Now we have spotted what we think is a second planet around this star.
The star Proxima Centauri is the smallest star in a triple system in the constellation of Centaurus.
Since it is the star in closest proximity to our sun, it is usually referred to as Proxima.
Like most stars, Proxima Centauri is a cool, small object known as ared dwarf star.
It is about eight times less massive than the sun and has about half its temperature.
The previously discovered planetProxima bis (most likely) a rocky planet orbiting the star within its habitable zone.
However, Proxima c orbits relatively far from its cool star and is therefore unlikely to be habitable.
If it doesnt have an atmosphere, it most likely has a temperature below -200C.
This is called the radial velocity technique.
The first signal was weak.
But further observations were made and existing ones reanalyzed to verify the planets existence.
The history of detecting and understanding exoplanets has been driven forward by a wide variety of techniques.
This discovery was subsequently awarded part of the2019 Nobel prize in Physics.
There have always been concerns, however, that apparent planetary signals might be due to stellar activity.
This made it a very challenging discovery.
These features need to be considered when searching for any planetary signals.
Y. Beletsky (LCO)/ESO/ESA/NASA/M.
For the sun this timescale is fairly consistent, but the number of sunspots remain infuriatingly difficult to predict.
Further observations can, however, strengthen the evidence for its existence.
The ideal way to verify its existence would be with a direct image.
But Proxima is a cool, dim star, making the contrast between star and its planets significantly easier.
Can we go there?
Proxima c is an ideal planet for follow-up studies compared to other planets discovered around more distant stars.
To confirm its existence and characterize its properties will require state-of-the-art technology.
However, at 4.2 light years, it is still immensely distant for humans.
If the distance between the Earth and the sun were 1cm, Proxima is 11km away.
Such a microchip starship might be propelled by lasers and reach the system a few decades from now.
This article is republished fromThe ConversationbyHugh Jones, Professor of Astrophysics,University of Hertfordshireunder a Creative Commons license.
