The Antares star is also known as a Scorpii and Alpha Scorpii. It is a class M(red) supergiant that is in the Scorpio constellation and lies about 424 light years from Earth. There is some debate as to whether it is the 15th or 16th brightest star in the night sky. It is the 15th if you lump the two brighter stars in the Capella quadruple system together and the 16th if you don not. It is one of the four brightest stars near the ecliptic. Aldebaran, Spica, and Regulus are the other three. Antares varies from .9 to 1.8 apparent magnitude.
The Antares star has a radius that is nearly 800 times that of the Sun. Antares is approximately 600 light years from our solar system. Its visual luminosity is about 10,000 times that of the Sun. Because the star radiates a considerable part of its energy in the infrared part of the spectrum, the bolometric luminosity equals roughly 65,000 times that of the Sun. The mass of Antares is 15 to 18 solar masses.
The best time to view the Antares star is on or around May 31 of each year, when the star is at opposition to the Sun. At this time, Antares rises at dusk and sets at dawn, and is thus in view all night. For approximately two to three weeks before and after November 30, Antares is not visible at all, being lost in the Sun’s glare; this period of invisibility is longer in the Northern Hemisphere than in the Southern, since the star’s declination is significantly south of the celestial equator.
The Antares star is one of the four first magnitude stars that lies within 5° of the ecliptic and therefore can be occulted by the Moon and rarely by the planets. On 31 July 2009, Antares was occulted by the moon. The event was visible in much of southern Asia and the Middle East. On 17 November 2400 Antares will be occulted by Venus. Of the 21 first-magnitude stars, the Antares star now lies farthest in angular distance from any other first-magnitude star; making it possible to draw a larger circle centered around Antares without including any other first-magnitude star inside that circle, than around any other first-magnitude star. The nearest first-magnitude star to Antares is Alpha Centauri.
The Antares star has fascinated man for centuries. There is an indepth article about the star here. Here on Universe Today we have a great article about the Scorpius constellation that contains the Antares star. Astronomy Cast offers a good episode about the large scale structure of the universe.
Reference:
http://en.wikipedia.org/wiki/Antares
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