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, after 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 25.3 light years (148.6 trillion miles) from Earth, and together with Arcturus and Sirius, one of the brightest stars in the Sun's neighbourhood.

Vega is a vertex of the Summer Triangle, which consists of Vega (in Lyra), Deneb (in Cygnus) and Altair (in Aquila). If one is to consider this asterism a right triangle, then Vega would correspond to its right angle. This triangle is very recognisable in the northern skies for there are few bright stars in its vicinity.

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.

In about AD 14,000, 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 also has 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 name Vega comes from the Arabic word waqi meaning "falling", via the phrase نسر الواقع an-nasr al-wāqi‘, translated "the swooping vulture". As part of the constellation Lyra it represents a jewel set in the body of the harp.

Possible planetary system

Vega has a disk of dust and gas around it, discovered by the IRAS satellite in the mid 1980s. This was initially thought to be a protoplanetary disk, but is now considered a "debris disk" due to the star's relatively young age of about 200 million years. In 1998 teams at the Joint Astronomy Centre and UCLA detected irregularities in it that suggest the presence of a planet.^[1] A 2003 paper hypothesizes these lumps could be caused by a Neptune-sized planet having migrated from 40 to 65 AU over 56 million years^[2], an orbit large enough to allow the formation of smaller rocky planets closer to Vega.^[3] These findings have yet to be fully confirmed, but since Vega is much more powerful than our Sun, scientists believe there is no life possible on any such suggested planets.

Cultural significance

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.

In Chinese mythology, there is a love story of Qi Xi 七夕 in which Niu Lang 牛郎 (Altair) and his two children (β and γ Aquilae) are separated forever from their mother Zhi Nü 織女(Vega) who is on the far side of the river, the Milky Way 銀河. The Japanese Tanabata festival is also based on this legend.

In Hindu astronomy, Vega is called Abhijit.

Medieval astrologers counted Vega one of the Behenian stars and related it to chrysolite and winter savory. Cornelius Agrippa listed its kabbalistic sign under Vultur cadens, a literal Latin translation of the Arabic name.

Science fiction

• In Carl Sagan's science fiction novel Contact (and the film adaptation), Earth receives a message from an extraterrestrial transmitter array orbiting 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 on human migration to Vega.
• In Robert A. 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 James Blish's Cities in Flight series, the Vega system is home to a civilization called the Vegan Tyranny, which the Earthmen must defeat before expanding out into the galaxy.
• In Star Trek, there are several references to a human colony situated in the Vega system. In his novelisation of the Original Series episode "Tomorrow is Yesterday", James Blish mentions the Vegan Tyranny from his Cities in Flight novels.
• In the DC Comics series Omega Men, the Vega star system is where a war among alien races takes place.
• In Roger Zelazny's book This Immortal, the Vegans are a species of humanoid aliens who use the Earth as a vacation resort.
• In Ivan Efremov's book Andromeda Nebula, expedition from Earth has visited Vegan system and found it to be lifeless.

Alternative and former names

• "The Falling Eagle"
• "The Harp Star"
• Wega (a closer transliteration of the 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"; Vultur cadens, "Falling vulture"

Alternative catalogue names include 3 Lyrae (Flamsteed); HD 172167; HR 7001

References

• ^ Joint Astronomy Centre, Hilo (April 21, 1998). Astronomers discover possible new Solar Systems in formation around the nearby stars Vega and Fomalhaut. Press Release.
• ^ The Royal Observatory, Edinburgh (December 1, 2003). New evidence for Solar-like planetary system around nearby star. Press Release.
• ^ Wyatt, Mark (2003). "Resonant Trapping of Planetesimals by Planet Migration: Debris Disk Clumps and Vega's Similarity to the Solar System". The Astrophysical Journal 598, 1321-1340. (Abstract)

External links

• Vega. SolStation. URL accessed on November 9, 2005.