What Is the Closest Star?

Proxima Centauri
Proxima Centauri as seen by the Hubble Space Telescope Credit: NASA

“What is the closest star?”

This is often a trick question given to students. Most people start trying to think of exotic sounding names like Rigel, Sirius or Betelgeuse. The answer is “The Sun”. Our Sun is a star, specifically a Main Sequence G-type star commonly known as a yellow dwarf.

When this question is asked, it is usually followed up by “Which star is closest to the Sun?”

The answer is Proxima Centauri. It is 4.24 light years or just under 40 trillion kilometers from the Sun. Proxima means “nearest to” so this makes it easy to remember Proxima Centauri is the star “nearest to” the Sun.

Proxima Centauri is part of a collection of three stars called Rigil Kentaurus meaining “Foot of the Centaur”. Rigil Kentaurus is part of the constellation Centaurus. It is the brightest star in the skies of the Southern Hemisphere. Astonomers thought Rigil Kentaurus was a single star until 1689 when it was discovered there were really two stars close together. These were named Alpha Centauri A and Alpha Centauri B. Proxima Centauri is much dimmer and is easily lost in the glare of Alpha Centauri. It was not discovered until 1915.