Proxima Centauri c

Proxima Centauri c (also called Proxima c[2] or Alpha Centauri Cc) is an exoplanet 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 (4.0×10¹³ km) from Earth in the constellation of Centaurus, making it and Proxima b the closest known exoplanets to the Solar System.

Proxima Centauri c

Discovery[1]
Discovered by	Damasso et al.
Discovery site	HARPS
Discovery date	January 2020
Detection method	Radial velocity
Orbital characteristics
Semi-major axis	1.489±0.049 AU[2]
Eccentricity	0.04±0.01[3]
Orbital period	1928±20 d[3]
Inclination	133±1[3]
Longitude of ascending node	331±1[3]
Longitude of periastron	−4±4[3]
Time of periastron	2456202±21[3]
Semi-amplitude	1.1±0.2[3]
Star	Proxima Centauri
Physical characteristics
Mass	7±1 M⊕[3]
Temperature	39 K (−234.2 °C; −389.5 °F)[1]

Proxima Centauri c is a super-Earth or mini-Neptune about 7 times as massive as Earth, orbiting at roughly 1.49 astronomical units (223,000,000 km) every 1,928 days (5.28 yr).[3] If Proxima b were equivalent to Earth, then Proxima c would be the system's Neptune. Due to its large distance from Proxima Centauri, the exoplanet is unlikely to be habitable, with a low equilibrium temperature of around 39 K.[1]

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 data from the ESO's HARPS instrument, indicating a possible second planet orbiting Proxima Centauri.[4] The discovery was published in January 2020.[1] In June 2020, the planet's existence was confirmed using Hubble astrometry data from c. 1995, allowing its inclination and true mass to be determined.[3][5] Also in June 2020, a possible direct imaging detection of Proxima c was published. The detected source is too bright for a planet of Proxima c's mass and age, implying that the planet may have a ring system with a radius of around 5 R_J.[6]

References

1. Damasso, Mario; et al. (January 2020). "A low-mass planet candidate orbiting Proxima Centauri at a distance of 1.5 AU". Science Advances. 6 (3): eaax7467. Bibcode:2020SciA....6.7467D. doi:10.1126/sciadv.aax7467. Retrieved 23 July 2020.
2. Kervella, Pierre; Arenou, Frédéric; Schneider, Jean (March 2020). "Orbital inclination and mass of the exoplanet candidate Proxima c". Astronomy & Astrophysics. 635: L14. arXiv:2003.13106. Bibcode:2020A&A...635L..14K. doi:10.1051/0004-6361/202037551.
3. Benedict, G. Fritz; McArthur, Barbara E. (June 2020). "A Moving Target—Revising the Mass of Proxima Centauri c". Research Notes of the AAS. 4 (6): 86. Bibcode:2020RNAAS...4...86B. doi:10.3847/2515-5172/ab9ca9. Retrieved 23 July 2020.
4. Billings, Lee (April 12, 2019). "A Second Planet May Orbit Earth's Nearest Neighboring Star". Scientific American. Retrieved April 12, 2019.
5. Benedict, Fritz (June 2, 2020). "Texas Astronomer Uses 25-year-old Hubble Data to Confirm Planet Proxima Centauri c". McDonald Observatory. University of Texas.
6. Gratton, R.; et al. (June 2020). "Searching for the near-infrared counterpart of Proxima c using multi-epoch high-contrast SPHERE data at VLT". Astronomy & Astrophysics. 638: A120. arXiv:2004.06685. Bibcode:2020A&A...638A.120G. doi:10.1051/0004-6361/202037594.