All About Exoplanets

Dimitar D. Sasselov

Harvard-Smithsonian Center for Astrophysics

Planets Orbiting Other Stars

Number of planets discovered around stars like our Sun:

123 planets 13 multiple planet systems

A new field with 3 basic questions:

• How do planets & planetary systems form

and survive ?

• What is the physical diversity of planets ?

• What is the planetary perspective to the

origin of life ?

Environments we can call home

A new field with 3 basic questions:

• How do planets & planetary systems form

and survive ?

• What is the physical diversity of planets ?

• What is the planetary perspective to the

origin of life ?

UpsAnd System vs. Solar System

Planets Form Shortly After Their Parent Stars:

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Galaxy Molecular Cloud Complex

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Star-Forming “Globule”

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Circumstellar Disk

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Extrasolar System

?

Methods for Planet Discovery:several, but only 3 have been

successful so far

• Radial Velocity Measurements (119) - looking for the Doppler shifts due to “Stellar

Wobble” as planet pulls on star,• Transit Measurements (3) - looking for periodic dimming as planet eclipses

star.& Gravitational Microlensing signal (1).

New Method of Discovery

Transit Measurements

Venus in Front of the Sun

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Transit Measurements

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Evidence for Planet OGLE-TR-56b

Transit Light Curve

Radial Velocities

Torres, Konacki, Sasselov,Jha, 2004, Astrophys. J.

What did we find ?

Unique Orbit

= 29 hours

Mass = 1.4 Jupiters Density = 1.0 g/cm3 denser than Saturn

Iron rain

OGLE-TR-113b

Transit Light Curve

Radial Velocities

Konacki, Torres,Sasselov, Jha (2004)

The Other Known Transiting Extrasolar Planet

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

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

Transits tell usDIRECTLY:Planet radius,

INDIRECTLY:Planet densityPlanet composition

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

The HAT Network: FLWO Mt.Hopkins AZ

The HAT Network: Mauna Kea Obs. Hawaii

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Survey for Transiting Exo-Planets in Stellar Systems

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Surveying Extrasolar Planets:the First Step

• MOST - “Microvariability & Oscillations of

Stars” - Canada’s First Space Telescope;

• We will use MOST to detect the reflected light

from known “hot Jupiters”;

• The details of the reflected light will tell us about

the particle size & composition of the planet’s

clouds.

Photometric Light Curves• Very slight changes in the light as planet changes phase,

• Requires precise photometry from space - MOST.

Scattered Light Curves: 3 Examples

Seager, Whitney, & Sasselov 2000Green, Matthews, et al. 2003

51 Peg @ 550 nm

Environments we can call home

One of Humankind’s Biggest Questions:

What is the path from Stars to Life ?

- a major inter-disciplinary effort, with - astrophysics providing the ‘stage’;- First step: to discover Earth twins.

What Would It Take ?

Lynnette Cook

KEPLER: Search for Earth Twins

NASA Mission - launch in 2007

Transit Search: ~100,000 stars

Can detect planets like our Earth

GOAL: discover 1,000’s of

medium and giant planets; also

~12 Earths in habitable zones.

Terrestrial Planet Finder

• Find and characterize Earth-like planets

• Reduce the glare of the parent star by one million to one billion

• Launch date 2015

• Observe stars within 50 light years

Alcatel Space Industries