Vega

This article is about Vega, the star. For other uses: see Vega (disambiguation)

Vega (Alpha Lyrae) is the lead star in the constellation Lyra, reaching near directly overhead in the mid-northern latitudes, during the summer. It is a "nearby star" at only 25 light years distance, and together with Arcturus and Sirius, one of the brightest stars in the Sun's neighbourhood. Vega is a vertex of the Summer Triangle. It is the fifth brightest star in the Northern night sky.

Its spectral class is A0V (Sirius, an A1V, is slightly less powerful) and it is firmly in the main sequence, fusing hydrogen to helium in its core. Since more powerful stars use their fusion fuel more quickly than smaller ones, Vega's life time is only one billion years, a tenth of our Sun's. Vega is two and a half times more massive than our Sun and burns at fifty times the power.

Vega has a disk of dust and gas around it, discovered by the IRAS satellite in the mid 1980s. This either signifies planets or that planets that may soon form. The protoplanetary disk, as can be guessed from its name, is believed to be a precursor to the formation of planets but can persist long after planets have been formed if there are no gas giant planets such as Jupiter.

In about 14,000 AD, Vega will become the North Star, owing to the precession of the equinoxes. See Polaris for more information.

Professional astronomers have used Vega for the calibration of absolute photometric brightness scales. When the magnitude scale was fixed, Vega happened to be close to zero magnitude. Therefore the visual magnitude of Vega was decided to be, by definition, zero at all wavelengths. It has also a relatively flat electromagnetic spectrum in the visual region (wavelength range 350-850 nanometers, most of which can be seen with the human eye), so the flux densities are roughly equal, 2000-4000 Jy. The flux density of Vega drops rapidly in the infrared, and is near 100 Jy at 5 micrometres.

Vega in Science Fiction

• Carl Sagan's science fiction novel and movie Contact feature wormhole travel to a planet near the star Vega.

• In the Traveller role playing game a planetary system near this star is inhabited by aliens called Vegans. They govern an automous region within the Imperium several parsecs large around Vega.

• In a rather old school Commodore 64 game named HOMER. Part of the story is centred around a human migration to Vega.

Mythology

See Chinese Valentine's Day.

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