Alpha Centauri

Alpha Centauri (also known as Rigil Kentaurus) is the brightest star in the southern Centaurus constellation.Other names are Rigil Kentaurus or Rigil Kent, Toliman and Bungula. Alpha Centauri A is also known as HD 128620, HR 5459, CP-60°5483, GCTP 3309.00A, and LHS 50.
Alpha Centauri B is also known as HD 128621, HR 5460, GCTP 3309.00B, and LHS 51. It is the fourth brightest star in the night sky, with a magnitude of -0.01. It is visible in the Southern Hemisphere, and is too far south for most of the Northern Hemisphere to see.

Alpha Centauri is a binary star system of two stars A & B. The distance between them is quite close. To the naked eye, the stars are too close for the eye to be able to see them as separate. Their orbit is about the distance of the giant planets from our Sun.

There is a third star, Proxima Centauri (or Alpha Centauri C). This is usually considered separately, but in fact it is also gravitationally connected to the other two. It is actually slightly closer to us, with a very much larger orbit around A and B.

 System 

Viewed as a triple star system, Alpha Centauri is the closest to our own, being 4.2-4.4 light years (ly) away. It consists of two main stars, Alpha Centauri A and Alpha Centauri B (which form a binary star together) at a distance of 4.36 ly, and a dimmer red dwarf named Proxima Centauri at a distance of 4.22 ly. Both of the two main stars are rather similar to the Sun. The larger star, Alpha Centauri A, is the most similar to the Sun, but a little larger and brighter.

The next closest star is Barnard's Star.

 Diameter and radius 
Alpha Centauri is 1,702,240 km in diameter and 851,120 km in radius.

 Future exploration 
Alpha Centauri is going to be the first target for a crewed or a robotic spacecraft mission.  Using current spacecraft technology, reaching Alpha Centauri would take thousands of years. However, with nuclear propulsion and solar sails, it could take several decades.

The existence of Proxima Centauri b, announced by the European Southern Observatory, could be a target for the first interstellar missions.

In 2069, NASA plans to send a space probe to Alpha Centauri, the closest star system to the Sun. The mission is supposed to launch on the 100th anniversary of Apollo 11.

 Related pages 
 Nature timeline

 Notes 

Category:Binary stars
Category:Red dwarfs