In section 1. Letters
Proxima’s orbit around Alpha Centauri
Alpha Centauri A and B, and Proxima Centauri are our closest stars. In addition, Proxima Centauri has recently been shown to host a small-mass planet in its so-called habitable zone. It is thus important to become better aquainted with these very close neighbours. From statistical arguments, there could be little doubt that Proxima Centauri is gravitationally bound to the binary system formed by Alpha Centauri A and B. Kervella and Thévenin analyze high-precision radial velocity and astrometric data to show, with a high level of confidence, that it is the case. They also derive the orbit of Proxima which has a period of approximately 550,000 years, an eccentricity of 0.5 and a periastron of 4300 au. Planet (and comet) formation in this triple system should be investigated on the basis of these measurements.