lecture iii: gas giant planets 1.from lecture ii: phase separation 2.albedos and temperatures...

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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

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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

H + He + rocky H + He + rocky corecore

Mass-Radius Plot for Hot Jupiters

H + HeH + He

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.

H + He + rocky H + He + rocky corecore

Mass-Radius Plot for Hot Jupiters

H + HeH + 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.

AlbedosAlbedos

Rowe et al.(2006)

HD 209458b AlbedosHD 209458b Albedos

New upperlimit on Ag

Rowe et al.(2006)(Rowe et al. 2008)

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:What is special about atomic Na and the alkali metals?

Seager & Sasselov (2000)

Atmosphere:

Theoretical Transmission Spectra of HD 209458 b

Wavelength (nm)

Occ

ulte

d A

rea

(%)

Seager & Sasselov (2000)

Atmosphere:The tricks of transmission spectroscopy:

Brown (2001)

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)

Direct Detection of

Thermal Emission

Model Constraints

Deming et al. 2005

Spitzer Limit Tb = 1130 K

Different atmospheres

blackbody

model

HD 209458bEquili

bri

um

Tem

pera

ture

SpectraFour observeddata points vs.

models

Burrows,Sudarsky, &Hubeny (2006)

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)

And b

The Spitzer IRphotometry at24 micron fit to

a model

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())

Scattered Light

Need to consider:• phase function• multiple scattering

Scattering Phase Functions and Polar Plots

Seager, Whitney, & Sasselov 2000Forward throwing & “glory”

MgSiO3 (solid), Al2O3 (dashed), and Fe(s)

Scattered Light Changes with Phase

Seager, Whitney, & Sasselov 200051 Peg @ 550 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 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

0.1 mag

0.02 mag

0.8 mmag

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

HD 209458b AlbedosHD 209458b Albedos

New upperlimit on Ag

Rowe et al.(2006)(Rowe et al. 2007)