ray sources exhibit a highly concentrated spatial distribution,
with 1075 sources located within the central 1 arcmin. We have successfully detected X-ray emissions from 126 out of the 166 known
massive stars of the cluster, and we have collected over 71 000 photons from the magnetar CXO J164710.20-455217.
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The Internal Structure of Asteroid (25143) Itokawa as Revealed by Detection o...WellingtonRodrigues2014
- The authors detected an acceleration in the rotation rate of asteroid (25143) Itokawa through photometric observations spanning 2001 to 2013.
- By measuring rotational phase offsets between observed and modeled lightcurves, they found a YORP acceleration of 3.54 ± 0.38 × 10−8 rad day−2, equivalent to a decrease in the asteroid's rotation period of about 45 ms per year.
- Thermophysical modeling of the detailed shape model from the Hayabusa spacecraft could not reconcile the observed YORP strength unless the asteroid's center of mass is shifted by about 21 m along its long axis. This suggests Itokawa has two components with different densities that merged, either from a
The internal structure_of_asteroid_itokawa_as_revealed_by_detection_of_yorp_s...Sérgio Sacani
The study detected an acceleration in the rotation rate of asteroid (25143) Itokawa through long-term photometric monitoring between 2001-2013. By measuring rotational phase offsets between observed and modeled lightcurves, a YORP acceleration of 3.54 ± 0.38 × 10−8 rad day−2 was measured, equivalent to a decrease in the asteroid's rotation period of about 45 ms per year. Thermophysical analysis of the detailed shape model from the Hayabusa spacecraft found that the center-of-mass must be offset by about 21 m along the long axis to reconcile the observed and theoretical YORP strengths, suggesting Itokawa is composed of two separate bodies with densities of 1750 ± 110 kg m
Evidence for reflected_lightfrom_the_most_eccentric_exoplanet_knownSérgio Sacani
Planets in highly eccentric orbits form a class of objects not seen within our Solar System. The most extreme case known amongst these objects is the planet orbiting HD 20782, with an orbital period of 597 days and an eccentricity of 0.96. Here we present new data and analysis for this system as part of the Transit Ephemeris Refinement and Monitoring Survey (TERMS). We obtained CHIRON spectra to perform an independent estimation of the fundamental stellar parameters. New radial velocities from AAT and PARAS observations during periastron passage greatly improve our knowledge of the eccentric nature of the orbit. The combined analysis of our Keplerian orbital and Hipparcos astrometry show that the inclination of the planetary orbit is > 1.22◦, ruling out stellar masses for the companion. Our long-term robotic photometry show that the star is extremely stable over long timescales. Photometric monitoring of the star during predicted transit and periastron times using MOST rule out a transit of the planet and reveal evidence of phase variations during periastron. These possible photometric phase variations may be caused by reflected light from the planet’s atmosphere and the dramatic change in star–planet separation surrounding the periastron passage.
This document presents an analysis of transit spectroscopy observations of three exoplanets - WASP-12 b, WASP-17 b, and WASP-19 b - using the Wide Field Camera 3 instrument on the Hubble Space Telescope. The observations achieved almost photon-limited precision but uncertainties in the transit depths were increased by the uneven sampling of the light curves. The final transit spectra for all three planets are consistent with the presence of a water absorption feature at 1.4 microns, though the amplitude is smaller than expected from previous Spitzer observations possibly due to hazes. Due to degeneracies between models, the data cannot unambiguously constrain the atmospheric compositions without additional observations.
Kepler’s last planet discoveries: two new planets and one single-transit cand...Sérgio Sacani
The Kepler space telescope was responsible for the discovery of over 2700 confirmed exoplanets, more than half of the total
number of exoplanets known today. These discoveries took place during both Kepler’s primary mission, when it spent 4 yr
staring at the same part of the sky, and its extended K2 mission, when a mechanical failure forced it to observe different parts of
the sky along the ecliptic. At the very end of the mission, when Kepler was exhausting the last of its fuel reserves, it collected
a short set of observations known as K2 Campaign 19. So far, no planets have been discovered in this data set because it only
yielded about a week of high-quality data. Here, we report some of the last planet discoveries made by Kepler in the Campaign
19 dataset. We conducted a visual search of the week of high-quality Campaign 19 data and identified three possible planet
transits. Each planet candidate was originally identified with only one recorded transit, from which we were able to estimate
the planets’ radii and estimate the semimajor axes and orbital periods. Analysis of lower-quality data collected after low fuel
pressure caused the telescope’s pointing precision to suffer revealed additional transits for two of these candidates, allowing
us to statistically validate them as genuine exoplanets. We also tentatively confirm the transits of one planet with TESS. These
discoveries demonstrate Kepler’s exoplanet detection power, even when it was literally running on fumes.
High-resolution UV/Optical/IR Imaging of Jupiter in 2016–2019Sérgio Sacani
Imaging observations of Jupiter with high spatial resolution were acquired beginning in 2016, with a cadence of 53
days to coincide with atmospheric observations of the Juno spacecraft during each perijove pass. The Wide Field
Camera 3 (WFC3) aboard the Hubble Space Telescope (HST) collected Jupiter images from 236 to 925 nm in 14
filters. The Near-Infrared Imager (NIRI) at Gemini North imaged Jovian thermal emission using a lucky-imaging
approach (co-adding the sharpest frames taken from a sequence of short exposures), using the M′ filter at 4.7 μm.
We discuss the data acquisition and processing and an archive collection that contains the processed WFC3 and
NIRI data (doi:10.17909/T94T1H). Zonal winds remain steady over time at most latitudes, but significant
evolution of the wind profile near 24°N in 2016 and near 15°S in 2017 was linked with convective superstorm
eruptions. Persistent mesoscale waves were seen throughout the 2016–2019 period. We link groups of lightning
flashes observed by the Juno team with water clouds in a large convective plume near 15°S and in cyclones near
35°N–55°N. Thermal infrared maps at the 10.8 micron wavelength obtained at the Very Large Telescope show
consistent high brightness temperature anomalies, despite a diversity of aerosol properties seen in the HST data.
Both WFC3 and NIRI imaging reveal depleted aerosols consistent with downwelling around the periphery of the
15°S storm, which was also observed by the Atacama Large Millimeter/submillimeter Array. NIRI imaging of
the Great Red Spot shows that locally reduced cloud opacity is responsible for dark features within the vortex. The
HST data maps multiple concentric polar hoods of high-latitude hazes.
The closest known_flyby_of_a_star_to_the_solar_systemSérgio Sacani
The closest known flyby of a star to the solar system was a low-mass binary star system called WISE J072003.20-084651.2, also known as "Scholz's star". By integrating the orbits of this 0.15 solar mass binary system and the Sun, astronomers found that it passed within 0.25 parsecs (52,000 AU) of the Sun about 70,000 years ago, within the outer bounds of the Oort Cloud. This is the closest encounter with a star to the solar system that has been well-constrained in distance and velocity. While the flyby likely had a negligible impact on long-period comets from the Oort Cloud, it highlights the possibility
Direct Measure of Radiative And Dynamical Properties Of An Exoplanet AtmosphereSérgio Sacani
Two decades after the discovery of 51Pegb, the formation processes and atmospheres of short-period gas giants
remain poorly understood. Observations of eccentric systems provide key insights on those topics as they can
illuminate how a planet’s atmosphere responds to changes in incident flux. We report here the analysis of multi-day
multi-channel photometry of the eccentric (e ~ 0.93) hot Jupiter HD80606b obtained with the Spitzer Space
Telescope. The planet’s extreme eccentricity combined with the long coverage and exquisite precision of new
periastron-passage observations allow us to break the degeneracy between the radiative and dynamical timescales
of HD80606b’s atmosphere and constrain its global thermal response. Our analysis reveals that the atmospheric
layers probed heat rapidly (∼4 hr radiative timescale) from<500 to 1400 K as they absorb ~20% of the incoming
stellar flux during the periastron passage, while the planet’s rotation period is 93 35
85
-
+ hr, which exceeds the predicted
pseudo-synchronous period (40 hr).
Key words: methods: numerical – planet–star interactions – planets and satellites: atmospheres – planets and
satellites: dynamical evolution and stability – planets and satellites: individual (HD 80606 b) – techniques:
photometric
ASTRONOMICAL OBJECTS DETECTION IN CELESTIAL BODIES USING COMPUTER VISION ALGO...csandit
Computer vision, astronomy, and astrophysics function quite productively together to the point where they are completely logical for each other. Out of computer vision algorithms the
progress of astronomy and astrophysics would have slowed down to reasonably a deadlock. The new researches and calculations can lead to more information as well as higher quality of data. Consequently, an organized view on planetary surfaces can change all in the long run. A new
discovery would be a puzzling complexity or a possible branching of paths, yet the quest to know more about the celestial bodies by dint of computer vision algorithms will continue. The detection of astronomical objects in celestial bodies is a challenging task. This paper presents
an implementation of how to detect astronomical objects in celestial bodies using computer vision algorithm with satisfactory performance. It also puts forward some observations linked
among computer vision, astronomy, and astrophysics.
WASP-69b’s Escaping Envelope Is Confined to a Tail Extending at Least 7 RpSérgio Sacani
Studying the escaping atmospheres of highly irradiated exoplanets is critical for understanding the physical
mechanisms that shape the demographics of close-in planets. A number of planetary outflows have been observed
as excess H/He absorption during/after transit. Such an outflow has been observed for WASP-69b by multiple
groups that disagree on the geometry and velocity structure of the outflow. Here, we report the detection of this
planet’s outflow using Keck/NIRSPEC for the first time. We observed the outflow 1.28 hr after egress until the
target set, demonstrating the outflow extends at least 5.8 × 105 km or 7.5 Rp This detection is significantly longer
than previous observations, which report an outflow extending ∼2.2 planet radii just 1 yr prior. The outflow is
blueshifted by −23 km s−1 in the planetary rest frame. We estimate a current mass-loss rate of 1 M⊕ Gyr−1
. Our
observations are most consistent with an outflow that is strongly sculpted by ram pressure from the stellar wind.
However, potential variability in the outflow could be due to time-varying interactions with the stellar wind or
differences in instrumental precision.
Studies of ngc_6720_with_calibrated_hst_wfc3_emission_line_filter_imagesSérgio Sacani
This study uses calibrated Hubble Space Telescope images of the Ring Nebula (NGC 6720) taken 12.925 years apart to measure tangential motions within the nebula. Individual features were measured in nitrogen emission line images as well as dark knots seen against oxygen emission. The results indicate that the nebula is expanding homologously, but at a faster rate along its major axis. Dark knots were found to expand more slowly than the nebular gas. The tangential motion measurements allow estimates of the nebula's distance and dynamic age to be about 720 pc and 4000 years, respectively.
Confirmation of the_ogle_planet_signature_and_its_characteristics_with_lens_s...Sérgio Sacani
O Telescópio Espacial Hubble e o Observatório W. M. Keck, no Havaí, fizeram confirmações independentes de um exoplaneta orbitando sua estrela central de uma distância bem grande. O planeta foi descoberto através de uma técnica chamada de microlente gravitacional.
Essa descoberta traz uma nova peça para o processo de caçada de exoplanetas: para descobrir planetas longe de suas estrelas, como Júpiter e Saturno estão do Sol. Os resultados obtidos pelo Hubble e pelo Keck apareceram em dois artigos da edição de 30 de Julho de 2015 do The Astrophysical Journal.
A grande maioria dos exoplanetas catalogados são aqueles localizados bem perto de suas estrelas, isso acontece porque as técnicas atuais de se caçar exoplanetas favorecem a descoberta de planetas com curtos períodos orbitais. Mas esse não é o caso da técnica de microlente gravitacional, que pode encontrar planetas mais frios e mais distantes com órbitas de longo período que outros métodos não são capazes de detectar.
A surge of light at the birth of a supernovaSérgio Sacani
It is difficult to establish the properties of massive stars that explode
as supernovae1,2
. The electromagnetic emission during the first
minutes to hours after the emergence of the shock from the stellar
surface conveys important information about the final evolution
and structure of the exploding star3–6. However, the unpredictable
nature of supernova events hinders the detection of this brief initial
phase7–9. Here we report the serendipitous discovery of a newly
born, normal type IIb supernova (SN 2016gkg)10, which reveals a
rapid brightening at optical wavelengths of about 40 magnitudes
per day. The very frequent sampling of the observations allowed
us to study in detail the outermost structure of the progenitor of
the supernova and the physics of the emergence of the shock. We
develop hydrodynamical models of the explosion that naturally
account for the complete evolution of the supernova over distinct
phases regulated by different physical processes. This result
suggests that it is appropriate to decouple the treatment of the
shock propagation from the unknown mechanism that triggers
the explosion.
Confirmation of the_planetary_microlensing_signal_and_star_and_planet_mass_de...Sérgio Sacani
This document summarizes follow-up Hubble Space Telescope observations of the planetary microlensing event OGLE-2005-BLG-169. The HST observations confirm the relative proper motion between the source and lens stars predicted by the planetary signal in the original light curve. This provides the first confirmation of a planetary microlensing signal. The HST observations also measure the brightness of the planetary host star, allowing a precise determination of the planet and host star masses as well as their projected separation. Combined with measurements from Keck adaptive optics, the HST observations confirm the identification of the lens star and characterization of the planetary system.
LHS 475 b: A Venus-sized Planet Orbiting a Nearby M DwarfSérgio Sacani
Based on photometric observations by TESS, we present the discovery of a Venussized planet transiting LHS 475, an M3 dwarf located 12.5 pc from the Sun. The mass
of the star is 0.274 ± 0.015 M. The planet, originally reported as TOI 910.01, has an
orbital period of 2.0291025 ± 0.0000020 days and an estimated radius of 0.955 ± 0.053
R⊕. We confirm the validity and source of the transit signal with MEarth ground-based
follow-up photometry of five individual transits. We present radial velocity data from
CHIRON that rule out massive companions. In accordance with the observed massradius distribution of exoplanets as well as planet formation theory, we expect this
Venus-sized companion to be terrestrial, with an estimated RV semi-amplitude close to
1.0 m/s. LHS 475 b is likely too hot to be habitable but is a suitable candidate for
emission and transmission spectroscopy.
An energetic stellar_outburst_accompanied_by_circumstellar_light_echoesSérgio Sacani
1) V838 Monocerotis (V838 Mon) underwent an energetic stellar outburst in early 2002, temporarily becoming the brightest star in the Milky Way. 2) Hubble Space Telescope images revealed expanding light echoes in the circumstellar dust surrounding V838 Mon, allowing astronomers to set a minimum distance of over 6 kiloparsecs. 3) The light echoes, combined with the object's high luminosity and evidence that it resides in a binary system, indicate that V838 Mon represents a new class of stellar outburst not fully explained by current models.
Planeta 9 - A Pan-STARRS1 Search for Planet NineSérgio Sacani
We present a search for Planet Nine using the second data release of the PanSTARRS1 survey. We rule out the existence of a Planet Nine with the characteristics
of that predicted in Brown & Batygin (2021) to a 50% completion depth of V = 21.5.
This survey, along with previous analyses of the Zwicky Transient Facility (ZTF) and
Dark Energy Survey (DES) data, rules out 78% of the Brown & Batygin parameter
space. Much of the remaining parameter space is at V > 21 in regions near and in the
area where the northern galactic plane crosses the ecliptic.
TOI-4600 b and c: Two Long-period Giant Planets Orbiting an Early K DwarfSérgio Sacani
We report the discovery and validation of two long-period giant exoplanets orbiting the early K dwarf TOI-4600
(V = 12.6, T = 11.9), first detected using observations from the Transiting Exoplanet Survey Satellite (TESS) by
the TESS Single Transit Planet Candidate Working Group. The inner planet, TOI-4600 b, has a radius of
6.80 ± 0.31 R⊕ and an orbital period of 82.69 days. The outer planet, TOI-4600 c, has a radius of 9.42 ± 0.42 R⊕
and an orbital period of 482.82 days, making it the longest-period confirmed or validated planet discovered by
TESS to date. We combine TESS photometry and ground-based spectroscopy, photometry, and high-resolution
imaging to validate the two planets. With equilibrium temperatures of 347 K and 191 K, respectively, TOI-4600 b
and c add to the small but growing population of temperate giant exoplanets that bridge the gap between hot/warm
Jupiters and the solar system’s gas giants. TOI-4600 is a promising target for further transit and precise RV
observations to measure the masses and orbits of the planets as well as search for additional nontransiting planets.
Additionally, with Transit Spectroscopy Metric values of ∼30, both planets are amenable for atmospheric
characterization with JWST. Together, these will lend insight into the formation and evolution of planet systems
with multiple giant exoplanets.
Observational constraints on mergers creating magnetism in massive starsSérgio Sacani
Massive stars (those ≥8 solar masses at birth) have radiative envelopes that cannot sustain the dynamos that produce magnetic fields in lower mass stars. Despite this, ∼7% of massive stars have observed magnetic fields. We use multi-epoch interferometric and spectroscopic observations to characterise a magnetic binary system formed of two massive stars. We find that only one star of the binary is magnetic. Using the non-magnetic star as an independent reference clock to estimate the age of the system, we show that the magnetic star appears younger than its companion. The system properties, and a surrounding bipolar nebula, can be reproduced by a model in which this system was originally a triple within which two of the stars merged, producing the magnetic massive star. Thus, our results provide observational evidence that magnetic fields form in at least some massive stars through stellar mergers.
Initial characterization of interstellar comet 2I/BorisovSérgio Sacani
Interstellar comets penetrating through the Solar System had
been anticipated for decades1,2
. The discovery of asteroidallooking ‘Oumuamua3,4 was thus a huge surprise and a puzzle.
Furthermore, the physical properties of the ‘first scout’ turned
out to be impossible to reconcile with Solar System objects4–6,
challenging our view of interstellar minor bodies7,8. Here, we
report the identification and early characterization of a new
interstellar object, which has an evidently cometary appearance. The body was discovered by Gennady Borisov on 30
August 2019 ut and subsequently identified as hyperbolic by
our data mining code in publicly available astrometric data.
The initial orbital solution implies a very high hyperbolic excess
speed of ~32 km s−1
, consistent with ‘Oumuamua9 and theoretical predictions2,7
. Images taken on 10 and 13 September
2019 ut with the William Herschel Telescope and Gemini
North Telescope show an extended coma and a faint, broad
tail. We measure a slightly reddish colour with a g′–r′ colour
index of 0.66 ± 0.01 mag, compatible with Solar System comets. The observed morphology is also unremarkable and best
explained by dust with a power-law size-distribution index
of –3.7 ± 1.8 and a low ejection speed (44 ± 14 m s−1
for β= 1
particles, where β is the ratio of the solar gravitational attraction to the solar radiation pressure). The nucleus is probably
~1 km in radius, again a common value among Solar System
comets, and has a negligible chance of experiencing rotational
disruption. Based on these early characteristics, and putting
its hyperbolic orbit aside, 2I/Borisov appears indistinguishable from the native Solar System comets.
Ähnlich wie Physical Characterization of Moon Impactor WE0913A (20)
The binding of cosmological structures by massless topological defectsSérgio Sacani
Assuming spherical symmetry and weak field, it is shown that if one solves the Poisson equation or the Einstein field
equations sourced by a topological defect, i.e. a singularity of a very specific form, the result is a localized gravitational
field capable of driving flat rotation (i.e. Keplerian circular orbits at a constant speed for all radii) of test masses on a thin
spherical shell without any underlying mass. Moreover, a large-scale structure which exploits this solution by assembling
concentrically a number of such topological defects can establish a flat stellar or galactic rotation curve, and can also deflect
light in the same manner as an equipotential (isothermal) sphere. Thus, the need for dark matter or modified gravity theory is
mitigated, at least in part.
EWOCS-I: The catalog of X-ray sources in Westerlund 1 from the Extended Weste...Sérgio Sacani
Context. With a mass exceeding several 104 M⊙ and a rich and dense population of massive stars, supermassive young star clusters
represent the most massive star-forming environment that is dominated by the feedback from massive stars and gravitational interactions
among stars.
Aims. In this paper we present the Extended Westerlund 1 and 2 Open Clusters Survey (EWOCS) project, which aims to investigate
the influence of the starburst environment on the formation of stars and planets, and on the evolution of both low and high mass stars.
The primary targets of this project are Westerlund 1 and 2, the closest supermassive star clusters to the Sun.
Methods. The project is based primarily on recent observations conducted with the Chandra and JWST observatories. Specifically,
the Chandra survey of Westerlund 1 consists of 36 new ACIS-I observations, nearly co-pointed, for a total exposure time of 1 Msec.
Additionally, we included 8 archival Chandra/ACIS-S observations. This paper presents the resulting catalog of X-ray sources within
and around Westerlund 1. Sources were detected by combining various existing methods, and photon extraction and source validation
were carried out using the ACIS-Extract software.
Results. The EWOCS X-ray catalog comprises 5963 validated sources out of the 9420 initially provided to ACIS-Extract, reaching a
photon flux threshold of approximately 2 × 10−8 photons cm−2
s
−1
. The X-ray sources exhibit a highly concentrated spatial distribution,
with 1075 sources located within the central 1 arcmin. We have successfully detected X-ray emissions from 126 out of the 166 known
massive stars of the cluster, and we have collected over 71 000 photons from the magnetar CXO J164710.20-455217.
The debris of the ‘last major merger’ is dynamically youngSérgio Sacani
The Milky Way’s (MW) inner stellar halo contains an [Fe/H]-rich component with highly eccentric orbits, often referred to as the
‘last major merger.’ Hypotheses for the origin of this component include Gaia-Sausage/Enceladus (GSE), where the progenitor
collided with the MW proto-disc 8–11 Gyr ago, and the Virgo Radial Merger (VRM), where the progenitor collided with the
MW disc within the last 3 Gyr. These two scenarios make different predictions about observable structure in local phase space,
because the morphology of debris depends on how long it has had to phase mix. The recently identified phase-space folds in Gaia
DR3 have positive caustic velocities, making them fundamentally different than the phase-mixed chevrons found in simulations
at late times. Roughly 20 per cent of the stars in the prograde local stellar halo are associated with the observed caustics. Based
on a simple phase-mixing model, the observed number of caustics are consistent with a merger that occurred 1–2 Gyr ago.
We also compare the observed phase-space distribution to FIRE-2 Latte simulations of GSE-like mergers, using a quantitative
measurement of phase mixing (2D causticality). The observed local phase-space distribution best matches the simulated data
1–2 Gyr after collision, and certainly not later than 3 Gyr. This is further evidence that the progenitor of the ‘last major merger’
did not collide with the MW proto-disc at early times, as is thought for the GSE, but instead collided with the MW disc within
the last few Gyr, consistent with the body of work surrounding the VRM.
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...Sérgio Sacani
We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest
imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters
spanning 0.4−0.9µm) and novel JWST images with 14 filters spanning 0.8−5µm, including 7 mediumband filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data
at > 2.3µm to construct an ultradeep image, reaching as deep as ≈ 31.4 AB mag in the stack and
30.3-31.0 AB mag (5σ, r = 0.1” circular aperture) in individual filters. We measure photometric
redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts
z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
M⋆ ∼ 107−108M⊙, and star-formation rates of SFR ∼ 0.1−1 M⊙ yr−1
. Our search finds no candidates
at 15 < z < 20, placing upper limits at these redshifts. We develop a forward modeling approach to
infer the properties of the evolving luminosity function without binning in redshift or luminosity that
marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the
impact of non-detections. We find a z = 12 luminosity function in good agreement with prior results,
and that the luminosity function normalization and UV luminosity density decline by a factor of ∼ 2.5
from z = 12 to z = 14. We discuss the possible implications of our results in the context of theoretical
models for evolution of the dark matter halo mass function.
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
Multi-source connectivity as the driver of solar wind variability in the heli...Sérgio Sacani
The ambient solar wind that flls the heliosphere originates from multiple
sources in the solar corona and is highly structured. It is often described
as high-speed, relatively homogeneous, plasma streams from coronal
holes and slow-speed, highly variable, streams whose source regions are
under debate. A key goal of ESA/NASA’s Solar Orbiter mission is to identify
solar wind sources and understand what drives the complexity seen in the
heliosphere. By combining magnetic feld modelling and spectroscopic
techniques with high-resolution observations and measurements, we show
that the solar wind variability detected in situ by Solar Orbiter in March
2022 is driven by spatio-temporal changes in the magnetic connectivity to
multiple sources in the solar atmosphere. The magnetic feld footpoints
connected to the spacecraft moved from the boundaries of a coronal hole
to one active region (12961) and then across to another region (12957). This
is refected in the in situ measurements, which show the transition from fast
to highly Alfvénic then to slow solar wind that is disrupted by the arrival of
a coronal mass ejection. Our results describe solar wind variability at 0.5 au
but are applicable to near-Earth observatories.
Gliese 12 b: A Temperate Earth-sized Planet at 12 pc Ideal for Atmospheric Tr...Sérgio Sacani
Recent discoveries of Earth-sized planets transiting nearby M dwarfs have made it possible to characterize the
atmospheres of terrestrial planets via follow-up spectroscopic observations. However, the number of such planets
receiving low insolation is still small, limiting our ability to understand the diversity of the atmospheric
composition and climates of temperate terrestrial planets. We report the discovery of an Earth-sized planet
transiting the nearby (12 pc) inactive M3.0 dwarf Gliese 12 (TOI-6251) with an orbital period (Porb) of 12.76 days.
The planet, Gliese 12 b, was initially identified as a candidate with an ambiguous Porb from TESS data. We
confirmed the transit signal and Porb using ground-based photometry with MuSCAT2 and MuSCAT3, and
validated the planetary nature of the signal using high-resolution images from Gemini/NIRI and Keck/NIRC2 as
well as radial velocity (RV) measurements from the InfraRed Doppler instrument on the Subaru 8.2 m telescope
and from CARMENES on the CAHA 3.5 m telescope. X-ray observations with XMM-Newton showed the host
star is inactive, with an X-ray-to-bolometric luminosity ratio of log 5.7 L L X bol » - . Joint analysis of the light
curves and RV measurements revealed that Gliese 12 b has a radius of 0.96 ± 0.05 R⊕,a3σ mass upper limit of
3.9 M⊕, and an equilibrium temperature of 315 ± 6 K assuming zero albedo. The transmission spectroscopy metric
(TSM) value of Gliese 12 b is close to the TSM values of the TRAPPIST-1 planets, adding Gliese 12 b to the small
list of potentially terrestrial, temperate planets amenable to atmospheric characterization with JWST.
Gliese 12 b, a temperate Earth-sized planet at 12 parsecs discovered with TES...Sérgio Sacani
We report on the discovery of Gliese 12 b, the nearest transiting temperate, Earth-sized planet found to date. Gliese 12 is a
bright (V = 12.6 mag, K = 7.8 mag) metal-poor M4V star only 12.162 ± 0.005 pc away from the Solar system with one of the
lowest stellar activity levels known for M-dwarfs. A planet candidate was detected by TESS based on only 3 transits in sectors
42, 43, and 57, with an ambiguity in the orbital period due to observational gaps. We performed follow-up transit observations
with CHEOPS and ground-based photometry with MINERVA-Australis, SPECULOOS, and Purple Mountain Observatory,
as well as further TESS observations in sector 70. We statistically validate Gliese 12 b as a planet with an orbital period of
12.76144 ± 0.00006 d and a radius of 1.0 ± 0.1 R⊕, resulting in an equilibrium temperature of ∼315 K. Gliese 12 b has excellent
future prospects for precise mass measurement, which may inform how planetary internal structure is affected by the stellar
compositional environment. Gliese 12 b also represents one of the best targets to study whether Earth-like planets orbiting cool
stars can retain their atmospheres, a crucial step to advance our understanding of habitability on Earth and across the galaxy.
The importance of continents, oceans and plate tectonics for the evolution of...Sérgio Sacani
Within the uncertainties of involved astronomical and biological parameters, the Drake Equation
typically predicts that there should be many exoplanets in our galaxy hosting active, communicative
civilizations (ACCs). These optimistic calculations are however not supported by evidence, which is
often referred to as the Fermi Paradox. Here, we elaborate on this long-standing enigma by showing
the importance of planetary tectonic style for biological evolution. We summarize growing evidence
that a prolonged transition from Mesoproterozoic active single lid tectonics (1.6 to 1.0 Ga) to modern
plate tectonics occurred in the Neoproterozoic Era (1.0 to 0.541 Ga), which dramatically accelerated
emergence and evolution of complex species. We further suggest that both continents and oceans
are required for ACCs because early evolution of simple life must happen in water but late evolution
of advanced life capable of creating technology must happen on land. We resolve the Fermi Paradox
(1) by adding two additional terms to the Drake Equation: foc
(the fraction of habitable exoplanets
with significant continents and oceans) and fpt
(the fraction of habitable exoplanets with significant
continents and oceans that have had plate tectonics operating for at least 0.5 Ga); and (2) by
demonstrating that the product of foc
and fpt
is very small (< 0.00003–0.002). We propose that the lack
of evidence for ACCs reflects the scarcity of long-lived plate tectonics and/or continents and oceans on
exoplanets with primitive life.
A Giant Impact Origin for the First Subduction on EarthSérgio Sacani
Hadean zircons provide a potential record of Earth's earliest subduction 4.3 billion years ago. Itremains enigmatic how subduction could be initiated so soon after the presumably Moon‐forming giant impact(MGI). Earlier studies found an increase in Earth's core‐mantle boundary (CMB) temperature due to theaccumulation of the impactor's core, and our recent work shows Earth's lower mantle remains largely solid, withsome of the impactor's mantle potentially surviving as the large low‐shear velocity provinces (LLSVPs). Here,we show that a hot post‐impact CMB drives the initiation of strong mantle plumes that can induce subductioninitiation ∼200 Myr after the MGI. 2D and 3D thermomechanical computations show that a high CMBtemperature is the primary factor triggering early subduction, with enrichment of heat‐producing elements inLLSVPs as another potential factor. The models link the earliest subduction to the MGI with implications forunderstanding the diverse tectonic regimes of rocky planets.
Climate extremes likely to drive land mammal extinction during next supercont...Sérgio Sacani
Mammals have dominated Earth for approximately 55 Myr thanks to their
adaptations and resilience to warming and cooling during the Cenozoic. All
life will eventually perish in a runaway greenhouse once absorbed solar
radiation exceeds the emission of thermal radiation in several billions of
years. However, conditions rendering the Earth naturally inhospitable to
mammals may develop sooner because of long-term processes linked to
plate tectonics (short-term perturbations are not considered here). In
~250 Myr, all continents will converge to form Earth’s next supercontinent,
Pangea Ultima. A natural consequence of the creation and decay of Pangea
Ultima will be extremes in pCO2 due to changes in volcanic rifting and
outgassing. Here we show that increased pCO2, solar energy (F⨀;
approximately +2.5% W m−2 greater than today) and continentality (larger
range in temperatures away from the ocean) lead to increasing warming
hostile to mammalian life. We assess their impact on mammalian
physiological limits (dry bulb, wet bulb and Humidex heat stress indicators)
as well as a planetary habitability index. Given mammals’ continued survival,
predicted background pCO2 levels of 410–816 ppm combined with increased
F⨀ will probably lead to a climate tipping point and their mass extinction.
The results also highlight how global landmass configuration, pCO2 and F⨀
play a critical role in planetary habitability.
Constraints on Neutrino Natal Kicks from Black-Hole Binary VFTS 243Sérgio Sacani
The recently reported observation of VFTS 243 is the first example of a massive black-hole binary
system with negligible binary interaction following black-hole formation. The black-hole mass (≈10M⊙)
and near-circular orbit (e ≈ 0.02) of VFTS 243 suggest that the progenitor star experienced complete
collapse, with energy-momentum being lost predominantly through neutrinos. VFTS 243 enables us to
constrain the natal kick and neutrino-emission asymmetry during black-hole formation. At 68% confidence
level, the natal kick velocity (mass decrement) is ≲10 km=s (≲1.0M⊙), with a full probability distribution
that peaks when ≈0.3M⊙ were ejected, presumably in neutrinos, and the black hole experienced a natal
kick of 4 km=s. The neutrino-emission asymmetry is ≲4%, with best fit values of ∼0–0.2%. Such a small
neutrino natal kick accompanying black-hole formation is in agreement with theoretical predictions.
Detectability of Solar Panels as a TechnosignatureSérgio Sacani
In this work, we assess the potential detectability of solar panels made of silicon on an Earth-like
exoplanet as a potential technosignature. Silicon-based photovoltaic cells have high reflectance in the
UV-VIS and in the near-IR, within the wavelength range of a space-based flagship mission concept
like the Habitable Worlds Observatory (HWO). Assuming that only solar energy is used to provide
the 2022 human energy needs with a land cover of ∼ 2.4%, and projecting the future energy demand
assuming various growth-rate scenarios, we assess the detectability with an 8 m HWO-like telescope.
Assuming the most favorable viewing orientation, and focusing on the strong absorption edge in the
ultraviolet-to-visible (0.34 − 0.52 µm), we find that several 100s of hours of observation time is needed
to reach a SNR of 5 for an Earth-like planet around a Sun-like star at 10pc, even with a solar panel
coverage of ∼ 23% land coverage of a future Earth. We discuss the necessity of concepts like Kardeshev
Type I/II civilizations and Dyson spheres, which would aim to harness vast amounts of energy. Even
with much larger populations than today, the total energy use of human civilization would be orders of
magnitude below the threshold for causing direct thermal heating or reaching the scale of a Kardashev
Type I civilization. Any extraterrrestrial civilization that likewise achieves sustainable population
levels may also find a limit on its need to expand, which suggests that a galaxy-spanning civilization
as imagined in the Fermi paradox may not exist.
Jet reorientation in central galaxies of clusters and groups: insights from V...Sérgio Sacani
Recent observations of galaxy clusters and groups with misalignments between their central AGN jets
and X-ray cavities, or with multiple misaligned cavities, have raised concerns about the jet – bubble
connection in cooling cores, and the processes responsible for jet realignment. To investigate the
frequency and causes of such misalignments, we construct a sample of 16 cool core galaxy clusters and
groups. Using VLBA radio data we measure the parsec-scale position angle of the jets, and compare
it with the position angle of the X-ray cavities detected in Chandra data. Using the overall sample
and selected subsets, we consistently find that there is a 30% – 38% chance to find a misalignment
larger than ∆Ψ = 45◦ when observing a cluster/group with a detected jet and at least one cavity. We
determine that projection may account for an apparently large ∆Ψ only in a fraction of objects (∼35%),
and given that gas dynamical disturbances (as sloshing) are found in both aligned and misaligned
systems, we exclude environmental perturbation as the main driver of cavity – jet misalignment.
Moreover, we find that large misalignments (up to ∼ 90◦
) are favored over smaller ones (45◦ ≤ ∆Ψ ≤
70◦
), and that the change in jet direction can occur on timescales between one and a few tens of Myr.
We conclude that misalignments are more likely related to actual reorientation of the jet axis, and we
discuss several engine-based mechanisms that may cause these dramatic changes.
The solar dynamo begins near the surfaceSérgio Sacani
The magnetic dynamo cycle of the Sun features a distinct pattern: a propagating
region of sunspot emergence appears around 30° latitude and vanishes near the
equator every 11 years (ref. 1). Moreover, longitudinal flows called torsional oscillations
closely shadow sunspot migration, undoubtedly sharing a common cause2. Contrary
to theories suggesting deep origins of these phenomena, helioseismology pinpoints
low-latitude torsional oscillations to the outer 5–10% of the Sun, the near-surface
shear layer3,4. Within this zone, inwardly increasing differential rotation coupled with
a poloidal magnetic field strongly implicates the magneto-rotational instability5,6,
prominent in accretion-disk theory and observed in laboratory experiments7.
Together, these two facts prompt the general question: whether the solar dynamo is
possibly a near-surface instability. Here we report strong affirmative evidence in stark
contrast to traditional models8 focusing on the deeper tachocline. Simple analytic
estimates show that the near-surface magneto-rotational instability better explains
the spatiotemporal scales of the torsional oscillations and inferred subsurface
magnetic field amplitudes9. State-of-the-art numerical simulations corroborate these
estimates and reproduce hemispherical magnetic current helicity laws10. The dynamo
resulting from a well-understood near-surface phenomenon improves prospects
for accurate predictions of full magnetic cycles and space weather, affecting the
electromagnetic infrastructure of Earth.
Extensive Pollution of Uranus and Neptune’s Atmospheres by Upsweep of Icy Mat...Sérgio Sacani
In the Nice model of solar system formation, Uranus and Neptune undergo an orbital upheaval,
sweeping through a planetesimal disk. The region of the disk from which material is accreted by
the ice giants during this phase of their evolution has not previously been identified. We perform
direct N-body orbital simulations of the four giant planets to determine the amount and origin of solid
accretion during this orbital upheaval. We find that the ice giants undergo an extreme bombardment
event, with collision rates as much as ∼3 per hour assuming km-sized planetesimals, increasing the
total planet mass by up to ∼0.35%. In all cases, the initially outermost ice giant experiences the
largest total enhancement. We determine that for some plausible planetesimal properties, the resulting
atmospheric enrichment could potentially produce sufficient latent heat to alter the planetary cooling
timescale according to existing models. Our findings suggest that substantial accretion during this
phase of planetary evolution may have been sufficient to impact the atmospheric composition and
thermal evolution of the ice giants, motivating future work on the fate of deposited solid material.
Exomoons & Exorings with the Habitable Worlds Observatory I: On the Detection...Sérgio Sacani
The highest priority recommendation of the Astro2020 Decadal Survey for space-based astronomy
was the construction of an observatory capable of characterizing habitable worlds. In this paper series
we explore the detectability of and interference from exomoons and exorings serendipitously observed
with the proposed Habitable Worlds Observatory (HWO) as it seeks to characterize exoplanets, starting
in this manuscript with Earth-Moon analog mutual events. Unlike transits, which only occur in systems
viewed near edge-on, shadow (i.e., solar eclipse) and lunar eclipse mutual events occur in almost every
star-planet-moon system. The cadence of these events can vary widely from ∼yearly to multiple events
per day, as was the case in our younger Earth-Moon system. Leveraging previous space-based (EPOXI)
lightcurves of a Moon transit and performance predictions from the LUVOIR-B concept, we derive
the detectability of Moon analogs with HWO. We determine that Earth-Moon analogs are detectable
with observation of ∼2-20 mutual events for systems within 10 pc, and larger moons should remain
detectable out to 20 pc. We explore the extent to which exomoon mutual events can mimic planet
features and weather. We find that HWO wavelength coverage in the near-IR, specifically in the 1.4 µm
water band where large moons can outshine their host planet, will aid in differentiating exomoon signals
from exoplanet variability. Finally, we predict that exomoons formed through collision processes akin
to our Moon are more likely to be detected in younger systems, where shorter orbital periods and
favorable geometry enhance the probability and frequency of mutual events.
Emergent ribozyme behaviors in oxychlorine brines indicate a unique niche for...Sérgio Sacani
Mars is a particularly attractive candidate among known astronomical objects
to potentially host life. Results from space exploration missions have provided
insights into Martian geochemistry that indicate oxychlorine species, particularly perchlorate, are ubiquitous features of the Martian geochemical landscape. Perchlorate presents potential obstacles for known forms of life due to
its toxicity. However, it can also provide potential benefits, such as producing
brines by deliquescence, like those thought to exist on present-day Mars. Here
we show perchlorate brines support folding and catalysis of functional RNAs,
while inactivating representative protein enzymes. Additionally, we show
perchlorate and other oxychlorine species enable ribozyme functions,
including homeostasis-like regulatory behavior and ribozyme-catalyzed
chlorination of organic molecules. We suggest nucleic acids are uniquely wellsuited to hypersaline Martian environments. Furthermore, Martian near- or
subsurface oxychlorine brines, and brines found in potential lifeforms, could
provide a unique niche for biomolecular evolution.
Continuum emission from within the plunging region of black hole discsSérgio Sacani
The thermal continuum emission observed from accreting black holes across X-ray bands has the potential to be leveraged as a
powerful probe of the mass and spin of the central black hole. The vast majority of existing ‘continuum fitting’ models neglect
emission sourced at and within the innermost stable circular orbit (ISCO) of the black hole. Numerical simulations, however,
find non-zero emission sourced from these regions. In this work, we extend existing techniques by including the emission
sourced from within the plunging region, utilizing new analytical models that reproduce the properties of numerical accretion
simulations. We show that in general the neglected intra-ISCO emission produces a hot-and-small quasi-blackbody component,
but can also produce a weak power-law tail for more extreme parameter regions. A similar hot-and-small blackbody component
has been added in by hand in an ad hoc manner to previous analyses of X-ray binary spectra. We show that the X-ray spectrum
of MAXI J1820+070 in a soft-state outburst is extremely well described by a full Kerr black hole disc, while conventional
models that neglect intra-ISCO emission are unable to reproduce the data. We believe this represents the first robust detection of
intra-ISCO emission in the literature, and allows additional constraints to be placed on the MAXI J1820 + 070 black hole spin
which must be low a• < 0.5 to allow a detectable intra-ISCO region. Emission from within the ISCO is the dominant emission
component in the MAXI J1820 + 070 spectrum between 6 and 10 keV, highlighting the necessity of including this region. Our
continuum fitting model is made publicly available.
Or: Beyond linear.
Abstract: Equivariant neural networks are neural networks that incorporate symmetries. The nonlinear activation functions in these networks result in interesting nonlinear equivariant maps between simple representations, and motivate the key player of this talk: piecewise linear representation theory.
Disclaimer: No one is perfect, so please mind that there might be mistakes and typos.
dtubbenhauer@gmail.com
Corrected slides: dtubbenhauer.com/talks.html
Current Ms word generated power point presentation covers major details about the micronuclei test. It's significance and assays to conduct it. It is used to detect the micronuclei formation inside the cells of nearly every multicellular organism. It's formation takes place during chromosomal sepration at metaphase.
ESPP presentation to EU Waste Water Network, 4th June 2024 “EU policies driving nutrient removal and recycling
and the revised UWWTD (Urban Waste Water Treatment Directive)”
Remote Sensing and Computational, Evolutionary, Supercomputing, and Intellige...University of Maribor
Slides from talk:
Aleš Zamuda: Remote Sensing and Computational, Evolutionary, Supercomputing, and Intelligent Systems.
11th International Conference on Electrical, Electronics and Computer Engineering (IcETRAN), Niš, 3-6 June 2024
Inter-Society Networking Panel GRSS/MTT-S/CIS Panel Session: Promoting Connection and Cooperation
https://www.etran.rs/2024/en/home-english/
Describing and Interpreting an Immersive Learning Case with the Immersion Cub...Leonel Morgado
Current descriptions of immersive learning cases are often difficult or impossible to compare. This is due to a myriad of different options on what details to include, which aspects are relevant, and on the descriptive approaches employed. Also, these aspects often combine very specific details with more general guidelines or indicate intents and rationales without clarifying their implementation. In this paper we provide a method to describe immersive learning cases that is structured to enable comparisons, yet flexible enough to allow researchers and practitioners to decide which aspects to include. This method leverages a taxonomy that classifies educational aspects at three levels (uses, practices, and strategies) and then utilizes two frameworks, the Immersive Learning Brain and the Immersion Cube, to enable a structured description and interpretation of immersive learning cases. The method is then demonstrated on a published immersive learning case on training for wind turbine maintenance using virtual reality. Applying the method results in a structured artifact, the Immersive Learning Case Sheet, that tags the case with its proximal uses, practices, and strategies, and refines the free text case description to ensure that matching details are included. This contribution is thus a case description method in support of future comparative research of immersive learning cases. We then discuss how the resulting description and interpretation can be leveraged to change immersion learning cases, by enriching them (considering low-effort changes or additions) or innovating (exploring more challenging avenues of transformation). The method holds significant promise to support better-grounded research in immersive learning.
The use of Nauplii and metanauplii artemia in aquaculture (brine shrimp).pptxMAGOTI ERNEST
Although Artemia has been known to man for centuries, its use as a food for the culture of larval organisms apparently began only in the 1930s, when several investigators found that it made an excellent food for newly hatched fish larvae (Litvinenko et al., 2023). As aquaculture developed in the 1960s and ‘70s, the use of Artemia also became more widespread, due both to its convenience and to its nutritional value for larval organisms (Arenas-Pardo et al., 2024). The fact that Artemia dormant cysts can be stored for long periods in cans, and then used as an off-the-shelf food requiring only 24 h of incubation makes them the most convenient, least labor-intensive, live food available for aquaculture (Sorgeloos & Roubach, 2021). The nutritional value of Artemia, especially for marine organisms, is not constant, but varies both geographically and temporally. During the last decade, however, both the causes of Artemia nutritional variability and methods to improve poorquality Artemia have been identified (Loufi et al., 2024).
Brine shrimp (Artemia spp.) are used in marine aquaculture worldwide. Annually, more than 2,000 metric tons of dry cysts are used for cultivation of fish, crustacean, and shellfish larva. Brine shrimp are important to aquaculture because newly hatched brine shrimp nauplii (larvae) provide a food source for many fish fry (Mozanzadeh et al., 2021). Culture and harvesting of brine shrimp eggs represents another aspect of the aquaculture industry. Nauplii and metanauplii of Artemia, commonly known as brine shrimp, play a crucial role in aquaculture due to their nutritional value and suitability as live feed for many aquatic species, particularly in larval stages (Sorgeloos & Roubach, 2021).
When I was asked to give a companion lecture in support of ‘The Philosophy of Science’ (https://shorturl.at/4pUXz) I decided not to walk through the detail of the many methodologies in order of use. Instead, I chose to employ a long standing, and ongoing, scientific development as an exemplar. And so, I chose the ever evolving story of Thermodynamics as a scientific investigation at its best.
Conducted over a period of >200 years, Thermodynamics R&D, and application, benefitted from the highest levels of professionalism, collaboration, and technical thoroughness. New layers of application, methodology, and practice were made possible by the progressive advance of technology. In turn, this has seen measurement and modelling accuracy continually improved at a micro and macro level.
Perhaps most importantly, Thermodynamics rapidly became a primary tool in the advance of applied science/engineering/technology, spanning micro-tech, to aerospace and cosmology. I can think of no better a story to illustrate the breadth of scientific methodologies and applications at their best.
Unlocking the mysteries of reproduction: Exploring fecundity and gonadosomati...AbdullaAlAsif1
The pygmy halfbeak Dermogenys colletei, is known for its viviparous nature, this presents an intriguing case of relatively low fecundity, raising questions about potential compensatory reproductive strategies employed by this species. Our study delves into the examination of fecundity and the Gonadosomatic Index (GSI) in the Pygmy Halfbeak, D. colletei (Meisner, 2001), an intriguing viviparous fish indigenous to Sarawak, Borneo. We hypothesize that the Pygmy halfbeak, D. colletei, may exhibit unique reproductive adaptations to offset its low fecundity, thus enhancing its survival and fitness. To address this, we conducted a comprehensive study utilizing 28 mature female specimens of D. colletei, carefully measuring fecundity and GSI to shed light on the reproductive adaptations of this species. Our findings reveal that D. colletei indeed exhibits low fecundity, with a mean of 16.76 ± 2.01, and a mean GSI of 12.83 ± 1.27, providing crucial insights into the reproductive mechanisms at play in this species. These results underscore the existence of unique reproductive strategies in D. colletei, enabling its adaptation and persistence in Borneo's diverse aquatic ecosystems, and call for further ecological research to elucidate these mechanisms. This study lends to a better understanding of viviparous fish in Borneo and contributes to the broader field of aquatic ecology, enhancing our knowledge of species adaptations to unique ecological challenges.
ESR spectroscopy in liquid food and beverages.pptxPRIYANKA PATEL
With increasing population, people need to rely on packaged food stuffs. Packaging of food materials requires the preservation of food. There are various methods for the treatment of food to preserve them and irradiation treatment of food is one of them. It is the most common and the most harmless method for the food preservation as it does not alter the necessary micronutrients of food materials. Although irradiated food doesn’t cause any harm to the human health but still the quality assessment of food is required to provide consumers with necessary information about the food. ESR spectroscopy is the most sophisticated way to investigate the quality of the food and the free radicals induced during the processing of the food. ESR spin trapping technique is useful for the detection of highly unstable radicals in the food. The antioxidant capability of liquid food and beverages in mainly performed by spin trapping technique.
ESA/ACT Science Coffee: Diego Blas - Gravitational wave detection with orbita...Advanced-Concepts-Team
Presentation in the Science Coffee of the Advanced Concepts Team of the European Space Agency on the 07.06.2024.
Speaker: Diego Blas (IFAE/ICREA)
Title: Gravitational wave detection with orbital motion of Moon and artificial
Abstract:
In this talk I will describe some recent ideas to find gravitational waves from supermassive black holes or of primordial origin by studying their secular effect on the orbital motion of the Moon or satellites that are laser ranged.
The technology uses reclaimed CO₂ as the dyeing medium in a closed loop process. When pressurized, CO₂ becomes supercritical (SC-CO₂). In this state CO₂ has a very high solvent power, allowing the dye to dissolve easily.
2. 2. Observations and Data Reduction
The data products used directly in this research are the time
history of reduced photometric brightness measurements (light
curves) taken from imagery data acquired with each telescope.
Astrometric position measurements are only used indirectly,
being needed for orbit determination to allow for later
trajectory propagation to support the reflective dynamics model
(see Sections 6.1.2 and 6.1.3). All the imagery data used were
collected from two telescopes located in Arizona, USA. Some
basic information for each of the sensors can be found in
Table 1.
All observations from Leo-20 were taken with an open/clear
filter, and those from RAPTORS I were taken using the Sloan
Digital Sky Survey g′ and r′ photometric filters with band
passes (>50% transmission) of 401–550 nm and 555–695 nm,
respectively. Visible spectra (450–950 nm) from RAPTORS I
were taken with a 30 line mm−1
transmission diffraction
grating installed in the light path, resulting in a 14.6 nm px−1
(R ∼ 30 at 450 nm) spectral resolution. Further details about the
gratingʼs throughput in each order and the process for
determining the spectral resolution can be found in Battle
et al. (2022, 2023). The observation geometry, dates, and
number of images taken can be found in Table 2.
The reduction and analysis of the telescope data are
accomplished by first calibrating all images with dark, bias,
and flat-field frames in order to reduce the amount of errant
noise and vignetting in the images caused by the sensor system.
Once the images are calibrated, the plate solution is calculated
using the GAIA Data Release 2 star catalog (Gaia
Collaboration 2018) and open-source software package Scamp
(Bertin 2006). After a successful plate solution is found, the
centroid and signal (flux) from the desired target (WE0913A)
may be extracted via aperture photometry, accomplished here
with the open-source software Source-Extractor (Bertin &
Arnouts 1996). Reported observations are flux calibrated with
up to a first-order correction calculated from solar analog stars
across all the frames in a data set. Solar analog stars are
selected based on the criteria given in Andrae et al. (2018).
Spectra are extracted from RAPTORS I images by summing
the flux in each column along the spectrum. Wavelength is
determined using the distance (in number of columns only)
from the centroid multiplied by the grating resolution. The flux
in each wavelength unit is divided by the flux in the same
wavelength unit for a solar analog spectrum to obtain a
reflectance value. The reflectance spectrum is then normalized
to unity at 700 nm.
3. WE0913A Trajectory Analysis
The Chang’e 5-T1 mission launched on 2014 October 23 at
18:00 UTC from the Xichang Satellite Launch Center, and
according to the Long March 3C user manual (Cen et al. 2011),
during a “typical flight sequence” the second third-stage
powered flight (which takes the payload from an Earth parking
orbit onto its translunar trajectory) occurs between 1323.2 and
1494.9 s post liftoff. Preceding this burn, the rocket/payload
combination is in a “coast phase” for roughly 11 minutes. This
point when the rocket/payload combination leaves its Earth
parking orbit marks the periapsis of its lunar transfer orbit.
Using observations collected in 2015 March, when
WE0913A was first observed by the Catalina Sky Survey, we
can fit an orbit and propagate the results backward in time to
observe the history of the trajectory of the object. A plot of the
trajectory of WE0913A is given in Figure 1.
Table 1
Relevant Parameters for the Sensors Used to Collect Data of the Chang’e 5-T1 R/B
Name Location Aperture (m) FOV (arcmin) Pixel Size (as px−1
)
Leo-20 Arizona, USA 0.52 81 × 81 2.4
RAPTORS I Arizona, USA 0.61 16 × 16 0.95
Note. FOV stands for Field of View.
Table 2
Summary of Observation Epochs and Geometry for the Collected Data
Name Date (UTC) Range (km) V Mag (Pred.) Phase Angle (°) No. of Obs.
Leo-20 2022/01/20 169,000 15.3 91.4 400
2022/02/08 144,000 15.2 102.5 300
RAPTORS I 2022/02/08 144,000 15.2 102.5 211
Figure 1. Example of the WE0913A orbit (black curve) from 2015 March 15
propagated backward until it hits its perigee on 2014 October 23. Orbits are
shown in the geocentric MEME J2000 equatorial reference frame. The Moon’s
orbit (gray curve) and Earth’s location (black dot) are included for reference.
The rocket body had close encounters with the moon on both 2015 February 13
and 2014 October 28.
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The Planetary Science Journal, 4:217 (12pp), 2023 November Campbell et al.
3. In Figure 2, we show a short ground track of the backward
propagation up to perigee (denoted by a dot). The Xichang
launch facility is also shown for reference (marked as a star).
The time of perigee in Figures 1 and 2 should correspond with
the time window between coast and translunar orbit injection
that we described above, and we find that indeed it does. By
following the description in the Long March 3C user manual,
this phase should have occurred between 18:22:03.2 and
18:24:54.9 UTC on 2014 October 23. The results of our
backward propagation put this perigee at 18:24:34.3 UTC.
Moreover, the Long March 3C user manual lists the expected
sublatitudes and sublongitudes for the launch vehicle during its
initial phases of flight. Figure 3 shows the two launch phases as
large dots and our derived perigee as a small dot. Again, the
launch facility is included as a star for reference. As can be
seen in this figure, the perigee falls squarely between these two
launch phases, both geographically and in time.
The mean residual in our orbit determination from the
observations of WE0913A used to recreate this trajectory is
0 3. In this model, we estimate parameters corresponding to
solar radiation pressure (SRP), which must be considered for
this length of propagation. For instance, without taking into
account SRP, the time of perigee for this object is delayed to
20:55:30.8 UTC on 2014 October 23. A difference of 2.5 hr
and a perigee slightly off-track from the launch path! However,
the SRP parameters for a tumbling rocket body can be
extremely hard to estimate and are, in fact, changing in time.
As such, the parameters used represent a mean fit.
Based on this analysis, we show that the trajectory of
WE0913A matches the nominal mission plan published in the
Long March 3C user manual (Cen et al. 2011). Additionally,
the WE0913A trajectory strongly indicates a launch from the
Xichang Satellite Launch Center on 2014 October 23 at
approximately 1800 UTC. As such, we may conclude that this
object is likely to be the Long March 3C R/B (NORAD ID
40284, COSPAR ID 2014-065B) that launched the Chang’e
5-T1 mission.
4. Spectral Analysis
Spectroscopy has been shown to be a useful tool to identify
space objects in Earth orbit based on their reflectance properties
in the visible wavelengths (0.4–1.0 μm; Battle et al. 2023).
Building upon the trajectory analysis results, we have spectral
observations that favor the conclusion that the observed object
was indeed the Chang’e 5-T1 R/B instead of the Falcon 9 R/B
from the DSCOVR mission. In order to support this
conclusion, we needed to observe comparison objects that
had been launched at a similar time as the Chang’e 5-T1 R/B
so that the materials used and any alterations from space aging
would be similar (Jorgensen et al. 2001). Observations were
taken of a Falcon 9 R/B (NORAD ID 40108, COSPAR ID
2014-046B) launched in 2014 August and a Long March 3C
R/B (NORAD ID 43875, COSPAR ID 2018-110B) launched
in 2018 December. These will be used to compare to the
targets: the Falcon 9 R/B (NORAD ID 40391, COSPAR 2015-
007B) used to launch the DSCOVR mission in 2015 February
and the Long March 3C R/B (NORAD ID 40284, COSPAR
ID 2014-065B) used to launch the Chang’e 5-T1 in 2014
October.
Figure 4 shows the collected spectrum of the lunar impactor
(WE0913A) with spectra of the comparison objects and error
bars representing the standard deviation of the reflectance
Figure 2. Ground track of WE0913A (red curve) showing the orbit propagated
backward to perigee (red dot) on 2014 October 23 at 18:24:34.3 UTC
(24 minutes after Chang’e 5-T1 launch). Only a short time near perigee is
shown for simplicity. The Xichang Satellite Launch Center, from which the
Chang’e 5-T1 mission was launched, is shown as a red star.
Figure 3. Zoomed-in view of the WE0913A calculated perigee (red dot) with
the context of the coast and final burn stages of launch (large blue dots). The
Chang’e 5-T1 R/B translunar trajectory should have a perigee between these
two points, and we see that this is the case. The time window between the two
launch phases is T + 22.053 minutes and T + 24.915 minutes and our
calculated perigee is at T + 24.572 minutes. The Xichang Satellite Launch
Center is again shown as a red star.
Figure 4. Normalized reflectance spectra from RAPTORS I showing a
comparison between a Falcon 9 R/B (squares), a Long March 3C R/B
(triangles), and the lunar impactor (dots). A third-order polynomial fit to the
WE0913A data is provided as a reference. It is clear from the figure that the
lunar impactor is a much closer spectral match to the Long March 3C R/B than
the Falcon 9 R/B.
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The Planetary Science Journal, 4:217 (12pp), 2023 November Campbell et al.
4. measured across multiple images taken during observations.
Since the WE0913A object was very faint for the RAPTORS I
telescope (V mag 15.2) during the observations, the resulting
low-resolution spectrum is noisy, so there is also included a
plot of a third-order polynomial fit to the data for reference.
The spectrum of the Falcon 9 R/B (denoted by squares in
Figure 4) is spectrally flat, reflecting blue (∼400 nm) and red
(∼900 nm) light almost equally. The spectra for both the
known Long March 3C R/B (triangles) and the lunar impactor
(dots) are red-sloped, reflecting more red light than blue light.
Although spectral slope is not necessarily diagnostic of what
material or object is being observed, we can use these results to
say which of the comparison objects the lunar impactor more
closely matches. Using the third-order polynomial as expected
values, we can use a Chi-squared measurement to quantify the
degree to which the observed Falcon 9 and Long March 3C
data match those of the lunar impactor. The Chi-squared value
for the Long March 3C R/B (0.83) is lower (better match) than
that of the Falcon 9 R/B (2.02), indicating that the Long March
3C R/B spectrum is a better match to the spectrum of the lunar
impactor, further supporting the hypothesis that the lunar
impactor was indeed the Long March 3C upper stage that
launched the Chang’e 5-T1 mission. We will refer to
WE0913A in the subsequent sections as the Chang’e 5-T1
R/B for clarity and conciseness.
Since all spectra involved in this analysis are relatively
featureless, it is worth discussing potential causes of the
difference in the spectral slopes seen in Figure 4 to better
understand the implications for the object’s origin. Potential
explanations for the differences between these spectra include
phase angle, space aging, and compositional differences
(Pearce et al. 2020; Battle et al. 2023). Comparison objects
were chosen that were launched at a similar time as the
proposed origins of WE0913A so that the space aging impacts
potentially would be similar and could largely be ignored. It is
possible that WE0913A received higher amounts of radiation in
deep space, and thus more space aging, compared to the
comparison R/B that remained in low-Earth orbit (Reitz 2008;
Restier-Verlet et al. 2021). Phase angle effects are harder to
address, since there is no singular library of space-aged
spacecraft material spectra at multiple phase angles to help
address how phase angle effects manifest for different
materials.
Additionally, we do not know the composition of the
comparison R/Bs, which makes all comparisons more
difficult. The major components of these R/B spectra,
however, will typically include a white thermal control paint
used on the exterior of the fuselage and the metal used for the
engines. The composition of the thermal control material
(TCM) used and its resistance to space aging may vary
drastically between the Falcon 9 R/B and the Long March 3C
R/B. Some white TCMs tend to yellow as they space age,
while others are resistant to the changes and maintain a white
appearance (Dever 1991; Bengtson et al. 2018; Goto et al.
2021). Although the exact paint is not known, it is plausible
that the paint used on the Long March 3C R/B tends to yellow
with exposure to the space environment, whereas the paint
used on the Falcon 9 does not. This would create the observed
difference in spectra between the two objects, despite similar
times on orbit.
5. Photometric Analysis
Light curve inversion is a topic that has been extensively
studied as it applies to asteroids and other natural bodies
(Kaasalainen et al. 2001; Kaasalainen & Torppa 2001;
Muinonen et al. 2020), the limitations of which, and general
ill-posed nature of the problem, are well understood (Calef
et al. 2006; Hinks et al. 2013); however, useful information can
still be learned from even ill-posed inverse problems. These
techniques have also been no less frequently applied toward
artificial objects (Linares et al. 2013, 2014, 2020; Linares &
Crassidis 2018). The focus has, however, almost exclusively
been for characterization of shape or object type. There have
been few attempts in the literature to apply these methods to a
(partially) known object to assess the performance of a model-
based approach with a comparison to real data. One such
example is by Campbell et al. (2022), where they use this
technique to look at cislunar object 2020 SO and recover
several dynamical and physical properties. Originally dis-
covered by Pan-STARRS1 and thought to be a natural object, it
was later shown that 2020 SO was actually the Centaur upper
stage from the Surveyor 2 mission. Another example (Santoni
et al. 2013) also looks at recovering properties other than
shape, but there are some clerical errors in the material
characteristics and thus only diffuse reflection is considered,
which is not sufficient for human-made objects with highly
specular components. Moreover, the techniques used are shape-
specific and significant rotational assumptions are made, so the
methods are not applicable in general.
The photometric measurements taken on 2022 January 20
and February 8 show a strong apparent periodicity in the light
curves of the Chang’e 5-T1 R/B that implies the object is
neither actively stabilized nor tumbling (in the complex sense),
but rather uniformly rotating (typically) about either its major
or minor principal axes of inertia. It is also typical for objects
rotating in this manner to then have a precession of this
rotational axis about the body’s angular momentum vector
(Benson et al. 2017). To quantify this observed periodicity, we
performed a four-parameter Fourier fit with least squares
minimization to the light curves taken just before each of two
sequential close Earth flybys. The results of these minimiza-
tions are in Figures 5(a) and (b).
Figures 5(a) and (b) show that the period of the light curve
changes between the two observing epochs, indicating a likely
change in the rotational period of the Chang’e 5-T1 R/B.
While the period of the light curve just before the second Earth
flyby is within the 2σ bounds of the first set of data, the reverse
is not true, indicating that this is likely a real change in the
rocket body’s rotational rate. A high-fidelity attitude simulation
and analysis may be able to lend insight into the impact of the
first Earth flyby on the Chang’e 5-T1 R/B rotational period,
but this is outside the scope of this work.
Using a predictive light curve model and Markov Chain
Monte Carlo (MCMC) sampling-based inversion using
astrometric and photometric data collected of the Chang’e
5-T1 R/B during both of its final close approaches with the
Earth before impacting the Moon, we recover likely
distributions for spin state and reflective properties. We
estimate nine parameters: primary body axis orientation (2),
angular velocity vector (3), diffusive/specular reflectivity
parameters (2), and surface anisotropic/roughness para-
meters (2).
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The Planetary Science Journal, 4:217 (12pp), 2023 November Campbell et al.
5. 6. Bayesian Inversion Methodology
Bayesian inversion relies heavily on a statistical forward
model that can map arbitrary samples in your chosen parameter
space to realistic samples in the desired observation space. It is
important to strike a good compromise between model fidelity
and computational requirements for said model, since there are
harsh diminishing returns for increased fidelity with ill-posed
inverse problems.
In this research, our forward model takes as input an
arbitrary set of the nine parameters we want to estimate:
primary body axis orientation (2), angular velocity vector (3),
diffusive/specular reflectivity parameters (2), and surface
anisotropic/roughness parameters (2). With these parameters
and a previously selected shape, the model generates an
associated light curve. An in-depth discussion of the model
used is given in Campbell et al. (2022), and a summary of this
model is given in Section 6.1, while a description of our
Bayesian inversion methodology is given in Section 6.2.
6.1. Dynamical Model
The forward light curve model used in this research is
composed of three parts. There is the attitude model, which
handles the orientation of the body; the translational model,
which handles the location of the body; and the reflective
model, which handles the apparent brightness of the body. A
complete description of each of these sections is given in
Campbell et al. (2022), but the relevant equations are given
below without derivation.
6.1.1. Attitude Dynamics
We represent a body’s orientation as a unit quaternion (q̄)
with Euler parameters defined as a single rotation of angle j
measured in a counterclockwise direction about some well-
chosen unit vector ê. The expression of Euler parameters as a
unit quaternion is given in Equation (1), where q and q4 are the
vector and scalar parts of the quaternion, respectively:
*
⎡
⎣
⎢
⎢
⎢
⎛
⎝
⎞
⎠
⎛
⎝
⎞
⎠
⎤
⎦
⎥
⎥
⎥
⎡
⎣
⎤
⎦
j
j
= =
¯
ˆ
( )
q
e
q
q
sin
2
cos
2
. 1
4
The time derivative of the Euler parameters is given as:
⎡
⎣
⎢
⎤
⎦
⎥
=
+
-
¯
[ ] [˜]
( )
q
I q
q
w
q
1
2
, 2
T
4 3
where w is the angular velocity of the target in the body
reference frame, [I3] is the 3 × 3 identity matrix, and [˜]
q is the
vector cross-product matrix of the vector components of the
attitude quaternion. The time derivative of the angular velocity
is derived from the expression for total angular momentum and
is given as Euler’s equations of rotational motion in
Equation (3):
= - +
-
[ ] ( [ ˜][ ] ) ( )
w J w J w L . 3
1
During the Bayesian inversion process, we only consider a
short time history of observations, typically a few minutes, and
our target body is uncontrolled. As such, we assume no
appreciable external torques on the system and therefore treat
the motion as torque-free rotation during simulation (L = 0).
We also take the inertia tensor [J] to be constant and symmetric
in the body frame.
6.1.2. Orbital Dynamics
Before the Chang’e 5-T1 R/B crashed into the Moon on
2022 March 4, it had two close approaches with the Earth. The
second close approach in early February marked the last time
that the rocket body would be optically visible until its collision
with the Moon due to low solar elongation. Figure 6 shows the
geocentric orbit of the Chang’e 5-T1 R/B (black) in the Earth
mean equator mean equinox (MEME) J2000 reference frame
from 2022 January to 2022 March. The Moon’s orbit (gray) is
included as a reference.
Using a sixth-degree zonal gravity model (Equation (4)), the
trajectory of the Chang’e 5-T1 R/B can be precomputed before
the actual Bayesian inversion process to reduce computation
time. The requisite solar and observer positions at the
appropriate observation epochs can also be precomputed to
further improve efficiency. The short time window of
Figure 5. Light curves of Chang’e 5-T1 R/B from before each of two
sequential close Earth flybys taken from the same observatory. The light curves
have been period wrapped by fitting a four-parameter Fourier series to the data
via least squares minimization. As can be seen by the fitted period in each plot,
the observed rotation rate of Chang’e 5-T1 changed substantially between the
two flybys.
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The Planetary Science Journal, 4:217 (12pp), 2023 November Campbell et al.
6. observations and relatively large distance to the Chang’e 5-T1
R/B mean that higher-order perturbations (such as tesseral or
sectoral harmonics) can be safely ignored during the trajectory
integration. Since this Bayesian inversion model is very
sensitive to attitude and reflective properties, any accuracy
benefits from higher-order perturbations (including SRP)
would be lost to the relative uncertainty of the inversion:
⎛
⎝
⎞
⎠
å
q j q
= Q
=
¥ +
( ) ( ) ( )
U r
r
A
, ,
1
cos . 4
l
l
l l
0
1
In Equation (4), U(r, θ, j) is the generalized zonal
gravitational potential of the Earth in spherical coordinates.
When considering only zonal effects, the j dependence
reduces to the degree-dependent constants Al and the θ
dependence reduces to the generalized (associated) Legendre
polynomials represented by q
Q ( )
cos
l .
6.1.3. Reflective Dynamics
The simulated data used in the estimation process are a
function of the location, shape, attitude, and reflective
properties of the target body (Chang’e 5-T1 R/B), as well as
the relative location of the Sun and observer (Linares et al.
2013). The simulated flux of the target at any instant in time
may be calculated by:
å
r
=
=
(ˆ · ˆ )(ˆ · ˆ )
( )
u n u n
F
A
d
. 5
i
N
i i sun i i
tgt
1
obs
2
The total flux received by a sensor from the target, Ftgt, may
be calculated as the sum of the flux from all facets of the target
body. In this case, the target body is represented as a digital
shape model described by many small triangular plates. A
diagram of the layout of an individual body facet is given in
Figure 7.
The BRDF contribution, ρi, from each facet is multiplied by
the area of each facet, Ai, projected in both the incident and
reflecting directions (given by the dot products of the unit
vectors in the Sun and observer directions with the surface
normal). The flux density decreases with d
1
2 , where d is the
observer–target distance (Hinks et al. 2013). According to the
modified Phong BRDF of Ashikmin & Shirley (2000), the total
reflectance for each facet is the sum of the specular, ρs,i, and
diffuse, ρd,i, components of the BRDF.
Modeling anisotropy in the desired material can be
controlled by the constants nu and nv, which influence the
specularity in each facet direction (see Figure 7 for the facet
basis definition and Campbell et al. 2022 for the specific form
of the BRDF used):
= - + ( )
m F K
2.5 log . 6
app 10 tgt
The total flux calculated may then be used as in Equation (6)
to calculate an estimated magnitude for the target object. The
constant K is any calibration that needs to be applied. This
calibration includes the zero-point offset for whichever spectral
band or filter you are working with, as well as any noise,
airmass extinction, or other effects being modeled that are not
included in Ftgt. In this paper, K needs only to be set to the
apparent solar magnitude in the appropriate filter for the
observations being processed. See Section 2 for details on the
filters used to collect observations.
6.2. Bayesian Estimation
In Bayesian statistics, the estimated posterior likelihood of
an event is determined by any observational data available and
any a priori assumptions about the system. Bayes’ rule allows
the estimation of the posterior conditional probability
distributions q
( ∣ ˜)
y
p with the aid of a probabilistic model that
associates all chosen parameters θ to observations ỹ via a
likelihood function (Aster et al. 2018):
ò
q
q q
q q q
=
( ∣ ˜)
( ˜∣ ) ( )
( ˜∣ ) ( )
( )
y
y
y
p
p p
p p d
. 7
The integral in the denominator of Equation (7) is just ( ˜)
y
p
and serves to normalize q
( ∣ ˜)
y
p so that it may be considered a
proper probability density function. Since direct computation of
the posterior distributions for an arbitrary choice of parameters
is challenging in a low-dimensional well-posed problem and
impossible in an ill-posed problem, we employ a method
known as MCMC sampling. This allows for the generation of
values from an estimated posterior distribution that fits the
observational data that you have and any a priori assumptions.
The Metropolis–Hastings (MH) sampling method for MCMC
simulations (Figure 8) is formulated so that the integral
Figure 6. Example of the Chang’e 5-T1 R/B orbit (black curve) showing close
approaches to the Earth between 2022 January until 2022 March, when it
collided with the Moon, shown in the geocentric MEME J2000 equatorial
reference frame. The Moon’s orbit (gray curve) and Earth’s location (black dot)
are included for reference.
Figure 7. Illustration of the reference basis and relevant observation vectors on
a shape model body facet.
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The Planetary Science Journal, 4:217 (12pp), 2023 November Campbell et al.
7. constant in the denominator of Equation (7) cancels out during
the computation, allowing for the posterior distributions to be
accurately estimated.
This Markov chain method tests candidate samples with the
acceptance probability α to ensure that the Markov chain tends
toward areas of the parameter phase space with a higher
posterior estimate. This means that we may use a computa-
tional model as described in Sections 6.1.1–6.1.3 together with
an evaluation of the goodness of fit to the observed data (sum
of square residuals) to evaluate the likelihood of each MH-
generated sample from the parameter phase space, q
( ˜∣ )
y
p . We
may also supply an a priori estimate of the distributions to
which our parameters belong (p(θ)), which can be unin-
formative (uniform distribution) if we have no strong a priori
information.
While this method does produce a valid Markov chain, the
Markov property is not what allows successful estimation of
the posteriors. It is instead the fact that the estimated
distributions are improved with each sampling, thus converging
to the true distributions in the limit. Through continued
generation of this Markov chain, we may accurately estimate
the posterior distributions and only need to check the Markov
chain for convergence to ensure a valid estimate of the
posteriors.
7. Bayesian Analysis and Results
We ran a total of 100,000 iterations of our MCMC inversion
on the data collected with the Leo-20 telescope on 2022
January 20 (see Table 2). Our prior distributions for each
estimated parameter are partially uninformative, in that they are
not true (infinite) uniform distributions, but rather finite
distributions constrained by what is reasonable for both the
model and the physics of the problem. A summary of the prior
distributions for each parameter is given in Table 3. The
parameters α and β describe the primary body axis orientation
at the start of the observation epoch, w1−3 make the angular
velocity vector, and ρ and F0 control the relative diffusivity and
specularity of the body, respectively. Last, nu and nv control the
amount of anisotropy in each of the body facet directions (see
Figure 7).
As is the case for the majority of inverse problems of even
moderate complexity, this estimation problem is ill-posed, so
the results presented here represent a “best estimate.” That is,
due to the difficulty of sampling the complete surface of the
Chang’e 5-T1 R/B and the large amount of symmetry on the
rocket body, recovering the true states from this analysis is
unlikely. However, there exist metrics that can be used to
gauge the quality of the resulting estimates to provide
confidence in the results.
By design, the MCMC estimation process is prone to getting
“stuck” near the initial state estimation for some time. In order
to ensure that the parameter space is diversely sampled and that
we are not just sampling near our initial guess, we can look at
the chain of all parameters chosen during the inversion process.
This inertia-like property of MCMC algorithms is known as
“burn-in” and is important to be aware of when using
uninformative prior distributions. Looking at Figure 9, we
see that the sampling chain, after the initial burn-in is removed,
is highly varied and thus samples the parameter space
sufficiently well.
A quick quantitative way to evaluate the performance of the
MCMC sampling is by checking the acceptance rate. Samples
are only added to the posterior distribution estimate if they pass
a strict sampling gate test. Ideally, the acceptance rate should
be between 20% and 50% (Aster et al. 2018), and for our test
we had an acceptance rate of 38.18%. If the acceptance rate is
too low, then the estimation did not sufficiently sample the span
of the parameter space and will not accurately portray the
regions of highest posterior density (HPD). Conversely, if the
acceptance rate is too high, then it is likely that the algorithm
was stuck in a local extremum, and again we cannot be
confident that it sufficiently sampled the span of the parameter
space for globally valid results.
Figure 10 shows diagrams of the posterior distribution
estimates for each parameter, and Table 4 summarizes the
relevant parameters associated with the distributions for each
parameter.
An important distinction for the values provided in Table 4 is
the subtle difference between frequentist and Bayesian statistics
as they are given here. The frequentist statistics (mean and
standard deviation) are indicative of how often an event occurs,
while the Bayesian statistics (maximum a posteriori, or MAP,
and HPD) provide how likely it is that an event occurs, given
the data you have and your understanding of the system.
Looking at Figure 10 and comparing the values in Table 4, we
see that in this case, the estimated distributions for our
parameters can be well approximated by Gaussian
Figure 8. Brief overview of the MH algorithm for MCMC sampling.
Table 3
Partially Uninformative Prior Distribution for Each Parameter to Be Estimated
by the Bayesian Inversion
Variable Initial Value Min Max Distribution
α 0.1 0 2π U(0, 2π)
β 0.1 0 2π U(0, 2π)
w1 0.000 1 −10 10 U(− 10, 10)
w2 0.000 1 −10 10 U(− 10, 10)
w3 0.000 1 −10 10 U(− 10, 10)
ρ 0.01 0 1 U(0, 1)
F0 0.001 0 1 U(0, 1)
nu 10 −1000 1000 U(− 1000, 1000)
nv 10 −1000 1000 U(− 1000, 1000)
7
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8. distributions. This is typically not the case in general, as the
estimated distributions from this process can be highly non-
Gaussian.
Estimating the complete distribution of each parameter not
only gives us insight into the global set of possible results, but
also allows sampling from each distribution to evaluate
behavior. In Figure 11, we took 1500 random samples from
each distribution and fed them back into our forward model.
Plotting the results and overlaying the raw Chang’e 5-T1 light
curve, we can see that the estimated parameters and forward
model fit the data very well. Note that the diagonal portion of
the plot between 17 and 21 minutes post-epoch is when there
were no data. Since it is possible for the “best estimate” to
converge on an incorrect or poorly fitted solution, evaluating
the results in this way offers a self-consistency check and
confidence that the estimated parameters well describe the data.
Based on the values in Table 4, it would appear that the
Chang’e 5-T1 R/B is very anisotropic (ratio of nu to nv). As a
reminder, these two parameters control the surface roughness and
the degree of anisotropic reflection in either the û or v̂ directions
for each body facet (see Figure 7). In Table 4, we see that the
estimated reflection is approximately 60 times greater in the û
direction than the v̂ direction. While it is quite likely that the
Chang’e 5-T1 R/B exhibits some anisotropy, this level is
unexpected. This result is likely due to the fact that the
observations used for this estimation spanned a short time
window, and so geometrically speaking, reflection in the
orthogonal axis may not have been as visible. This is further
supported by the rotation of the body being that of a very stable
spin, implying that body surfaces are observed from the same
geometry over short timescales as the body rotates. This is
opposed to a complex tumbling body, where the observer–target
body surface geometry may not be as periodic during rotation.
The strong periodic fits seen in Figures 5(a) and (b) imply
that the Chang’e 5-T1 R/B was in a very uniform spin during
the observations. This is reflected in our results by the
estimated angular velocity (Table 4). Note that it is almost
identically equal to a uniform spin about a single (the principal)
body axis. This is somewhat unexpected for a typical rocket
body, especially one that has been on-orbit for almost a decade
and has had multiple close encounters with the Earth and
Moon. In a typical (empty) rocket upper stage, the majority of
Figure 9. Time history of parameter sampling from the Bayesian inversion where the first 55,000 samples have been removed to avoid burn-in.
8
The Planetary Science Journal, 4:217 (12pp), 2023 November Campbell et al.
9. its mass is concentrated toward the engines, giving an
appreciable center-of-mass–center-of-figure (COM–COF) off-
set. This COM–COF offset can cause perturbations such as
SRP or gravity gradient torque to have a larger destabilizing
effect, giving rise to more complicated motion than just simple
spin (i.e., precession, nutation, complex tumble, etc.; Takahashi
et al. 2013), which is one possible explanation of the results
seen in Campbell et al. (2022). However, we see no such
evidence for perturbations in the spin of the Chang’e 5-T1
R/B, implying that the COM–COF offset may be smaller than
expected. This would be the case if there was additional mass at
the front of the rocket body, opposite the engines. This
additional mass at the front of the body would bring the COM
forward, closer to the COF, and thus reduce the effect of these
destabilizing perturbations.
The Chang’e 5-T1 R/B hosted a secondary payload (in
addition to the Chang’e 5-T1 spacecraft) that was comprised of
two instruments and dubbed the Manfred Memorial Moon
Mission by LuxSpace (Siddiqi 2018). This payload has a
published mass of 10–14 kg and was permanently affixed to the
front of the Chang’e 5-T1 R/B (Clark 2014; Moser et al. 2015;
Siddiqi 2018). It is unclear if, or how, the upper stage was
Figure 10. Final estimates of the posterior distributions of each parameter.
Table 4
Bayesian and Frequentist Statistics for the Estimated Posterior Distributions of
Each Parameter
Variable MAP 95% HPD Mean STD
α 0.002 [0.0000, 0.0204] 0.008 0.008
β 0.287 [0.2473, 0.3008] 0.282 0.013
w1 0.000 [–0.0001, 0.0001] 0.000 0.000
w2 0.000 [–0.0001, 0.0001] 0.000 0.000
w3 0.017 [0.0174, 0.0176] 0.017 0.000
ρ 0.004 [0.0025 0.0054] 0.004 0.001
F0 0.037 [0.0276, 0.0500] 0.037 0.006
nu 30.203 [30.1695, 30.2221] 30.197 0.013
nv 0.497 [0.3995, 0.4999] 0.465 0.030
9
The Planetary Science Journal, 4:217 (12pp), 2023 November Campbell et al.
10. modified to accommodate this payload vis-à-vis structural
support or additional equipment that might affect the final mass
distribution, but the published mass of these instruments is only
up to 14 kg, which is not enough to appreciably move the COM
forward from the large mass of the dual-mounted YF-75
engines on its own (Cen et al. 2011).
One way to verify the hypothesis that there was additional
mass in the front of the rocket body is to look for the crater that
would result from the Chang’e 5-T1 R/B impact with the lunar
surface. Craters have been found previously on the lunar
surface following the impacts of rocket bodies from the Apollo
missions. However, searching for a small impact crater among
the plethora of craters on the Moon is challenging at best.
Hence, predicting the precise location of the impact is critical
for any hope of verifying this hypothesis.
8. Lunar Impact Location Prediction
The ephemeris of the Chang’e 5-T1 R/B was estimated by
fitting orbits to right ascension and declination measurements
reported by ground-based optical telescopes. A total of 508
observations were reported by 26 different stations from 2021
July 8 to 2022 February 10.
It was evident early on as observations accumulated that
nongravitational accelerations had a significant effect on the
trajectory. We used a typical radiation-based nongravitational
perturbation model, where the accelerations radial, transverse,
and normal to the heliocentric orbit are given in Equation (8)
(Marsden et al. 1973):
⎛
⎝
⎞
⎠
⎛
⎝
⎞
⎠
⎛
⎝
⎞
⎠
=
=
= ( )
a A
r
a A
r
a A
r
1 au
1 au
1 au
. 8
R
T
N
1
2
2
2
3
2
A1, A2, and A3 are estimable parameters during the orbit
fitting process. This model substantially improved fits over a
purely ballistic trajectory, though it was nevertheless an
imperfect match to the observations. This may have been due
to outgassing from the rocket body or caused by a complex
shape or rotation state. To limit the prediction errors stemming
from the nongravitational perturbation model, we substantially
shortened the fitted data arc, eventually settling on two orbit
solution cases: one long and one short arc. After outlier
rejection, the long arc included 162 observations spanning 57
days from 2021 December 15 to 2022 February 10. The short
arc was of approximately half the duration, with 154
observations covering 28 days from 2022 January 13 to 2022
February 10. We also tested a simplified nongravitational
acceleration model that included only the A1 term (represent-
ing SRP).
Figure 12 shows the predictions for these four test solutions,
along with their associated 3σ uncertainty ellipses. The limited
overlap among these solutions emphasizes the difficulty in
nongravitational perturbation modeling. As a result, we elected
to use the three-parameter nongravitational perturbation model
in light of the optimistic uncertainties demonstrated by the one-
parameter model. Thus, solution S23 was the final prediction,
for which we document the orbital parameters in Table 5. The
estimated radial term of the nongravitational acceleration
Figure 11. The 97.5% HPD region (light gray) in light curve phase space as
estimated by 1500 random samples from the posterior estimates generated with
data taken from the Leo-20 telescope on 2022 January 20. The observed light
curve of the Chang’e 5-T1 R/B has been overlaid in black. The diagonal
portion of the light curve from approximately 17–21 minutes post-epoch is a
period with no data.
Figure 12. Impact prediction for several trajectory solutions as described in the
text. The final delivered prediction was for solution “S23.”
Table 5
Estimated Nongravitational and Osculating Orbital Parameters for Solution S23
Giving the Predicted Lunar Impact Location
Parameter Value 1σ Uncertainty
Epoch (TDB) 2022 Feb 05 00:00:00 N/A
a (km) 321774.936 0.317
e 0.912983869 2.96E-7
i (deg) 31.4782088 4.52E-5
ω (deg) 151.4305753 8.02E-5
Ω (deg) 14.3057527 5.80E-5
ν (deg) 196.0218047 2.69E-5
A1 (km s−2
) 42.597E-12 1.505E-12
A2 (km s−2
) –1.808E-12 0.936E-12
A3 (km s−2
) 2.079E-12 0.523E-12
Note. Osculating elements are given in the Earth-centered MEME J2000
equatorial reference frame.
10
The Planetary Science Journal, 4:217 (12pp), 2023 November Campbell et al.
11. model (A1) corresponds to an area-to-mass ratio of approxi-
mately 0.01 m2
kg−1
. Based on the scatter among the
predictions seen in Figure 12, we increased the impact location
prediction uncertainties to ±4 km in longitude and +1/−3 km
in latitude. Figure 12 also depicts the reported impact location
from the Lunar Reconnaissance Orbiter (LRO), which indicates
that the prediction was in error by 7.0 km in longitude and
2.7 km in latitude.
9. Impact Crater Morphology
Given the relatively high degree of certainty of the impact
location of the Chang’e 5-T1 R/B on the lunar surface, there
was a decent chance that it could be found. Fortunately, based
on our predicted impact location, the LRO was able to find and
image the impact site using the LRO narrow-angle camera
(Robinson et al. 2010). Comparing LRO images of the impact
site both pre- and post-impact gave rise to new questions.
Instead of one round, or elongated, crater, such as what was
seen when the Apollo Saturn IV-B rockets were sent into the
Moon, there are two distinct craters side by side that were made
by the Chang’e 5-T1 R/B. Figures 13(a) and (b) show the
relevant section of lunar terrain both pre- and post-impact.
The double crater (pictured in Figure 14) formed by the
Chang’e 5-T1 R/B impact with the Moon was unexpected
when considering what has been seen from other rocket body
impacts with the Moon (Figure 15). Four Apollo Saturn IV-B
rocket bodies were crashed into the Moon and created
somewhat elongated craters, though they had shallow impact
angles. The Chang’e 5-T1 R/B impact with the surface came
from roughly 15° off vertical (75° impact angle), so that is not
the case here. Moreover, the appearance of the craters is not of
one elongated shape made from a single impact, but rather two
distinct craters of similar size formed from separate impacts of
similar energy. This supports our hypothesis that there was
additional mass on the front end of the Chang’e 5-T1 R/B,
creating the second crater during impact.
As noted earlier, there were additional instruments affixed to
the front of the Chang’e 5-T1 R/B that were to stay attached to
the rocket body post spacecraft detachment. The published
mass of these instruments is only up to 14 kg (Clark 2014;
Moser et al. 2015; Siddiqi 2018), which is not enough alone to
account for the double crater seen post-impact.
Figure 13. These are approximately 500 m sections of the lunar terrain captured by LRO showing the Chang’e 5-T1 R/B impact site and double crater that was
formed. Before is from LRO image M1400727806L and after is from M1407760984R (NASA/GSFC/Arizona State University). Other visual differences in the
terrain are caused primarily by the difference in the angle of solar incidence, which was approximately 28° during the before image and 59° in the after image. This
section of terrain is near the Hertzsprung crater on the lunar far side.
Figure 14. Zoomed-in view of the double crater formed by the Chang’e 5-T1
R/B impact with the Moon. Context images in Figures 13(a) and (b). Data
from LRO image M1407760984R (NASA/GSFC/Arizona State University).
11
The Planetary Science Journal, 4:217 (12pp), 2023 November Campbell et al.
12. 10. Conclusions
In late 2021, it was discovered that an object (WE0913A)
would impact the Moon in 2022 March after several close flybys
of the Earth and the Moon over the coming months. The true
identity of this object was up for debate, with two possibilities:
(1) the Falcon 9 R/B from the DSCOVR mission; and (2) the
Long March 3C R/B from the Chang’e 5-T1 mission. Our
trajectory and spectroscopic analyses using ground-based
telescope observations show conclusively that WE0913A is in
fact the Chang’e 5-T1 R/B. Analysis of photometric light
curves gave a spin period of 185.221 ± 6.540 s at a 1σ
confidence level in the light curve of the Chang’e 5-T1 R/B just
before the first close Earth flyby and a period of
177.754 ± 0.779 s at a 1σ confidence level just before the
second close Earth flyby. Using MCMC sampling and a
predictive light curve simulation based on an anisotropic Phong
reflection model, we estimate both physical and dynamical
properties of the Chang’e 5-T1 R/B at the start of an
observation epoch. The Bayesian analysis implies that there
was an additional mass at the front of the R/B that stabilizes the
spin characteristics. We used the observations acquired to
pinpoint the location of the impact on the lunar surface, which
enabled the LRO to find and photograph the crater site. Our
predicted location is within 7 km in longitude and 2.7 km in
latitude from where the crater was eventually found by LRO.
Comparing the pre- and post-impact images of the location
shows two distinct craters side by side that were made by the
Chang’e 5-T1 R/B. The double crater supports the hypothesis
that there was additional mass at the front end of the rocket
body, opposite the engines, in excess of the published mass of
the secondary permanently affixed payload.
Acknowledgments
This work is supported in part by the state of Arizona
Technology Research Initiative Fund (TRIF) grant (PI: Prof.
Vishnu Reddy). A portion of this work was conducted at the Jet
Propulsion Laboratory, California Institute of Technology, under a
contract with the National Aeronautics and Space Administration.
ORCID iDs
Tanner Campbell https:/
/orcid.org/0000-0001-9418-1663
Adam Battle https:/
/orcid.org/0000-0002-4412-5732
Steven R. Chesley https:/
/orcid.org/0000-0003-3240-6497
Davide Farnocchia https:/
/orcid.org/0000-0003-0774-884X
Neil Pearson https:/
/orcid.org/0000-0002-0183-1581
Vishnu Reddy https:/
/orcid.org/0000-0002-7743-3491
Roberto Furfaro https:/
/orcid.org/0000-0001-6076-8992
References
Andrae, R., Fouesneau, M., Creevey, O., et al. 2018, A&A, 616, A8
Ashikmin, M., & Shirley, P. 2000, Journal of Graphics Tools, 5, 25
Aster, R., Borchers, B., & Thurber, C. 2018, Parameter Estimation and Inverse
Problems (Amsterdam: Elsevier)
Battle, A., Reddy, V., Furfaro, R., & Campbell, T. 2023, AcAau, submitted
Battle, A., Reddy, V., Sanchez, J., et al. 2022, PSJ, 3, 226
Bengtson, M., Maxwell, J., Hoffmann, R., et al. 2018, in The Advanced Maui Optical
and Space Surveillance Technologies Conf., ed. S. Ryan (Kihei, HI: AMOS),33
Benson, C., Scheeres, D., & Moskovitz, N. 2017, in 7th European Conf. on
Space Debris (Paris: ESA), 117
Bertin, E. 2006, in ASP Conf. Ser. 351, Astronomical Data Analysis Software
and Systems XV, ed. C. Gabriel et al. (San Francisco, CA: ASP), 112
Bertin, E., & Arnouts, S. 1996, A&AS, 117, 393
Calef, B., Africano, J., Birge, B., Hall, D., & Kervin, P. 2006, Proc. SPIE,
6307, 63070E
Campbell, T., Furfaro, R., Reddy, V., et al. 2022, JAnSc, 69, 95
Cen, Z., Gao, R., & Shen, L. 2011, LM-3A Series Launch Vehicle User's
Manual (Beijing: China Academy of Launch Vehicle Technology)
Christensen, E., Africano, B., Farneth, G., et al. 2018, AAS/DPS Meeting, 50,
310.10
Clark, S. 2018, Spaceflight Now, https://spaceflightnow.com/2014/10/25/
first-commercial-mission-to-the-moon-launched-from-china/
Dever, J. 1991, Low Earth Orbital Atomic Oxygen and Ultraviolet Radiation
Effects on Polymers NASA-TM-103711, NASA Lewis Research Center,
https://ntrs.nasa.gov/citations/19910009981
Gaia Collaboration 2018, Gaia Data Release 2 (Gaia DR2), ESA, doi:10.5270/
esa-ycsawu7
Goto, A., Umeda, K., Yukumatsu, K., & Kimoto, Y. 2021, CEAS, 13, 415
Hinks, J., Linares, R., & Crassidis, J. 2013, in AIAA Guidance, Navigation,
and Control (GNC) Conf. (Reston, VA: AIAA), 5005
Jorgensen, K., Culp, R., & Clark, R. 2001, in Proc. of the Third European
Conference on Space Debris (Noordwijk: ESA), 385
Kaasalainen, M., & Torppa, J. 2001, Icar, 153, 24
Kaasalainen, M., Torppa, J., & Muinonen, K. 2001, Icar, 153, 37
Linares, R., & Crassidis, J. 2018, JGCD, 41, 47
Linares, R., Crassidis, J., Wetterer, C., Hill, K., & Jah, M. 2013, Astrometric
and Photometric Data Fusion for Mass and Surface Material Estimation
using Refined Bidirectional Reflectance Distribution Functions-Solar
Radiation Pressure Model Tech. Rep. ADA593458, Pacific Defense
Solutions LLC, https://apps.dtic.mil/sti/tr/pdf/ADA593458.pdf
Linares, R., Furfaro, R., & Reddy, V. 2020, JAnSc, 67, 1063
Linares, R., Jah, M., Crassidis, J., & Nebelecky, C. 2014, JGCD, 37, 13
Marsden, B., Sekanina, Z., & Yeomans, D. 1973, AJ, 78, 211
Moser, H., Ruy, G., Schwarzenbarth, K., et al. 2015, in 29th Annual AIAA/
USU Conf. on Small Satellites, SSC15–V–7, https://digitalcommons.usu.
edu/cgi/viewcontent.cgi?article=3200&context=smallsat
Muinonen, K., Torppa, J., Wang, X., Cellino, A., & Penttilä, A. 2020, A&A,
642, A138
Pearce, E., Weiner, B., & Krantz, H. 2020, JSSE, 7, 376
Reitz, G. 2008, Zeitschrift für Medizinische Physik, 18, 233
Restier-Verlet, J., El-Nachef, L., Ferlazzo, M., et al. 2021, International Journal
of Molecular Sciences, 22, 3739
Robinson, M., Brylow, S., Tschimmel, M., et al. 2010, SSRv, 150, 81
Santoni, F., Cordelli, E., & Piergentili, F. 2013, JSpRo, 50, 701
Siddiqi, A. 2018, Beyond Earth: A Chronicle of Deep Space Exploration,
1958–2016, Vol. 4041 (Washington, DC: NASA)
Takahashi, Y., Busch, M., & Scheeres, D. 2013, AJ, 146, 95
Wenbin, W. 2022, in Foreign Ministry Spokesperson Wang Wenbin's Regular
Press Conference, February 21, 2022 (Ministry of Foreign Affairs of the
People’s Republic of China), https://www.fmprc.gov.cn/mfa_eng/xwfw_
665399/s2510_665401/202202/t20220221_10644075.html
Figure 15. Images of craters formed by the intentional impacts of the Apollo Saturn IV stages with the lunar surface. Note the round or elongated shapes, but all being
explicitly one crater. (NASA/GSFC/Arizona State University).
12
The Planetary Science Journal, 4:217 (12pp), 2023 November Campbell et al.