1. Edmund Bertschinger MIT Department of Physics and Kavli Institute for Astrophysics and Space Research We are not alone: Other planets, other earths?

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3. 3 Earth and Mars – or Mars and Earth? Mars is drier than the Atacama (or Sahara) desert.

4. 4 Life on Mars? R. Villard, STScI

5. 5 Martian Meteorite found in Antarctica McKay et al. 1996: carbonate globules – evidence for microbial life? Lunar and Planetary Institute

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7. 7 Methane rivers and oceans on Titan (Huygens lander, European Space Agency)

8. 8 Family Portrait: 4 rocky planets, 2 gas giants, 2 ice giants

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10. 10 Planets around other stars: exoplanets After 10 years of study, 170 known (California- Carnegie Planet Search, G. Marcy)

11. 11 How to find other planetary systems Doppler measurement of stellar wobble: planets’ gravity pulls on star

12. 12 Figure from California-Carnegie Planet Search First success: 1995, Mayor and Queloz

13. 13 How to find other planetary systems Transit: planet passes in front of star, dims the light a tiny amount

14. 14 Both the Doppler and Transit methods can much more easily find close-in, Jupiter mass planets than earth-like planets

15. 15 How to find other planetary systems Infrared emission from dusty disks

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17. 17 How to find other planetary systems Direct imaging

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19. 19 How to find other planetary systems Gravitational Microlensing

20. 20 The gravity of a planet orbiting a star causes light rays to bend, changing the amount of light reaching the earth. Background star Enhanced image at earth 25 January 2006: the star OGLE-2005-BLG-390L has a planet of mass about 5 earth masses, in a 10-year orbit!

21. 21 Family Comparison

22. 22 Family Comparison R. Villard, STScI

23. 23 What have we learned? At least a few percent of sunlike stars have massive planets

24. 24 What have we learned? Surprise: “Hot Jupiters” on wildly eccentric orbits (California -Carnegie Planet Search)

25. 25 What have we learned? Stars with more heavy elements are more likely to host planets (California -Carnegie Planet Search)

26. 26 What have we learned? Some planets likely have right conditions for liquid water (it’s 300K in here!)

27. 27 J.F. Kasting et al. Habitable zone for life Darren Williams, Penn State Erie

28. 28 J.F. Kasting et al. Extrasolar planets Habitable zone for life Darren Williams, Penn State Erie

29. 29 Future: search for earthlike planets and life Kepler: 2008 launch scheduled Search method: transits European Corot mission may scoop US. Terrestrial Planet Finder: 2015 or later Atmospheric Spectroscopy

30. 30 Additional Credits and Information Credits: Water on Mars: antwrp.gsfc.nasa.gov/apod/ - Astronomy Picture of the Day Sahara Desert and Mars: Lunar and Planetary Institute “Hubble detects a transiting planet” and Beta Pictoris images: Space Telescope Science Institute Black hole embedding diagram: Scott Hughes, MIT Figures showing Mean Orbital Distance created online at http://extrasolar.net/charts.asp Kepler and TPF: NASA/Jet Propulsion Laboratory Books: Origins: Fourteen Billion Years of Cosmic Evolution, Neil deGrasse Tyson and Donald Goldsmith Earth: An Intimate History, Richard Fortey The Ancestor’s Tale: A Pilgrimage to the Dawn of Evolution, Richard Dawkins

31. 31 Websites for more information Extrasolar.net – General information about exoplanets Exoplanets.org – California-Carnegie exoplanet searches www.astrobio.net - Astrobiology Solstation.com – General astronomy information, sky maps antwrp.gsfc.nasa.gov/apod/ - Astronomy Picture of the Day