Animation comparing the size of the planet Proxima b with the Earth and other bodies, including its parent star Proxima Centauri. The discovery of Proxima b was announced in August 2016, and is notable for several reasons. Proxima Centauri is the closest star to the Sun, at just 4.25 light years. On top of this, Proxima b was found to be an Earth-like, rocky planet, and it also orbits withing the habitable zone, at the right distance from its star for there to be the possibility of liquid water on its surface. Earth has an equatorial diameter of some 12, 756 kilometres. The largest planet in our Solar System, Jupiter, is 11.2 times wider. The Sun has a diameter 109 times that of Earth. The main star in the Alpha Centauri system, A, is 1.227 times wider than our Sun, with Alpha Centauri B slightly smaller, 0.865 times the Sun's width. Proxima itself is a red dwarf star, barely larger than Jupiter at 0.141 solar diameters. Proxima b's exact size has not been determined, but it is thought to be around 1.4 times Earth's width. |