Vega
Vega is also a municipality in Norway, see Vega, Norway.
Vega (Alpha Lyrae) is the lead star in the constellation Lyra, reaching near directly overhead the mid-northern latitudes, during the summer. It's a "nearby star" at only 25 light years distant and together with Arcturus and Sirius, one of the brightest stars in the Sun's neighbourhood. Vega is a vertex of the Summer Triangle.
Its spectral class is A0V (Sirius, an A1V, is slightly less powerful) and it's 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 planets that may soon form. The protoplanetary disk is, as can be guessed from its name, believed to be a precursor to the formation of planets but it 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 take over from Polaris as 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 magnitudes. 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 micrometers.
