ESO: Orbit of Proxima Centauri Determined

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ESO: Orbit of Proxima Centauri Determined

Post by bystander » Fri Dec 23, 2016 3:10 pm

Orbit of Proxima Centauri Determined After 100 Years
ESO Announcement | 2016 Dec 22

Strongest evidence yet that Proxima Centauri orbits Alpha Centauri pair
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Interest in our neighbouring Alpha Centauri star system has been particularly high since the recent discovery of an Earth-mass planet, known as Proxima b, orbiting the system’s third star — and the closest star to the Sun — Proxima Centauri. While the system’s larger stellar pair, Alpha Centauri A and B, appear to have a proper motion on the sky that is very similar to that of the smaller, fainter Proxima Centauri, it has not been possible to demonstrate that the three stars do actually form a single, gravitationally bound, triple system.

Now three astronomers, Pierre Kervella, Frédéric Thévenin and Christophe Lovis, have concluded that the three stars do indeed form a bound system. In the century since it was discovered, Proxima Centauri’s faintness has made it extremely difficult to reliably measure its radial velocity — the speed at which it moves towards and away from Earth. But now ESO’s planet-hunting HARPS instrument has provided an extremely precise measurement of Proxima Centauri’s radial velocity, and even greater accuracy has been achieved by accounting for other subtle effects.

As a result, the astronomers have been able to deduce very similar values for the radial velocities of the Alpha Centauri pair and Proxima Centauri, lending credence to the idea that they form a bound system. Taking account of these new measurements, calculations of the orbits of the three stars indicate that the relative velocity between Proxima Centauri and the Alpha Centauri pair is well below the threshold above which the three stars would not be bound together by gravity. ...

Proxima's Orbit around Alpha Centauri - P. Kervella, F. Thévenin, C. Lovis
Attachments
Credit: P. Kervella (CNRS/U. of Chile/Observatoire de Paris/LESIA), <br />ESO/Digitized Sky Survey 2, D. De Martin/M. Zamani
Credit: P. Kervella (CNRS/U. of Chile/Observatoire de Paris/LESIA),
ESO/Digitized Sky Survey 2, D. De Martin/M. Zamani
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