Ursa Major

Ursa Major, Esparron La Bâtie, Alpes-de-Haute Provence, Alt 1500 m., 13 juillet 2015

Nikon 5500, 10’ , Jacques HONNORAT.

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.  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. The ability to resolve the two stars with the naked eye is often quoted as a test of eyesight, although even people with quite poor eyesight can see the two stars.

·         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.