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Life in the Universe 029:062 Guest Lecture Catherine Whiting Life in the Universe • What are the chances of extraterrestrial life in the universe? – How common are extrasolar planets? – How many of these planets are suitable for life? (at least earth-like life) – What characteristics would this life possess? – How would we make contact? Extrasolar Planets • Detection Methods Extrasolar Planets • Detection Methods – Eclipses Extrasolar Planets • Detection Methods – Doppler Shifts – planet causes star to wobble Extrasolar Planets • Detection Methods – Imaging HR 8799 Infrared Image Planets only 60 million years oldstill glowing from formation Extrasolar Planets • Detection Methods – Eclipses, Doppler Shifts, Imaging – Subject to selection effects- meaning we tend to detect mostly Jupiter-like planets that are close to their stars because our detection methods are best-suited to detecting Jupiter-like planets – Earth-like planets now being detected - Kepler Mission Example: Gliese 581 • Red dwarf star • 20.3 light years away • At least 6 known planets- some could support life Habitable Zone • Life on Earth appears to require water • Planets with water may be the most promising places for life • In order to have liquid water, the temperature of the planet must be between freezing and boiling points • This limits its distance from its star- Habitable Zone- Habitable Zone More than 450 new planets have been discovered since 1995 99% of all organic material consists of 4 elements: Hydrogen, Carbon, Oxygen, Nitrogen Chemical Abundances in Stars Ammonia, Methane, Water + Lightning= Amino Acids ! Miller-Urey Experiment • Cosmos Episode 2: time: 46:15 • http://www.youtube.com/watch?v=p1Zh69TB 0lU Drake Equation • Carl Sagan Video: • http://www.youtube.com/watch?v=MlikCebQ SlY&feature=related • Carl Sagan translated for rednecks: • http://www.youtube.com/watch?v=DI9ImScQ GAo&feature=related What would aliens look like? • Cosmos Episode 2: time: 52:50 http://www.youtube.com/watch?v=p1Zh69TB0l U Discussion Questions • Would alien civilizations be hostile? • Are aliens already secretly here? – Colonization, government conspiracy – Would we even be able to comprehend them? SETI (Search for ExtraTerrestrial Intelligence) • If there are other civilizations out there, are they trying to contact us? • There are active searches for ET signals, mainly in the radio, some using visible light. Arecibo Message Voyager Voyager Decoded Voyager Message • http://voyager.jpl.nasa.gov/spacecraft/index.h tml Discussion Questions • If we were to send another Voyager or Arecibo message, what would you include? – Instruments? – Music? – Videos? – Sounds? – Information?