McAlister, Harold A. Center for High Angular Resolution Astronomy, Georgia State University, Atlanta, Georgia.
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The fifth brightest of all stars and the third brightest in the northern sky. It will be the north polar star in about 12,000 years. In moving through the Milky Way Galaxy, the Sun is generally heading toward the position now occupied by Vega. At a distance of 7.8 parsecs (25.3 light-years, or 2.4 × 1014 km, or 1.49 × 1014 mi), Vega, or α Lyrae, is the prototypical star of spectral class A0V, indicating that it has an effective surface temperature of 9600 K (16,800°F) and derives its energy from the thermonuclear burning of hydrogen in a stable core region. Stars of this class have main-sequence lifetimes of about 5 × 108 years, 20 times shorter than the Sun. Vega's spectrum shows strong features due to hydrogen in the star's outer layers. The sharpness of these features implies that Vega is pointing its rotation axis nearly at the Sun. In comparison with the Sun, Vega is approximately 2.9 times larger in diameter, 2.5 times more massive, and 60 times more luminous. See also: Precession of equinoxes; Spectral type
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