Regulus is Alpha Leonis, apparent magnitude 1.35, at about 79 light years, and it is one of the more physically extreme bright stars.
It rotates extraordinarily fast. The equatorial surface velocity is around 320 kilometres per second, which is roughly 96 percent of the speed at which the star would break up. The consequence is a markedly oblate shape, the equatorial diameter substantially exceeds the polar, and a phenomenon called gravity darkening: the poles are hotter and per unit area about five times brighter than the equator. Regulus is not a sphere and it is not uniformly bright.
It is a quadruple system: Regulus A, itself a spectroscopic binary whose faint companion is probably a white dwarf, together with the more distant pair Regulus B and C.
The fact of greatest astrological consequence is positional. Regulus lies 0.465 degrees from the ecliptic, closer than any other first-magnitude star. It is therefore occulted by the Moon regularly, and it sits almost exactly on the path the Sun and planets follow. A star that the Sun effectively passes over every year, and that the Moon repeatedly covers, is going to be noticed by any tradition watching the ecliptic, and Regulus is prominent in Babylonian, Greek, Persian, Indian and Arabic astronomy alike.
The Latin Regulus, little king, is Copernicus's rendering of the Greek Basiliskos; the Babylonian name means the star of the king, and the Arabic Qalb al-Asad and the Latin Cor Leonis both mean the Lion's heart.
Sources AstronomyAndrew Fraknoi, David Morrison, and Sidney C. Wolff (OpenStax) with Almagest (Mathematike Syntaxis)Claudius Ptolemy