1. 1 The Search for Other Earths Ray Villard STScI August 17, 2009

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3. 3 “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.” Epicurius c. 300 B.C

4. 4 Galileo, 1609

5. 5 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... 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

6. 6 Exoplanet Discovery Timeline Past 1992Pulsar planets 1994Protoplanetary disks resolved in visible light 1995Radial velocity extrasolar planet discovery 1999Extrasolar planet transits observed 2001Extrasolar planet atmospheres measured 2003New planets discovered with transit method 2004Planet discovered with microlensing method 2006Transit planet day side temperature measured Present Transiting hot Jupiter atmospheres measured in detail First transiting super- Earths Direct imaging of young hot Jupiters Future 2011 Statistical frequency of earthlike planets determined (Kepler) 2011Planets found around Alpha Centauri?? 2013 JWST: transits and eclipses of planet around nearby red dwarfs 2015 Search for nearby Earths and super Earths 2030Definitive sampling of biospheres on exoplanet survey 2040? Direct imaging of all sizes of exoplanets 2101?First interstellar AI mission to directly sample exobiology

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10. 10 THE OBSERVABLE DRAKE EQUATION ETL = N P X F TP X FP w X FP L ETL = Planets with extraterrestrial life in the Galaxy Np = Number of exoplanets Fpt = Fraction of terrestrial planets FPw = Fraction of terrestrial planets with liquid water FPl = Fraction of terrestrial planets with carbon-based life

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18. 18 Planet Detection

19. 19 Detectability of the Solar System Precision: 3 m/s Saturn saturn

20. 20 Mayor & Queloz 1995, Nature, 378, 355. Marcy & Butler 1996, Ap.J.Lett., 464, L147. ~

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25. 25 Sagittarius Window Eclipsing Extrasolar Planet Search

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52. 52 An optical/near-infrared space telescope with a filled aperture of at least 8-meters will probably be required to definitively answer the question “Are we alone?” HST 2.4-mJWST 6.5-mATLAST 8-mATLAST 16-m

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63. 63 Life in the Universe All Life Liquid water Carbon -based Chemical Energy

64. 64 A thermodynamic disequilibrium An environment capable of maintaining links between carbon, hydrogen, and other atoms A liquid environment A molecular system that can support Darwinian evolution.

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71. 71 Total number of stars >100 billion Total number of planets ~ several trillion ? Total number of moons ~ 10s of trillions ? Earthlike Planets?.01% = 1 billion??

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