Proxima Centauri b: The Closest Exoplanet to Earth

​The closest exoplanet to Earth in terms of distance is Proxima Centauri b, located just 4.2 light-years away, in the constellation Centaurus. This exoplanet orbits the red dwarf star Proxima Centauri and is within its star's habitable zone, which is the region where liquid water could exist on a planet's surface. It is the closest star to our Sun. Discovered in 2016 via Doppler spectroscopy, it is a Super Earth exoplanet with a 1.07 Earth mass and a radius of about 1.3 times that of Earth. It orbits its Sun in 11.2 Earth days.
 
Exoplanets are a major focus in the search for life beyond Earth, as some may have conditions suitable for liquid water and habitability. For example, Proxima Centauri b, a nearby super-Earth, is considered a candidate for habitability. An exoplanet, also called an extrasolar planet, is any planet that exists outside our Solar System and orbits a star other than the Sun. Exoplanets vary widely in characteristics. They can be gas giants like Jupiter, icy planets like Neptune, or rocky planets similar to Earth or Mars. Many exoplanets have no direct analogues in our Solar System, including types such as super-Earths (larger than Earth but smaller than Neptune), mini-Neptunes, hot Jupiters (gas giants orbiting very close to their stars), and lava worlds with extremely high surface temperatures.
 
By habitable zone, it indicates that Proxima Centauri b receives about 65–70% of the energy from its Sun, just like Earth gets from her Sun. However, Proxima Centauri is a flare star, emitting intense bursts of radiation, including ultraviolet and X-rays, which could strip away the planet’s atmosphere and affect its potential habitability. It is unknown whether Proxima Centauri b has an atmosphere. The high radiation environment makes atmospheric retention challenging, but volcanic activity or comet impacts could potentially replenish or rebuild an atmosphere. The planet is likely tidally locked, meaning one side always faces the star, creating extreme climate conditions with potentially only a portion of the surface being habitable. Simulations suggest a range of possible climates—from ice-covered worlds to planets with oceans or dry land, depending on atmospheric and orbital properties.
 
As the closest exoplanet to Earth, Proxima Centauri b is a prime target for future robotic exploration and studies of exoplanetary atmospheres and habitability. While its location in the habitable zone is promising, the unknowns about its atmosphere and the harsh stellar environment mean it’s true habitability remains uncertain.
 
References
(2025, May 24). Proxima Centauri b. In Wikipedia, https://en.wikipedia.org/wiki/Proxima_Centauri_b
 
Ribas, I., Bolmont, E., Selsis, F., Reiners, A., Leconte, J., Raymond, S.N., Engle, S.G., Guinan, E.F., Morin, J., Turbet, M., & Anglada-Escude, G. (2016, August 24). The Habitability of Proxima Centauri b. Astronomy & Astrophysics. EDP Sciences. https://www.aanda.org/articles/aa/full_html/2016/12/aa29576-16/aa29576-16.html