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System Summary

Also known as Alpha Lyrae, Vega is located within 25.3 light-years (ly) away from our Sun, Sol, as the brightest star in Constellation Lyra, the Lyre or Harp. Its name (more correctly "Wega") is derived from the Arabic for "Swooping Eagle" ("Al Nasr al Waki"). The star is the lower right member (18:36:56.34+38:47:01.29, ICRS 2000.0) of the "Summer Triangle" of first magnitude stars viewed from the northern hemisphere, formed with Altair (Alpha Aquilae) at the lower left, and Deneb (Alpha Cygni) at upper right. This zero-magnitude star is visible with the naked eye as the third brightest star after Sirius A and Arcturus in Earth's northern skies, and is fifth brightest star overall. Due to the slowly changing orientation of Earth's axis in space (which is also known as the Precession of the Equinoxes), Vega was the North Celestial Pole Star some 12,000 years ago and will be again in another 10,000 years.

Vega was the first star to be photographed, exposed for 100 seconds with the daguerreotype process through a 15-inch refractor at Harvard Observatory on the night of July 16-17, 1850. Two nearby stars have been determined in subsequent observations to be optical companions only. In late 2003, astronomers announced that the latest computer models indicate that the structure of a faint dust disk observed around Vega can be best explained by the presence of Neptune-sized and Jupiter-sized planets orbiting at distances roughly similar to those held by their apparent "cousins" in the Solar System (more discussion below -- ROE press release). On January 10, 2005, astronomers using the infrared Spitzer Space Telescope announced that the dust disk is bigger than previously estimated and was probably created by collisions of protoplanetary objects as big as the planet Pluto, up to 2,000 kilometers (about 1,200 miles) in diameter (press release -- more below). On January 10, 2006, astronomers using the infrared Center for High Angular Resolution Astronomy (CHARA) Array announced their finding that Vega rotates so fast that it is cooler as well as 23 percent wider along its equator than at its poles due to the gravitational effect of its "middle bulge" (NOAO press release; AAS 207 session summary; and Aufdenberg et al, 2006 -- more below).

The Star

Vega is a slightly bluish, white main sequence dwarf star of spectral and luminosity type A0 V, like Sirius. According to various estimates, the star has 2.3 to 3.1 times Sol's mass, 2.73 0.01 times its diameter (Aufdenberg et al, 2006; and Ciardi et al, 2001), and 37 3 times (true A0V average derived by Aufdenberg et al, 2006) to 58 times (pole on) its luminosity. Like Sirius, however, Vega radiates much more in ultraviolet wavelengths than Sol, and, not surprisingly, the European Space Agency has used ultraviolet spectral flux distribution data to determine stellar effective temperatures and surface gravities, including those of Vega. The star may be about only 63 percent as enriched as Sol with elements heavier than hydrogen ("metallicity") based on its abundance of iron (D. Gigas, 1986, but more recent findings on Vega's mild underabundance of metals can be found in Ilijic et al, 1998). On the other hand, its iron metallicity has been measured anywhere from four to 115 percent of Sol's (Cayrel de Strobel et al, 1991, page 31).

Vega may be only about 350 million years old (Maeder and Meynet, 1988). However, it is so much bigger and hotter than Sol that it will exhaust its core hydrogen after only another 650 million years or so (for a total life of around a billion years) and turn into a red giant or Cepheid variable before puffing away its outer layers to reveal a remnant core as a white dwarf. The star is a rapidly rotating star whose apparent "pole-on" view from Earth distorts its various stellar characteristics (Aufdenberg et al, 2006; and Gulliver et al, 1994).