Havard Center for Astrophysics
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Havard Center for Astrophysics

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  • How do we discover planets orbiting other stars? Direct detection still does not work. The most successful methods are indirect - Doppler shift wobble of the star due to the gravitational pull of the planet(s) and the transit method.
  • Here is the full light curve of hot Jupiter HD189733b showing both the transit and the secondary eclipse (in infrared light). The wavelike change between transit and eclipse is due to changing thermal emission from the planet - allowing to map its surface. Spitzer 8 micron observations.
  • Just to remind you, that this transiting planet was first discovered by the standard spectroscopic “wobble” technique, and only afterwards were transits detected.
  • .
  • Here is the full light curve of hot Jupiter HD189733b showing both the transit and the secondary eclipse (in infrared light). The wavelike change between transit and eclipse is due to changing thermal emission from the planet - allowing to map its surface. Spitzer 8 micron observations.

Havard Center for Astrophysics Presentation Transcript

  • 1. The Search for Life in the Universe Dimitar Sasselov Department of Astronomy Harvard Origins of Life Initiative
  • 2. Planets orbiting other stars: 340 planets 30 multiple planet systems discovered as of Feb. ‘09
  • 3. The Planets - our Solar System
  • 4. Super-Earths Rocky vs. Ocean
  • 5. Super-Earths vs. Super-Neptunes (Sasselov 2008) Image: S.Cundiff
  • 6. Direct Detection of Planets
    • Direct detection is challenging because of the technical
    • limits of
    • telescopic
    • observations
  • 7. Direct Detection of Planets
    • Three planets
    • orbiting HR8799
    (Marois et al. 2008)
  • 8. Transits: A Method for Planet Discovery and Study
    • Please see YouTube video:
    • http://www.youtube.com/watch?v=Pc3M7on9gwU
  • 9. Transit & eclipse of HD189733b Heather Knutson & Dave Charbonneau (2007)
  • 10. What can we learn from transiting extrasolar planets HD 209458b: Dimming of light due to transit, observed with HST. Brown, Charbonneau, Gilliland, Noyes, Burrows (2001) Tells us DIRECTLY: Planet radius, INDIRECTLY: Planet density Planet composition
  • 11. The HAT Network: FLWO Mt.Hopkins & Hawaii ( Bakos et al. 2006 )
  • 12. A New super-Neptune: HAT-P-11b Bakos, Noyes, Pal, Latham, Sasselov et al. (2009)
  • 13. Super-Earths: vs. Super-Neptunes (Sasselov 2008) Image: S.Cundiff
  • 14. Model: Seager & Sasselov 2000 Detection: Charbonneau et al 2002
  • 15. A study of an extrasolar planet Spitzer Telescope data: Heather Knutson, Charbonneau et al. (2007)
  • 16. Direct Detection of Thermal Emission Infrared Eclipses of Hot Jupiters: Spitzer Space Telescope
  • 17. New 2  m Spectrum for HD 189733b (Swain et al. 2008)
  • 18. NASA Kepler mission: transit search for planets Cygnus / Lyra (RA=19h23m, Dec=44.5d)
  • 19. KEPLER: Search for Earth Twins GOAL: to discover ~30 Earths and ~300 super-Earths in habitable zones; NASA Mission - launch in 2009 Transit Search: ~150,000 stars Can detect planets like our Earth
  • 20. Completing the Copernican Revolution: the discovery of “New Earth” NASA Mission - Mar. 2009
  • 21. Kepler is ready to launch: Mar. 5, 2009 Assembly at Ball Aerospace Kepler expected yields: ~ 300 super-Earths, ~ 30 Earth analogs; (5-10% good radii)
  • 22. Kepler is ready to launch: Mar. 5, 2009 Assembly at Ball Aerospace Kepler expected yields: ~ 300 super-Earths, ~ 30 Earth analogs; (5-10% good radii)
  • 23. New Earths Facility
    • Discovery and Surface Conditions on Earth-like planets.
    • Synergy with NASA Kepler :
    • which pinpoints exo-Earths and
    • measures radii - we measure mass &
    • mean density, hence composition!
    • HARPS-NEF spectrograph:
    • An ongoing Harvard/SAO/Geneva
    • collaboration.
    • Femtosecond laser astro-comb -
    • a breakthrough in calibration
  • 24. Summer 07 : Ti:sapphire femtosecond laser comb Fall 2007 : characterize with astro spectrograph 2008 : develop high-rep rate comb for astro applications and demo on mountain-top 2009 : Optimized system for 1 cm/s Doppler shift precision Harvard/Smithsonian/MIT astro-comb project Li et al. (2008, Nature, Apr.)
  • 25. Do super-Earths have a high habitability potential ? (as compared to 1 M Earth planets)
    • Yes:
      • many (though, not all) are expected to have same geophysics & geochemistry as Earth;
      • have stable surface conditions -
        • keep atmospheres easily;
        • have plate tectonics, hence stable geo-cycles;
        • stable dynamics (orbits & rotation).
  • 26. Super-Earths geochemistry, e.g. the Carbonate-silicate cycle, or Sulfur cycle, etc. Planets of different initial conditions are “driven” to a set of geochemical equilibria by global geo-cycles over geological timescales. e.g., Halevy & Schrag (2008)
  • 27.  
  • 28. Bernard de Fontenelle “ Conversations on the Plurality of Worlds” (1686)
  • 29. Diversity from Uniformity
    • All life on Earth shares the same
    • system of molecules and basic processes -
    • the unity of biochemistry .
    • Despite its amazing diversity!
  • 30. The Tree of Life (G. Klimt)
  • 31. What is the diversity of planets ? Does it imply a diversity of possible biochemistries ? The two main questions:
  • 32. The Plurality of Worlds ?
  • 33. Summary
    • Our team’s ambition : - to be the place where the first Earth-like planets are discovered and studied, and to complete the Copernican Revolution.
    • To begin writing the next chapter - what is life’s place in the universe?
    Origins of Life: the Planetary Perspective
  • 34. Life as a planetary phenomenon