Shining at magnitude 3.35, Alpha Reticuli is the brightest star in the modern constellation Reticulum, the Net. The star is easily visible only from south of the Tropic of Cancer, and is largely ignored by the research community since the great majority of astronomers are in the northern hemisphere, where they cannot see it.
Properties and Evolution
Lying at a distance of 163 light years, α Ret is a yellow class G8 II bright giant. Radiating with a luminosity of 237 suns from a 4940 K surface, the star has a radius 21 times the Sun's. Its rotation period is long enough that it has never been measured, though it has an upper limit of 130 days. The star does, however, produce X-rays, which shows magnetic activity that is likely induced by rotation.
α Ret's temperature and luminosity suggest a mass of 3.5 suns. Only 300 million years ago, the star was a luminous, blue, class B main-sequence star, fusing hydrogen into helium at its core; currently is it fusing its core helium into carbon and oxygen. After burning up the rest of its internal helium, it will undergo a great brightening phase, becoming a red supergiant, and then expel its outer envelope as it prepares to become a white dwarf.
Companion
All of this action will be witnessed by a small, 12th-magnitude class M0 V red dwarf companion. Over the past 150 years, the companion has kept the same motion as the giant, showing that the two really are related, and not just a line of sight coincidence. Their separation of 49" translates into a minimum physical separation of 2450 AU, and an orbital period of at least 60,000 years.
[Adapted from STARS by Jim Kaler, Professor Emeritus of Astronomy, University of Illinois]