New Worlds of Cosmos


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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.

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New Worlds of Cosmos

  1. 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. 2. Temporal evolution of the discoveries Towards lower masses First 10 years Now Now Future Neptunes Super-Earths !"#$%&#' Earth ()*)+,-' Jupiter 8 !x&a-solar Planet" Why? How? What are we finding? What next?
  3. 3. Five planets were known from the ancients who saw them move on the night sky Mercury, Venus, Mars, Jupiter and Saturn were the “wandering stars” (from the greek “!"#$%&'(”) 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. 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. 5. '()ar and planetary forma*o+ Collapse of a gas cloud Discs : natural by-product of stellar formation => nursery of planets
  6. 6. Hubble space telescope Stellar & planetary formation zone
  7. 7. Star forming regions Molecular hydrogen clouds Protostellar discs Older stars:debris disks
  8. 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. 9. Further out, accretion of gas on the previously formed solid cores Solar System Planets
  10. 10. How many planets? How many stars? Billions of stars…
  11. 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. 12. How to detect those planets Stars are a billion times brighter…
  13. 13. …than the planet …hidden in the glare Like this firefly.
  14. 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. 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. 16. Light pollution Mont Wilson observatory in Californie 31
  17. 17. La Silla, Chile Swiss in the southern hemisphere Euler+Coralie – La Silla (Chile - ESO site) ~ 55 planets
  18. 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. 19. Pegase 51 b Surprise !!! Prototype of “Hot Jupiters” Formation? Lynette Cook Migration -> centre Need to stop !!! G. Bryden
  20. 20. /arious 0pes of sys(m" A large diversity! Soleil 55 Cnc
  21. 21. After 10 years... ~200 exoplanets discovered, but .... mainly “Jupiters” Where are the small planets?
  22. 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. 23. HARPS : The swiss precision 1igh-precision -> zoom 2ward lower-mass planet" p = 9.5 d mpl = 10.5 MEarth
  24. 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. 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. 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. 27. James-Webb Space Telescopes (2013) D=6.5m Observatoire européen de Paranal (Very Large Telescope, Chili)
  28. 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. 29. European-Extremely Large Telescopes 984 x 1.45m = 42m The power of giant telescopes: resolution and collecting area 58
  30. 30. Are we alone ? 2 8e(c*on of $e 5Pale Blue Dot7 Search for biotracers on planets twins of the Earth
  31. 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. 32. (Franck Selsis, priv comm) Super-Earths… 1 M! 1 R! 8 M! 1.75 R!
  33. 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. 34. 8e(c*on of $e 5Pale Blue Dot7 Search for biotracers on planets twins of the Earth LIF E LIF E 68
  35. 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. 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