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 1,000oC 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. Early in 2001 about 50 exoplanets have been described.
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.
European astrophysicists are proposing the construction of a six-telescope infrared interferometer to study the atmospheres of exoplanets. The mission called Darwin-IRSI is presently under study. The detection of an electromagnetic signal (via the SETI program) would be more convincing, but probably more problematic.
Figure (c) ESA Illustration by Medialab. Darwin's
six telescopes look at light from space and analyse the atmospheres of
Earth-like planets. For further information please visit http://sci.esa.int/darwin/