Thanks to James B. Kaler. These contents are the property of the author and are reproduced from original without the author's express consent because of fair use and valid educational purposes.

ADHARA

The names of all the first magnitude stars ring clearly to us; even the names of those in the southern hemisphere are well known. Adhara has escaped the fame it deserves. Also known as Epsilon Canis Majoris, it is actually the second brightest star in the constellation, and helps form the western leg of Canis Major, the larger dog. Look just below Sirius to find an outstanding triangle of bright stars. Adhara is at the lower right. The ancient Arabs referred to this small three-star pattern as "the virgins," to which the name "Adhara" actually refers. No one knows why the name was given or who they were. Adhara has an apparent magnitude of 1.50, and therefore is sometimes referred to as the last of the "first magnitude" stars or as the brightest of the "second magnitude." The latter view and the star's rather southern position in the sky has led to its being somewhat ignored. In fact, Adhara is quite the magnificent star. One of the hottest of all the bright stars, Adhara shines with a surface temperature of some 20,000 degrees Kelvin (above absolute zero), which gives it a sparkling bluish cast. From its distance of 425 light years we calculate a luminosity to the eye of 3700 times that of the Sun. If at the distance of Sirius, which dominates Canis Major, Adhara would shine at apparent magnitude -7, 15 times brighter than Venus at its most luminous. Because of the star's high temperature it radiates a good portion of its energy in the invisible ultraviolet. If that is taken into account, Adhara is actually 15,000 times more luminous than the Sun! The star, having ceased hydrogen fusion in its core, is actually in the beginning of its death stages, and is now in its "giant" state. It is very popular among those who study local interstellar matter, as its spectrum is used to examine the stuff that lies between it and the Sun.