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Document related concepts
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Transcript 
The Search for
Other Earths
Ray Villard
STScI
August 17, 2009
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“There are infinite
worlds both like and
unlike this world of
ours...We must
believe that in all
worlds there are living
creatures and planets
and other things we
see in this world.”
Epicurius
c. 300 B.C
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Galileo, 1609
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1584
"There are countless suns
and countless earths all
rotating around their suns
in exactly the same way as
the seven planets of our
system . . . The countless
worlds in the universe are
no worse and no less
inhabited than our Earth”
Giordano Bruno
in De L'infinito
Universo E Mondi
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Exoplanet Discovery Timeline
Past
•
•
•
•
•
•
•
•
1992
1994
1995
1999
2001
2003
2004
2006
Pulsar planets
Protoplanetary disks resolved in visible light
Radial velocity extrasolar planet discovery
Extrasolar planet transits observed
Extrasolar planet atmospheres measured
New planets discovered with transit method
Planet discovered with microlensing method
Transit planet day side temperature measured
Present
•
•
Transiting hot Jupiter atmospheres measured in detail
First transiting super- Earths
Direct imaging of young hot Jupiters
•
Future
•
•
•
•
•
•
•
2011
2011
2013
2015
2030
2040?
2101?
Statistical frequency of earthlike planets determined (Kepler)
Planets found around Alpha Centauri??
JWST: transits and eclipses of planet around nearby red dwarfs
Search for nearby Earths and super Earths
Definitive sampling of biospheres on exoplanet survey
Direct imaging of all sizes of exoplanets
First interstellar AI mission to directly sample exobiology
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THE OBSERVABLE DRAKE EQUATION
ETL = NP X FTP X FPw X FPL
ETL = Planets with extraterrestrial life in the Galaxy
Np = Number of exoplanets
Fpt = Fraction of terrestrial planets
FPw = Fraction of terrestrial planets with liquid water
FPl = Fraction of terrestrial planets with carbon-based life
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Planet Detection
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Detectability of the Solar System
Precision: 3 m/s
saturn
Saturn
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Mayor & Queloz 1995, Nature, 378, 355.
Marcy & Butler 1996, Ap.J.Lett., 464, L147.
~
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Sagittarius Window Eclipsing Extrasolar Planet Search
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An optical/near-infrared space telescope with a filled
aperture of at least 8-meters will probably be required to
definitively answer the question “Are we alone?”
HST 2.4-m JWST 6.5-m ATLAST 8-m
ATLAST 16-m
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10000
Solar Type Stars
All Stars
1000
100
10
1
2-m
4-m
8-m
16-m
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Life in the Universe
All Life
Chemical
Carbon
Energy
-based
Liquid
water
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• A thermodynamic disequilibrium
• An environment capable of maintaining
links between carbon, hydrogen, and
other atoms
• A liquid environment
• A molecular system that can support
Darwinian evolution.
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Total number of stars >100 billion
Total number of planets ~ several trillion ?
Total number of moons ~ 10s of trillions ?
Earthlike Planets? .01% = 1 billion??
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