Vega

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

Vega (α Lyr / α Lyrae / Alpha Lyrae) is the brightest star in the constellation Lyra, and the fifth brightest star in the sky. It is the second brightest star in the Northern night sky, second to Arcturus, and can often be seen near the zenith in the mid-northern latitudes during the Northern Hemisphere summer.

It is a "nearby star" at only 26 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.

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 the presence of planets or that planets 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 (this is no longer the case, as apparent magnitude is now most commonly defined in terms of the flux from the star). 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.

The star has been the subject of many 'firsts' in Astronomy; in 1850 it became the first star to be photographed, and in 1872 the first to have its spectrum photographed. It was also debatably the first star to have its parallax measured, in the pioneering experiments of Friedrich Struve in 1837. Finally, it became the first star to have a car named after it, when Chevrolet launched the 'Vega' in 1971.

The name Vega comes from the Arabic word waqi meaning "falling", applied via the phrase نسر الواقع an-nasr al-wāqi‘ meaning "the falling vulture". As part of the constellation Lyra it represents a jewel set in the body of the harp.

Contents

1 Science fiction 2 Facts 3 Alternative and former names 4 Mythology

Science fiction

• In Carl Sagan's science fiction novel Contact, and the movie that was adapted from it, Earth receives a message from an extraterrestrial transmitter array orbiting the star Vega.
• In the Traveller role playing game a planetary system near Vega is inhabited by aliens called Vegans. They govern an autonomous region within the Imperium several parsecs large around Vega.
• In a Commodore 64 computer game named HOMER, part of the story is centred around human migration to Vega.
• In Robert Heinlein's novel Have Spacesuit, Will Travel, Vega hosts the planet of an advanced civilization which is the local representative and overseer of the Three Galaxies federation, and the curator of humanity after its discovery by the Three Galaxies.
• In Star Trek there are several references to a human colony being situated in the Vega system.
• In the Foundation novels by Isaac Asimov, Vega is the central system of the Galactic Empire, and in which lies the planet Trantor.

Facts

• Right ascension (J2000): 18h36m56.3s
• Declination (J2000): +38°47'01"
• Distance from Earth: 25.3 light years
• Parallax: 0.133"
• Apparent visual magnitude in the modern system: 0.03
• Apparent visual magnitude in the old magnitude system: 0 by definition
• Absolute visual magnitude: 0.58
• Spectral type: A0Va
• Mass: 3 Solar masses
• Radius: 2.5 Solar radii
• Luminosity: 50 times Solar luminosity

Alternative and former names

• "The Falling Eagle"
• "The Harp Star"
• Wega (the more correct transliteration of the original Arabic)
• Akkadian: Tir-anna, "Life of Heaven"
• Babylonian: Dilgan, "the Messenger of Light"
• Chinese: Zhi Nü, "the Weaver"
• Greek: Allore
• Sanskrit: Abhijit, "Victorious"
• Latin: Fidis, "Lyre"

Alternative catalogue names include HD 172167; HR 7001

Mythology

In Chinese mythology, there is a love story of Qi Xi in which Niu Lang (Altair) and his two children (Aquila -β and -γ) are separated forever from their mother Zhi Nü (Vega) who is on the far side of the river, the Milky Way.ca:Vega de:Vega (Stern) es:Vega fa:ونَند fi:Vega fr:Véga he:וגה it:Vega ja:ベガ nl:Wega pl:Wega sv:Vega (stjärna)