Lecture III: Gas Giant Planets 1.From Lecture II: Phase separation 2.Albedos and temperatures 3.Observed transmission spectra 4.Observed thermal spectra 5.Observations of reflected light

H + He + rocky core Mass-Radius Plot for Hot Jupiters H + He

Its current luminosity is ~50% greater than predicted by models that work for Jupiter: A Problem with Saturn ?... Fortney & Hubbard (2004) If modelled like Jupiter, Saturn reaches its current T eff (luminosity) in only 2 Gyr !

 One idea for resolving the discrepancy - phase separation of neutral He from liquid metallic H (Stevenson & Salpeter 1977): for a saturation number fraction of the solute (He), phase separation will occur when the temperature drops below T : x = exp (B - A/kT) where x=0.085 (solar comp., Y=0.27), B=const.(~0), A~1-2 eV (pressure- dependent const.), therefore T = 5, ,000 K A Problem with Saturn ?…

Phase diagram for H & He: A Problem with Saturn ?... Fortney & Hubbard (2004) Model results: Stevenson (‘75) vs. Pfaffenzeller et al. (‘95) - different sign for dA/dP !

New models: A Problem with Saturn ?... Fortney & Hubbard (2004) Model results: The modified Pfaffenzeller et al. (‘95) phase diagram resolves the discrepancy. Good match to observed helium depletions in the atmospheres of Jupiter (Y=0.234) & Saturn (Y~0.2).

Cooling curves: Evolution Models of Exo-planets: Fortney & Hubbard (2004) Models: All planets have 10 M E cores & no irradiation. The models with He separation have ~2 x higher luminosities.

H + He + rocky core Mass-Radius Plot for Hot Jupiters H + He

Atmosphere: In general - outer boundary for planet’s thermal evolution - the extrasolar planets have introduced conditions which had never been modeled. Clouds & (photo)chemistry Evaporation (very hot & hot Jupiters) Transits make easier the spectroscopic studies of a planet’s atmosphere.

Albedos Rowe et al.(2006)

HD b Albedos New upper limit on A g Rowe et al.(2006) (Rowe et al. 2008)

Models Constraints sigma limit – or - ~ sigma limit Spitzer Limit Different atmospheres blackbody model Rowe et al Rowe et al. (in prep) best fit Equilibrium Temperature

The Close-in Extrasolar Giant Planets Type and size of condensate is important Possibly large reflected light in the optical Thermal emission in the infrared Seager & Sasselov 2000

Atmosphere: What is special about atomic Na and the alkali metals? Seager & Sasselov (2000)

Atmosphere: Theoretical Transmission Spectra of HD b Wavelength (nm) Occulted Area (%) Seager & Sasselov (2000)

Atmosphere: The tricks of transmission spectroscopy: Brown (2001)

The actual detection (with the HST): a 5  signal 2x weaker than model expected, but within errors Might indicate high clouds above terminator, but … Charbonneau et al. (2002)

Direct Detection of Thermal Emission

Model Constraints Deming et al Spitzer Limit T b = 1130 K Different atmospheres blackbody model HD b Equilibrium Temperature

Spectra Four observed data points vs. models Burrows, Sudarsky, & Hubeny (2006)

Infrared Eclipses in HD : Measuring the Emitted Heat Time (in fraction of day) Orbital phase Relative Intensity or Brightness Detection (Feb. 20, 2006) by Deming et al. using the Spitzer Space Telescope

Variability in IR Eclipse Depths Rauscher et al. (2006) Temperature map of a partially eclipsed face of HD209458b in a model with 400 m/s winds.

Variability in IR Eclipse Depths Rauscher et al. (2006) Temperature map of a partially eclipsed face of HD209458b in a model with 400 m/s winds.

 And b The Spitzer IR photometry at 24 micron: A) Raw data B) Corrected for zodiacal foreground Harrington, et al. (2006)

 And b The Spitzer IR photometry at 24 micron fit to a model Harrington, et al. (2006)

Lecture II: Observed Spectra of EGPs 1.Albedos and temperatures 2.Observed transmission spectra 3.Observed thermal spectra 4.Observations of reflected light

Observations for Reflected Light ● Sudarsky Planet types  I : Ammonia Clouds  II : Water Clouds  III : Clear  IV : Alkali Metal  V : Silicate Clouds ● Predicted Albedos:  IV : 0.03  V : 0.50 Sudarsky et al Picture of class IV planet generated using Celestia Software

Photometric Light Curves Micromagnitude variability from planet phase changes Space-based: MOST (~2005), COROT (~2007), Kepler (~2008)  m=2.5 (R p /D) 2 2/3/  (sin(  ) + (  -  )cos(  ))

Scattered Light Need to consider: phase function multiple scattering

Scattering Phase Functions and Polar Plots Seager, Whitney, & Sasselov 2000 Forward throwing & “glory” MgSiO 3 (solid), Al 2 O 3 (dashed), and Fe(s)

Scattered Light Changes with Phase Seager, Whitney, & Sasselov nm

Mission  Microvariability and Oscillations of STars / Microvariabilité et Oscillations STellaire  First space satellite dedicated to stellar seismology  Small optical telescope & ultraprecise photometer  goal: ~ few ppm = few micromag MOST at a glance Canadian Space Agency (CSA)

 circular polar orbit  altitude h = 820 km  period P = 101 min  inclination i = 98.6º  Sun-synchronous  stays over terminator  CVZ ~ 54° wide  -18º < Decl. < +36º  stars visible for up to 8 wks  Ground station network  Toronto, Vancouver, Vienna MOST at a glance MOST orbit normal vector to Sun CVZ = Continuous Viewing Zone Orbit

Lightcurve Model for HD b ● Relative depths  transit: 2%  eclipse: 0.005% ● Duration  3 hours ● Phase changes of planet Phase Relative Flux EclipseTransit

The Lightcurve from MOST 45 days 0.03 mag ● 2004 data : 14 days, 4 orbital cycles ● 2005 data : 45 days, 12 orbital cycles ● duty cycle : ~90% ● observations ● 3 mmag point-to-point precision 2005 observations, 40 minute binned data

0.1 mag 0.02 mag 0.8 mmag

Albedo Results ● Best fit parameters:  Albedo : 0.07 ± 0.05  stellar radius : ± R Jup ● Other Parameters:  stellar mass: M sun  inclination:  period : days see Knutson et al Geometric Albedo Radius (Jupiter) 1,2,3 sigma error contours Rowe et al. (in prep)

Atmospheres MOST bandpass Geometric Albedo ● HD b is darker than Jupiter ● Rule out class V planet with bright reflection silicon clouds Marley et al. 1999

HD b Albedos New upper limit on A g Rowe et al.(2006) (Rowe et al. 2007)