Rigil Kentaurus - Alpha Centauri

Rigil Kentaurus (Rigel Kent) or Alpha Centauri (Alp Cen) is the brightest naked eye star in the constellation Centaurus. With an apparent magnitude of -0.28, Alpha Centauri is the 3rd brightest star in the entire sky (see: 50 Brightest Stars ). Its absolute magnitude is 4.34 and its distance is 4.37 light years. The Equinox J2000 equatorial coordinates are RA = 14h 39m 36.5s, Dec = -60° 50' 02".

Although it appears as a single star to the unaided eye, Alpha Centauri is actually a binary star system. Its individual component stars are named Alpha Centauri A and Alpha Centauri B.

Alpha Centauri A has a spectral type of G2V (like the Sun), a surface temperature of 5790° Kelvin, and a luminosity 1.519 times the Sun. It has a mass of 1.1 solar masses and a diameter 1.23 times the Sun.

Alpha Centauri B has a spectral type of K1V, a surface temperature of 5260° Kelvin, and a luminosity 0.50 times the Sun. It has a mass of 0.91 solar masses and a diameter 0.87 times the Sun.

During the stars' 79.91 year orbit about a common center, the distance between them varies from about that between Pluto and the Sun to that between Saturn and the Sun.

A third star, known as Proxima Centauri, Proxima or Alpha Centauri C, is probably gravitationally associated with Alpha Centauri AB. Proxima is now placed at the slightly smaller distance of 4.24 light years (1.29 parsecs) making it the closest star to the Sun. The true separation of Proxima from Alpha Centauri AB is about 0.2 light years (13,000 astronomical units), or 400 times the size of Neptune's orbit.

The image above shows the uncropped view of Alpha Centauri (North is up) through the Nikkor 300mm f/2.8 lens.

Part of the description above is based on the Alpha Centauri entry in Wikipedia. For more information about Alpha Centauri, see Stars (Jim Kaler).

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