Aldebaran

Spectral class: K5III
Galactic coordinates:

l 181.33

b -19.65

Plane dist 61.44

Surface temperature: 3950 K
Rotation period: 63,000 days
Diameter: 60 million km

Also known as Alpha Tauri, 87 Tauri and HIP 21421, Aldebaran is a giant type K5 III star. It is the primary component of the Aldebaran system, a binary system. The other component, Aldebaran B, is a dim red dwarf at a distance of 607 AUs.

As a star that has evolved out of the "main sequence" now primarily fusing helium instead of hydrogen, the main star has expanded to a diameter of approximately 5.3 × 107 km. It is 65.1 light years away from the central UCP star system of Sol, and it shines with 150 times Sol's luminosity. It is slightly variable, of the irregular variable type, by about 0.2 magnitude. This helium-burning, orange-red giant stage is relatively brief, lasting tens to hundreds of million years.

Eventually, the star will lose much of its current mass, from an intensified stellar wind that eventually puffs out its outer gas envelopes of hydrogen and helium (and lesser amounts of higher elements such as carbon and oxygen) into interstellar space as a planetary nebula. The result will be a planet-sized, white dwarf core that gradually cools and fades in brightness from the shutdown of thermonuclear fusion. (Nearby white dwarfs include solitary Van Maanen's Star and the dim companions of Sirius, Procyon, and 40 Eridani.)

A possible large planet (or small brown dwarf) companion, Aldebaran Ab, was reported, orbiting at a distance of 1.35 AU.