Beta Crucis

Beta Crucis, also known as Mimosa or Becrux, is the second brightest star in the constellation Crux (after Alpha Crucis or Acrux) and is the 19th brightest star in the night sky. It forms part of the prominent asterism called the Southern Cross, which appears on five national flags. Although Beta Crucis, "Becrux", is at roughly −60° declination, and therefore not visible north of 30°, in the time of the ancient Greeks and Romans it was visible north of 40° due to the precession of equinoxes, and these civilizations regarded it as part of the constellation Centaurus. Its modern name, Mimosa, which is derived from the Latin word for "actor", may come from the flower of the same name.

Properties

Beta Crucis is believed to be the hottest first-magnitude star, with an apparent visual magnitude of 1.25. Based on parallax measurements, it is located at a distance of 280 ly (86 pc) from the Earth. In 1957, German astronomer Wulff-Dieter Heintz discovered that it is a spectroscopic binary with components that are too close together to resolve with a telescope. The pair orbit each other every 5 years with an estimated separation that varies from 5.4 to 12.0 Astronomical Units. The system is only 8 to 11 million years old.