Regulus A

Spectral type: B7 V
U-B color index: −0.36/0.54
B-V color index: −0.11/0.87
Variable type: Slightly
Diameter: 5.8 million km

The central component of Regulus system, Regulus (α Leo / α Leonis / Alpha Leonis) is a young star only a few hundred million years old. It is spinning extremely rapidly, with a rotation period of only 15.9 hours, which causes it to have a highly oblate shape. This results in gravity darkening: its poles are considerably hotter and five times as bright (per unit surface area) than its equator. If it were rotating only 16% faster the centripetal force of gravity would not be enough to keep it from tearing itself apart.

This star has a pair of small, faint companions (Regulus B and Regulus C) in the form of a binary star system. These stars are separated by about 100 AUs and orbit each other every 2,000 years. This pair is separated from the much larger Regulus A by about 4,200 AU and orbit the main star with a period of over 130,000 years.

Name

The name "Regulus" is of human origin and means "prince." The star is also known as Qalb Al Asad, from قلب الأسد qalb[u] al-´asad, meaning "the heart of the lion." This phrase is sometimes approximated as Kabelaced, or translated into Latin as Cor Leonis.