Extra Solar Planets
The discovery of the first extrasolar planet orbiting around an 8 Ga old star called 51 Pegasus, forty-two light years away within the Milky Way, was announced on October 6, 1995. The suspected planet takes just four days to orbit 51 Pegasus. It has a surface temperature around 1,000°C and a mass about 0.5 the mass of Jupiter.
One year later, seven other extrasolar planets were identified.
Among them, 47 Ursa Major has a planet with a surface temperature
estimated to be around that of Mars (-90 to -20°C) and the 70 Virginis
planet has a surface temperature estimated around 70-160°C. The latter
is the first known extrasolar planet whose temperature might allow the
presence of liquid water.
The Extrasolar Planets Encyclopaedia www.exoplanet.eu regularly updates the list of detected exoplanets (almost 2000 planet detected at the end of 2014).
Extrasolar life - if it exists - will not be reachable by missions in the mid-term future. This formidable challenge must therefore be tackled by astronomers and radioastronomers in the next century. The detection of water and ozone (an easy detectable telltale signature of oxygen) in the atmosphere will be a strong indication but not an absolute proof of life. Other anomalies in the atmospheres of telluric exoplanets such as the presence of methane could be the signature of extrasolar life.
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