Ursa Minor
Channel: 宇宙のすべての知識 プリンシピア
Date: 2019-01-04

Ursa Minor, by Wikipedia https://en.wikipedia.org/wiki?curid=31773 / CC BY SA 3.0

Ursa Minor

Ursa Minor (Latin: "Lesser Bear", contrasting with Ursa Major), also known as the Little Bear, is a constellation in the Northern Sky. Like the Great Bear, the tail of the Little Bear may also be seen as the handle of a ladle, hence the North American name, Little Dipper: seven stars with four in its bowl like its partner the Big Dipper. It was one of the 48 constellations listed by the 2nd-century astronomer Ptolemy, and remains one of the 88 modern constellations. Ursa Minor has traditionally been important for navigation, particularly by mariners, because of Polaris being the North Star.

Polaris, the brightest star in the constellation, is a yellow-white supergiant and the brightest Cepheid variable star in the night sky, ranging from an apparent magnitude of 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. Kochab and magnitude 3 Gamma Ursae Minoris have been called the "guardians of the pole star". Planets have been detected orbiting four of the stars, including Kochab. 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 K.

In the Babylonian star catalogues, Ursa Minor was known as the "Wagon of Heaven" (, also associated with the goddess Damkina). It is listed in the MUL.APIN catalogue, compiled around 1000 BC among the "Stars of Enlil"—that is, the northern sky.

According to Diogenes Laertius, citing Callimachus, Thales of Miletus "measured the stars of the Wagon by which the Phoenicians sail". Diogenes identifies these as the constellation of Ursa Minor, which for its reported use by the Phoenicians for navigation at sea were also named "Phoinikē". 
The tradition of naming the northern constellations "bears" appe...