Properties
Adhara is a binary star, estimated by the Hipparcos astrometry satellite to lie about 430 light years away from Earth. The main star possesses an apparent magnitude of +1.5 and belongs to the spectral classification B2. Its color is blue or blueish-white, due to the surface temperature of 22,200K. It emits a total radiation equal to 38,700 times that of the Sun. This star is one of the brightest known extreme ultraviolet sources in the sky. It is the strongest source of photons capable of ionizing hydrogen atoms in interstellar gas near the sun, and is very important in determining the ionization state of the Local Interstellar Cloud.
The +7.5 magnitude companion star (the absolute magnitude amounts to +1.9) is at 7.5" away with a position angle of 161° of the main star. Despite the relatively large angular distance the components can only be resolved in large telescopes, since the main star is approximately 250 times brighter than its companion.
A few million years ago, Adhara was much closer to the Sun than it is at present, causing it to be a much brighter star in the night sky. About 4,700,000 years ago, Adhara was 34 light years from the Sun, and was the brightest star in the sky with a magnitude of –3.99. No other star has attained this brightness since, nor will any other star attain this brightness for at least five million years.
Read more about this topic: Epsilon Canis Majoris
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—Ralph Waldo Emerson (1803–1882)
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—John Locke (1632–1704)