V Aquilae
V Aquilae is a deep-red carbon star just above the center in this image. It is located in the constellation of Aquila, 41 arcminutes east of 4th magnitude 12 Aquilae. V Aquilae is a semi-regular pulsating variable star that varies in magnitude from 6.6 to 8.4. Because it doesn't have a tremendous brightness range like some carbon stars, and because it is relatively bright even at its dimmest, it is a showpiece deep-sky object that can easily be found even in binoculars. V Aquilae has a spectral type classification of CII and is a late-type giant star with a high abundance of carbon in its atmosphere which filters out the blue light, causing its vivid red color. These types of stars will soon eject their outer layers to form a planetary nebula. They will then evolve into a white dwarf. V Aquilae has a B-V index of +4.0. Astronomers calculate the "redness" of a star by measuring it through B (blue) and V (visual) filters and then subtracting the V value from the B value. The higher the plus number, the redder the star is. Stars range in color from -0.5 for a very blue star to over +5 for very red stars. In the 1990's the Hipparcos astrometry satellite discovered that V Aquilae is actually a close binary system with a separation of just 0.2 arcseconds. V Aquilae is located 1,200 light-years away and was discovered by George Knott in 1861. North is to the top in the above image.
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