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.

VEGA

One of the most famed stars of the sky, Vega is the luminary of the dim but exquisite constellation Lyra, the Lyre, which represents the harp of the great mythical musician Orpheus. Its name derives from an Arabic phrase that means "the swooping eagle." Vega is one of three brilliant stars that divide the northern heavens into thirds, the others Arcturus and Capella, and with Altair and Deneb forms the great Summer Triangle, lying at its northwestern apex. At magnitude zero, it is the sky's fifth brightest star, falling just behind Arcturus and just ahead of Capella. It is also one of the closer stars to the Earth, lying just 25 light years away. Though its proximity helps make it bright in our skies, it is also inherently luminous, some 50 times brighter than our Sun. Vega is a classic white main sequence star, like the Sun quietly running off the nuclear fusion of hydrogen deep in its core, with a surface temperature of about 9500 degrees Kelvin. Its color and apparent brightness made it the basic standard against which the apparent magnitudes of all other stars are ultimately compared. Because it is 2.5 times as massive as the Sun, it uses its internal fuel much faster and will burn out in less than a billion years, less than 10 percent of the solar lifetime. Vega was one of the first stars to be discovered with a large luminous infrared-radiating halo that suggests a circumstellar cloud of warm dust. Since Vega seems to be rotating with its pole directed toward the Earth, the dust cloud probably represents a face-on disk that may not be unlike the disk surrounding the Sun and that contains the planets. Several other stars similar to Vega (Denebola, Merak, for example) possess similar disks, and astronomers speculate that they may indicate the existence of planetary systems, though no planets have ever been detected. Even if they exist, it seems unlikely that life would have developed to any degree because of the short lifetimes of these hot stars.