1 / 33

Signatures of Exoplanets HD209458b: a Hot Jupiter Orbiting a Bright Star

Signatures of Exoplanets HD209458b: a Hot Jupiter Orbiting a Bright Star. Sara Seager Carnegie Institution of Washington. Image credit: NASA/JPL-Caltech/R. Hurt (SSC). Signatures of Exoplanets HD209458b: a Hot Jupiter Orbiting a Bright Star. Introduction Models Data HD209458b Near Future.

tilly
Download Presentation

Signatures of Exoplanets HD209458b: a Hot Jupiter Orbiting a Bright Star

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Signatures of ExoplanetsHD209458b: a Hot Jupiter Orbiting a Bright Star Sara Seager Carnegie Institution of Washington Image credit: NASA/JPL-Caltech/R. Hurt (SSC)

  2. Signatures of ExoplanetsHD209458b: a Hot Jupiter Orbiting a Bright Star IntroductionModelsDataHD209458bNear Future

  3. The Solar System 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

  4. Solar System at 10 pc Fp/F* = p Rp2/a2 Fp/F* = Tp/T* Rp2/R*2 = (R*/2a)1/2[f(1-A)]1/4 Star Hot Jupiters J V E M Seager 2003

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

  6. Transiting Planets • Transit [Rp/R*]2 ~ 10-2 • Transit radius • Emission spectraTp/T*(Rp/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[Rp/a]2~10-5 • Albedo, phase curve • Scattering atmosphere Before direct detection Seager, in preparation

  7. 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

  8. Signatures of Exoplanets Introduction Models Data HD209458b Near Future

  9. Hot Jupiter Spectra Seager et al. 2000 • Teff = 900 - 1700 K • Major absorbers are H2O, CO, CH4, Na, K, H2 Rayleigh scattering • High temperature condensate clouds may be present: MgSiO3, Fe • Scattered light at visible wavelengths • Thermal emission at IR wavelengths See also Barman et al. 2001, Sudarsky et al. 2003, Burrows et al. 2005, Fortney et al 2005, Seager et al. 2005

  10. Giant PlanetSpectra 20 pc 0.05AU 0.1 AU 0.5 AU • 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.

  11. 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

  12. Photochemistry Karkoschka Icarus 1994 • Jupiter and Saturn have hydrocarbon hazes--mute the albedo and reflection spectrum • Hot Jupiters have 104 times more UV flux = more hydrocarbons? • Much higher hydrocarbon destruction rate • normal bottleneck reaction is fast • less source from CH4 • additional consequence: huge H reservoir from H2O Liang, Seager et al. ApJL 2004 Liang et al. ApJL 2003

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

  14. Signatures of Exoplanets Introduction Models Data HD209458b Near Future

  15. Hot Transiting PlanetsOrbiting Bright Stars • Transit [Rp/R*]2 ~ 10-2 • Transit radius • Emission spectraTp/T*(Rp/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[Rp/a]2~10-5 • Albedo, phase curve • Scattering atmosphere Pushing the limits of telescope instrumentation Seager, in preparation

  16. Thermal Emission: Spitzer 24 micron flux • Secondary eclipse • Thermal emission detected at 24 m • Direct measurement of planetary flux • Brightness temperature at 24 m is derived 1130 +/- 150 K • Deming, Seager, Richardson, Harrington 2005

  17. Thermal Emission: NASA IRTF 2.2 m Constraint • Secondary eclipse • Spectral peak at 2.2 m due to H2O 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 Richardson, et. al., in prep

  18. Reflected Light: MOST Geometric Albedo Upper Limit • Geometric albedo preliminary upper limit is 0.4 • Jupiter’s geometric albedo in the MOST bandpass is 0.5 • Bond albedo is almost 1.5 x lower than the geometric albedo for the solar system gas giant planets

  19. 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)

  20. Signatures of Exoplanets Introduction Models Data HD209458b Near Future

  21. HD209458b: Interpretation I • Basic picture is confirmed • Thermal emission data • T24 = 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

  22. HD209458b: Interpretation II • Models are required to interpret 24 m data • H2O opacities shape spectrum • T24 is not the equilibrium T • T24 = 1130 +/- 150 K • A wide range of models match the 24 m flux/T • Teq is a global parameter of model • Energy balance, albedo, circulation regime • E.g. Teq = 1700 K implies that AB is low and absorbed energy is reradiated on the day side only

  23. HD209458b: Interpretation II • Models are required to interpret 24 m data • H2O opacities shape spectrum • T24 is not the equilibrium T • T24 = 1130 +/- 150 K • A wide range of models match the 24 m flux/T • Teq is a global parameter of model • Energy balance, albedo, circulation regime • E.g. Teq = 1700 K implies that AB is low and absorbed energy is reradiated on the day side only

  24. HD209458b: Interpretation III • Models with strong H2O absorption ruled out • Hottest models are ruled out • Isothermal hot model is ruled out by T24 = 1130 +/- 150 K • Steep T gradient hot model would fit T24 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 T24--doesn’t cross cloud condensation curves • Confirmed by MOST

  25. HD209458b: Interpretation III • Beyond the “standard models” • Low H2O abundance would fit the data • C/O > 1 is one way to reach this • See Kuchner and Seager 2005

  26. HD209458b C/O > 1

  27. 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

  28. Signatures of Exoplanets Introduction Models Data HD209458b Near Future

  29. Near Future Data from Seager et al. 2005

  30. Signatures of ExoplanetsHD209458b: a Hot Jupiter Orbiting a Bright Star 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

  31. Extrasolar Planet Discovery Timeline • Past • 1992 pulsar 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!

  32. HD209458b Exosphere Detection • 15% deep Lyman alpha transit 4.3RJ • Requires exospheric temperature ~ 10,000K! • High exospheric temperatures on solar system giant planets are not well understood (order of magnitude) • XUV heating (Lammer 2003) a first step • Upper atmospheric T, atmospheric expansion, and mass loss are coupled • If significant mass loss, how does it affect the atmospheric signature? • No UV followup measurements possible

  33. Tracer Temp pv Cho et al. ApJL 2003 Atmospheric Circulation • Tidally locked hot Jupiters; but simple day/night picture is naive • Spectral signatures depend on T and T gradient • Chemical species will be transported • Not yet incorporated into radiative transfer models Showman & Guillot A&A 2002

More Related