
science & techESA/Hubble
Hubble's sharp portrait of Alpha Centauri A and B, the nearest star system to Earth
Alpha Centauri is the closest star system to Earth, about 4.3 light-years away in the constellation Centaurus. This Hubble image shows its two bright stars, Alpha Centauri A and B, glowing like headlights against the dark. The picture was taken with the Wide Field and Planetary Camera 2, the instrument that was Hubble's workhorse for its first 13 years until it was replaced in 2009. The two stars are close to the Sun in type: A is a G2 star like our own, and B is a slightly smaller K1 star. They orbit a shared centre of gravity roughly every 80 years. Because the system is so close, astronomers have studied it intensively, and a planet has already been found orbiting Alpha Centauri B.
Being the nearest system makes Alpha Centauri a natural first target for the search for habitable worlds. Its nearby neighbour Proxima Centauri has a planet in its habitable zone, so the system is central to the question of whether life could exist elsewhere nearby.
Alpha Centauri is a triple system, with the faint red dwarf Proxima Centauri as its third member.
