ZUBENESCHAMALI (Beta Librae). Pronounced, zoo-ben-es-sha-mali, this tongue twister is among the better known of star names, along with that of its partner Zubenelgenubi, respectively the Beta and Alpha stars of Libra, the Scales. The pair, the only modestly bright stars in Libra, are still of only third magnitude (Beta coming in at 2.61). Libra is the only constellation of the Zodiac -- the band of constellations containing the Sun's path -- that is not a living thing, the term Zodiac meaning "circle of animals." Appropriate to its name, Libra once held the autumnal equinox (it no longer does because of precession, the 26,000-year wobble of the Earth's axis). But "Libra" is a more modern appellation, its two brigher stars once representing (and of course still doing so) the outstretched claws of Scorpius, the Scorpion. Indeed, the name Zubeneschamali, the northern one of the two, comes from an Arabic phrase meaning "the northern claw," that of the Alpha star meaning "the southern claw." Zubeneschamali is a hot "main sequence" (hydrogen fusing) class B (B8) dwarf star with a surface temperature of close to 12,000 Kelvin, double that of the Sun. While such stars are normally considered blue-white in color, Zubeneschamali has long had a reputation of being the only naked eye star that oddly appears GREEN to the human eye. Others have claimed that it merely appears white. No doubt the argument will persist. From its distance of 160 light years, we calculate that the star is about 130 times more luminous than the Sun. Its high temperature makes for a simple spectrum (its rainbow of colors) and it is therefore ideal for examining the medium of interstellar gas and dust that like between us and the Sun. Like many stars of its kind, it is spinning rapidly, over 100 times faster than the Sun. Though not considered a variable star, ancient astronomers claimed it to be as bright or brighter than first magnitude Antares right next door in Scorpius. We will probably never know if that is true, or, if it is, how Zubeneschamali could have faded so fast.
Written by Jim Kaler. Return to STARS.