Xi Ursae Majoris: A Binary Star Close to Home

Xi Ursae Majoris, also known as Alula Australis, is a double star in Ursa Major. It’s best viewed in winter. This binary system is notable for many reasons: It’s a close binary system to earth — only 25 light years away. It was the first binary system to be discovered. William Herschel discovered it inContinueContinue reading “Xi Ursae Majoris: A Binary Star Close to Home”

Cor Caroli: A Binary Star with a Heart of a King

Cor Caroli is a double star in the constellation Canes Venatici. It’s best viewed in spring. The primary star, at a magnitude of 2.9, shines a white blue, while the dimmer companion, at a magnitude of 5.5, shines a warm yellow. This contrast of color makes for an attractive pair in the warming spring sky.