Alan Gould - ISE Webinar: NASA Kepler Mission
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This third ISE webinar is dedicated to the NASA Kepler mission. The NASA Kepler Mission has a number of excellent educational resources on its website. Here you can learn about: modeling the transit method of planet finding using a light sensor and orrery; making and using a starfinder that has naked eye stars known to have exoplanets; online interactives that show how light curves are used to discover exoplanets. Find out more: http://www.inspiringscience.eu/event/ise-webinar-nasa-kepler-mission
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Alan Gould - ISE Webinar: NASA Kepler Mission
- 1. A Search for Habitable Planets ISE Webinar: NASA Kepler Mission Alan Gould agould@berkeley.edu Kepler Mission Co-Investigator Lawrence Hall of Science University of California Berkeley
- 2. A Search for Habitable PlanetsKepler Mission Goal Kepler seeks evidence of Earth-size planets in the habitable zone of Sun-like stars.
- 3. A Search for Habitable Planets What is Earth-size & Sun-size?
- 4. A Search for Habitable Planets What is the habitable zone?
- 5. A Search for Habitable Planets What’s this?
- 6. A Search for Habitable Planets ISE Webinar: NASA Kepler Mission (part B) Alan Gould agould@berkeley.edu Kepler Mission Co-Investigator Lawrence Hall of Science University of California Berkeley
- 7. A Search for Habitable Planets Kepler’s Third Law If R = average distance of a planet from the Sun (in AU) and T = it’s period (in Earth years) then R3 = T2 For a star of mass Ms (solar masses) R3 = MsT2
- 8. A Search for Habitable Planets Linear Plot: Kepler’s 3rd Law
- 9. A Search for Habitable Planets TransitTracksp.13 50403020 7060105432 87610.5 0.60.40.30.20.1 1000 500 400 300 200 600 100 50 40 30 20 60 10 5 4 3 2 6 1 0.5 0.4 0.3 0.2 0.6 0.1 0.05 0.07 0.06 Mercury Venus Earth Mars Asteroid Belt Jupiter Saturn Uranus Neptune Pluto Keplers’s 3rd Law G raph of Whole Solar System with Logarithmic Scales R = Orbital Radius (AU) [Semi-major axis] T=OrbitalPeriod(years) 100 Kepler’s 3rd Law R3 = T2 R, in Years T, in Astronomical Units, AU Note: All objects -- planets, moons, asteroids, comets, meteoroids, dwarf planets -- all obey Kepler’s 3rd Law.
- 10. A Search for Habitable Planets TransitTracksp.13 50403020 7060105432 87610.5 0.60.40.30.20.1 1000 500 400 300 200 600 100 50 40 30 20 60 10 5 4 3 2 6 1 0.5 0.4 0.3 0.2 0.6 0.1 0.05 0.07 0.06 Mercury Venus Earth Mars Asteroid Belt Jupiter Saturn Uranus Neptune Pluto Keplers’s 3rd Law G raph of Whole Solar System with Logarithmic Scales R = Orbital Radius (AU) [Semi-major axis] T=OrbitalPeriod(years) 100 Kepler’s 3rd Law R3 = T2 R, in Years T, in Astronomical Units, AU Note: All objects -- planets, moons, asteroids, comets, meteoroids, dwarf planets -- all obey Kepler’s 3rd Law.
- 11. A Search for Habitable Planets TransitTracksp.13 50403020 7060105432 87610.5 0.60.40.30.20.1 1000 500 400 300 200 600 100 50 40 30 20 60 10 5 4 3 2 6 1 0.5 0.4 0.3 0.2 0.6 0.1 0.05 0.07 0.06 Mercury Venus Earth Mars Asteroid Belt Jupiter Saturn Uranus Neptune Pluto Keplers’s 3rd Law G raph of Whole Solar System with Logarithmic Scales R = Orbital Radius (AU) [Semi-major axis] T=OrbitalPeriod(years) 100 Kepler’s 3rd Law R3 = T2 R, in Years T, in Astronomical Units, AU Note: All objects -- planets, moons, asteroids, comets, meteoroids, dwarf planets -- all obey Kepler’s 3rd Law. 1.88 years
- 12. A Search for Habitable Planets TransitTracksp.13 50403020 7060105432 87610.5 0.60.40.30.20.1 1000 500 400 300 200 600 100 50 40 30 20 60 10 5 4 3 2 6 1 0.5 0.4 0.3 0.2 0.6 0.1 0.05 0.07 0.06 Mercury Venus Earth Mars Asteroid Belt Jupiter Saturn Uranus Neptune Pluto Keplers’s 3rd Law G raph of Whole Solar System with Logarithmic Scales R = Orbital Radius (AU) [Semi-major axis] T=OrbitalPeriod(years) 100 Kepler’s 3rd Law R3 = T2 R, in Years T, in Astronomical Units, AU Note: All objects -- planets, moons, asteroids, comets, meteoroids, dwarf planets -- all obey Kepler’s 3rd Law. 1.88 years
- 13. A Search for Habitable Planets TransitTracksp.13 50403020 7060105432 87610.5 0.60.40.30.20.1 1000 500 400 300 200 600 100 50 40 30 20 60 10 5 4 3 2 6 1 0.5 0.4 0.3 0.2 0.6 0.1 0.05 0.07 0.06 Mercury Venus Earth Mars Asteroid Belt Jupiter Saturn Uranus Neptune Pluto Keplers’s 3rd Law G raph of Whole Solar System with Logarithmic Scales R = Orbital Radius (AU) [Semi-major axis] T=OrbitalPeriod(years) 100 Kepler’s 3rd Law R3 = T2 R, in Years T, in Astronomical Units, AU Note: All objects -- planets, moons, asteroids, comets, meteoroids, dwarf planets -- all obey Kepler’s 3rd Law. 1.88 years 1.52 AU
- 14. A Search for Habitable Planets TransitTracksp.10 Kepler’s 3rd Law G raphs Kepler’s 3rd Law G raph for Periods less than 10 days Kepler’s 3rd Law G raph for Periods Less Than 100 D ays Kepler’s 3rd Law G raph for the Inner Solar System (periods less than 2 years) Transit Tracks: Student Worksheet © 2008 by theRegentsof theUniversity of California
- 15. A Search for Habitable Planets What is the period of Kepler-4b?
- 16. A Search for Habitable Planets Light curve for Kepler-4b
- 17. A Search for Habitable Planets Kepler’s 3rd Law G raphs Kepler’s 3rd Law G raph for Periods less than 10 days Kepler’s 3rd Kepler’s 3rd
- 18. A Search for Habitable Planets Kepler’s 3rd Law G raphs Kepler’s 3rd Law G raph for Periods less than 10 days Kepler’s 3rd Kepler’s 3rd Kepler 4-b
- 19. A Search for Habitable Planets TransitTracksp.10 Kepler’s 3rd Law G raphs Kepler’s 3rd Law G raph for Periods less than 10 days Kepler’s 3rd Law G raph for Periods Less Than 100 D ays Kepler’s 3rd Law G raph for the Inner Solar System (periods less than 2 years) Transit Tracks: Student Worksheet © 2008 by theRegentsof theUniversity of California
- 20. A Search for Habitable Planets
- 21. A Search for Habitable Planets
- 22. A Search for Habitable Planets
- 23. A Search for Habitable Planets
- 24. A Search for Habitable Planets
- 25. A Search for Habitable Planets
- 26. A Search for Habitable Planets
- 27. A Search for Habitable Planets ISE Webinar: NASA Kepler Mission (part C) Alan Gould agould@berkeley.edu Kepler Mission Co-Investigator Lawrence Hall of Science University of California Berkeley
- 28. A Search for Habitable Planets Kepler Website: kepler.nasa.gov
- 29. A Search for Habitable Planets Uncle Al's Starwheels Northern Hemisphere: •English •Higher latitude (60°+) •Kepler •Japanese •Icelandic •Blank starwheel (no lines or labels) Southern Hemisphere •English •Español •Português •Pulsar (Parks Radio Telescope) http://store.lawrencehallofscience.org/Item/sky-challenger
- 30. A Search for Habitable Planets Reminder Paste Kepler Resources URLs into Chat
- 31. A Search for Habitable Planets Which of these is the smallest planet?
- 32. A Search for Habitable Planets
- 33. A Search for Habitable Planets 33 Transiting Planets pre-Kepler Orbital Period in days SizeRelativetoEarth
- 34. A Search for Habitable Planets 34 34 Candidates as of June 2010 Data: May-Sep 2009 Orbital Period in days SizeRelativetoEarth Jun 2010
- 35. A Search for Habitable Planets
- 36. A Search for Habitable Planets
- 37. A Search for Habitable Planets
- 38. A Search for Habitable Planets
- 39. A Search for Habitable Planets 1,284 new Kepler planets confirmed; 550 are possibly rocky and 9 of those reside in habitable zone.
- 40. A Search for Habitable Planets
- 41. A Search for Habitable Planets
- 42. A Search for Habitable Planets
- 43. A Search for Habitable Planets Kepler-22b Kepler-69c Kepler-62e Kepler-62f Earth [April 2013: Relative sizes of Kepler habitable zone planets discovered.]
- 44. A Search for Habitable Planets
- 45. A Search for Habitable Planets A guy who’s thought a lot about planets More information: kepler.nasa.gov ( By permission Sternwarte Kremsmünster)
Hinweis der Redaktion
- Title slide
- Statement of the Kepler Mission Goal. Kepler seeks evidence of Earth-size planets in the habitable zone of Sun-like stars.
- The Sun (in ultraviolet light) and Earth to actual size scale. (Obviously, the distance between them is wrong.) The Earth is the tiny dot below the word Earth. The solar image was taken by the SOHO spacecraft, and the “Earth” was added to the photograph. For comparison, it would take 109 of the “earth-dots” to make a single line across the diameter of the disk of the Sun. The Sun is a star: self luminous. The Earth is a planet, and does not make its own light. If you combined all of the planets, moons, comets, asteroids, meteorids, and Kuiper belt objects in the solar system, they would equal less than 1% the mass of the Sun. Stars are big; planets are debris…..and so they are hard to find.
- The habitable zone of stars depends upon the temperature of the star. The hotter the star, the farther out the habitable zone is from the star. In this graphic, the habitable zone is green. The red area is “too hot” and the blue area is “too cold” for liquid water on the surface of the planet, which is the definition of habitable that the Kepler Mission uses. An animation of this images can be downloaded at: http://kepler.nasa.gov/multimedia/animations/
- A transit is seen when planet is seen to cross in front of a star. This requires that the observer (on Earth in this case), the planet (Venus or Mercury), and the Sun all line up. The Sun’s apparent size is ½ degree, and so this is a rare event. The orbits of the Earth, Venus, and Mercury are all tilted with respect to each other. With respect to Earth’s orbit (aka, the ecliptic), Venus’ orbit is tilted by 3.4 degrees and Mercury’s is tilted 7 degrees. As a consequence, the Venus and Mercury do not often transit the Sun as see from Earth. Transits across the face of the Sun can only occur when the planet is crossing the plane of the ecliptic at same the time it lies between the Earth and the Sun. Mercury’s orbit is complex, and the transits occur every few years. For Venus, transits come in pairs, about 8 years apart, and then more than a century goes by before the next pair. The next transit of Mercury is on May 9, 2016 , and the last transit of Venus was June 5/6, 2012 and the next is December 1011, 2117. For further information on transits, go to: http://eclipse.gsfc.nasa.gov/transit/venus0412.html Or see: “Transit of Mercury”: http://en.wikipedia.org/wiki/Transit_of_Mercury “Transit of Venus”: http://en.wikipedia.org/wiki/Transit_of_Venus
- Title slide
- This is a plot of the planet’s semi-major axis (roughly, the average distance) in astronomical units (1 AU = the “average” distance of the Earth from the Sun) vs orbital length (planetary year). Note that all of the inner terrestrial planets are jammed together. Next chart is a log-log plot of the same information. In Kepler’s time, the geometry of the solar system was understood, but the absolute size (aka, distances in miles/kilometers) was not. He could draw up the orbits of the planets in a diagram, but did not know the actual scale. Hence, all distances were measured relative the Earth’s orbit, with a semi-major axis equaling the “Astronomical Unit.” Determining the value of the AU began with observing the transits of Venus and Mercury without definitive results. Other methods were developed, each with problems. Finally, in the 1960s a radar beam was bounced off of Venus using the Arecibo telescope to measure the Earth-Venus distance accurately. From that measurement, the AU was accurately determined. Subsequently, an absolute length has been defined, and it is about the mean distance of the Earth from the Sun. A well-written history of the determination of the AU is published on Wikipedia at: http://en.wikipedia.org/wiki/Astronomical_unit About Kepler’s 3rd Law: All objects in orbit about a central gravitational mass (aka the Sun, for the Solar System, or a planet for moons) obey Kepler’s 3rd Law of Planetary Motion: the 8 planets, the moons orbiting them, the asteroids, comets, meteoroids, and the dwarf planets like Pluto, They all belong on the graph.
- The log-log plot of Kepler’s 3rd Law. Note, the inner planets, asteroids and Pluto are all included—they obey Kepler’s 3rd Law too.
- How to use this graph: The Orbital Period (in years) = T. From this, and distance can be obtained. The orbital period for Mars 1.88 years
- How to use this graph: The Orbital Period (in years) = T. From this, and distance can be obtained. The orbital period for Mars 1.88 years
- The distance to Mars, in astronomical units (AU), is just over 1.5 AU. It’s 1.5 time farther from the Sun than Earth. Students can use this graph to interpret the Kepler Mission light curves (page 13 of the PDF file, “Transit Tracks,”) but may find it challenging to interpolate on a log-log scale. A series of linear plots for distances out to Mars are provided as they are easier for students to use.
- The distance to Mars, in astronomical units (AU), is just over 1.5 AU. It’s 1.5 time farther from the Sun than Earth. Students can use this graph to interpret the Kepler Mission light curves (page 13 of the PDF file, “Transit Tracks,”) but may find it challenging to interpolate on a log-log scale. A series of linear plots for distances out to Mars are provided as they are easier for students to use.
- Discuss these linear plots of Kepler’s 3rd Law with your students before launching the activity. Note that the two upper graphs show orbits in “DAYS” rather than “YEARS” because most of the light curves the students will interpret show very short period orbits.
- Use Kepler 4-b as an example. The period is 3.2 days. Suggest that students count up several intervals and take an average by dividing days elapsed by the number of orbits.
- This is the actual light curves for Kepler 4b. The upper light curve shows the “dips” on a period of 3.2135 days. The lower chart shows the transit in detail. Kepler 4b transits it star in about 5 hours, from beginning to end of the transit. Note that the upper curve is scaled against “DAYS” (HJD = Heliocentric Julian Days, a precise way in which astronomers measure time, counting days), hence the transits are sharp, pointed dips because they last less than one day. The lower curve is “stretched out” into “HOURS” so that the shape of the transit looks different. The sloping sides show that the light diminishes slowly as the planet begins to block some of the star’s light. It’s flat on the bottom when the planet is entirely in front of the disk of the star, and then sloped again when the transit ends as the planet is exiting from in front of the star. For each Kepler system, these plots are available in the scientific literature. They are also posted on the Kepler website via the “Discoveries” table. Go to: http://kepler.nasa.gov/Mission/discoveries/ Click on the individual planet name (e.g., Kepler-4b) to go to a page with an animation of the system (based on real data), and excerpts from the scientific publication like the plots on this slide.
- The period of Kepler-4b is 3.2 days. Select the graph that shows 10 days or less.
- Find 3.2 days on the vertical axis—the observed period—and draw a line to the graph which shows Kepler’s 3rd Law plotted. Then draw a line down (perpendicular) to the horizontal axis (distance in millions of km), and find the semi-major axis of the orbit—the average distance of the planet. To find the result in AU, divide by 150,000,000 km/AU. Planets on these very close in orbits are almost entirely on circular orbits. So the semi-major axis is equivalent to the radius of the orbit.
- The three linear graphs of Kepler’s 3rd Law for orbital periods of less than 100 days.
- Display of Kepler-1b to Kepler-4b. Note on nomenclature: each star observed by Kepler receives a numeric designation. For stars that have confirmed planets, they are then named in the published catalog: Kepler-1, Kepler-2 etc. The star in each case is Kepler-1a, Kepler-2a, etc. The “a” is not shown. Then the first planet discovered and confirmed is Kepler-1b, Kepler-2b, etc. For systems with multiple planets, the planets are named in the order discovered, not necessarily in the order according to distance (although this does also happen). Kepler-1b: this transiting planet was knows from ground-based discoveries prior to launch. TrES is the Transiting Exoplanet Search project. Kepler-2b and Kepler-3b: Like Kepler 1-b, these were known from ground-based discoveries prior to launch. HAT-P is the Hungarian Transiting Planet project. Kepler observed these three known planets to prove that the Kepler spacecraft technology was functioning correctly. The space-based observations were much more precise than the ground-based observations, and they appear as the first three discoveries, with appropriate credit, in the Kepler catalog.
- Kepler-5 to Kepler-8, original discoveries, announced January 2010.
- Kepler 9: original discovery, announced in August, 2010. Kepler 10: original discovery announced in January 2010: first rocky, Earth-size planet. Not a good place to live—very close to it’s star, and very hot. Mystery Planet: there are two planets in this system, one shows the signature of a Earth-size planet on a one-year orbit—a habitable place to live. So far, Kepler has not observed just such a planet, although it has identified about 50 planet candidates (to be confirmed) in the habitable zone of their stars. (As of April, 2011).
- Kepler-11 system has 6 known planets (February 2011). All transit, and all are closer to their star than the planet Mercury is to the Sun. Thus, they have very short-period orbits. The transit light curves are divided into two sets to make is simpler to analyze. The next slide (#33) shows the light curves, color coded, for all six planets together.
- Kepler 11: original discovery of a system with 6 planets, Announced February 2011.
- Provided to allow teachers to discuss the work students need to do. Use page 9 for classes that will interpolate distances from periods using the plots of Kepler’s 3rd Law. Note: All light curves are adapted from genuine Kepler data EXCEPT the Mystery planets which are “simulated” data so that there is an Earth-size planet in the set. As Kepler publishes discoveries on planets that are farther from their stars, this lesson will be altered to include planets with longer orbital periods.
- Provided to allow teachers to discuss the work students need to do. Use page 10 for students that will calculate the planetary distances and sizes using mathematics. Calculators recommended. Note: All light curves are adapted from genuine Kepler data EXCEPT the Mystery planets which are “simulated” data so that there is an Earth-size planet in the set. As Kepler publishes discoveries on planets that are farther from their stars, this lesson will be altered to include planets with longer orbital periods.
- Title slide
- Note: The radius may be different than those that your students derive from the data in the exercise which was simplified for classroom use. This shows the actual light curves, orbital periods, and size of the first 5 planets discovered by Kepler Mission, announced January 2010. The size is expressed in terms of “Earth radii.” Kepler 4b is 4.31 time the radius of Earth, and is the smallest planet of this group. For comparison, Jupiter is more than 11 times the radius of Earth. Thus, all the other planets shown are larger than Jupiter.
- Note: The radius may be different than those that your students derive from the data in the exercise which was simplified for classroom use. This shows the actual light curves, orbital periods, and size of the first 5 planets discovered by Kepler Mission, announced January 2010. The size is expressed in terms of “Earth radii.” Kepler 4b is 4.31 time the radius of Earth, and is the smallest planet of this group. For comparison, Jupiter is more than 11 times the radius of Earth. Thus, all the other planets shown are larger than Jupiter.
- Note the majority are large-Jupiters. These were discovered by the European space observatory, COROT, and ground-based observatories.
- Look at trend with Kepler discoveries—toward smaller planets. From the first 4 months of Kepler data, announced in June 2010.
- January, 2013: small planet candidates dominate the new discoveries
- Kepler scientists are seeking small planets in the lower right-hand corner of the graph: Earth-size planets in the habitable zone of Sun-like stars.
- Summary of planet sizes as of February 2012. These are confirmed planets, and their sizes are determined from the depth of the transit (% of light blocked) and the size of the star, which is determined from Earth-based observations or from Kepler data about the star. See slide 61 for derivation.
- These are the planet candidates sorted by sizes into a histogram. Of these, about 50 are thought to be in the habitable zone of their stars.
- The axis now changes to size vs. equilibrium temperature in Kelvin. The green band indicates the “habitable zone.” For the Kepler Mission, the habitable zone is defined as the temperature that would allow liquid water to exist on the surface of a planet (or moon orbiting a large planet like Jupiter). The question of habitability is broadly discussed in the scientific community, including discussions of habitable regions beneath the surfaces of planets and moons. But, for the Kepler mission, the simpler definition of water on the surface of the object is used. The planetary equilibrium temperature is a theoretical temperature that the planet would be at when considered simply as if it were an object (black body) being heated only by its parent star. In this model, the presence or absence of an atmosphere is not factored in.
- April 2013: The diagram compares the planets of the inner solar system to Kepler-62, a five-planet system about 1,200 light-years from Earth in the constellation Lyra. The five planets of Kepler-62 orbit a star classified as a K2 dwarf, measuring just two thirds the size of the sun and only one fifth as bright. At seven billion years old, the star is somewhat older than the sun. Much like our solar system, Kepler-62 is home to two habitable zone worlds, Kepler-62f and Kepler-62e. Kepler-62f orbits every 267 days and is only 40 percent larger than Earth, making it the smallest exoplanet known in the habitable zone of another star. The other habitable zone planet, Kepler-62e, orbits every 122 days and is roughly 60 percent larger than Earth. More information at: http://kepler.nasa.gov/multimedia/artwork/diagrams/?ImageID=258
- The diagram compares the planets of the inner solar system to Kepler-69, a two-planet system about 2,700 light-years from Earth in the constellation Cygnus. The two planets of Kepler-69 orbit a star that belongs to the same class as our sun, called G-type. Kepler-69c, is 70 percent larger than the size of Earth, and is the smallest yet found to orbit in the habitable zone of a sun-like star. Astronomers are uncertain about the composition of Kepler-69c, but its orbit of 242 days around a sun-like star resembles that of our neighboring planet Venus. The companion planet, Kepler-69b, is just over twice the size of Earth and whizzes around its star once every 13 days. The artistic concepts of the Kepler-69 planets are the result of scientists and artists collaborating to help imagine the appearance of these distant worlds.
- April 2013: Relative sizes of Kepler habitable zone planets discovered. Left to right: Kepler-22b, Kepler-69c, Kepler-62e, Kepler-62f, and Earth (except for Earth, these are artists' renditions).
- Enlarged section with the habitable zone between about 185 K and 310 K. (-83 C to ~37 C). This is an “expanded” habitable zone to account for the impact of an atmosphere on a planet. An atmosphere can warm a planet through the greenhouse effect, and so the cold range of the habitable zone is extended. In the case of the Earth, the warming impact of our atmosphere is about 33 C (59°F); without an atmosphere, the surface of the Earth would be below the freezing point of water. The freezing point of water is- 32°F, 0 C, and 273.15 K. and the boiling point is 212°F, 100 C and 374.15 K. Note: there are several planets just a bit larger than the Earth in the Habitable Zone.
- Transit Tracks powerpoint slides prepared by Edna DeVore, adapted from a presentation originally prepared by Alan Gould. DeVore and Gould co-lead the education and outreach program for NASA’s Kepler Mission. Contact: Edna DeVore: edevore@seti.org Alan Gould: agould@berkeley.edu