Regulus, the brightest star in the constellation Leo. It is also called Alpha Leonis and Cor Leonis. Regulus has a magnitude of 1.36 and is about 84 light-years distant from the earth. In 1959 the planet Venus passed between Regulus and the earth, giving astronomers a rare opportunity to study the upper atmosphere of Venus by observing changes in the light of Regulus as it went into and out of eclipse.