Astronomers at the European Southern Observatory have discovered a planet approximately the same size as Earth orbiting Alpha Centauri B, one of the closest stars to our own.
The Alpha Centauri system is only 4.3 light years away, and it is the most logical destination for the first interstellar spacecraft. Until now no planets had been detected in this system, which has two co-orbiting stars. The newly discovered planet orbits Alpha Centauri B, which is 90% as massive and 50% as luminous as our Sun. The planet completes an orbit every 3.2 days at a distance of 0.04 AU, far to close to support liquid water. However this discovery indicates that Earth-mass planets are within our ability to detect in nearby star systems. The planet was detected using the HARPS instrument on the 3.6-metre telescope at ESO’s La Silla Observatory in Chile. The results will appear online in the journal Nature on 17 October 2012.