Transcript Farthest Known Planet Opens the Door for Finding New Earths

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:
Galaxy
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Molecular Cloud Complex
Star-Forming “Globule”
Extrasolar System
Circumstellar Disk
?
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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
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/cm3
denser than Saturn
Iron rain
OGLE-TR-113b
Radial Velocities
Transit Light Curve
Konacki, Torres,
Sasselov, Jha (2004)
The Other Known Transiting
Extrasolar Planet
HD 209458b: 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
The HAT Network: FLWO Mt.Hopkins AZ
The HAT Network: Mauna Kea Obs. Hawaii
Mochejska 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 ?
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