Ursa Minor

Ursa Minor
Ursa Minor (Little Bear) is a constellation in the northern sky. It is colloquially known as the Little Dipper because its seven brightest stars appear to form the shape of a ladle (diagram pictured). It was one of the 48 constellations listed by the 2nd-century astronomer Ptolemy, and it remains one of the 88 modern constellations. Polaris, its brightest star, is currently less than one degree away from the north celestial pole. Because this position stays nearly fixed as the Earth rotates, the star has traditionally been important for navigation, particularly by mariners. Polaris is a yellow-white supergiant and the brightest Cepheid variable star in the night sky, ranging in apparent magnitude from 1.97 to 2.00. Beta Ursae Minoris, also known as Kochab, is an aging star that has swollen and cooled to become an orange giant with an apparent magnitude of 2.08, only slightly fainter than Polaris. The constellation also contains an isolated neutron star—Calvera—and H1504+65, the hottest white dwarf yet discovered, with a surface temperature of 200,000 degrees Kelvin. Planets have been detected orbiting four of the constellation's stars, including Kochab.