Artist's impression from a point in the Alpha Centauri triple star system, showing the newly discovered planet orbiting around Alpha Centauri B, with Alpha Centauri A in the distance (Image: ESO)
The HARPS spectrograph and the 3.6-meter (11.8-ft) telescope at La Silla (Photo: ESO)
The orbit of Alpha Centauri A and B, plotted about the location of A (Image: SiriusB)
European astronomers working from the European Southern Observatory (ESO) in Chile have discovered a planet slightly more massive than Earth, orbiting a star in the Alpha Centauri triple star system – the nearest stellar system to our planet. Alpha Centauri Bb (as the new exoplanet is called, the star being Alpha Centauri B) is the first Earth-sized body found orbiting a Sun-like star and was discovered by measuring the tiny wobbles of Alpha Centauri B as it moves in response to the gravitational pull of the orbiting planet. It is orbiting Alpha Centauri B every three days and six hours at an orbital radius of six million kilometers (3.7 million miles). The proximity to the star leads to a surface temperature of some 1,500º K (2,250º F/1,232º C) – hot enough to melt granite.
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