At about 4.25 light-years from the Sun, Proxima Centauri is our nearest individual stellar neighbor. It is also Alpha Centauri C, the third member of our nearest neighboring star system. Its companions, Alpha Centauri A and B, are about 4.37 light-years away. All three belong to one gravitationally bound system.
Proximity does not guarantee brightness. Proxima is a small, faint red dwarf, invisible to the unaided eye and requiring a telescope. Alpha Centauri A/B appears as one brilliant naked-eye star, although a telescope can separate its two components under suitable conditions. A finder must therefore place Proxima at its own position rather than mark it at the bright pair.
The angular gap is about 2.2 degrees, roughly four full-Moon widths. The physical separation is enormous too: Proxima is about 13,000 Earth–Sun distances, or 0.2 light-years, from A/B. Our closeness to this system makes that spacing conspicuous across the sky. Being gravitationally bound does not require stars to look close together; their relative speed must be low enough that they remain bound.
Proxima follows a very wide orbit around the bright pair, with an estimated period of roughly 550,000 years. Meanwhile, A and B orbit one another in about 80 years. These nested orbits make the three stars a family even though Proxima is far from its companions.
Proxima is currently approaching the Sun at about 22 kilometres per second along our line of sight, approximately 49,000 miles per hour. This radial velocity describes the changing distance, not its full motion through space. The whole Alpha Centauri system shares the broad approach; Proxima’s much slower motion around A/B is a separate contribution.
We are not seeing Proxima at its closest. A published trajectory calculation estimated a closest passage about 27,000 years from now, at roughly 3.1 light-years, before it recedes again. These are rounded predictions based on measured stellar motion. Even at stellar speeds, interstellar distances make the encounter unfold over tens of thousands of years.
Sources: Kervella, Thévenin and Lovis, “Proxima’s orbit around Alpha Centauri” (2017), and the Observatoire de Paris account of that work; García-Sánchez and colleagues, “Stellar encounters with the solar system” (2001), for the closest-approach estimate; ESO’s annotated Alpha Centauri and Proxima sky image.
