In 1995, two Swiss astronomers became the first to detect a planet in orbit around a far off star similar to our Sun. Since then, more than 400 of these worlds, called exoplanets, have been found. With the discoveries come hopes for finding life outside our solar system. Stephane Udry, an astrophysicist from the University of Geneva, is part of a team leading the search for exoplanets. In 2007, he was among scientists to discover a celestial body within the “habitable zone” of its solar system in orbit around a red dwarf star called Gliese 581, some 20 light-years away near the constellation Libra. Being in the habitable zone means that any water on its surface could exist in liquid form as it does here on Earth. Could life flourish there, too? On Sunday, February 28, 2010, Professor Udry invites the swissnex San Francisco audience to join him for an enlightening journey into the questions and methodology behind his work. He’ll explain how astronomers go about searching for exoplanets, how they now view planet formation, and what new findings mean for the future and for the search for life beyond Earth.

1. !xoplanet"
#e o$er worlds of $e cosmo"
%aseous giants - super-Ear$"
!ar$ twins ? Life?
Stéphane Udry
Geneva University
In 1995, a breakthrough:
the first planet around another Sun
Michel Mayor & Didier Queloz
A Swiss team from the Geneva Universtity discovers a planet –
51 Pegasi b – 48 light years from Earth.
7
Artist's concept of an extrasolar planet (Greg Bacon, STScI)

2. Temporal evolution of the discoveries
Towards lower masses
First 10 years Now Now Future
Neptunes
Super-Earths
!"#$%&#'
Earth
()*)+,-'
Jupiter
8
!x&a-solar Planet"
Why?
How?
What are we finding?
What next?

3. Five planets were known from the ancients who
saw them move on the night sky
Mercury, Venus, Mars, Jupiter and
Saturn were the “wandering stars”
(from the greek “!"#$%&'(”)
2
Plurality of distant worlds?
Thousands of years ago, Greek philosophers speculated...
Epicurius (341 - 270 AC)
Letters to Hérodotus
“There are infinite worlds
both like and unlike this
world of ours...We must
believe that in all worlds
there are living creatures and
planets and other things we
see in this world.”

4. And so did medieval
scholars....
at the cost of their lives
The year 1584
"There are countless suns and
countless earths all rotating around
their suns in exactly the same way
as the seven planets of our system.
We see only the suns because they
are the largest bodies and are
luminous, but their planets remain
invisible to us because they are
smaller and non-luminous. The
countless worlds in the universe
are no worse and no less inhabited
than our Earth.”
Giordano Bruno
in De L'infinito Universo E Mondi
4
The Solar System

5. '()ar and planetary forma*o+
Collapse of a gas cloud
Discs : natural by-product of
stellar formation
=> nursery of planets

6. Hubble space telescope
Stellar & planetary formation zone

7. Star forming regions
Molecular hydrogen clouds Protostellar discs
Older stars:debris disks

8. Planets buid up from the gas and dust particles in
the protoplanetary discs
15
Evaporation of the gas in the inner regions
=> solid planets

9. Further out, accretion of gas on the previously formed solid cores
Solar System Planets

10. How many planets? How many stars?
Billions
of
stars…

11. If every star had a planet?
Billions of stars=> Billions of planets
Planets are common
bodies in the universe
Deep Universe
Endless number of
galaxies

12. How to detect those planets
Stars are a billion times brighter…

13. …than the planet
…hidden
in the glare
Like this firefly.

14. Detection methods: 2 body motion property
,ndirect de(c*on me$od: measure of star veloci-
Principle:
Measurement of the
Doppler shift
Period:
star-planet separation
Amplitude:
component masses

15. Precision: 3-10 m/s - Jupiter-Sun : 12 m/s
Radial velocities - Saturne-Sun : 3 m/s
- Earth-Sun : 9 cm/s
Observatoire de
The 1st planet: 51 Pegasis Haute-Provence
Telescope:193 cm
Mpl = 0.5 MJup
P = 4.2 jours
a = 0.04 UA

16. Light pollution
Mont Wilson observatory in Californie
31

17. La Silla, Chile
Swiss in the southern hemisphere
Euler+Coralie – La Silla (Chile - ESO site)
~ 55 planets

18. .ensus of RV programme" Elodie (1994-2006)
>4000 stars
>400 planets -> Sophie (2006-...)
Others
- Tautenburg
- Texas/HET
- Japan
- Canary Islands
- etc
Keck (1997-….)
HARPS (2003-...)
Coralie (1998-...)
Lick (1992-…) AAT (1998-...)
Extra-solar planets
1995-2009: >~400 planets
F G K M
Statistical properties
– Percentage
~7% of observed stars
~1% of Hot Jupiters
– Mass distribution
0.016 MJup < Mpl < 20 MJup
– Period
1.2 d < P < …
– Mass-period distribution
– Eccentricity-period distribution
0 < e < 0.93
– Proprerties of host stars
metallicity, mass, binarity

19. Pegase 51 b
Surprise !!!
Prototype of
“Hot Jupiters”
Formation?
Lynette Cook
Migration -> centre
Need to stop !!!
G. Bryden

20. /arious 0pes of sys(m"
A large diversity!
Soleil
55 Cnc

21. After 10 years...
~200 exoplanets discovered, but ....
mainly “Jupiters”
Where are the small planets?

22. The planets discovered so far are closer in
mass to Jupiter.
This is what
we’ve found
This is what we are
looking for
Jupiter’s diameter is eleven times greater than the Earth’s, and it
has over 300 times the mass.
- Observatoire de Genève
1ARPS: stability at 1 m/s -
-
Physikalisches Institut, Bern
Observatoire Haute-Provence
- Service d’Aéronomie, Paris
- ESO
Very stable
Very precise
Pressure controlled Temperature controlled

23. HARPS : The swiss precision
1igh-precision -> zoom 2ward lower-mass planet"
p = 9.5 d
mpl = 10.5 MEarth

24. HD 69830: un trio de Neptunes
P1 = 8.67 j a = 0.078 AU M sini = 10.2 MTerre
P2 = 31.6 j a = 0.186 AU M sini = 11.8 MTerre
P3 = 197. j a = 0.63 AU M sini = 18.1 MTerre
HARPS@3.6-m telescope, ESO La Silla
Lovis et al., Nature 2006
A 3 super-Earth system
P1 = 4.31 jours
m1 sini = 4.3 M!
P2 = 9.62 jours
m2 sini = 6.9 M!
P3 = 20.5 jours
m3 sini = 9.7 M!

25. Two super-Earth (5-7 MEarth) in a 4-planet system
+ a very light planet of 1.94 MEarth Gl 581,
M3V star
6 M. Mayor et al.: A Earth-type planet in GJ 581 planetary system
P = 3.15 day ; m sin i = 1.94M⊕ 1.25
Ca II H+K
1
5
0.75
RV1 [m s−1 ]
0.5
0
3000 3500 4000 4500 5000
Barycentric Julian Date - 2450000.0 [day]
−5 0.5
Power
0.25
P = 5.37 day ; m sin i = 15.7M⊕
20
0
10 100 101 102 103 104
Period [day]
P 1 = 3. 1 5 d M1=1.94MEarth
RV2 [m s−1 ]
0 Fig. 3. The Ca  H+K index as function of the Julian dates (upper panel)
and its periodogram (lower panel).
−10 P2=5.37d M2=15.7MEarth
observational bias to detect these low mass companions, we
−20
can see a rise of the distribution towards super-Earth planets
(cf. Fig. 7 of the above mentionned reference). P3=12.9 d M3=5.4MEarth
P = 12.9 day ; m sin i = 5.4M⊕ − The majority of systems having planets with masses in the
5
range of super-Earths and Neptunes are multiplanetary sys-
tems. Among the 6 planetary systems having a detected P4= 66.8 d M4= 7.1 MEarth
super-Earth, (GJ 876, HD 40307, HD 7924, GJ 176, GJ 581,
HD 181433) two-third are multiplanetary systems. These
RV3 [m s−1 ]
systems are of different types : 2 systems with one super-
0 Earth plus one or two gaseous giant planets (GJ 876, HD
181433), 2 systems with several planets on non resonant or-
bits (HD 40307, GJ 581) and two systems with only one de-
−5 tected planet (GJ 176, HD 7924). However we cannot ex-
clude that other planets could be detected in the future in
one of these two systems. Some hints of additional planets
P = 66.8 day ; m sin i = 7.1M⊕ are observed in the periodogram of HD 7924 (Howard et al.
2009).
− Low mass planetary systems seem not to be more frequent
5 around metal-rich host stars (Udry et al. 2006).
− Based on a preliminary analysis of the radial velocity mea-
RV4 [m s−1 ]
surements of the 200 solar-type stars of our HARPS high
0 precision survey, we have detected low mass close-in plan-
ets (P< 50d and m sin i < 30M⊕ ) around 30% of these stars
(Lovis et al. 2009).
−5
Multiplanetary systems with several low mass close-in plan-
ets are interesting as providing constraints for models of plane-
0 0.25 0.5 0.75 1 tary formation. We can specially emphazise the three systems :
φ HD 69830 (3 planets), HD 40307 (3 planets) and GJ 581 (4 plan-
10 ets).
Terquem & Papaloizou (2007) have studied the migration
of cores and terrestrial planets induced by their interaction with
5
the protoplanetary disk. “Their results indicate that if hot super-
O−C [m s−1 ]
Earths or Neptunes form by mergers of inwardly migrating
'ys(ms wi$ Neptunes and super-Ear$"
0 cores, then such planets are most likely not isolated. We would
expect to always find at least one, more likely a few, companions
on close and often near-commensurable orbits”. The high per-
−5 centage of multiplicity observed in the above-mentionned sys-
tems has to be noted in comparison with that model. However
we can also remark that observed periods are always quite far to
3n emerging new popula*o+
−10
53000 53500 54000 54500 55000 be near-commensurable.
Julian date −2,400,000.0 [day] Observable consequences of planet formation models in sys-
tems with close-in terrestrial planets have been addressed by
Fig. 2. Radial velocity curves for planets e, b, c and d from top to bot-
tom. The residual velocities to the four planets keplerian fit are plotted
=> 30% solar-0pe stars hos4
on the lowest panel.
56olid7 planet"
Properties?
comparison with giant panets?

26. Goal “The Pale Blue Dot”
The race is on...
Keck Interferometer
Large Binocular Telescope Interferometer Kepler Spitzer Space Telescope
…on the
ground
and in
space. 19
SIM PlanetQuest Terrestrial Planet Finders (NASA)/ Darwn (ESA)
Spitzer: IR proche
observation de gaz “froid”
formation stellaire et planétaire
Herschel: mid-IR
Lancement: 14 mai 2009, 15h09
Plus grand télescope en vol

27. James-Webb Space Telescopes (2013)
D=6.5m
Observatoire européen de Paranal
(Very Large Telescope, Chili)

28. 'PHERE
Spectro-Polarimetric High-contrast
Exoplanet REsearch
Un “appareil photo” pour le VLT
En cours de développement
Installation sur le ciel: 2011
The giants of the future
GMT (Canada-USA)
Giant Mirror Telescope
7 x 8.4m = 25m
TMT (USA)
Thirty Meter Telescope
492 x 1.4m = 30m

29. European-Extremely Large Telescopes
984 x 1.45m = 42m
The power of giant telescopes: resolution and collecting area
58

30. Are we alone ?
2
8e(c*on of $e 5Pale Blue Dot7
Search for biotracers on planets
twins of the Earth

31. Many of the new planets get too
hot or too cold to support life.
Too hot! Just right! Too cold!
Need existence of liquid water
Habitable Zone
Earth
of the star
y
semi-major axis

32. (Franck Selsis, priv comm)
Super-Earths…
1 M!
1 R!
8 M!
1.75 R!

33. Signs Of Life On An Earth-like Planet
Needed
for life Primordial;
& bacteria
Plant product
product
Plant Bacteria
life
observed
Vegetation Ozone Water Carbon Methane Nitrous
dioxide oxide
Oxygen
65

34. 8e(c*on of $e 5Pale Blue Dot7
Search for biotracers on planets
twins of the Earth
LIF
E
LIF
E
68

35. Hypertelescopes
collectors
A fleet of small telescope collectors
working as a dilutated giant mirror.
Resolution = big telescope one
Possible base > 150 km
Antoine Labeyrie
Hypertelescopes
Images of planets
continents
vegetation

36. Epicure 341 - 270To improve life here,
AC Lettres à Hérodote
To extend life to there,
To find life beyond.
“There are infinite worlds both like and
unlike this world of ours...We must
believe that in all worlds there are living
creatures and planets and other things we
see in this world.”
Giordano Bruno
1548-1600
“Un univers infini et
une infinité de Mondes"
One day maybe....
we might turn again to poets, artists and
philosophers….
to better understand ourselves.
We shall not cease from exploration
And the end of all our exploring
Will be to arrive where we started
And know the place for the first time.
! T.S. Eliot
Four Quartets
26