Alpha Centauri Bb, the closet extrasolar planet to Earth ever discovered has disappeared. A team of European observers announced its existence in October 2012. However, the announcement was met by questioning attitude by some astronomers, who believed that the European team was over-interpreting its data.
The questioning attitude of some astronomers forced a group of other researchers to study the data in detail and their recent study suggests it never actually existed outside of a blip in the data. Alpha Centauri bb appeared to have a mass similar to Earth and was orbiting its star at a distance similar to Mercury. It was only 4.3 light-years away – awhole lot closer than most other Earth-like exoplanets.
But a year after its discovery, a separate group of researchers suggested Alpha Centauri Bb a ‘Ghost’ in the data. They found very weak evidence of its existence.
Planets are usually detected in two ways, by scientists observing a dip in the light from a star – a sign of a planet orbiting in front of it – or by noticing a ‘wobble’ in a star, which suggests that it’s being pulled around by a small planet in orbit.
Radical Velocity method(Wobble system), was used to detect Alpha Centauri bb. The new study shows that it can be incredibly challenging to distinguish a genuine signal from the background noise, especially if the star system isn’t being monitored constantly, as Alpha Centauri wasn’t.
Most exoplanets won’t be at risk of this type of mistake, as now they’ve been detected by Kepler, a spacecraft that stares constantly at one patch of sky for years, which means it’s unlikely to be tricked by background noise.