Hellenica World


Regulus A/B/C

Regulus is located at the lower right on this map of the constellation.
Observation data
Epoch J2000
Right ascension A: 10h 08 min 22.3s
BC: 10h 08 min 12.8/14s
Declination A: +11° 58' 02"
BC: +11° 59' 48"
Apparent magnitude (V) 1.35/8.14/13.5
Spectral type B7 V/K1-2 V/M5 V
U-B color index −0.36/0.54
B-V color index −0.11/0.87
Variable type Slightly
Radial velocity (Rv) +5.9 km/s
Proper motion (μ) RA: 249 mas/yr
Dec.: 2 mas/yr
Parallax (π) 42.09 ± 0.79 mas
Distance 77 ± 1 ly
(23.8 ± 0.4 pc)
Absolute magnitude (MV) −0.52/4.2/9.5
Mass 3.5/0.8/0.2 M
Radius 3.15–4.15/0.5/? R
Luminosity 150/0.31 L
Temperature 10,300–15,400/? K
Rotation 315 km/s. (15.9 hours)/?
Age 5 × 107 years
Other designations
Alpha Leonis, 32 Leo, Cor Leonis, Basilicus, Lion’s Heart, Rex,

Kalb al Asad, Kabeleced, GJ 9316, HR 3982, BD +12° 2149/2147,

HD 87901/87884, GCTP 2384.00, LTT 12716/12714,

SAO 98967/98966, FK5 380, HIP 49669.

Database references

Regulus (α Leo / α Leonis / Alpha Leonis) is the brightest star in the constellation Leo and one of the brightest stars in the nighttime sky. Regulus is approximately 77.5 light years from Earth’s Solar System. Regulus is considered the last first magnitude star in the sky because the next brightest star, Adhara, has a magnitude of 1.50, officially making it a second magnitude star.

Of the brightest stars in the sky, Regulus is closest to the ecliptic, and is regularly occulted by the Moon. Occultations by the planets Mercury and Venus are also possible but rare. The last occultation of Regulus by a planet was on July 9, 1959, by Venus. The next will occur on October 1, 2044, also by Venus. Other planets will not occult Regulus over the next few millennia because of their node positions.

The Sun makes its closest approach to Regulus around August 23 of each year. For most Earth observers, the heliacal rising of Regulus occurs in the first week of September. Every 8 years, Venus passes Regulus around the time of the star's heliacal rising, most recently in 2006.

Regulus has about 3.5 times the Sun’s mass and is a young star of only a few hundred million years. It is spinning extremely rapidly, with a rotation period of only 15.9 hours, which causes it to have a highly oblate shape.[1] 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. If it were rotating only 16% faster, centripetal force would overcome gravity and the star would tear itself apart.

Regulus is a multiple star system composed of a hot, bright, bluish-white star with a pair of small, faint companions. The pair orbits the much-larger Regulus A with a period of over 130,000 years at a distance of some 4,200 AU. The companion pair have an orbital period of 2,000 years and are separated by about 100 AU.

Etymology and Cultural Associations

Regulus is Latin for 'prince' or 'little king'. The Greek variant Basiliscus is also used. It is known as Qalb Al Asad, from the Arabic قلب لأسد or Qalb[u] Al-´asad, meaning 'the heart of the lion'. This phrase is sometimes approximated as Kabelaced and translates into Latin as Cor Leonis. It is known in Chinese as 轩辕十四, the Fourteenth Star of Xuanyuan, the Yellow Emperor. In Hindu astronomy, Regulus corresponds to the Nakshatra Magha.

Persian astrologers around 3000 BC knew Regulus as Venant, one of the four 'royal stars'. It was one of the fifteen Behenian stars known to medieval astrologers

See also

* Regulus in fiction


1. ^ McAlister, H. A., ten Brummelaar, T. A., et al. (2005). "First Results from the CHARA Array. I. An Interferometric and Spectroscopic Study of the Fast Rotator Alpha Leonis (Regulus).". The Astrophysical Journal 628: 439-452. doi:10.1086/430730. 

* Fred Schaaf, “Horrorfications of the Lion’s heart,” Sky & Telescope, April 2006.


Retrieved from "http://en.wikipedia.org/"
All text is available under the terms of the GNU Free Documentation License