Alpha Centauri: Uncovering the Secrets of Our Nearest Celestial Neighbor

The two bright stars are (left) Alpha Centauri and (right) Beta Centauri, both binaries. The faint red star in the center of the red circle, at right angles to both and south-east of Alpha is Proxima Centauri, intensely red, smaller in size, weaker in brightness and a distant third element in a triple star system with the main close pair forming Alpha Centauri. Taken with Canon 85mm f/1.8 lens with 11 frames stacked, each frame exposed 30 seconds.

Alpha Centauri is the nearest star system and nearest planetary system to our Solar System at 1.34 parsecs (4.37 light-years) from the Sun. It is a beautiful triple star system, consisting of three stars: α Centauri B (officially Toliman), α Centauri A (officially Rigil Kentaurus), and α Centauri C (officially Proxima Centauri).

Alpha Centauri B and A are Sun-like stars (Class K and G), and together they create the binary star Alpha Centauri AB. The two principal components appear to be one star with a visible magnitude of −0.27, the brightest star in the southern constellation of Centaurus and the third most luminous in the night sky to the natural eye outshone only by Canopus and Sirius.

Alpha Centauri A has around 1.1 times the mass and 1.519 times the Sun luminosity, while Alpha Centauri B is cooler and smaller, at 0.907 times the Sun’s mass and 0.445 times its luminosity. The two-orbit around a common center with an orbital period of 79.91 years. Their oval orbit is eccentric so that the distance between B and A varies from 35.6 AU (astronomical units), or about the distance between Sun and Pluto, to 11.2 AU, or about the distance between Sun and the Saturn.

Proxima Centauri or Alpha Centauri C is a faint and small red dwarf (Class M). Though not noticeable to the naked eye, Proxima Centauri is the nearest star to the Sun at a distance of 1.30 pc (4.24 light-years ), slightly closer than Alpha Centauri AB. The distance between Alpha Centauri AB and Proxima Centauri is about 13,000 astronomical units (0.21 ly), equal to around 430 times the Neptune’s orbit radius.

Studying Alpha Centauri is not easy because it is far away. It took astronomers 60 years and five satellites to know more about Alpha Centauri B and for it to be detected.

Proxima Centauri surprisingly has a couple of planets: Proxima b, an Earth-sized exoplanet in the habitable zone (goldy-lock zone) observed in 2016 CE; and Proxima c, a super-Earth 1.5 AU away, which is perhaps enclosed by a vast ring system, discovered in 2019 CE. Alpha Centauri A might have a Neptune-sized habitable-zone planet. However, it is not yet known to be planetary and could be an artifact of the development mechanism. Alpha Centauri B has no identified planets: planet Bb, discovered in 2012 CE, was proved to be an artifact, and a separate transiting planet has yet to be verified.

The prospects for finding alien life is exciting. And the prospect of having an actual tangible living planet close by is even more exciting. Planets around Alpha Centauri fit the bill, and they’re our best known bet to find life elsewhere in the universe.

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