Regulus, also known as α Leonis, is a triple star system located around 77 light years from Earth. The component stars, a highly luminous blue dwarf and two fainter stars comprising an orange dwarf and a red dwarf, together form the brightest point in the constellation Leo. Regulus was mentioned in episode 19 of the anime.
Regulus and Nephrite
Regulus was the star consulted by Nephrite as he sought information on Sailor Moon's weaknesses. The star revealed her infatuation with Tuxedo Mask, and inspired Nephrite to pose as Tuxedo Mask and send love letters to all of the girls in the area, hoping that one of them would be Sailor Moon. During the ensuing confrontation between Sailor Moon and Nephrite in the Shinjuku MS Department Store, Nephrite called upon the power of Regulus again, and created the Youma Regulus.