Earth mass planet uncovered around nearby star

Astronomers using a telescope at the La Silla observatory, in Chile, claim to have discovered an approximately one Earth mass planet orbiting the nearby star Alpha Centauri B. The planet, known as Alpha Centauri Bb, speeds around its parent star in 3.2 days and occupies an orbit that is far closer to Alpha Centauri B than Mercury is to our own Sun.

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An artist’s impression of the newly discovered world. Credit: ESO/L. Calçada/N. Risinger (skysurvey.org)

Astronomers using a telescope at the La Silla observatory, in Chile, claim to have discovered an approximately one Earth mass planet orbiting the nearby star Alpha Centauri B. The planet, known as Alpha Centauri Bb, speeds around its parent star in 3.2 days and occupies an orbit that is far closer to Alpha Centauri B than Mercury is to our own Sun.

The discovery was made using the European Southern Observatory’s HARPS instrument attached to a 3.6m aperture telescope. HARPS (the High Accuracy Radial Velocity Planet Searcher) studies the light from distant stars for signs of perturbations in their movement, which may indicate the presence of a planet. To discover Alpha Centauri Bb, HARPS made a detection of unprecedented precision – identifying a ‘wobble’ in the movement of Alpha Centauri B of just 51 cm per second.

The findings are detailed in a Nature paper, published today, which also explains the extraordinary lengths the astronomers went to to detect the signal of the planet. These included taking into account the effects of the varying activity of Alpha Centauri B and even the granulation (huge roiling cells of hot plasma) on the star’s surface.

Aside from the Earth-like mass of the planet, what is perhaps most interesting about the discovery is the location of Alpha Centauri Bb relative to Earth. Lying just 4.3 lightyears away, the Alpha Centauri system (comprised of the stars Alpha Centauri A and B as well as Proxima Centauri) is the closest group of stars to us. “This result represents a major step towards the detection of a twin Earth in the immediate vicinity of the Sun. We live in exciting times!” said Xavier Dumusque – one of the astronomers who worked on the study – in a press release issued by ESO.


 

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