Proxima Centauri

Proxima Centauri is the closest known star to the Sun — a small red M5.5 Ve dwarf only 4.246 light-years away, gravitationally bound to the bright Alpha Centauri AB pair as the third member of that triple system. Its visual magnitude is 11.0, well below naked-eye visibility despite being our nearest neighbour. Proxima hosts at least three confirmed planets, including the rocky Earth-mass Proxima Centauri b in the habitable zone, discovered in 2016.

Visible only from southern latitudes (declination −62.7°). Even from there, Proxima is faint and tucked away 2.2° south-west of Alpha Centauri AB — a small telescope and a good finder chart are essential. The reward is observing the very nearest star to our Sun. Best in the southern autumn evenings.

Robert Innes discovered Proxima in 1915 from the Union Observatory in Johannesburg, recognising its high proper motion as a marker of nearness. Parallax measurements over the next decade confirmed it as the nearest star known. The 2016 detection of Proxima b, an Earth-mass planet in the habitable zone, made it the most-observed exoplanet host star in modern astronomy.