Mimosa (star)

Lore & Background

Mimosa bears the traditional name Mimosa, derived from the Latin for 'actor' and possibly from the flower of the same name, and the historical name Becrux, a contraction of its Bayer designation. In 2016, the International Astronomical Union's Working Group on Star Names approved Mimosa as the star's official proper name. Although now invisible north of 30° latitude, precession of the equinoxes meant it was visible north of 40° in ancient Greek and Roman times, when it was regarded as part of the constellation Centaurus. In Chinese astronomy, it belongs to an asterism called the Cross, along with Acrux, Gacrux, and δ Crucis. The Mursi people of Ethiopia call it Thaadoi, forming an asterism with δ Crucis, β Centauri, and α Centauri.

Reader's Guide

Mimosa is a β Cephei variable star, pulsating in three non-radial modes with periods between 4.03 and 4.59 hours. Its high effective temperature of about 27,000 K places it at the hot edge of the instability strip for such variables. The primary component, a blue giant that has exhausted its core hydrogen, generates a strong stellar wind losing mass at a rate equivalent to one solar mass every 100 million years, with wind speeds of 2,000 km/s or more. With a mass 15 times that of the Sun, it is sufficiently massive to end its life as a supernova, expected in roughly 6 million years. The system is a member of the Lower Centaurus–Crux sub-group of the Scorpius–Centaurus association. Culturally, Mimosa appears as one of the five stars of the Southern Cross on the flags of Australia, New Zealand, Samoa, and Papua New Guinea, and represents the State of Rio de Janeiro on the flag of Brazil.

Did You Know?

• Mimosa is a triple star system, with the primary being a spectroscopic binary discovered in 1957.
• The primary star has three different pulsation modes, none of which are radial, with periods of 4.03–4.59 hours.
• Mimosa is the most massive star for which age has been derived using asteroseismic methods.
• The star's projected rotational velocity and inclination of 46° yield an azimuthal rotational velocity of about 120 km/s.