Regulus (star)

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Alpha Leonis A
Imperiumgrey-2.jpg
Spectral B8 IVn
Type Subgiant
Luminosity 288 LSol
Absolute magnitude -0.52
Mag Terra 1.40
Temperature 12,460° K
Mass 3.8 MSol
Radius 3.09 RSol
Companion Alpha Leonis Ab / Alpha Leonis BC
Alpha Leonis Ab
Imperiumgrey-2.jpg
Spectral D
Type White Dwarf
(Degenerate Dwarf)
Multiple Close Companiion
Luminosity LSol
Absolute magnitude
Temperature ° K
Mass ~0.3 MSol
Alpha Leonis B
Imperiumgrey-2.jpg
Spectral K2 V
Type Main Sequence
Multiple Binary
Luminosity 0.5 LSol
Absolute magnitude 6.3
Mag Terra 8.13
Temperature 4885° K
Mass 0.8 MSol
Radius 0.5 RSol
Companion Alpha Leonis C
Alpha Leonis C
Imperiumgrey-2.jpg
Spectral M4 V
Type Main Sequence
Multiple Companion
Luminosity LSol
Absolute magnitude 11.6
Mag Terra 13.5
Temperature ° K
Mass 0.3 MSol
Alpha Leonis D
Imperiumgrey-2.jpg
Spectral  ?
Type Main Sequence
Luminosity LSol
Absolute magnitude
Mag Terra 12
Temperature ° K
Companion Alpha Leonis ABC

The star Alpha Leonis (known variously as Regulus, Basiliscus, Kabelaced and/or Cor Leōnis) is a quadruple star system composed of four stars that are organized into two pairs. The spectroscopic binary Regulus A consists of a blue-white main-sequence star and its companion (Regulus Ab), which has not yet been directly observed, but is probably a white dwarf. Located farther away is the pair Regulus B and Regulus C, which are dim main-sequence stars.

Description (Specifications)[edit]

Regulus A is a binary star consisting of a blue-white main sequence star of spectral type B7-8 IV-V, which is orbited by a binary companion (Regulus Ab) of at least 0.3 solar masses that is probably a white dwarf. The two stars take approximately 40 days to complete an orbit around their common center of mass, and are separated by about 0.35AU.

  • The primary Regulus A has about 3.5 times the mass of Sol and is spinning extremely rapidly, with a rotation period of only 15.9 hours. This high rotation rate results in an extremely oblate shape, as well as a phenomenon known as gravity darkening - the photosphere at Regulus's poles is considerably hotter than at the equator, and five times brighter per unit surface area. If Regulus A were rotating only 15% faster, the star's gravity would be insufficient to hold it together, and it would spin itself apart.
  • The binary pair Regulus B and Regulus C are a K2V star and an M4V star, respectively, and separated from one another by approximately 95AU. The Regulus BC pair is ~5,000AU distant from Regulus A, and the Regulus BC pair orbits Regulus A with an orbital period of about 130,000 years. The BC-companion pair has an orbital period of about 600 years.
  • A fifth star, Regulus D, is a 12th magnitude companion, which shares a common motion with the four other stars, but may or may not be gravitationally bound to the Regulus system.

The Regulus star system is approximately 24.3pc from Terra, and is located in a Rimward/Rimtrailing direction from Terra at bearing 226.4o Galactic Longitude and +48.9o North Galactic Latitude.

History & Background (Dossier)[edit]

No information currently available.

References & Contributors (Sources)[edit]

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