![]() The discovery image of Candidate 1, taken by the NEAR instrument at ESO's Very Large Telescope in 2021. | |
Discovery [1] | |
---|---|
Discovered by | K. Wagner, et al. |
Discovery date | 2021 |
Direct imaging | |
Designations | |
Alpha Centauri Ab, Rigil Kentaurus b, C1 | |
Orbital characteristics | |
1.1 AU | |
~360 d | |
Inclination | ~70° |
Star | Alpha Centauri A |
Physical characteristics | |
3.3-7 R🜨 | |
Mass | ~20-50 ME |
Candidate 1 (also known as C1 or Alpha Centauri Ab) is an exoplanet candidate directly imaged around Alpha Centauri A in February 2021. If confirmed as an exoplanet, it would orbit at approximately 1.1 AU away from Alpha Centauri A with a period of about a year and would have a mass between that of Neptune and one-half that of Saturn and would therefore likely be a gas giant. [1] Despite being a gas giant, due to its position in its orbit with Alpha Centauri A, it could have habitable moon(s) in its own orbit. The planet candidate is yet to be confirmed as an exoplanetary signal; additional observations are needed to confirm its true nature.
Astronomers from the Breakthrough Watch Initiative directly imaged the habitable-zone candidate using a newly developed system for mid-infrared exoplanet imaging. [2] Previous observations from years before ruled out the possibility of it being a background star. The team presented the discovery of the exoplanet candidate in a publication in Nature Communications titled “Imaging low-mass planets within the habitable zone of Alpha Centauri.” [3] However, the observation arc, being only 100 hours long, is not enough to determine whether a signal is planetary in nature, and it may be zodiacal dust or an instrumental artifact.
The possible detection of the planet is extremely preliminary, and the object may not even count as a planetary candidate. [4]
While little is known about the candidate planet, there are some characteristics that may be inferred based on its observations. It would have an orbital inclination of ~70° relative to Earth's point of view, consistent with the inclination of the Alpha Centauri system as a whole. Because of the detection algorithm, it would be somewhere around Neptune's mass, and would be no larger than 7 R🜨 as its mass would exceed the radial-velocity threshold of ~50 ME, [5] but no smaller than 3.3 R🜨 as that would not render the signature given in the paper. Due to this large size, it is highly unlikely to be rocky and is probably a Neptune-sized planet. Follow-up observations will be needed to determine whether it is a planet, cloud of dust, or simply an artifact due to its short observation arc.
Alpha Centauri is a triple star system in the southern constellation of Centaurus. It consists of three stars: Rigil Kentaurus, Toliman, and Proxima Centauri. Proxima Centauri is the closest star to the Sun at 4.2465 light-years (1.3020 pc).
An exoplanet or extrasolar planet is a planet outside the Solar System. The first possible evidence of an exoplanet was noted in 1917 but was not then recognized as such. The first confirmation of the detection occurred in 1992. A different planet, first detected in 1988, was confirmed in 2003. According to statistics from the NASA Exoplanet Archive, As of 8 August 2024, there are 5,743 confirmed exoplanets in 4,286 planetary systems, with 961 systems having more than one planet. The James Webb Space Telescope (JWST) is expected to discover more exoplanets, and to give more insight into their traits, such as their composition, environmental conditions, and potential for life.
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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.
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Margaret Carol "Maggie" Turnbull is an American astronomer and astrobiologist. She received her PhD in Astronomy from the University of Arizona in 2004. Turnbull is an authority on star systems which may have habitable planets, solar twins and planetary habitability. She is also an expert on the use of the coronagraph in the direct detection of exoplanets.
Any planet is an extremely faint light source compared to its parent star. For example, a star like the Sun is about a billion times as bright as the reflected light from any of the planets orbiting it. In addition to the intrinsic difficulty of detecting such a faint light source, the light from the parent star causes a glare that washes it out. For those reasons, very few of the exoplanets reported as of January 2024 have been observed directly, with even fewer being resolved from their host star.
A Super-Earth is a type of exoplanet with a mass higher than Earth's, but substantially below those of the Solar System's ice giants, Uranus and Neptune, which are 14.5 and 17 times Earth's, respectively. The term "super-Earth" refers only to the mass of the planet, and so does not imply anything about the surface conditions or habitability. The alternative term "gas dwarfs" may be more accurate for those at the higher end of the mass scale, although "mini-Neptunes" is a more common term.
This page describes exoplanet orbital and physical parameters.
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An exoplanet is a planet located outside the Solar System. The first evidence of an exoplanet was noted as early as 1917, but was not recognized as such until 2016; no planet discovery has yet come from that evidence. What turned out to be the first detection of an exoplanet was published among a list of possible candidates in 1988, though not confirmed until 2003. The first confirmed detection came in 1992, with the discovery of terrestrial-mass planets orbiting the pulsar PSR B1257+12. The first confirmation of an exoplanet orbiting a main-sequence star was made in 1995, when a giant planet was found in a four-day orbit around the nearby star 51 Pegasi. Some exoplanets have been imaged directly by telescopes, but the vast majority have been detected through indirect methods, such as the transit method and the radial-velocity method. As of 24 July 2024, there are 7,026 confirmed exoplanets in 4,949 planetary systems, with 1007 systems having more than one planet. This is a list of the most notable discoveries.
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Proxima Centauri b, also referred to as Alpha Centauri Cb, is an exoplanet orbiting within the habitable zone of the red dwarf star Proxima Centauri, which is the closest star to the Sun and part of the larger triple star system Alpha Centauri. It is about 4.2 light-years from Earth in the constellation Centaurus, making it and Proxima d, along with the currently disputed Proxima c, the closest known exoplanets to the Solar System.
Proxima Centauri c is a controversial exoplanet candidate claimed to be orbiting the red dwarf star Proxima Centauri, which is the closest star to the Sun and part of a triple star system. It is located approximately 4.2 light-years from Earth in the constellation of Centaurus, making it, Proxima b, and Proxima d the closest known exoplanets to the Solar System.
GJ 3470, proper name Kaewkosin, is a red dwarf star located in the constellation of Cancer, 96 light-years away from Earth. With a faint apparent magnitude of 12.3, it is not visible to the naked eye. It hosts one known exoplanet, GJ 3470 b.
Kepler-1708b is a Jupiter-sized exoplanet orbiting the Sun-like star Kepler-1708, located in the constellation of Cygnus approximately 5,600 light years away from Earth. It was first detected in 2011 by NASA's Kepler mission using the transit method, but was not identified as a candidate planet until 2019. In 2021, a candidate Neptune-sized exomoon in orbit around Kepler-1708b was found by astronomer David Kipping and colleagues in an analysis using Kepler transit data. However, subsequent research has raised discrepancies about the possible existence of an exomoon, similar to that of Kepler-1625b.