Proxima Centauri c (also called Proxima c or Alpha Centauri Cc) is a controversial

exoplanet An exoplanet or extrasolar planet is a planet outside the Solar System. The first confirmed detection of an exoplanet was in 1992 around a pulsar, and the first detection around a main-sequence star was in 1995. A different planet, first det ...

candidate, claimed to be orbiting the

red dwarf A red dwarf is the smallest kind of star on the main sequence. Red dwarfs are by far the most common type of fusing star in the Milky Way, at least in the neighborhood of the Sun. However, due to their low luminosity, individual red dwarfs are ...

star

Proxima Centauri Proxima Centauri is the nearest star to Earth after the Sun, located 4.25 light-years away in the southern constellation of Centaurus. This object was discovered in 1915 by Robert T. A. Innes, Robert Innes. It is a small, low-mass st ...

, which is the closest star to the

Sun The Sun is the star at the centre of the Solar System. It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light a ...

and part of a triple

star system A star system or stellar system is a small number of stars that orbit each other, bound by gravity, gravitational attraction. It may sometimes be used to refer to a single star. A large group of stars bound by gravitation is generally calle ...

Characteristics

It is located approximately from

Earth Earth is the third planet from the Sun and the only astronomical object known to Planetary habitability, harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all ...

in the constellation of

Centaurus Centaurus () is a bright constellation in the southern sky. One of the 88 modern constellations by area, largest constellations, Centaurus was included among the 48 constellations listed by the 2nd-century astronomer Ptolemy, and it remains one ...

, making it,

Proxima b Proxima Centauri b is an exoplanet orbiting within the habitable zone of the red dwarf star Proxima Centauri in the constellation Centaurus. It can also be referred to as Proxima b, or Alpha Centauri Cb. The host star is the closest star to th ...

, and

Proxima d Proxima Centauri d (also called Proxima d) is a candidate 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 Pr ...

the closest known exoplanets to the

Solar System The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Sola ...

. Proxima Centauri c is a

super-Earth A super-Earth is a type of exoplanet with a mass higher than Earth, but substantially below those of the Solar System's ice giants, Uranus and Neptune, which are 14.5 and 17.1 times Earth's, respectively. The term "super-Earth" refers only to t ...

mini-Neptune A Mini-Neptune (sometimes known as a gas dwarf or transitional planet) is a planet less massive than Neptune but resembling Neptune in that it has a thick hydrogen-helium atmosphere, probably with deep layers of ice, rock or liquid oceans (made o ...

about 7 times as massive as Earth, orbiting at roughly every . Due to its large mass and its distance from Proxima Centauri, the exoplanet is uninhabitable and too cold for liquid water to exist on the surface, with an equilibrium temperature of approximately . The planet is not transiting its parent star from the point of view of an Earth-based observer.

Discovery

The planet was first reported by Italian astrophysicist Mario Damasso and his colleagues in April 2019. Damasso's team had noticed minor movements of Proxima Centauri in the

radial velocity The radial velocity or line-of-sight velocity of a target with respect to an observer is the rate of change of the vector displacement between the two points. It is formulated as the vector projection of the target-observer relative velocity ...

data from the ESO's

HARPS The High Accuracy Radial Velocity Planet Searcher (HARPS) is a high-precision Echelle grating, echelle planet-finding spectrograph installed in 2002 on the ESO 3.6 m Telescope, ESO's 3.6m telescope at La Silla Observatory in Chile. The First l ...

instrument, analyzed earlier by Ukrainian astrophysicist Yakiv Pavlenko and his colleagues at the

Instituto de Astrofísica de Canarias The Instituto de Astrofísica de Canarias (IAC) is an astrophysical research institute located in the Canary Islands, Spain. It was founded in 1975 at the University of La Laguna. It operates two astronomical observatories in the Canary Islands: ...

, indicating a possible second planet orbiting Proxima Centauri. The discovery was published on 15 January 2020.In June 2020, the planet's existence was initially confirmed using Hubble

astrometry Astrometry is a branch of astronomy that involves precise measurements of the positions and movements of stars and other Astronomical object, celestial bodies. It provides the kinematics and physical origin of the Solar System and this galaxy, th ...

data from , allowing its

inclination Orbital inclination measures the tilt of an object's orbit around a celestial body. It is expressed as the angle between a reference plane and the orbital plane or axis of direction of the orbiting object. For a satellite orbiting the Eart ...

and true mass to be determined. Also in June 2020, a possible directly imaged counterpart of Proxima c was detected in the infrared with

SPHERE A sphere (from Ancient Greek, Greek , ) is a surface (mathematics), surface analogous to the circle, a curve. In solid geometry, a sphere is the Locus (mathematics), set of points that are all at the same distance from a given point in three ...

, but the authors admit that they "did not obtain a clear detection". If their candidate source is in fact Proxima Centauri c, it is too bright for a planet of its mass and age, implying that the planet may have a

ring system A ring system is a disc or torus orbiting an astronomical object that is composed of solid material such as dust, meteoroids, planetoids, moonlets, or stellar objects. Ring systems are best known as planetary rings, common components of sate ...

with a radius of around 5 . However, a 2022 study questioned the planetary nature of the observed

signal corresponding to Proxima c, whose detection could not be recreated, attributing it to systematic effects. If this is the case, it is unclear why

astrometric Astrometry is a branch of astronomy that involves precise measurements of the positions and movements of stars and other celestial bodies. It provides the kinematics and physical origin of the Solar System and this galaxy, the Milky Way. History ...

observations detected what appeared to be a similar planetary signature.

References

{{Sky, 14, 29, 42.9487, -, 62, 40, 46.141, 4.243 Exoplanets discovered in 2020 Exoplanets detected by radial velocity Exoplanets detected by astrometry Proxima Centauri Planetary rings Exoplanet candidates

Characteristics

Discovery

See also

References