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Alpha Centauri B

November 12,  2015

The discovery of Earth-like planets in the habitable zone of Sun-like stars is difficult, mainly because the star is so much brighter than the planet. In 2012, however, a group reported the detection of a roughly Earth-mass planet in the vicinity of Alpha Centauri B, one of our nearest stellar neighbors. The data is based on measurements of the radial velocity of the star and allows conclusions as to how strongly the star is attracted by its planet. The planet has at least 1.13 earth masses and orbits Alpha Centauri B once in 3.2 days. This corresponds to a distance of 0.04 astronomical units from the star. Even if this planet is much too hot for the kind of life we know, its discovery is still promising. It shows nevertheless that in the early history of Alpha Centauri the formation of planets was once possible. The system could contain other undiscovered objects.

In October 2015 the discovery had to be revised. A new analysis of the data showed that the found periodicity was likely an artifact of data collection and was probably not due to an actual planet.

[1] X. Dumusque, F. Pepe, C. Lovis, D. Ségransan, J. Sahlmann, W. Benz, F. Bouchy, M. Mayor, D. Queloz, N. Santos & S. Udry (2012): An Earth-mass planet orbiting Alpha Centauri B. Nature 491, 207-211
[2] V. Rajpaul, S. Aigrain, S. j. Roberts (2015): Ghost in the time series: no planet for Alpha Cen B. Angenommen von MNRAS Letters.

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