Proxima Centauri is the nearest star to the Sun, and possesses at least one known inner planet, Proxima Centauri b, a terrestrial planet in a close orbit around the star. There are also strong indications of two further planets in the system, designated Proxima Centauri c and Proxima Centauri d.
Proxima Centauri c is the outermost of the planets in the Proxima system, with a relatively eccentric orbit (if it were within the Solar System, its distance from the Sun would vary between approximately the orbits of Earth and Mars). Proxima is a very low luminosity star, however, and so Proxima Centauri c receives far less energy from its star than either Earth or Mars. This means that Proxima c is a cold planet, falling far outside the habitable zone for its faint parent star.
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Proxima Centauri c has a mass some seven times that of Earth, and so it appears to belong to the ' super Earth' classification, relating to terrestrial planets with unusually high mass values (alternatively, it may be a small ice giant planet). Shifts in the pattern of its light as the planet travels along its orbit suggest the possibility that it possesses a significant ring system.
It should be noted that, since the original reporting of the detection of this
planet, some doubts have been raised about the interpretation of the relevant data. So, while planets b and d of the Proxima system are confirmed, the existence of Proxima Centauri c is formally considered to be unconfirmed and under dispute.