The star Proxima Centauri isn’t visible to the eye, but it’s one of the most noted stars in Earth’s sky. That’s because it is considered to be part of the Alpha Centauri star system, a triple system, and the nearest star system to our sun. Of the three stars in Alpha Centauri, Proxima is thought to be the one actually closest to our sun, solar system and Earth. This image – from the Hubble Space Telescope – is one of the best we’ve seen at showing Proxima clearly.
Hubble’s Wide Field and Planetary Camera 2 (WFPC2) captured this view.
If it’s so nearby, why can’t we see Proxima Centauri with the eye? It’s because Proxima is so small. It’s red dwarf star with only about an eighth of the mass of the sun. Faint red Proxima Centauri – at only 3,100 K and 500 times less bright than our sun – is nearly a fifth of a light year from Alpha Centauri A and B.
This great distance from the two primary stars in the system is what calls into question its status as part of a triple star system.
On the other hand, although Proxima is far from Alpha Centauri A and B, it is not very far from us. And thus – over time – we can see its motion through space.
Bottom line: Hubble’s Wide Field and Planetary Camera 2 (WFPC2) captured this view of the Alpha Centauri system, the star system closest to our sun and Earth. Proxima Centauri, one of three stars in the Alpha Centauri system, is our sun’s nearest known neighbor among the stars. It’s 4.22 light-years away.
Deborah Byrd created the EarthSky radio series in 1991 and EarthSky.org in 1994. Today, she serves as Editor-in-Chief of this website. She has won a galaxy of awards from the broadcasting and science communities, including having an asteroid named 3505 Byrd in her honor. A science communicator and educator since 1976, Byrd believes in science as a force for good in the world and a vital tool for the 21st century. "Being an EarthSky editor is like hosting a big global party for cool nature-lovers," she says.