Ursa Major

Ursa Major (Latin: "Larger Bear"; also known as the Great Bear and Charles' Wain) is a constellation visible throughout the year in most of the northern hemisphere. It can be seen best in the month of April. It is dominated by the widely recognized asterism known as the Big Dipper or the Plough, which is a useful pointer towards the north, and it has mythological significance in numerous world cultures. ... Asterisms. The seven brightest stars of Ursa Major form the asterism known as the Big Dipper in the USA and Canada, the Plough in the United Kingdom, the Großer Wagen in Germany & Austria and the Saptarshi in India. Six of these seven stars are of 2nd magnitude, just the central star is of 3rd magnitude. Another asterism known as the "Three Leaps of Gazelle" is recognized in Arab culture, a series of three pairs of stars: ν and ξ Ursae Majoris, Alula Borealis and Australis, the "first leap"; λ and μ Ursae Majoris, Tania Borealis and Australis, the "second leap"; ι and κ Ursae Majoris, Talitha Borealis and Australis, the "third leap". These stars are found along the southwest border of the constellation. ... Stars. The "Big Dipper" (or "Plough") asterism within Ursa Major is made up of seven bright stars that together comprise one of the best-known patterns in the sky, while also forming the hindquarters and tail of the Great Bear. Starting with the "ladle" portion of the dipper and extending clockwise through the handle, these stars are the following: α Ursae Majoris, known by the Arabic name Dubhe ("the bear"), which at a magnitude of 1.79 is the 35th brightest star in the sky and the second brightest of Ursa Major. β Ursae Majoris, called Merak ("the loins of the bear"), with a magnitude of 2.37. γ Ursae Majoris, or Phecda ("thigh"), with a magnitude of 2.44. δ Ursae Majoris, or Megrez, meaning "root of the tail," an appropriate name given its location as the intersection of the body and tail of the bear (or the ladle and handle of the dipper). ε Ursae Majoris, known as Alioth, a name which refers not to a bear but to a "black horse," the name corrupted from the original and mis-assigned to the similarly named Alcor, the naked-eye binary companion of Mizar. Alioth is the brightest star of Ursa Major and the 33rd brightest in the sky, with a magnitude of 1.76. It is also the brightest of the "peculiar A (Ap) stars," magnetic stars whose chemical elements are either depleted or enhanced, and appear to change as the star rotates. ζ Ursae Majoris, Mizar, the second star in from the end of the handle of the Big Dipper, and the constellation's fourth brightest star. Mizar, which means "girdle," forms a famous double star, with its optical companion Alcor (80 Ursae Majoris), the two of which were termed the "horse and rider" by the Arabs. η Ursae Majoris, known as either Alkaid or Benetnash, both meaning the "end of the tail." With a magnitude of 1.85, Alkaid is the third-brightest star of Ursa Major. Except for Dubhe and Alkaid (Eta Ursae Majoris), the stars of the Big Dipper all have proper motions heading toward a common point in Sagittarius. A few other such stars have been identified, and together they are called the Ursa Major Moving Group. The stars Merak (β Ursae Majoris) and Dubhe (α Ursae Majoris) are known as the "pointer stars" because they are helpful for finding Polaris, also known as the North Star or Pole Star. By visually tracing a line from Merak through Dubhe and continuing, one's eye will land on Polaris, accurately indicating true north. ... Deep-sky objects. 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 spiral northeast of η Ursae Majoris. The spiral galaxies Messier 108 and Messier 109 are also found in this constellation. The bright planetary nebula Owl Nebula (M97) can be found along the bottom of the bowl of the Big Dipper. ... Meteor showers. The Kappa Ursae Majorids are a newly discovered meteor shower, peaking between November 1 and November 10. [Ursa Major. Wikipedia]