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Lecture III: Gas Giant Planets
1. From Lecture II: Phase separation2. Albedos and temperatures3. Observed transmission spectra
4. Observed thermal spectra
5. Observations of reflected light
Its current luminosity is ~50% greater than predictedby models thatwork for Jupiter:
A Problem with Saturn ?...
Fortney & Hubbard (2004)
If modelled like Jupiter,Saturn reaches its currentTeff (luminosity) in only2 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 - 10,000 K
A Problem with Saturn ?…
Phase diagram for H & He:
A Problem with Saturn ?...Fortney & Hubbard (2004)
Model results:
Stevenson (‘75)vs.Pfaffenzelleret al. (‘95) -
different signfor dA/dP !
New models:
A Problem with Saturn ?...Fortney & Hubbard (2004)
Model results:
The modified Pfaffenzelleret al. (‘95) phase diagramresolves the discrepancy.
Good match to observedhelium depletions in theatmospheres of Jupiter (Y=0.234) & Saturn (Y~0.2).
Cooling curves:
Evolution Models of Exo-planets:Fortney & Hubbard (2004)
Models:
All planets have 10 ME
cores & no irradiation.
The models with Heseparation have ~2 xhigher luminosities.
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.
Models Constraints
2004 1 sigma limit – or - ~2005 3 sigma limit
Spitzer Limit
Different atmospheres
blackbody
model
Rowe et al. 2006Rowe et al. (in prep)
best fit
Equili
bri
um
Tem
pera
ture
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
Seag
er &
Sas
selo
v 20
00
Atmosphere:
Theoretical Transmission Spectra of HD 209458 b
Wavelength (nm)
Occ
ulte
d A
rea
(%)
Seager & Sasselov (2000)
The actual detection (with the HST):
• a 5signal• 2x weaker than
model expected, but within errors
• Might indicate high clouds above terminator, but …
Charbonneau et al. (2002)
Model Constraints
Deming et al. 2005
Spitzer Limit Tb = 1130 K
Different atmospheres
blackbody
model
HD 209458bEquili
bri
um
Tem
pera
ture
Infrared Eclipses in HD 189733: Measuring the Emitted Heat
Time (in fraction of day)
Orbital phase
Rel
ativ
e In
tens
ity
or B
righ
tnes
s
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 apartially eclipsed face ofHD209458b in a modelwith 400 m/s winds.
Variability in IR Eclipse Depths
Rauscher et al. (2006)
Temperature map of apartially eclipsed face ofHD209458b in a modelwith 400 m/s winds.
And bThe Spitzer IRphotometry at24 micron:
A) Raw data
B) Correctedfor zodiacalforeground
Harrington,et al. (2006)
Lecture II: Observed Spectra of EGPs
1. Albedos and temperatures2. 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. 2000 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 (Rp/D)22/3/(sin() + (-)cos())
Scattering Phase Functions and Polar Plots
Seager, Whitney, & Sasselov 2000Forward throwing & “glory”
MgSiO3 (solid), Al2O3 (dashed), and Fe(s)
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 209458b
● Relative depths transit: 2% eclipse: 0.005%
● Duration 3 hours
● Phase changes of planet
PhaseR
ela
tive F
lux
Eclipse Transit
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%● 473 896 observations● 3 mmag point-to-point precision
2005 observations, 40 minute binned data
Albedo Results
● Best fit parameters: Albedo : 0.07 0.05 stellar radius : 1.346 0.005 RJup
● Other Parameters: stellar mass: 1.101 Msun inclination: 86.929 period : 3.52... days see Knutson et al. 2006
Geometric Albedo
Radiu
s (J
upit
er)
1,2,3 sigmaerror contours
Rowe et al. (in prep)
Atmospheres
MOST bandpass
Geom
etr
ic A
lbed
o● HD 209458b is darker than Jupiter● Rule out class V planet with bright reflection silicon clouds
Marley et al. 1999