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Are we Alone? - The Search for Life beyond the Earth. Ian Morison Emeritus Professor of Astronomy Gresham College Star-stuff Ring Nebula M1 The Crab Nebula Elsewhere in our own Solar System We could find other simple life-forms here. Canals on Mars? The Face on Mars! Valleys and Volcanoes Olympus Mons Islands and Channels Viking on Mars • Two Viking Spacecraft landed on Mars in 1976 to search for evidence of life. Spirit and Opportunity Martian Dust Devils Phoenix Lander Jupiter 4 major moons – discovered by Galileo Io Europa Ganymede Callisto Io Jupiter’s Moon Europa Breaking up of the surface • Icebergs! Water Plumes! Searching for Life! Finding Evidence of Simple Life on other Planets Can we see any exo-planets? A real problem due to the overwhelming brightness of the star orbited by the planet. Infrared observations by one of the KECK telescopes HR 8799 with three planets HST using a coronograph • The Hubble Space Telescope has observed a planet in orbit around the star Formalhaut. Indirect Detection Methods The RADIAL VELOCITY or DOPPLER WOBBLE method 51 Pegasi b • The first planet detected around a normal star. • Period just 4 days! • A gas giant very close to its star. Planetary Transits Detect the transit of a planet as it crosses the face of the star. This results in a slight drop in luminosity. This can only work if the orbital plane of the planet includes the Earth. HD 209458 transit HD 209458 b • 150 light years from Earth. • Planet orbits every 3.5 days. • 4 million miles from its star. • Atmospheric temperature ~2000K. Evidence for Life? We could detect evidence of life by observing the spectra of the planet’s atmosphere. Study the Infra-Red Spectrum What does it tell us? SETI The Search for Extraterrestrial Intelligence The Seminal Paper • In 1959 Giuseppe Cocconi and Phillip Morrison published a paper in Nature in which they pointed out that given two telescopes of the size of the newly built 250ft Mk1 Radio Telescope at Jodrell Bank it would, in principle, be possible to communicate across inter-stellar distances. Where to look? Locations • They suggested that any search should target the nearest Sun-like stars as these live long enough and are hot enough to allow life a chance to evolve on a planet at a suitable distance from them. • A target list was provided including Tau Ceti and Epsilon Eridani. Where to look? Frequency • They pointed out that the background noise (atmosphere, Galaxy, CMB etc.) was a minimum between ~1 to 10 GHz. • This band included the (radio) Hydrogen Line at 1.4 GHz and the OH Lines at ~ 1.6 GHz. • The band from 1.4 to 1.6 GHz is called the Water Hole Project Ozma • In 1960 Frank Drake and his colleagues at Green Bank, West Virginia, used the Tatel 85ft telescope to make the very first SETI observations in what was called Project Ozma. Project Ozma • They were given use of a new, state of art, low noise parametric amplifier and made observations over a 400 KHz band around the Hydrogen Line at 1420 MHz. • They observed Tau Ceti and Epsilon Eridani for a total of two months, but only detected the, then top secret, U2 Spy plane! The Voyager Record Numbers and DNA Continental Drift Birth Arecibo Radio Telescope Arecibo Message How does what we have learnt about other planetary systems affect the likelyhood of other life being present in our galaxy? The Drake Equation Number of Stars born per year in the Milky Way • Recent estimate of current SFR = 7 stars/yr Fraction of Sun-type stars • ~73-84% of the stars in the Milky Way are M type – too cool • Upper limit of 21% of stars in the Milky Way are like our Sun. So about 1 suitable star is born per year Fraction of Sun-type Stars with Planets • We do not yet know. • As time goes by we will be able to detect many more. • There may be 10-30% of stars with planetary systems. Fraction of stars with terrestrial planets within their solar systems • Again we do not know – but we are finding many solar systems where we do NOT believe there can be EarthLike planets. • Hopefully this is because solar systems like ours are rather hard to find! Number of Planets in a Star’s Habitable Zone • 8 planets; many satellites • Earth, Mars; (Europa) Fraction of habitable planets where life arises • Wild optimism: the fraction where life arises = 100% Simple Life could be very common. How often will simple life evolve into intelligent life? This, in my view is the most difficult part of this equation to estimate. • Our Moon has stabilised our rotation axis Its formation gave us a thinner crust. • Recycling of CO2 COMETS Fraction inhabited by intelligent beings • One needs, we believe, a very long time to allow life to evolve. • Really difficult to estimate how often a planet will have a temperate climate for long enough Perhaps our human race is rather special.