1. Towards a Physical Characterization of Extrasolar Planets Sara Seager Carnegie Institution of Washington Image credit: NASA/JPL-Caltech/R. Hurt (SSC)

2. Towards a Physical Characterization of Extrasolar Planets Transiting Planets Models Data HD209458b Near Future Earths

3. Planet sizes are to scale. Separations are not. Characterizing extrasolar planets: very different from solar system planets, yet solar system planets are their local analogues The Solar System

4. Known Extrasolar Planets Based on data compiled by J. Schneider (As of 24 MAY 2005)

5. Direct Detection Challenge Nearby M dwarf star with brown dwarf companion Jupiter would be  10 x closer in  1 million times fainter Gliese 229 and 229B - Hubble Space Telescope (Kulkarni, Golimowski, NASA)

6. Star J M V E Seager 2003 Hot Jupiters F p /F * = p R p 2 /a 2 F p /F * = T p /T * R p 2 /R * 2 = (R * /2a) 1/2 [f(1-A)] 1/4 Solar System at 10 pc

7. a Zone where transit can be seen from Geometric Transit Probability P ~ (R * /a) P(0.05 AU) = 10% P(1 AU) = 0.5% P(5 AU) = 0.1 % 1 radial velocity planet is known to transit its star

8. Transiting planets allow us to move beyond minimum mass and orbital parameters without direct detection. HD209458b. November 1999. Lynnette Cook. Venus. Trace Satellite. June 8 2004. Schneider and Pasachoff. Mercury. Trace Satellite. November 1999. Transiting Planets

9. Planet Transit Surveys Survey thousands of stars simultaneously Measure drop in starlight due to transiting planet Huge number of false positives Over 20 groups running planet transit surveys Require radial velocity followup to determine mass Six short-period planets successfully discovered Two OGLE transiting planets.

10. Planet Transit Surveys Survey thousands of stars simultaneously Measure drop in starlight due to transiting planet Huge number of false positives Over 20 groups running planet transit surveys Require radial velocity followup to determine mass Six short-period planets successfully discovered Two OGLE transiting planets. Brown et al. ApJ 2001

11. Why Transiting Planets? Planetary bulk composition  H-He gas giant?  Super Earth?  Water world?  Rocky planet? Evolutionary history  HD 209458b -- too big!  HD 149026 -- too small! Courtesy Jeremy Richardson

12. Seager, in preparation Transiting Planets Transit [R p /R * ] 2 ~ 10 -2  Transit radius Emission spectra T p /T * (R p /R * ) 2 ~10 -3  Emitting atmosphere  ~2/3  Temperature and  T Transmission spectra [atm/R * ] 2 ~10 -4  Upper atmosphere  Exosphere (0.05-0.15) Reflection spectra p[R p /a] 2 ~10 -5  Albedo, phase curve  Scattering atmosphere  Polarization Before direct detection

13. Compelling Questions for Hot Jupiter Atmospheres Do their atmospheres have ~ solar composition?  Or are they metal-rich like the solar system planets?  Has atmospheric escape of light gases affected the abundances? Are the atmospheres in chemical equilibrium?  Photoionization and photochemistry? How is the absorbed stellar energy redistributed in the atmosphere?  Hot Jupiters are tidally locked with a permanent day side  And are in a radiation forcing regime unlike any planets in the solar system

14. Towards a Physical Characterization of Exoplanets Transiting Planets Models Data HD209458b Near Future Earths

15. Giant Planet Spectra dI(s, , )/ds = -  (s, )I(s, , ) + j(s, , );  (s, ) ~ T,P; T,P ~ I(s, , ); 1D models Governed by opacities “What you put in is what you get out” Seager, in preparation FKSI Danchi et al. 20 pc 0.05AU 0.1 AU 0.5 AU

16. Hot Jupiter Spectra Scattered light at visible wavelengths Thermal emission at IR wavelengths Teff = 900 - 1700 K H 2 O, CO, CH 4, Na, K, H 2 Rayleigh scattering High T condensate clouds? MgSiO 3, Fe? See also Barman et al. 2001, Sudarsky et al. 2003, Burrows et al. 2005, Fortney et al 2005, Seager et al. 2005 Seager et al. 2000

17. Clouds Spectra of every solar system body with an atmosphere is affected by clouds For extrasolar planets1D cloud models are being used Cloud particle formation and subsequent growth based on microphysical timescale arguments Cloud models have their own uncertainties Homogenous, globally averaged clouds Marley et al. 1999 Ackerman & Marley, Cooper et al. 2003; Lunine et al. 2001

18. Liang, Seager et al. ApJL 2004 Liang et al. ApJL 2003 Photochemistry Jupiter and Saturn have hydrocarbon hazes--mute the albedo and reflection spectrum Hot Jupiters have 10 4 times more UV flux = more hydrocarbons? Much higher hydrocarbon destruction rate  normal bottleneck reaction is fast  less source from CH 4  additional consequence: huge H reservoir from H 2 O Karkoschka Icarus 1994

19. Large Range of Parameters Forward problem is straightforward despite uncertainties Clouds  Particle size distribution, composition, and shape  Fraction of gas condensed  Vertical extent of cloud Seager et al. 2000 Opacities Non-equilibrium chemistry Atmospheric circulation of heat redistribution Internal luminosities (mass and age dependent)

20. Towards a Physical Characterization of Exoplanets Transiting Planets Models Data HD209458b Near Future Earths

21. Observations of HD 209458 b Na (Charbonneau et al. 2001) Lyman-alpha (Vidal-Madjar et al. 2003) C and O* (Vidal-Madjar et al. 2004) CO upper limit (Deming et al. 2005a) Thermal emission 24  m (Deming et al. 2005) TrES-1 at 4.5 and 8  m (Charbonneau et al 2005) CH 4 upper limit 3.6  m (Richardson et al. 2003a) H 2 O upper limit 2.2  m (Richardson et al. 2003b) MOST albedo upper limit (Rowe et al. 2005) Primary EclipseSecondary Eclipse

22. Thermal Emission  Detected from two transiting planets during secondary eclipse  Brightness T  HD 209458 b 24  m  1130 +/- 150 K  TrES-1 4.5 and 8  m  1010 +/- 60 K/1230 +/- 110 K  Opens the door for many more measurements Deming, Seager, Richardson, Harrington 2005 Charbonneau et al. 2005

23. Richardson, et. al., in prep Thermal Emission: NASA IRTF 2.2  m Constraint Secondary eclipse Spectral peak at 2.2  m due to H 2 O and CO Data from NASA IRTF  R = 1500  Richardson, Deming, Seager 2003; Differential measurement only Upper limit of the band depth on either side of the 2.2 micron peak is 1 x 10 -4 or 200  Jy

24. Transmission Spectra: HST STIS and Keck Probes planetary limb Na (Charbonneau et al. 2002) CO upper limit (Deming et al. 2005)  Consistent with high clouds  Or low Na and CO abundance H Lyman alpha ( Vidal-Madjar et al. 2003)

25. Transmission Spectra: HD209458b Exosphere 15% deep Lyman alpha transit 4.3R J Requires exospheric T ~ 10,000K! High exospheric T on solar system giant planets are not well understood (order of magnitude) EUV heating Upper atmospheric T, atmospheric expansion, and mass loss are coupled Escape rates are high but atmosphere is stable over billions of years No UV followup possible

26. Secondary Eclipse: Albedo Upper Limit from MOST Microvariability and Oscillations of STars Space-based photometer for stellar seismology and exoplanet studies - ppm photometry “Suitcase” in space  54 kg, 60x60x30  15-cm telescope  Single broadband filter  380 ≤ λ ≤ 750 nm Launch 30 June 2003  Russian Rockot = old ICBM Cost  Can$10M US$7M Euro$6M PI Jaymie Matthews UBC

27. Secondary Eclipse: Albedo Upper Limit from MOST Microvariability and Oscillations of STars Space-based photometer for stellar seismology and exoplanet studies - ppm photometry “Suitcase” in space  54 kg, 60x60x30  15-cm telescope  Single broadband filter  380 ≤ λ ≤ 750 nm Launch 30 June 2003  Russian Rockot = old ICBM Cost  Can$10M US$7M Euro$6M PI Jaymie Matthews UBC

28. MOST Albedo Upper Limit HD209458 b albedo < 0.25 (1  ) in the MOST bandpass Jupiter’s albedo is 0.5 HD 209458 b is dark! MOST will reach 0.13 in current observing campaign Rowe et al. 2005

29. Towards a Physical Characterization of Exoplanets Transiting Planets Models Data HD209458b Near Future Earths

30. HD209458b: Interpretation I Basic picture is confirmed Thermal emission data  T 24 = 1130 +/- 150 K  The planet is hot!  Implies heated from external radiation Transmission spectra data  Presence of Na A wide range of models fit the data Seager et al. 2005

31. HD209458b: Interpretation II Models are required to interpret 24  m data  H 2 O opacities shape spectrum T 24 is not the equilibrium T  T 24 = 1130 +/- 150 K  A wide range of models match the 24  m flux/T T eq is a global parameter of model  Energy balance, albedo, circulation regime  E.g. T eq = 1700 K implies that A B is low and absorbed energy is reradiated on the day side only

32. HD209458b: Interpretation II Models are required to interpret 24  m data  H 2 O opacities shape spectrum T 24 is not the equilibrium T  T 24 = 1130 +/- 150 K  A wide range of models match the 24  m flux/T T eq is a global parameter of model  Energy balance, albedo, circulation regime  E.g. T eq = 1700 K implies that A B is low and absorbed energy is reradiated on the day side only

33. HD209458b: Interpretation III Models with strong H 2 O absorption ruled out Hottest models are ruled out  Isothermal hot model is ruled out by T 24 = 1130 +/- 150 K  Steep T gradient hot model would fit T 24 but is ruled out by 2.2  m constraint Coldest models are ruled out  High albedo required--very unusual  Cold isothermal model required to fit T 24 --doesn’t cross cloud condensation curves  Confirmed by MOST

34. HD209458b: Interpretation III Beyond the “standard models”  Low H 2 O abundance would fit the data  C/O > 1 is one way to reach this  See Kuchner and Seager 2005 Solar System giant planets have 3x solar metallicity  Jupiter may have C/O >~ 1, but spectra look similar to C/O=0.5

35. HD209458b C/O > 1

36. HD209458b Interpretation Summary Data for day side  Spitzer 24 microns  IRTF 2.2 micron constraint  MOST albedo upper limit A wide range of models fit the data  Confirms our basic understanding of hot Jupiter atmospheric physics Some models can be ruled out  Hot end of temperature range  Cold end of temperature range  Any model with very strong H2O absorption at 2.2 microns Non standard models  C/O > 1 could fit the data

37. Towards a Physical Characterization of Exoplanets Transiting Planets Models Data HD209458b Near Future Earths

38. Seager, in preparation Hot Transiting Planets Orbiting Bright Stars Transit [R p /R * ] 2 ~ 10 -2  Transit radius Emission spectra T p /T * (R p /R * ) 2 ~10 -3  Emitting atmosphere  ~2/3  Temperature and  T Transmission spectra [atm/R * ] 2 ~10 -4  Upper atmosphere  Exosphere (0.05-0.15) Reflection spectra p[R p /a] 2 ~10 -5  Albedo, phase curve  Scattering atmosphere Pushing the limits of telescope instrumentation

39. Near Future Data from Seager et al. 2005

40. Near Future Data New transiting planets orbiting bright stars HD 209458 b  Spitzer thermal emission 3.6, 4.5, 8, 10 microns  HST/STIS primary transit  MOST albedo limit  HST/NICMOS: H 2 O Spitzer  3 transiting planets orbiting bright stars  6 non-transiting planets SOFIA, Kepler, JWST Cho et al. ApJL 2003 Tracer pv Temp

41. Hot Super Earths New Super Earths  M=7.5 M E, P=1.9d, Rivera et al. 2005  Msini =14 M E, P=9.5d, Santos et al. 2004  M=18M E, P=2.8d, 4-planet system,McArthur et al. 2004  Msini=21M E, P=2.6d, M star, Butler et al. 2004 Solar System planet masses  Uranus: 17.2 M E  Neptune: 14.6 M E  Jupiter: 318 M E  Saturn 95 M E What is the nature of these planets?? An Artist's depiction of the new planet orbiting Gliese 436. Credit: NASA/JPL. Credit: NASA/JPL.

42. Towards a Physical Characterization of Exoplanets Transiting Planets Models Data HD209458b Near Future Earths

43. Are We Alone? Are there Earth-like planets? Are they common? Do they harbor life?

44. Evolution of the planetary atmosphere is determined by many factors: atmospheric escape gas-surface reactions spectral energy distribution of host star geologic activity initial volatile inventory active biology atmospheric circulation will drive climate But, Venus and Earth look the same to Kepler and SIM Terrestrial Planets

45. Find and characterize Earth-like planets around nearby stars Need to null out parent star by 10 6 to 10 10 Look for biomarker gases Launch date: 2014 TPF-C 2019 TPF-I mid-IR spectra NASA’s Terrestrial Planet Finder

46. Woolf, Smith, Traub, Jucks, ApJ, 2002 Modeling 1D Earth spectra is made easier by the right input data! Earth as an Extrasolar Planet

47. rotational period weather presence of oceans reconstruct map? Ford, Seager, & Turner, Nature 2001 High contrast between land and ocean causes changes in flux Earth as an Extrasolar Planet

48. S. Seager Institute for Advanced Study, Princeton, July 2002 Vegetation as a Surface Biomarker

49. S. Seager Vegetation as a Surface Biomarker

50. Surface Biosignature Chlorophyll causes strong absorption blueward of 0.7  m Light scattering in air gaps between water- filled plant cells causes strong red reflectance Plants absorb energy at short wavelengths for photosynthesis; reflect and transmit radiation at long wavelengths for thermal balance Reflection favored over transmission? CO 2 more accessible to plants with airgaps Photosynthetic plants cause a global spectral signature even though Earth is not completely plant covered Clark 1993; Seager et al. 2004

51. Woolf, Smith, Traub, Jucks, ApJ, 2002 Modeling 1D Earth spectra is made easier by the right input data! Earth as an Extrasolar Planet

52. Beyond Earth PaleoEarth  Large amount of CH 4 ?  Snowball Earth  Pangea  Early faint sun paradox Sun was 30% cooler 4 billion years ago  CH 4 ? NH 3 ? CO 2 ? Varying orbital and physical planet parameters  Rotation rates, obliquities, eccentricities  Surface temperatures? Cloud cover fractions and patterns? Spectral signatures? Kristine Bryan Pangea: 225 million years ago Cho and Seager in prep

53. Towards a Physical Characterization of Extrasolar Planets Transiting planet atmospheres can be characterized without direct detection Models are maturing, ideas beyond the solar abundance, chemical equilibrium models are being considered A growing data set for HD209458b

54. Extrasolar Planet Discovery Timeline Past 1992pulsar planet 09/1995 Doppler extrasolar planet discoveries take off 11/1999 extrasolar planet transit 11/2001 extrasolar planet atmosphere 1/2003 planet discovered with transit method 4/2004 planet discovered with microlensing method Present 2005 transit planet discoveries take off 2005 transit planet day side temperature 2005 hot Jupiter albedo Future 2008 hundreds of hot Jupiter illumination phase curves 2011 Frequency of Earths and super earths 2016 First directly detected Earth-like planet 2025 Unthinkable diversity of planetary systems!