Proxima Centauri c is a super-Earth-sized exoplanet discovered in 2019 using the radial velocity method. Its estimated radius is 0.16 times that of Jupiter (1.8 times that of Earth), and its estimated mass is 0.03 times that of Jupiter (9.54 times that of Earth). Its host star is Proxima Centauri (an M-type star located approximately 4.2 light-years from the Sun), and Proxima Centauri c orbits at a distance of about 1.5 AU from the star, completing one orbit in approximately 5.3 years. Furthermore, its orbit lies just outside that of Proxima Centauri b, which is known as the closest potentially habitable planet to Earth. Proxima Centauri c itself lies far outside the star’s habitable zone and, with an estimated blackbody temperature of -231°C, is considered uninhabitable.
(※For more information on the host star Proxima Centauri, be sure to check out the article on Proxima Centauri b!)
It is generally believed that super-Earth-sized planets form near their host star’s snow line. However, in the case of Proxima Centauri c, Proxima Centauri’s snow line is located around 0.088 AU, while Proxima Centauri c is approximately 1.5 AU from its host star; therefore, this planet appears to challenge that theory. On the other hand, it is possible that this planet does not actually exist. Currently, space telescopes such as Gaia, launched by the ESA, are attempting to confirm the existence of Proxima Centauri c.
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References:
1) Proxima Centauri c, ExoKyoto, http://www.exoplanetkyoto.org/exohtml/Proxima_Centauri_cJP.html
2) “A second planet might orbit the closest star to the sun, and astronomers think it’s a super-Earth”, INSIDER,
https://www.businessinsider.com/super-earth-orbits-proxima-centauri-closest-star-to-sun-2020-1
Artist’s concept of Proxima Centauri c (Scenario 1: a rocky planet)
(Image Credit: Yuna Watanabe, Habitable Research Group Moriyama Junior High School )
Artist’s concept of Proxima Centauri c (as a rocky planet, part 2)
(Image Credit: Yuna Watanabe, Habitable Research Group Moriyama Junior High School )
Artist’s concept of Proxima Centauri c (as a gas giant)
(Image Credit: Yuna Watanabe, Habitable Research Group Moriyama Junior High School )
