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Regulus
From Wikipedia, the free encyclopedia
 Regulus is located at the lower right on this map of the constellation. |
|
| Observation data Epoch J2000 |
|
|---|---|
| Constellation (pronunciation) |
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 | |
| 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.
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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.
- ^ 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.