HowDoWhy

We’ve already answered in a previous post that the Sun is the closest star to the Earth, but when most people ask this they’re really asking, what is the closest star to the Sun. The closest star to the Sun is Proxima Centauri at 4.2 light-years away.

Interestingly, most folks often think of Alpha Centauri as the nearest star but there are two misconceptions there. First, Alpha Centauri is actually a binary pair of stars rather than one star. They are known as Alpha Centauri A and Alpha Centauri B. Second, while nearly as close as Proxima Centauri, the Alpha Centauri pair are slightly further away at 4.3 light-years.

Other interesting facts about these stars:

• The Centauri group is believed to actually be a triple star system, with Alpha Cent A and B orbiting each other and Proxima orbiting in a massive circle around the two of them.
• Alpha Centauri A is about 1.2 times the size of the Sun.
• Alpha Centauri B is about .86 times the size of the Sun.
• Tiny Proxima Centauri is only 1.5 times the size of Jupiter but 150 more massive.
• Proxima Centauri is barely massive enough to ignite its hydrogen. Much smaller and it would have been a failed star known as a Brown Dwarf.