Changes

==The Star==

==The Star==

Vega is a main sequence star of spectral class A0 V, much like [[Sirius]].  Vega is 2.3 to 3.2 times as massive as our Sun, and some 2.73 times times its diameter<ref>http://lanl.arxiv.org/abs/astro-ph/0603327</ref>.  Vega is considerably more luminous, being 37 times the Sun's luminosity at the equator and 58 times as much at the poles.  Like all class A stars, most of the radiation from Vega is in the [[ultraviolet]].  Vega is only some 63 percent as enriched as the [[Sun]], based on its abundance of [[iron]]<ref>http://adsbit.harvard.edu/cgi-bin/nph-iarticle_query?1986A%26A...165..170G</ref>.

Vega is a main sequence star of spectral class A0 V, much like [[Sirius]].  Vega is 2.3 to 3.2 times as massive as our Sun, and some 2.73 times its diameter<ref>http://lanl.arxiv.org/abs/astro-ph/0603327</ref>.  Vega is considerably more luminous, being 37 times the Sun's luminosity at the equator and 58 times as much at the poles.  Like all class A stars, most of the radiation from Vega is in the [[ultraviolet]].  Vega is only some 63 percent as enriched as the [[Sun]], based on its abundance of [[iron]]<ref>http://adsbit.harvard.edu/cgi-bin/nph-iarticle_query?1986A%26A...165..170G</ref>.

Vega is considered a very young star, and is estimated to be only some 350 million years old<ref>http://adsbit.harvard.edu/cgi-bin/nph-iarticle_query?1988A%26AS...76..411M</ref>.  Because it is far larger and hotter then our Sun, Vega will exhaust its core hydrogen only after another 650 million years or so, and least the main sequence turning into a red giant or a Cepheid variable.

Vega is considered a very young star, and is estimated to be only some 350 million years old<ref>http://adsbit.harvard.edu/cgi-bin/nph-iarticle_query?1988A%26AS...76..411M</ref>.  Because it is far larger and hotter then our Sun, Vega will exhaust its core hydrogen only after another 650 million years or so, and leaving the main sequence turning into a red giant or a Cepheid variable.

Vega rotates so fast that it only takes some 12.5 hours to complete one rotation, in comparison the Sun takes 25.4 days to complete one rotation.    This rotation is so fast that observations suggest that the star is rotating at some 91 perfect the angular velocity needed to cause the star to physically fly apart.  Vega is thus 23 percent wider along its equator than at its poles, as well as some 2300K cooler<ref>http://www.noao.edu/outreach/press/pr06/pr0603.html</ref>.  Here on Earth, Vega is seen as pole on (looking directly at its pole).

Vega rotates so fast that it only takes some 12.5 hours to complete one rotation, in comparison the Sun which takes 25.4 days to complete one rotation.    This rotation is so fast that observations suggest that the star is rotating at some 91 perfect of the angular velocity needed to cause the star to physically fly apart.  Vega is thus 23 percent wider along its equator than at its poles, as well as some 2300K cooler<ref>http://www.noao.edu/outreach/press/pr06/pr0603.html</ref>.  Here on Earth, Vega is seen as pole on (looking directly at its pole).

Vega, like many young stars, is orbited by a disk of fine dust and ice that was first discovered in 1998.  In 2005, using the Spitzer Space Telescope, NASA astronomers observed that the disk was actually far larger then originally thought, and extends outwards to as much as 850 AU.  Because the circumstellar disk of dust around Vega is partial gathered into larger clumps, some astronomers believe this is caused by the gravity of a giant planet in orbit<ref>http://www.space.com/scienceastronomy/astronomy/dusty_worlds_020123-1.html</ref>.  However, so far no substellar companions of Vega have been confirmed.  In 2006 a second inner disk of dust was observed using the CHARA array at Mt. Wilson in 2006 shown to be within 8 AU of the star<ref>http://adsabs.harvard.edu/abs/2006A&A...452..237A</ref>.

Vega, like many young stars, is orbited by a disk of fine dust and ice, first discovered in 1998.  In 2005, using the Spitzer Space Telescope, NASA astronomers observed that the disk was actually far larger then originally thought, and extends outwards to as much as 850 AU.  Because the circumstellar disk of dust around Vega is partially gathered into larger clumps, some astronomers believe this is caused by the gravity of a giant planet in orbit<ref>http://www.space.com/scienceastronomy/astronomy/dusty_worlds_020123-1.html</ref>.  However, so far no substellar companions of Vega have been confirmed.  In 2006, the CHARA array at Mt. Wilson observed a second inner disk of dust within 8 AU of the star<ref>http://adsabs.harvard.edu/abs/2006A&A...452..237A</ref>.

Vega's [[habitable zone]] where liquid water could exist on the surface of an [[Earth|Earth-like]] world is centered on 7.1 AU, a distance between the orbit of [[Jupiter]] and [[Saturn]].

Vega's [[habitable zone]], where liquid water could exist on the surface of an [[Earth|Earth-like]] world, is centered on 7.1 AU, a distance between the orbit of [[Jupiter]] and [[Saturn]].

[[Category:Astronomy]]

[[Category:Astronomy]]