Proxima Centauri is a red dwarf star that is likely a part of the Alpha Centauri star system and is the closest star to the Sun at a distance of 4.22 light-years (3.99×1013 km; 2.48×1013 mi). It is in the constellation of Centaurus.
In 1951, Harlow Shapley said that Proxima Centauri was a flare star. Recorded photographs showed that the star became measurably brighter about 8% of the time, making it the most active flare star then found.
Red dwarfs are usually far too faint to be seen with the naked eye, that means without a telescope. Proxima Centauri has an apparent magnitude of 11 while its absolute magnitude is a very dim 15.5. Even from Alpha Centauri A or B, Proxima would only be seen as a 5th magnitude star.
Proxima Centauri has been the closest star to the Sun for about the last 32,000 years. Barnard's Star will make its closest approach to the Sun around AD 11,700, when it approaches to within about 3.8 light-years. However, at that time, it will not be the nearest star, since Proxima Centauri will then have moved even closer to the Sun. Six stars will come closer to Earth in the next 45,000 years.
In 2016, a exoplanet was found by the European Southern Observatory around Proxima Centauri, Proxima Centauri b (or Proxima b). It was found in the habitable zone, and was thought to be Earth-like, with an ESI of 0.87. While being Earth-like, it may not be habitable on the surface, since Proxima Centauri gives off strong solar flares and high solar winds, which could strip away parts of the atmosphere of the planet, making it less habitable.
Another planet, Proxima Centauri c, much farther out than b, was discovered in 2019. It is seven times heavier (more massive) than Earth. It is too cold to be habitable. Because it showed up brighter than expected when photos of it were taken, it may have a ring system five times wider than that of Jupiter.
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- Same source: The close approach of stars in the Solar neighborhood. Matthews R.A.J. 1994. Quarterly Journal of the Royal Astronomical Society, 35, #1, p1.
- http://phl.upr.edu/press-releases/proxb | A Potentially Habitable World in Our Nearest Star | Aug 17, 2016
- https://www.space.com/39829-nearest-exoplanet-proxima-b-superflare.html | Superflare Blasts Proxima b, the Nearest Exoplanet, Dimming Hopes of Life | By Mike Wall | February 28, 2018
- "Planet in star system nearest our Sun 'may have oceans'", Phys.org, Retrieved 6 October 2016
- Billings, Lee (April 12, 2019). "A Second planet may orbit Earth's nearest neighboring star". Scientific American. Retrieved April 12, 2019.