At magnitude 2.58, Alpha Leporis is the brightest star in the little constellation Lepus, the Hare, which lies south of Orion, and represents the Hunter's prey. The star is easy to find, as it is makes the southern apex of a triangle with the two bottom stars of Orion, Rigel and Saiph (β and κ Ori). Alpha Leporis also has the traditional name Arneb (meaning "hare" in Arabic).
Properties
Arneb is a class F0 Ib supergiant, like a more distant version of Canopus. Though Canopus is sometimes classed as a bright giant, the two are quite similar. From its distance of 1300 light years (four times farther than Canopus), the star to has a luminosity of 13,000 suns, which coupled with its 7000 K surface temperature gives it a diameter 75 times solar - enough to make it almost the size of Mercury's orbit.
Arneb seems to be single, an apparent dim companion half a minute of arc away probably just lying in the line of sight.
Evolution
Arneb ceased fusing hydrogen into helium in its core long ago, and has expanded to its present proportions and cooled at its surface. It may become a larger red supergiant, fusing helium into carbon and oxygen, or may have already been a red supergiant and is now shrinking and heating a little. In either case, stars like Arneb and Canopus are quite rare because of the speed with which they evolve.
The aging process has left Arneb with an odd chemical composition. Its nitrogen content is five times higher than the Sun's; this is the result of the fusion of hydrogen into helium through the C-N-O cycle, in which carbon is used as a nuclear catalyst, nitrogen is produced as a by-product, and then brought to the surface. Arneb also has twice the Sun's sodium abundance (as does Canopus), as a result of a similar nuclear reaction cycle that involves neon.
With a birth mass 8 to 10 suns, the star will probable die as a tiny, dense white dwarf about the size of Earth, though perhaps an rare one made of neon and oxygen. If it is at the heavier end of its estimated mass, it may end in a supernova explosion.
[Adapted from STARS by Jim Kaler, Professor Emeritus of Astronomy, University of Illinois]