The spectroscopic binary Regulus A consists of a blue-white main-sequence star and its companion, which has not yet been directly observed, but is probably a white dwarf.

The BC pair lies at an angular distance of 177 arc-seconds from Regulus A, making them visible in amateur telescopes.

[29] The center of the shadow path passed through New York and eastern Ontario, but no one is known to have seen it, due to cloud cover.

In other words, Kepler's third law, which holds exactly only for two point-like masses, would no longer be valid for the Regulus system.

Regulus A was long thought to be fairly young, only 50–100 million years old, calculated by comparing its temperature, luminosity, and mass.

[16] 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.

[18] The star's surface at the equator rotates at about 320 kilometres per second (199 miles per second), or 96.5% of its critical angular velocity for break-up.

A and BC share a common proper motion and are thought to orbit each other[5] taking several million years.

[16] A far more distant brown dwarf named SDSS J1007+1930 (full name: SDSS J100711.74+193056.2) may be bound to the Regulus system, it share similar proper motion and radial velocity and has a similar metal abundance to Regulus B, which hints for a physical connection between both systems.

In the future it will either be stripped away by stellar encounters because it is so weakly bound to the system, or it was once closer and got ejected by dynamical interactions.

[41] It is also known as Qalb al-Asad, from the Arabic قلب الأسد, meaning 'the heart of the lion', a name already attested in the Greek Kardia Leontos[39][42] whose Latin equivalent is Cor Leōnis.

In India it was known as Maghā ("the Mighty"), in Sogdiana Magh ("the Great"), in Persia Miyan ("the Centre") and also as one of the four 'royal stars' of the Persian monarchy.

[43] It was one of the fifteen Behenian stars known to medieval astrologers, associated with granite, mugwort, and the kabbalistic symbol .

In the Babylonian MUL.APIN, Regulus is listed as Lugal, meaning king, with co-descriptor, "star of the Lion's breast".