Regulus

Regulus A/B/C

Regulus is located at the lower right on this map of the constellation.
Observation data Epoch J2000
Constellation	Leo
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
Characteristics
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
Astrometry
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
Details
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
SIMBAD	data

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. Ocultations by Mercury and Venus are also possible, but very rarely. The last occultation of Regulus by a planet was on July 9th, 1959 by Venus, the next one will occur on October 1st, 2044 also by Venus. The other planets cannot occult Regulus in the next and the last millenia as a result 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 is Latin for “prince” or “little king.” The Greek variant of Basiliscus is also used. It is further known as Qalb Al Asad, from Arabic قلب الأسد qalb[u] al-´asad, meaning “the heart of the lion.” This phrase is sometimes approximated as Kabelaced, or translated into Latin as Cor Leonis. In Hindu astronomy, Regulus corresponds to the Nakshatra Magha. It’s known as 轩辕十四 (the Fourteenth Star of Xuanyuan) in Chinese. Xuanyuan is the name of Yellow Emperor.

Regulus has about 3.5 times the Sun’s mass, and is a young star only a few hundred million years old. 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 gravity darkening: its poles are considerably hotter and five times as bright (per unit surface area) than its equator. If it were rotating only 16% faster the centripetal force of gravity would not be enough to keep it from tearing itself apart.

This star has a pair of small, faint companions in the form of a multiple star system. These stars are separated by about 100 AUs and orbit each other every 2,000 years. This pair is separated from the much larger Regulus A by about 4,200 AU and orbits the main star with a period of over 130,000 years.

Astrology

Venant (Regulus) was one of the four “royal stars” of the Persian astrologers around 3000 BC. It was one of the fifteen Behenian stars to medieval astrologers, associated with granite, mugwort, and the kabbalistic symbol .

In the religion of Stregheria, Regulus is a fallen angel and quarter guardian of the southern gate.

See also

• Regulus in fiction

References

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. 

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

External links

• Astronomers: ‘Bullet star’ shines 350 times brighter than the sun
• Portrait of a Star on the Edge
• Egg-Shaped Regulus is Spinning Fast
• Regulus as Astronomy Picture of the Day of 19th june 2006
• Regulus 3. SolStation. Retrieved on December 1, 2005.

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