new worlds of cosmos
DESCRIPTION
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.TRANSCRIPT
!xoplanet"#e o$er worlds of $e cosmo"
%aseous giants - super-Ear$"!ar$ twins ? Life?
Stéphane UdryGeneva University
In 1995, a breakthrough:the first planet around another Sun
A Swiss team from the Geneva Universtity discovers a planet – 51 Pegasi b – 48 light years from Earth.
Artist's concept of an extrasolar planet (Greg Bacon, STScI)7
Michel Mayor & Didier Queloz
8
Temporal evolution of the discoveries
!"#$%&#'
()*)+,-'
NeptunesSuper-Earths
Jupiter
Earth
Towards lower masses
First 10 years Now Now Future
!x&a-solar Planet"
Why?
How?
What are we finding?
What next?
2
Five planets were known from the ancients who saw them move on the night sky
Mercury, Venus, Mars, Jupiter and Saturn were the “wandering stars” (from the greek “!"#$%&'(”)
Epicurius (341 - 270 AC)
Letters to Hérodotus
Plurality of distant worlds? Thousands of years ago, Greek philosophers speculated...
“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.”
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
'()ar and planetary forma*o+ Collapse of a gas cloud
Discs : natural by-product of
stellar formation
=> nursery of planets
Hubble space telescope
Stellar & planetary formation zone
Protostellar discsMolecular hydrogen clouds
Star forming regions
Older stars:debris disks
15
Planets buid up from the gas and dust particles in
the protoplanetary discs
Evaporation of the gas in the inner regions
=> solid planets
Further out, accretion of gas on the previously formed solid cores
Solar System Planets
How many planets? How many stars?
Billions
of
stars…
If every star had a planet?
Planets are common
bodies in the universe
Billions of stars=> Billions of planets
Deep Universe
Endless number of galaxies
How to detect those planets
Stars are a billion times brighter…
…than the planet
…hidden in the glare
Like this firefly.
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
Precision: 3-10 m/s - Jupiter-Sun : 12 m/s
Radial velocities - Saturne-Sun : 3 m/s - Earth-Sun : 9 cm/s
The 1st planet: 51 Pegasis Observatoire deHaute-Provence
Telescope:193 cm
Mpl = 0.5 MJup
P = 4.2 joursa = 0.04 UA
31
Light pollution
Mont Wilson observatory in Californie
La Silla, Chile
Swiss in the southern hemisphereEuler+Coralie – La Silla (Chile - ESO site)
~ 55 planets
Keck (1997-….)
.ensus of RV programme"
Lick (1992-…)
Elodie (1994-2006)
-> Sophie (2006-...)
HARPS (2003-...)
Coralie (1998-...)
>4000 stars
>400 planets
Others - Tautenburg - Texas/HET - Japan - Canary Islands - etc
AAT (1998-...)
Extra-solar planets1995-2009: >~400 planets
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
F G K M
Pegase 51 b
Surprise !!!
Prototype of “Hot Jupiters”
Formation?
Lynette Cook
Migration -> centre Need to stop !!!
G. Bryden
/arious 0pes of sys(m"
A large diversity!
Soleil
55 Cnc
~200 exoplanets discovered, but ....
mainly “Jupiters”
Where are the small planets?
After 10 years...
The planets discovered so far are closer in mass to Jupiter.
Jupiter’s diameter is eleven times greater than the Earth’s, and it has over 300 times the mass.
This is what we are looking for
This is what we’ve found
1ARPS: stability at 1 m/s
Pressure controlled Temperature controlled
- Observatoire de Genève- Physikalisches Institut, Bern- Observatoire Haute-Provence- Service d’Aéronomie, Paris- ESO
Very stable
Very precise
HARPS : The swiss precision
1igh-precision -> zoom 2ward lower-mass planet"
p = 9.5 d mpl = 10.5 MEarth
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
Lovis et al., Nature 2006
[email protected] telescope, ESO La Silla
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!
A 3 super-Earth system
Two super-Earth (5-7 MEarth) in a 4-planet system+ a very light planet of 1.94 MEarth
P1=3.15d M1=1.94MEarth
P2=5.37d M2=15.7MEarth
P3=12.9 d M3=5.4MEarth
P4= 66.8 d M4= 7.1 MEarth
Gl 581, M3V star
6 M. Mayor et al.: A Earth-type planet in GJ 581 planetary system
P = 66.8 day ; m sin i = 7.1M!
!5
0
5
RV4
[ms"
1]
RV4
[ms"
1]
0 0.25 0.5 0.75 1!!
P = 12.9 day ; m sin i = 5.4M!
!5
0
5
RV3
[ms"
1]
RV3
[ms"
1]
P = 5.37 day ; m sin i = 15.7M!
!20
!10
0
10
20
RV2
[ms"
1]
RV2
[ms"
1]
P = 3.15 day ; m sin i = 1.94M!
!5
0
5
RV1
[ms"
1]
RV1
[ms"
1]
!10
!5
0
5
10
O!
C[m
s"1]
O!
C[m
s"1]
53000 53500 54000 54500 55000
Julian date !2,400,000.0 [day]Julian date !2,400,000.0 [day]
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 plottedon the lowest panel.
0.5
0.75
1
1.25
Ca
IIH
+K
Ca
IIH
+K
3000 3500 4000 4500 5000
Barycentric Julian Date - 2450000.0 [day]Barycentric Julian Date - 2450000.0 [day]
0
0.25
0.5
Pow
erPow
er
100 101 102 103 104
Period [day]Period [day]
Fig. 3. The Ca !!H+K index as function of the Julian dates (upper panel)and its periodogram (lower panel).
observational bias to detect these low mass companions, wecan see a rise of the distribution towards super-Earth planets(cf. Fig. 7 of the above mentionned reference).
! The majority of systems having planets with masses in therange of super-Earths and Neptunes are multiplanetary sys-tems. Among the 6 planetary systems having a detectedsuper-Earth, (GJ 876, HD 40307, HD 7924, GJ 176, GJ 581,HD 181433) two-third are multiplanetary systems. Thesesystems are of di!erent types : 2 systems with one super-Earth plus one or two gaseous giant planets (GJ 876, HD181433), 2 systems with several planets on non resonant or-bits (HD 40307, GJ 581) and two systems with only one de-tected planet (GJ 176, HD 7924). However we cannot ex-clude that other planets could be detected in the future inone of these two systems. Some hints of additional planetsare observed in the periodogram of HD 7924 (Howard et al.2009).
! Low mass planetary systems seem not to be more frequentaround metal-rich host stars (Udry et al. 2006).
! Based on a preliminary analysis of the radial velocity mea-surements of the 200 solar-type stars of our HARPS highprecision 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).
Multiplanetary systems with several low mass close-in plan-ets are interesting as providing constraints for models of plane-tary formation. We can specially emphazise the three systems :HD 69830 (3 planets), HD 40307 (3 planets) and GJ 581 (4 plan-ets).
Terquem & Papaloizou (2007) have studied the migrationof cores and terrestrial planets induced by their interaction withthe protoplanetary disk. “Their results indicate that if hot super-Earths or Neptunes form by mergers of inwardly migratingcores, then such planets are most likely not isolated. We wouldexpect to always find at least one, more likely a few, companionson close and often near-commensurable orbits”. The high per-centage of multiplicity observed in the above-mentionned sys-tems has to be noted in comparison with that model. Howeverwe can also remark that observed periods are always quite far tobe near-commensurable.
Observable consequences of planet formation models in sys-tems with close-in terrestrial planets have been addressed by
'ys(ms wi$ Neptunes and super-Ear$"3n emerging new popula*o+
Properties?
comparison with giant panets?
=> 30% solar-0pe stars hos4 56olid7 planet"
19
Goal “The Pale Blue Dot”The race is on...
…on the ground and in space.
Keck Interferometer
Spitzer Space Telescope
SIM PlanetQuest
KeplerLarge Binocular Telescope Interferometer
Terrestrial Planet Finders (NASA)/ Darwn (ESA)
Spitzer: IR procheobservation de gaz “froid”formation stellaire et planétaire
Herschel: mid-IRLancement: 14 mai 2009, 15h09Plus grand télescope en vol
James-Webb Space Telescopes (2013)D=6.5m
Observatoire européen de Paranal (Very Large Telescope, Chili)
'PHERE
En cours de développementInstallation sur le ciel: 2011
Spectro-Polarimetric High-contrast
Exoplanet REsearch
Un “appareil photo” pour le VLT
TMT (USA)Thirty Meter Telescope
492 x 1.4m = 30m
The giants of the future
GMT (Canada-USA)Giant Mirror Telescope
7 x 8.4m = 25m
European-Extremely Large Telescopes984 x 1.45m = 42m
58
The power of giant telescopes: resolution and collecting area
2
Are we alone ?
8e(c*on of $e 5Pale Blue Dot7Search for biotracers on planets
twins of the Earth
Need existence of liquid water
Many of the new planets get too hot or too cold to support life.
Too hot! Too cold!Just right!
Habitable Zone
y
Earth
semi-major axis
of th
e st
ar
(Franck Selsis, priv comm)
Super-Earths…
1 M!
1 R!
8 M!
1.75 R!
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Signs Of Life On An Earth-like Planet
Vegetation
Plantproduct
Plant life
Bacteria
observed
Water
Oxygen
Carbondioxide
Methane Nitrousoxide
Ozone
Needed for life Primordial;
& bacteria product
8e(c*on of $e 5Pale Blue Dot7Search for biotracers on planets
twins of the Earth
68
LIFE
LIFE
Hypertelescopes
A fleet of small telescope collectors working as a dilutated giant mirror.
Resolution = big telescope one
Possible base > 150 km
Antoine Labeyrie
collectors
Hypertelescopes
Images of planetscontinentsvegetation
Giordano Bruno1548-1600
“Un univers infini et une infinité de Mondes"
Epicure 341 - 270 AC Lettres à Hérodote
“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.”
To improve life here, To extend life to there,To find life beyond.
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
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One day maybe....
we might turn again to poets, artists and philosophers….
to better understand ourselves.