All About Exoplanets Dimitar D Sasselov HarvardSmithsonian Center

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 ?

Ups. And System vs. Solar System

Planets Form Shortly After Their Parent Stars: Galaxy Molecular Cloud Complex Star-Forming “Globule” Extrasolar System Circumstellar Disk ?

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

Transit Measurements

Evidence for Planet OGLE-TR-56 b Radial Velocities Transit Light Curve Torres, Konacki, Sasselov, Jha, 2004, Astrophys. J.

What did we find ? Unique Orbit = 29 hours Mass = 1. 4 Jupiters Density = 1. 0 g/cm 3 denser than Saturn Iron rain

OGLE-TR-113 b Radial Velocities Transit Light Curve Konacki, Torres, Sasselov, Jha (2004)

The Other Known Transiting Extrasolar Planet HD 209458 b: Dimming of light due to transit, observed with HST. Transits tell us DIRECTLY: Planet radius, INDIRECTLY: Planet density Planet composition Brown, Charbonneau, Gilliland, Noyes, Burrows (2001)

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

The HAT Network: FLWO Mt. Hopkins AZ

The HAT Network: Mauna Kea Obs. Hawaii

Mochejska et al. 2002 -2004

Gaudi et al. 2002 -2004 Survey for Transiting Exo-Planets in Stellar Systems

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 51 Peg @ 550 nm Seager, Whitney, & Sasselov 2000 Green, Matthews, et al. 2003

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