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The QuestionsThe QuestionsAre there other planetary systems?How do we detect other planetary
systems?What is Life?How common are the conditions
favorable to life?How might we detect other life?
Are there other Planetary Are there other Planetary Systems?Systems?An old questionWe are hereScience FictionHow do stars form?
– Gravitational collapse– Protostar– Protostellar disks
How do we detect other planetary How do we detect other planetary systems?systems?Direct imaging
– Benefits– Drawbacks– Transits
Astrometry– Benefits– Drawbacks
Doppler Shift Technique– Method of choice
Direct ImagingDirect Imaging
Relative Brightness– Searchlight and Firefly
Angular Separation– From the surface of the Earth
• Keck (0.5”, 0.04” with adaptive optics)
– From Space• HST (0.04”)
– 1 AU is 1” at 1 pc• Most stars are much further away
Direct Imaging--The FutureDirect Imaging--The Future
Best Hope: InterferometryTerrestrial Planet Finder (NASA)Darwin (ESA)Simulated Interferometric Image
– Venus, Earth, Mars
AstrometryAstrometry
The wobble of the Sun due to Jupiter as seen from 10 pc (2 million Astronomical Units)
The Planets So Far (>50!) No. NAME Msini P SMA Ecc. Vel (Mjup) (d) (m/s) 1 HD83443 0.35 2.986 0.038 0.08 56.0 2 HD46375 0.25 3.024 0.041 0.02 35.2 3 HD187123 0.54 3.097 0.042 0.01 72.0 . . . 8 51Peg 0.46 4.231 0.052 0.01 55.2 . . . 54 GJ876c 0.56 30.12 0.13 0.27 81 55 HD168443b 7.73 58.10 0.29 0.53 473 56 HD179949 0.86 3.092 0.043 0.0 112 57 HD160691 1.87 743 1.6 0.62 54 58 HD27442 1.13 426 1.15 0.02 34
Sample of Systems DiscoveredSample of Systems Discovered
The First: 51 Pegasi– Mayor & Queloz (1995)– Why did it take so long?
Upsilon Andromeda47 Ursa MajorisThe most recent: Eta EridaniMany with small, elliptical orbits
What is life?What is life?Replication? Motion?Problems with definition?What is intelligence?How does intelligence arise?
Astrobiology (SETI Online)Astrobiology (SETI Online)
“The development of Exobiology and Astrobiology as interdisciplinary research fields has brought together astronomers, biologists and funding opportunities in a way that wasn't possible ten years ago.”
“Much of the organic material found on the Earth in its earliest years probably had an interstellar heritage.”
Looking for Organic MoleculesLooking for Organic Molecules
On Earth (Miller-Urey Experiment) In the Interstellar Medium (molecular lines)
– Ethyl alcohol (CH3CH2OH)
– Formaldehyde (H2CO)
– Methyl Cyanoacetylene (CH3C3N)
– Acetylaldehyde (CH3CHO)
Radio waves penetrate the ISM
Conditions Favorable to LifeConditions Favorable to LifeLifetime of parent star
– High Mass Stars (millions of years)– Low Mass Stars (billions of years)– Most stars are low mass
The “Habitable Zone”– Temperature Gradient– Tidal Forces might extend zone
Liquid Water
Should we look for other Should we look for other civilizations?civilizations?
The Drake EquationN = R* × fp × ne × fl × fi × fc × L
Solid: Star formation rate, fraction of stars with planets, number of Earth-like planets,
Shaky: Chance that life arises, chance that intelligent life arises, . . .
How might we detect civilizations?How might we detect civilizations?SETI (Search for ExtraTerrestrial
Intelligence)Radio TelescopesThe “Water Hole”
What Kinds of Messages are we What Kinds of Messages are we Sending into the Universe?Sending into the Universe?
Recent ProposalRecent Proposal
e.g. Rare Earth, Peter D. Ward & Donald Brownlee
“the alien search is likely to fail…”
(Paul) Allen Telescope Array (Paul) Allen Telescope Array (ATA)(ATA)$12.5 MillionScanning Program“Frequency Space”
ConclusionsConclusions
Planetary systems and life-supporting conditions are abundant
In 10-15 years, we may have a list of 100s of planetary systems
With new telescopes, we will be able to explore atmospheres of other planets
Detecting communicative intelligent life might be possible in the Galaxy