Proxima Centauri d is an exoplanet orbiting the red dwarf star Proxima Centauri, the closest star to the Sun and part of the Alpha Centauri triple star system. Together with two other planets in the Proxima Centauri system, it is the closest known exoplanet to the Solar System, located approximately 4.2 light-years away in the constellation of Centaurus. The first signs of the exoplanet emerged as a weak 5.15-day signal in radial velocity data taken from the Very Large Telescope during a 2020 study on Proxima b's mass. This signal was formally proposed to be a candidate exoplanet by Faria et al. in a follow-up paper published in February 2022.
Artistic depiction of Proxima Centauri d, with Proxima Centauri and Alpha Centauri A & B visible in the background
Proxima Centauri is a small, low-mass star located 4.2465 light-years (1.3020 pc) away from the Sun in the southern constellation of Centaurus. Its Latin name means the 'nearest [star] of Centaurus'. It was discovered in 1915 by Robert Innes and is the nearest-known star to the Sun. With a quiescent apparent magnitude of 11.13, it is too faint to be seen with the unaided eye. Proxima Centauri is a member of the Alpha Centauri star system, being identified as component Alpha Centauri C, and is 2.18° to the southwest of the Alpha Centauri AB pair. It is currently 12,950 AU (0.2 ly) from AB, which it orbits with a period of about 550,000 years.
False color Hubble Space Telescope WFPC2 image taken in 2013. The bright lines are diffraction spikes.
Alpha Centauri A and B are the bright apparent star to the left, which are in a triple star system with Proxima Centauri, circled in red. The bright star system to the right is the unrelated Beta Centauri.
Schematic of the three planets (d, b and c) of the Proxima Centauri system, with the habitable zone identified
Overview and comparison of the orbital distance of the habitable zone.