Monday, December 10, 2007
REGULUS
REGULUS - 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, 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 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.”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. 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.