Lecture 16: Searching for Habitable Planets: Remote Sensing

• Methods and parameters we can measure• Mean density measurements: internal structure• Measurements of surface temperature• Atmospheric composition and temperatures• Mapping of the surface

Star-to-planet inequalities:

• In light: 1010 (optical) to 107 (infrared)

• In mass: 105 to 103

• In size: 102 to 10.

HD 209458b: a Hot Jupiter

Methods: Mass Determination

Newton’s law of universal gravitation & equality of forces: Msas = Mpap (center of mass)

Mass:

Radial velocities seenin star HD 209458 -the variation is dueto a planet that is lessmassive than Jupiter.

(Mazeh et al. 1999;Marcy et al. 2000)

More on Orbits: Angular Momentum

• Conservationof AngularMomentum

Mass:

• For HD 209458b: Mp sin(i) = Ms vs P / 2 ap

= const. x (Ms

/1.1MSun) Mjup

+ 0.018 + 0.1• Transit light curve helps derive the orbit

inclination: i = 86o.7 + 0.2

• Both Mp and Rp determined to better than 5%!

What can we learn from transiting extrasolar

planetsHD 209458b: Dimming of light due to transit, observed with HST.

Brown, Charbonneau, Gilliland, Noyes, Burrows (2001)

Tells usDIRECTLY:Planet radius,

INDIRECTLY:Planet densityPlanet composition

Mass-RadiusDiagram:

Hot Jupiters

Super-Earths

Rocky & Water Planets

Credit: S. Cundiff

Mass (Earth mass)

Rad

ius

(E

arth

rad

ius)

Transiting Planets on the Mass-Radius Diagram

10 20 301

1

2

3

4

5

Earth

Kepler-10b

CoRoT-7b

GJ1214b

Earth composition

50% H2O

20% H/He Uranus

Neptune Kepler-4b

HAT-P-11b

GJ436b

Mass [MEarth]

Radius [REarth]

1.00.1 10

0.5

1.0

2.0

2.5

EV

M

Kepler-10b

Earth and Super-Earth Mass–Radius Domain

Batalha et al (2011)Zeng & Sasselov (2011)

1.5

50.5

10% H/He

GJ1214b

CoRoT-7b

Kepler-11b

Kepler-11f

Model: Seager & Sasselov 2000Detection: Charbonneau et al 2002

HD 209458b: a Hot Jupiter

Atmosphere:What is special about atomic Na and the

alkali metals?

Seager & Sasselov (2000)

Atmosphere: Theoretical Transmission Spectra of HD 209458 b

Wavelength (nm)

Occulted Area (%)

Seager & Sasselov (2000)

Atmosphere:The tricks of transmission spectroscopy:

Brown (2001)

A star and its planet in infrared

light

(Artist conception)

Direct Detection of Thermal EmissionInfrared Eclipses of Hot Jupiters:

Spitzer Space Telescope

First detection oflight from planetsorbiting other stars

D. Charbonneau, & D. Deming et al. March 2005

Infrared Eclipses

QuickTime™ and a

MPEG-4 Video decompressorare needed to see this picture.

Infrared Eclipses in HD 189733: Measuring the

Emitted Heat

Time (in fraction of day)

Orbital phaseRelative Intensity or Brightness

Eclipse detection (Feb. 20, 2006) by Deminget al. using the SpitzerSpace Telescope - in infrared light (heat)

SpectraObserved IR data points

vs. models

Knutson,Charbonneau, et al. (2007)

A study of an extrasolar planet

Heather Knutson & Dave Charbonneau (2007)

A map of an extrasolar planet

Heather Knutson & Dave Charbonneau (2007)

QuickTime™ and aYUV420 codec decompressor

are needed to see this picture.

Main points to take home:

1) Methods and parameters we can measure2) Mean density measurements: internal structure3) Measurements of surface temperature4) Atmospheric composition and temperatures5) Mapping of the surface