Regulus

Regulus (Latin, "prince" or "little king") is the brightest star in the constellation Leo (Latin, "lion") and one of the brightest stars in the nighttime sky, and lies approximately 77.5 light years from Earth. Regulus is a multiple star system composed of four stars which are organised into two pairs.

Of the brightest stars in the sky, Regulus is closest to the ecliptic, and is regularly occulted (i.e. blocked from view) by the Moon. Occultations by the planets Mercury and Venus are also possible but rare. The last occultation of Regulus by a planet was on July 7, 1959, by Venus. The next will occur on October 1, 2044, also by Venus. Other planets will not occult Regulus over the next few millennia because of their node positions.

Regulus has about 3.5 times the Sun’s mass and is a young star of only a few hundred million years. 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 so-called gravity darkening: the photosphere at Regulus' poles is considerably hotter, and five times brighter per unit surface area, than its equatorial region. If it were rotating only 16% faster, the star's gravity would provide insufficient centripetal force to hold it together, and it would tear itself apart.