Antares, also called Alpha Scorpii, is the brightest star in the constellation Scorpius. Antares is an extremely large star and is classified as a red supergiant. It has a diameter roughly 700 times as large as that of the sun. However, Antares is much cooler than the sun, and so the star appears reddish. Its surface temperature is only about half that of the sun’s.
Astronomers call Antares a semiregular variable because it changes in brightness over varying periods of time. In its normal range of brightness, Antares is a star of the first magnitude—that is, one of the brightest stars (see Magnitude ). It is a binary star, having a small, hot companion star. This companion revolves around Antares, orbiting within the mass of gases escaping from the surface of the larger star.
Antares is more than 600 light-years from Earth. One light-year, the distance that light travels in a vacuum in a year, equals about 5.88 trillion miles or 9.46 trillion kilometers (see Light-year ). The best time to view the star is from May through July.
See also Astronomy .
