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COR CAROLI
Though this star is third magnitude, it is easy to find and is important all out of proportion to its brightness. Cor Caroli, which means "Charles' Heart" in honor of England's King Charles II, is the brightest star of the modern constellation Canes Venatici, the Hunting Dogs, invented in the 17th century by the astronomer Hevelius to help fill in the blanks left over by the ancients. If you look on the line perpendicular to the Big Dipper's handle just toward the south, you find a pair of stars extending parallel to the handle; the brighter is Cor Caroli, the Alpha star. In a telescope it is paired with a fainter fifth magnitude star of little interest, the fainter called Alpha-1, the brighter, really Cor Caroli itself, Alpha-2. It is a white star with a surface temperature of 10,000 Kelvin, about double that of the Sun. Though almost 50 times more luminous than the Sun its distance of 130 light years renders it relatively faint compared with others of its class. Much more interestingly, Cor Caroli (Alpha-2) is a "magnetic star," and possesses one of the strongest known magnetic fields among otherwise normal "main sequence" stars, youthful unevolved stars like the Sun. The Sun has an overall magnetic field that is only a few time stronger than Earth's; Cor Caroli's, on the other hand, has one 1500 times stronger. The star also has a weird chemical composition in which elements such as silicon, mercury, and rarer elements such as europium are locally enormously enhanced. Astronomers think the magnetic field is responsible for helping to redistribute the elements in the star's atmosphere, apparently enriching some, depleting others.