The familiar constellation of the Great Bear, Ursa Major, is visible in the north, although it may appear “upside down” to anyone from the higher latitudes.
The seven brightest stars, located in the Bear's hindquarters and tail, form the well-known Big Dipper asterism. (In Britain, this asterism is known as the Plough.) The stars Merak (β Ursae Majoris) and Dubhe are known as the "pointer stars" because they are helpful for finding Polaris, also known as the North Star. By visually tracing a line from Merak through Dubhe and continuing, one's eye will land on Polaris, accurately indicating true north.
Mizar, a star in the Big Dipper, forms the famous optical double star with Alcor.
Several bright galaxies are found in Ursa Major, including the pair Messier 81 (one of the brightest galaxies in the sky) and Messier 82 above the bear's head, and Pinwheel Galaxy (M101), a beautiful spiral northwest of η Ursae Majoris.
Polaris, sometimes known as the Lodestar, is the brightest star in the constellation Ursa Minor. It is very close to the north celestial pole (42′ away as of 2006), making it the current northern pole star.
Polaris has the common reputation of being the brightest star in the sky, whereas near dead-on second magnitude (2.02) it comes in at number 48. Its lower rank, however, is largely determined by its great distance of 430 light years. The star is actually an evolved class F (F7) yellow supergiant 2500 times more luminous than our Sun with a temperature of about 6000 Kelvin, which leads to a radius 45 times that of the Sun and a mass of six times solar. Hydrogen fusion has stopped in the star's core, and it is now passing through a phase of instability wherein it pulsates over a period of about four days, almost invisibly changing its brightness as the brightest "Cepheid" variable star in the sky.
Polaris has the distinction of having a pair of companions, one near, the other far. About 18 seconds of arc away lies an eighth magnitude F3 1.4 (or so) solar mass dwarf, which at the distance of Polaris must be at least 2400 Astronomical Units away and take at least 42,000 years to orbit. Much closer is an F7 dwarf (noted from spectroscopy and resolved by the Hubble Space Telescope, giving us three F stars in one pot), that at a measured average distance of only 17 AU takes but 29.6 years to go around, a high eccentricity running it between 27 and 6.7 AU.
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