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Did you know? Alpha Centauri

This month . . . Meet the neighbours! Alpha Centauri - the closest star system to our solar system.

The Alpha Centauri system consists of three stars: a binary pair Alpha Centauri and Beta Centauri: and Proxima Centauri which at 4.22 light years is the closest star to Earth after the Sun.

Image below: Alpha Centauri image form the Hubble Space telescope, ESA/NASA


The Jesuit priest, Jean Richaud, first recognised Alpha Centauri as a binary system in December 1689. It wasn’t until 1915 that the system’s third member, Proxima Centauri, was discovered by Robert Innes from the Cape Observatory.

Alpha Centauri is located in the southern part of the sky and is not visible beyond 29 degrees north.

However, in much of the southern hemisphere Alpha Centauri is circumpolar and never sets, meaning that it can be viewed the whole year near the Southern Cross constellation.

Even though Alpha Centauri is “in our backyard” it is still more than 4 light-years, or 37.8 trillion kilometres away. According to NASA, even using the space shuttle (retired in 2012) which travels at 28,000 kilometres per hour it would still take over 148,000 years to reach Alpha Centauri. Hardly a quick jaunt across the cosmos to visit the neighbours!

The stars of Alpha Centauri are slowly moving toward Earth. They will be closest to our solar system in around 30,000 years, when they will be about 3 light-years away. Then 3,000 years later, the star system will begin to move away from the solar system again, and Proxima Centauri will no longer be the Sun's closest neighbour.

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