RELATED: Welcome to Proxima b, Our Nearest 'Earth-like' Neighbor
Though we know that Proxima b is there, we can only guess at its composition and have no clue whether or not it possesses any water. But new evidence suggesting Proxima Centauri is indeed a distant sibling of the Alpha Centauri could help us find out.
Proxima Centauri was only discovered a century ago and, since then, astronomers have been trying to understand its motion in the sky, a task that becomes very complicated when considering how dim it is. Red dwarfs are many times smaller and produce only a fraction of the light of our sun. But using the High Accuracy Radial velocity Planet Searcher (HARPS) instrument at the ESO's La Silla Observatory in Chile, astronomers have, for the first time, gained precision measurements of the dim star's radial velocity, a key metric if we are to understand if it is in any way related to Alpha Centauri.
The HARPS instrument is extremely sensitive to the wobble of stars as small exoplanets orbit around them, gravitationally tugging at them. Indeed, it was the HARPS instrument that discovered the tiny wobble of Proxima Centauri, revealing the presence of Proxima b. But this time, HARPS was able to deduce the velocity at which the tiny star is moving away from us and compared it with the radial velocity of Alpha Centauri. Both radial velocities closely match, which means that, in all likelihood, Proxima Centauri has a wide orbit around Alpha Centauri. They are therefore, probably, gravitationally bound.