Vega
Vega is the brightest star in Lyra, and the fifth brightest star in the sky. It is the third brightest star in the Northern night sky, after Sirius and Arcturus, and can often be seen near the zenith in the mid-northern latitudes during the Northern Hemisphere summer.
It is a "nearby star" 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 recognizable in the northern skies for there are few bright stars in its vicinity.
Its spectral class is A0 V (Sirius, an A1 V, is slightly less luminous) and it is firmly in the main sequence (dwarf), fusing hydrogen to helium in its core. It is twice as massive as our Sun and about fifty times as luminous.
Vega's current age is about 500 million years. Since more powerful stars use their fusion fuel more quickly than smaller ones, Vega's estimated lifetime is only one billion years, approximately a tenth that of our Sun.
After it leaves the main sequence, Vega is likely to become a yellow giant similar to Capella and Eta2 Hydri before entering the red giant stage, after which it will eventually shed its outer layers to become a white dwarf.
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 for many years (this is no longer the case, as the apparent magnitude zero point is now most commonly defined in terms of a particular numerically specified flux).
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.
W e s e e V e g a f r o m w i t h i n 5 d e g r e e s o f t h e p o l a r ( r o t a t i o n ) a x i s , b u t i f y o u w e r e l o o k i n g a l o n g t h e p l a n e o f t h e e q u a t o r , V e g a w o u l d l o o k a b o u t 2 3 % f a t t e r a t t h e e q u a t o r b e c a u s e V e g a r o t a t e s a t 9 3 % o f t h e s p e e d t h a t w o u l d c a u s e i t t o s t a r t b r e a k i n g u p f r o m c e n t r i f u g a l e f f e c t s ( w i t h a r o t a t i o n p e r i o d o f a b o u t 1 2 . 5 h o u r s ) . T h i s r e s u l t s i n a n e f f e c t c a l l e d g r a v i t y d a r k e n i n g : V e g a ' s p o l a r t e m p e r a t u r e i s 1 0 , 0 0 0 K ( 1 7 , 5 0 0 F ) , w h i l e i t s e q u a t o r a l t e m p e r a t u r e i s 7 , 6 0 0 K ( 1 3 , 2 0 0 F ) [ 1 ] , w h i c h h a s t o b e t a k e n i n t o a c c o u n t w h e n i n v e s t i g a t i n g p r o p e r t i e s o f t h e s t a r ' s d u s t d i s k a n d e n v i r o n m e n t .
T h e n a m e V e g a c o m e s f r o m t h e A r a b i c w o r d w a q i m e a n i n g " f a l l i n g " , v i a t h e p h r a s e " t h e s w o o p i n g v u l t u r e " . A s p a r t o f t h e c o n s t e l l a t i o n L y r a i t r e p r e s e n t s a j e w e l s e t i n t h e b o d y o f t h e h a r p .
Dust disk
In 1983, an orbiting satellite called IRAS discovered far more infrared radiation coming from Vega than expected for small interstellar dust grains found around young, early-type stars. The radiation is coming from a huge circular shell of dust surrounds the star extending outwards to 140 AU in radius, much like those that encompass Fomalhaut, Beta Pictoris, and Denebola. The disk is thought to be made of icy dust particles that have been warmed by the star which tends to develop after most of the surrounding nebulae of gas has been absorbed or expelled from the developing star.
In 1998, British and American astronomers obtained the first pictures of a huge disk-like structure of dust enshrouding Vega in a roughly circular envelope. The "sub-millimeter" image shows emissions from tiny dust particles in orbit around Vega. Yellow to red areas of the image indicate the highest concentrations of cold dust, while blue to black areas suggest very little dust. In JAC's image the brightest emission area which indicates the greatest concentration of dust, is centered not on Vega but on a spot located from the star about twice the distance between Pluto and the Sun in the Solar system. A search with the Keck Telescope by the JAC astronomers failed to reveal infrared light from possible planets or brown dwarfs. If the blob of dust is associated with Vega, it could be a dust cloud around a giant planet orbiting Vega.
On January 10, 2005, astronomers using the infrared Spitzer Space Telescope announced that the dust disk is bigger than previously estimated. The disk appears to be mostly composed of fine dust particles that are probably created by the collision of protoplanetary bodies within approximately 90 AUs of the star but are then blown away by its intense radiation. On the other hand, the mass and short lifetime of these small particles indicate that the disk detected was created by a large and relatively recent collision that may have involved objects as big as the planet Pluto (up to 2,000 kilometers or around 1,200 miles in diameter).
On April 11, 2006, an international team of astronomers announced the detection of a weak near-infrared flux in the vicinity of Vega (78 times less important than that of the star) thanks the CHARA array located at Mount Wilson, CA[2]. This flux is thought to come from dust particles located at only a fraction of an astronomical unit from Vega (much closer than the dust previously detected around Vega and other Vega-type stars) and heated by the star to temperatures close to 1300 °C.
The dust grains are suspected to be on average smaller that in our Solar system, with typical diameters below one micrometre (equivalent to particles constituting cigarette smoke). Such small grains should normally be rapidly blown out by the radiation pressure created by the intense stellar flux. Their abundance thus proves that they are produced in permanence, probably in a phase of intense meteoritic and cometary bombardment like those experienced by the Earth at the origins of the solar system. The dust production rate would correspond in the daily passing of 13 large comets in the environment of Vega.
In 2000, a team of astronomers announced that modeling of the asymmetric circumstellar disk infalling into Vega suggests that there may be a planet twice the mass of Jupiter at an orbital distance of about 50 to 60 AU from the star.
At the January 2002, 199th Meeting of the American Astronomical Society in Washington, DC, two teams of astronomers announced that the cold dust in Vega's circumstellar disk is at least partly gathered into large clumps, in a characteristic shape that suggests the gravitational influence of a giant planet in an eccentric orbit.
The two teams, led by David Koerner using the Owens Valley Radio Observatory, collected millimeter-wavelength observations that were sensitive to structures as small as 20 AUs. They managed to resolve two knots in the circumstellar dust that were offset at 60 and 75 AUs from Vega. The dust would tend to become trapped in the hypothesized planet's mean-motion resonances around Vega. Detailed study of features in its dust cloud is possible because Vega is viewed nearly pole-on from Earth.
Modeling simulations by Wilner's team suggested that the semimajor axis of the planet's orbit may center around 30 AUs. The simulations also indicated that the planet must be smaller than 30 times Jupiter's mass. A larger planetary mass would cause the observed dust clumps to overlap by destroying and the hypothesized orbital resonances, according to Marc Kuchner, the team's theorist.
Other simulations of an observed dust disk ring arc at 95 AUs also suggested that there may be a sub-Jovian planet between 90 to 100 AUs out from Vega. The simulations indicated that one (or more) very massive planet within 50 to 60 AUs may have destroyed the inner circumstellar dust disk by gravitational scattering.
In 2003, astronomers announced that "new computer modelling techniques" show that observations of the structure of the faint dust disk around Vega can be best explained by the presence of Neptune-sized and Jupiter-sized planets orbiting at distances roughly similar to those held by the same planets in the Solar System.
The modelling suggested that a Neptune-like planet actually formed much closer to Vega and was pushed by a Jupiter-like planet in an inner orbit out to its current wide orbit around 80 AUs away from Vega over about 56 million years, sweeping many comets out with it and causing the dust disk to become clumpy. This same process is thought to have happened in the Solar System as well under a new theory.
The star, Vega, 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.
Babylonia: Dilgan - 'The Messenger of Light'
Akkadia: Tir-anna - 'Life of Heaven'
Greece: Allore, Alahore, and Alohore
Arabic: Wega
China: Zhi-Nu - 'The Weaver' - and her beloved shepherd, Altair, who meet once a year, crossing the Milky Way.
Hindu: Sanskrit: Abhijit "Victorious"
Latin: Fidis, "Lyre"; Vultur cadens, "Falling vulture"
Medieval astrologers counted Vega as 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.
Vega was one of the stars in the Hindu 20th nakshatra, Abhtlit, "Victorious", the most northern of these stellar divisions and far out of the moon's path [usually the stars in moon mansions are ecliptic stars], but apparently utilized to bring in this splendid object; or, as Mueller says, because it was of specially good omen, for under its influence the gods had vanquished the Asuras; these last being the Hindu divinities of evil, similar to the Titans of Greece.
Ancient Hindus saw it as a triangle, or as the three-cornered nut of the aquatic plant Cringata. Vega, along with Deneb Adige in the Swan, and Altair in the Eagle, forms the Great Summer Triangle. The summer triangle consists of Deneb - Altair - and Vega.
Bright Star Vega's Secret Revealed Discovery - April 14, 2006
Vega is the very bright bluish star that now rises in the northeast between 9 and 10 p.m. and will soon take its traditional place as the brightest star in the early summer night sky of the Northern Hemisphere. For generations of astronomers Vega has been the epitome of stability and light quality.
As a result it has become the stellar standard: the star to which all others are astronomically compared.But technology has caught up with Vega. New super high-resolution telescopic observations reveal a violently spinning star that only appears stable and extra bright to us because of the unusual angle visible from Earth: Almost straight down one of its poles.
Dusty Aftermath Of Pluto-Sized Collision Science Daily - January 2005
Unmasking Vega: Solar System Like Ours Emerges Space.com - December 2003
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