Alpha Horologii

Horologium, the Clock, trails down the southern sky parallel to Eridanus. It is so obscure that its brightest star, α Hor, is only magnitude 3.86; the rest are fifth magnitude and fainter.

Properties

Alpha Horologii is a common class K1 III orange giant with a surface temperature of 4650 K. At a distance of 117 light years, the star has a luminosity 47 times the Sun's, a radius 11 times solar, and a mass around double the Sun's. About a billion years old, it was a white class A star much like Sirius or Vega at the time of its birth. Today, it is a "clump giant" that is quietly fusing its core helium into carbon and oxygen. The star will eventually run out of core helium, and will brighten as it prepares to eject its outer envelope and become a white dwarf.

Alpha Horologii has no companion. Indeed, it is so quiet and stable that it makes a fine standard against which other stars may be compared observationally.

[Adapted from STARS by Jim Kaler, Professor Emeritus of Astronomy, University of Illinois]