Alpha Centauri
Written by Jerry Coffey
Alpha Centauri is known by many names: Rigil Kentaurus, Rigil Kent, and Toliman. It is the brightest star in the constellation of Centaurus. It is also an established binary system. It can be seen with the unaided eye, but it appears as a single star. With a telescope it is really two stars in close orbit. Its -0.27 visual magnitude makes is the third brightest star in the night sky. Alpha Centauri is the star system that is closest to the Milky Way. It is only 1.34 parsec(4.37 light years) from the our sun.
Alpha Centauri A and Alpha Centauri B are the two stars in the system. A mere 2.18° away there is a third star called Proxima Centauri. This third star is only viewable with a telescope. It is thought that all three stars are gravitational linked in some way although there is no direct proof of that, yet.
Alpha Centauri A is the primary in the system. It is slightly larger(10%in mass and 23% in radius) than our Sun. It has a similar yellowish color with a stellar classification of spectral type G2 V. It also rotates about three days faster than our Sun. 22 days compared to 25. The secondary, Alpha Centauri B, is slightly smaller and has a spectral type of K1 V. It is more orangish-yellow than the primary. It is 90% as massive as our Sun and about 14% smaller in radius. It rotates in 41 days.
The two stars in Alpha Centauri are too close to see individually with the unaided eye, but cal easily be resolved with binoculars or a small 5 cm telescope. In the southern hemisphere, Alpha Centauri is one of the stars of The Pointers or The Southern Pointers. Both stars directly point towards the constellation Crux. Centauri B lies some 4.5° west, mid-way between the Crux and Centauri A. South of about ?29° S latitude, Centauri A is circumpolar and never sets below the horizon. Both stars, including the Crux, are too far south to be visible for mid-latitude northern observers. Below about +29° N latitude to the equator during the northern summer, Centauri l A lies close to the southern horizon. The star culminates each year at midnight on 24 April or 9 p.m. on June 8th.
The discovery of planets around similar binary systems raises the possibility that Alpha Centauri may support such solar bodies. These planets could be in orbit around either of the binaries or in a large orbit around both. So far all attempts to find evidence of planets in the system have been thwarted.
There is a good article about Alpha Centauri here and another one here. We have a great article about the binary system here on Universe Today. Astronomy cast offers a nice episode about interstellar travel. It is relevant since Alpha Centauri is the nearest system to our Sun.
Filed under: Astronomy
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- Why Haven't Planets Been Detected Around Alpha Centauri?
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