Regulus

Regulus is the brightest star in the constellation Leo at magnitude 1.35 and the 21st brightest in the night sky. It is a blue-white main-sequence star of spectral type B7V, located about 79 light-years from Earth. Regulus is about 3.5 times the mass of the Sun and roughly 288 times more luminous. It rotates extremely rapidly — once every 15.9 hours — giving it a significantly oblate shape. Regulus is actually a quadruple star system with two widely separated pairs.

Regulus sits at the base of the distinctive Sickle asterism in Leo, making it easy to find. It lies almost exactly on the ecliptic, so the Moon and planets frequently pass very close to it or even occult it — watching for these conjunctions is rewarding. The wide companion Regulus B/C (magnitudes 8.1 and 13.5) lies about 177 arcseconds away and is an easy target for small telescopes. Best observed from February through June.

Regulus means 'little king' in Latin, a name given by Copernicus. Earlier names include 'Cor Leonis' (Heart of the Lion) in Latin and 'Basiliskos' (little king) in Greek. It was one of the four Royal Stars of ancient Persia, marking the summer solstice around 3000 BC. Regulus was important in ancient astrology and was associated with royalty and power across many cultures.