1: Sun’s Nearest Star System
Alpha Centauri is our nearest star neighbor, and is a mere 4.37 light years from the Sun. More accurately, though, it is the nearest ‘star system’ as it actually consists of a binary pair, Alpha Centauri A and Alpha Centauri B, with a third star, Proxima Centauri, located closer still at 4.22 light-years distant. Proxima Centauri is therefore the Earth’s nearest neighboring star, although it would still take one of our current spacecraft around 50,000 years for to reach it.
2: Proxima Centauri Our Nearest Star
Interestingly, it is Proxima Centauri’s separation of 0.21 light years (1.17 trillion kms) from its companion stars that has made astronomers wonder whether it is part of a triple star system at all, and may not even be gravitationally bound to that binary system. While Alpha Centauri A+B revolve around each other once every 80 years, Proxima may be orbiting them every 500,000 years or so.
3: Binary System Status Discovered in 1689
Alpha Centauri was first recognized as a binary system in 1689 by Jean Richaud, a Jesuit priest, who was observing a serendipitously passing comet while he was observing from Puducherry in India. The only other known binary system at that time was in the Crux constellation, of which Acrux was the most luminous member, and a confirmed binary star. It wasn’t until 1915 that the system’s third member, Proxima Centauri, was discovered by Robert Innes from the Cape Observatory.
4: Third Brightest Star in Sky
To the naked eye, the Alpha Centauri system appears as a single star with a visual magnitude of -0.28, making it the third brightest star behind Sirius (-1.46) and Canopus (-0.72). Taken on its own merit, however, Alpha Centauri A would appear to be the night sky’s fourth brightest star, with an apparent magnitude of 0.02.
5: Yellow, Orange and Red Stars
Alpha Centauri A is a yellow star much like our sun, Alpha Centauri B is an orange star, and Proxima Centauri is a red dwarf roughly seven times smaller than our sun. All three stars are around 4.85 billion years old, making them slightly older than the sun, which is around 4.6 billion years old.
Alpha Centauri A has the same spectral classification as our Sun, and has many similar characteristics including its mass (1.100 solar), radius (1.227 solar), and a luminosity (1.519 solar). This star is also known as Rigil Kentaurus, Rigil Kent, Toliman, and Bungula. Likewise, Alpha Centauri B’s statistics are as follows’ mass, (0.907 solar), radius (0.865 solar), and luminosity (0.500 solar); whilst Proxima Centauri is much smaller at mass (0.123 solar), radius (0.141 solar), and luminosity (0.0017 solar).
7: Not Visible Beyond 29 Degrees North
Alpha Centauri is located in the southern part of the sky’s dome, and so is not visible beyond 29 degrees north from northern latitudes, including most of the USA. In America, the line of visibility runs close to Houston and Orlando, but even from as far south as the Florida Keys, Alpha Centauri only rises a few degrees above the horizon, which makes it difficult to observe in all but the darkest of skies. In much of the southern hemisphere, however, Alpha Centauri is circumpolar and never sets, such that it can be viewed the whole year round near the Southern Cross.
8: Belongs To Constellation Of Centaurus
Alpha Centauri is located in the constellation of Centaurus, which is believed to represent a wise centaur from Greek mythology who featured in the lives and times of Jason and Heracles. As the tale states, Heracles killed the centaur by mistake, which resulted in Zeus placing him amongst the stars, with Alpha Centauri marking the Centaur’s right front hoof.
9: Known To Ancient People
It is known, however, that Alpha Centauri featured strongly in ancient Egypt, where many temples to various deities were built to have their principal features aligning with the point on the horizon where the star rose. Alpha Centauri was also known to the ancient Chinese, who knew it as the “Second Star of the Southern Gate”, whilst amongst the Australian Boorong people the star together with Epsilon Centauri was known as “Bermbermgle”, in reference to two brave brothers who slayed the Emu, represented by the Coal Sack nebula in the nearby Crux constellation.
10: Contains Closest Exoplanet to Earth
Orbiting around Proxima Centauri is an exoplanet named Proxima Centauri b, which at 4.25 light-years distant is the closest planet discovered outside of our own solar system. Scientist believe that it is most likely tidally locked with one side permanently facing Proxima Centauri, but is also located in the habitable zone of Proxima Centauri which would enable it to retain liquid water, leading to speculation that it may be habitable.