Vega is Alpha Lyrae, apparent magnitude 0.03, at 25 light years, spectral type A0Va. It is the fifth-brightest star in the sky and the second-brightest in the northern celestial hemisphere.
Its importance to astronomy is largely technical. Vega was for a long time the zero point of the magnitude scale, the star against which brightnesses were defined, so that its magnitude was zero by convention. It served the same role for colour indices. Modern systems have moved on, but Vega-relative magnitudes are still in use and the star remains one of the most heavily observed calibration objects in the sky. It was also the first star other than the Sun to be photographed, at Harvard in 1850.
Two physical facts complicate the calibration. Vega rotates extremely rapidly and is seen nearly pole-on, which means it is substantially oblate and its apparent surface is hotter and brighter than its equator, the star we measure is not the star an equatorial observer would measure. And it has an infrared excess, discovered by the IRAS satellite in 1983, indicating a surrounding disc of dust. Vega was the first star found to have such a debris disc, and the discovery opened the study of planetary system formation around other stars. It is the archetype of what are still called Vega-like stars.
The name is from Arabic, from a phrase meaning the swooping or falling eagle or vulture.
Vega forms one corner of the Summer Triangle with Deneb and Altair. The three are strikingly unequal: Vega is nearby and modest, Altair nearer still, and Deneb lies at something like 2,600 light years and is one of the most luminous stars known, appearing comparable only because it is so far away. The triangle demonstrates neatly that apparent brightness says nothing about a star until its distance is known.
Sources AstronomyAndrew Fraknoi, David Morrison, and Sidney C. Wolff (OpenStax) with Almagest (Mathematike Syntaxis)Claudius Ptolemy