Ursa Major and Ursa Minor
Ursa Major (ûr`sə) and Ursa Minor
[Lat.,=the great bear; the little bear], two conspicuous northern constellationsconstellation,in common usage, group of stars that appear to form a configuration in the sky; properly speaking, a constellation is a definite region of the sky in which the configuration of stars is contained.
..... Click the link for more information. . Known to many peoples from ancient times, these constellations have had various names; the configuration of the seven brightest stars has been called the Bear, Septentriones (the seven plowing oxen), the Plow, Charles's Wain, and the Wagon. Ursa Minor was once known as Cynosura (from the Greek for "dog's tail"). In the United States part of Ursa Major is called the Big Dipper (or the Drinking Gourd) and part of Ursa Minor, the Little Dipper. Four of the seven bright stars in the Big Dipper form the bowl and three the handle; five of these stars are of second magnitude. The middle star in the handle of the Big Dipper is Mizar (Zeta Ursae Majoris). A fainter star, Alcor, which appears to be near Mizar, was observed from ancient times. These two stars are sometimes called a double star, but since they do not revolve around a common center of gravity they are not true doubles. Mizar itself is, however, a visual binary starbinary star
or binary system,
pair of stars that are held together by their mutual gravitational attraction and revolve about their common center of mass. In 1650 Riccioli made the first binary system discovery, that of the middle star in the Big Dipper's handle, Zeta
..... Click the link for more information. and was the first to be recognized as such—by G. B. Riccioli in 1650. It was also the first spectroscopic binary to be discovered; this observation resulted from studies of the spectrum of the brighter component of Mizar, which revealed it as a binary consisting of a pair of stars of almost equal brightness. The two end stars in the bowl of the Big Dipper are known as the Pointers. A line extending through them to about five times the distance between them leads to the polestar (PolarisPolaris
or North Star,
star nearest the north celestial pole (see equatorial coordinate system). It is in the constellation Ursa Minor (see Ursa Major and Ursa Minor; Bayer designation Alpha Ursae Minoris) and marks the end of the handle of the Little Dipper.
..... Click the link for more information. , or the North Star). Polaris is at the extreme end of the Little Dipper. Including Polaris there are three stars in the handle of the Little Dipper and four forming the bowl. The handles of the two Dippers extend in opposite directions, and when one bowl is upright the other is inverted. Ursa Major reaches its highest point in the evening sky in April and Ursa Minor its highest point in June. However, for observers in the middle and northern latitudes of the Northern Hemisphere both constellations are circumpolar and thus are visible throughout the year.