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Are We Alone?

Are We Alone?. Chris De Pree RARE CATS June 2002. The Questions. Are 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 Systems?.

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Are We Alone?

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  1. Are We Alone? Chris De Pree RARE CATS June 2002

  2. The Questions • Are 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?

  3. Are there other Planetary Systems? • An old question • We are here • Science Fiction • How do stars form? • Gravitational collapse • Protostar • Protostellar disks

  4. Protostellar Disks: Beta Pictoris

  5. How do we detect other planetary systems? • Direct imaging • Benefits • Drawbacks • Transits • Astrometry • Benefits • Drawbacks • Doppler Shift Technique • Method of choice

  6. Direct 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

  7. Direct Imaging: HST(Gliese 229A and 229B)

  8. Spectra of Planetary Atmospheres

  9. Planetary Transits

  10. Direct Imaging--The Future • Best Hope: Interferometry • Terrestrial Planet Finder (NASA) • Darwin (ESA) • Simulated Interferometric Image • Venus, Earth, Mars

  11. DARWIN • 2015 Launch • 6 1.5m Tel. • Formation flying

  12. Astrometry • The wobble of the Sun due to Jupiter as seen from 10 pc (2 million Astronomical Units)

  13. Doppler Shift Technique

  14. 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

  15. Sample of Systems Discovered • The First: 51 Pegasi • Mayor & Queloz (1995) • Why did it take so long? • Upsilon Andromeda • 47 Ursa Majoris • The most recent: Eta Eridani • Many with small, elliptical orbits

  16. 51 Pegasus (look for the wobble!)

  17. Upsilon Andromeda

  18. 47 Ursa Majoris (~3 year period)

  19. Epsilon Eridani (~7 year period)

  20. What is life? • Replication? Motion? • Problems with definition? • What is intelligence? • How does intelligence arise?

  21. 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.”

  22. Looking 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

  23. Conditions Favorable to Life • Lifetime 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

  24. Habitable Zones around known stars

  25. Should we look for other civilizations? • The Drake Equation • N = 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, . . .

  26. How might we detect civilizations? • SETI (Search for ExtraTerrestrial Intelligence) • Radio Telescopes • The “Water Hole”

  27. The “Water Hole”

  28. Will Life Always Arise?

  29. Can Life Survive Long Term?

  30. What Kinds of Messages are we Sending into the Universe?

  31. Recent Proposal • e.g. Rare Earth, Peter D. Ward & Donald Brownlee • “the alien search is likely to fail…”

  32. (Paul) Allen Telescope Array (ATA) • $12.5 Million • Scanning Program • “Frequency Space”

  33. Conclusions • 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

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