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Search for Extraterrestrial Intelligence

Search for Extraterrestrial Intelligence. SETI. Michael L. Sitko University of Cincinnati June 29, 2004. Early Speculations. c. 400 BCE - Metrodorus of Chios - "It is unnatural in a large field to have only one shaft of wheat and in the infinite universe only one living world.”

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Search for Extraterrestrial Intelligence

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  1. Search for Extraterrestrial Intelligence SETI Michael L. Sitko University of Cincinnati June 29, 2004

  2. Early Speculations c. 400 BCE - Metrodorus of Chios - "It is unnatural in a large field to have only one shaft of wheat and in the infinite universe only one living world.” c. 50 BCE - Lucretius - "Nothing in the universe is unique and alone, and therefor in other regions there must be other Earths inhabited by different tribes of men and breeds of beasts.” Giordano Bruno - there must be "an infinite number of suns with planets and life around them". Burned at the stake in 1600 CE

  3. “Attempts” at Communication c. 1820 Karl Gauss - plant huge forest of trees in the form of a right triangle Look at Mars for same? c. 1840 Joseph von Littrow - light trenches filled with kerosene 1899 - N. Tesla attempts to send a powerful burst of radio noise as a "message" and then listen for a reply. 1922 - G. Marconi, tries to listen for radio signals from a boat in a remote oceanic location.

  4. OZMA - The first modern radio search 1959 - David Morrison & Giuseppi Cocconi propose radio search for signals from intelligent extraterrestrials (September 19 issue of Nature) 1960 - Frank Drake looks at 2 stars (Tau Ceti & Epsilon Eridani) at 1 wavelength (H I 21-cm line) with 85-ft NRAO dish for a few months. SETI established as an experimental science

  5. How Many Intelligent Civilizations Are There?

  6. Rate of Star Formation The Milky Way Galaxy is about 14x109 years old It contains roughly 200x109 stars Mean rate of star formation: But most of this occurred early on - the rate is probably about 1/10 of this, about 2 stars/year.

  7. Finding Extrasolar Planets • Direct Imaging • Proper Motion Studies • Doppler Searches • Transit Searches

  8. Doppler Searches

  9. Epsilon Eridani - an original Ozma target

  10. Transit Searches HD 209458b

  11. Ne Most dynamic models of 1990s suggested ~1 terrestrial planet in CHZ. Most KNOWN planetary systems dominated by HOT JUPITERS! Ne may be small!!

  12. Probability of Having Planets Searches for extrasolar planets suggests that this number is 0.2 or greater. Current searches are still not complete. This depends on the metallicity of the star!

  13. Darwin (ESO) & TPF (NASA)

  14. Ecozone Issues Energy absorbed by planet: Written another way: Energy emitted by planet: Equilibrium T for planet:

  15. Example: Our Solar System: Planet dp a Predicted T Observed T Mercury 5.8x1012 0.056 440 100-620 Venus 1.1x1013 0.76 230 750 Earth 1.5x1013 0.39 250 180-330 (290 avg.) Mars 2.3x1013 0.16 220 130-290 (SubSolEq) Jupiter 7.8x1013 0.51 104 160 (cloud tops) Saturn 1.4x1014 0.61 81 90 (cloud tops) What Goes?

  16. Simulate Evolution • Rate of outgassing of volatiles (H, C, N, O) from the interior • Condensation of H2O vapor into oceans • Solution of atmospheric gases into oceans • Photodissociation of H2O in the upper atmosphere • Escape of H from the uppermost atmosphere (exosphere) • Chemical reactions in atmospheric gases • Presence of life and variations in biomass • Photosynthesis and burial of organic sediments • Urey reaction (CaSiO3+CO2CaCO3+SiO2) • Oxidation of surface minerals (2FeO+OFe2O3) • Variations in the luminosity of the Sun • Variations in the albedo of the Earth • Greenhouse effect

  17. Hart Models (1980)

  18. Continuously Habitable Zones Michael Hart (1980) Require liquid water for 0.8 Gyrs, etc. Stellar Mass Spectral Type Inner r of CHZ Outer r of CHZ Thickness (solar masses) (AU) (AU) (AU) >1.20 Red Giant Too Soon 1.20 F7 1.616 1.668 0.054 1.15 F8 1.420 1.481 0.061 1.10 F9 1.240 1.310 0.069 1.05 G0 1.086 1.150 0.064 1.00 G2 0.958 1.004 0.046 0.95 G5 0.837 0.867 0.030 0.90 G8 0.728 0.743 0.015 0.85 K0 0.628 0.629 0.001 0.835 K1 0.598 0.598 0.000 In all cases, thickness is less than 0.1 AU

  19. Recent Models - Kasting et al. Newer models handle CH3 and NH3 more realistically. Suggests

  20. Life Issues Probability that Life Evolves - Life appeared on Earth as soon as it was climatologically possible. Existence of “extremophiles” suggests PL~1 . But we may be fooling ourselves - only 1 example. Probability that Life Develops “Intelligence” - again only 1 example. PI~1?? Lifetime of Intelligent Communicative Life - We have had the ability to “communicate” for ~50 years. Might have been as small as 10 years (Cuban Missile Crisis), but we or others might survive for the lifetime of the Sun. Lic~10-1010 yrs??

  21. Put It All Together Obviously very uncertain! The only way to know for sure is to LOOK!

  22. Search Strategies Directed - use a major facility for short periods of time. Target Search - look at specific, promising stars Sky Survey - look everywhere Shared - use observations from other projects. You can analyze old data, or make "parasitic" observations. Dedicated - use a facility exclusively (or at least primarily) for SETI work (in Target Search or Sky Survey)

  23. Signal Types - Radio

  24. Programs - Past, Present, and Future 1960 - Ozma Frank Drake 1973-1997 - OSU

  25. Megachannel Extraterrestrial Assay (META) Paul Horowitz META Processors Harvard 26-m radio telescope

  26. NASA SETI Sky Survey 16 million channels - 1-10 GHz - equivalent to 10 billion “Ozmas” Target Search 14 million channels - 1-3 GHz - looking at 1000 stars Project cancelled by US Congress after 2 megachannel receiver/processor began.

  27. BETA Main BETA rack - containing 63 FFT boards (each processing 4 million channels) BETA

  28. SETI Institute (founded in 1984) &Project Phoenix Continuation of Target Search under Private Funding! Parkes 210-ft, Green Bank 140-ft, Arecibo 1000-ft telescopes

  29. Allen Telescope Array

  30. Optical SETIProposed in 1961 by R. Schwartz & C. TownesFirst carried out in 1990 by Stuart Kingsley in Columbus, OH High-power narrow-band lasers can outshine the Sun at the emitting wavelengths Look for short pulses with coincidence counters

  31. What Would a Message Look Like? Binary (or Morse Code) strings of “special” numbers - primes, etc. Message Transmitted from Arecibo - 1974

  32. What if We Hear “Them”? - SETI Protocol 1. Is it really extraterrestrial? 2. Get confirmation from other astronomers. (If extraterrestrial, tell your government about it). 3. If convincing: announce to International Astronomical Union, Secretary General of the UN, inform SETI groups. 4. Make the first public announcement 5. Make data available to all. 6. Everyone carefully record & disseminate signals 7. Protect frequencies. 8. Don't broadcast back to the ETs! Requires Debate. 9. Study signals. The SETI Committee of the International Academy of Astronautics keeps a list of experts to call on.

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