Taurus (constellation)

Taurus (Latin, 'Bull') is one of the constellations of the zodiac and is located in the northern celestial hemisphere. Taurus is a large and prominent constellation in the Northern Hemisphere's winter sky. It is one of the oldest constellations, dating back to the Early Bronze Age at least, when it marked the location of the Sun during the spring equinox. Its importance to the agricultural calendar influenced various bull figures in the mythologies of Ancient Sumer, Akkad, Assyria, Babylon, Egypt, Greece, and Rome. Its traditional astrological symbol is (♉︎), which resembles a bull's head.

A number of features exist that are of interest to astronomers. Taurus hosts two of the nearest open clusters to Earth, the Pleiades and the Hyades, both of which are visible to the naked eye. At first magnitude, the red giant Aldebaran is the brightest star in the constellation. In the northeast part of Taurus is Messier 1, more commonly known as the Crab Nebula, a supernova remnant containing the Crab Pulsar. One of the closest regions of active star formation, the Taurus-Auriga complex, crosses into the northern part of the constellation. The variable star T Tauri is the prototype of a class of pre-main-sequence stars.

Taurus is a large and prominent constellation in the Northern Hemisphere's winter sky, between Aries to the west and Gemini to the east; to the north lies Perseus and Auriga, to the southeast Orion, to the south Eridanus, and to the southwest Cetus. In late November-early December, Taurus reaches opposition (furthest point from the Sun) and is visible the entire night. By late March, it is setting at sunset and completely disappears behind the Sun's glare from May to July.

This constellation forms part of the zodiac and hence is intersected by the ecliptic. This circle across the celestial sphere forms the apparent path of the Sun as the Earth completes its annual orbit. As the orbital plane of the Moon and the planets lie near the ecliptic, they can usually be found in the constellation Taurus during some part of each year. The galactic plane of the Milky Way intersects the northeast corner of the constellation and the galactic anticenter is located near the border between Taurus and Auriga. Taurus is the only constellation crossed by all three of the galactic equator, celestial equator, and ecliptic. A ring-like galactic structure known as Gould's Belt passes through the constellation.

The recommended three-letter abbreviation for the constellation, as adopted by the International Astronomical Union in 1922, is "Tau". The official constellation boundaries, as set by Belgian astronomer Eugène Delporte in 1930, are defined by a polygon of 26 segments. In the equatorial coordinate system, the right ascension coordinates of these borders lie between 03^h 23.4^m and 05^h 53.3^m , while the declination coordinates are between 31.10° and −1.35°. Because a small part of the constellation lies to the south of the celestial equator, this can not be a completely circumpolar constellation at any latitude.

Bayer gave the most prominent stars Bayer designations Alpha through Omega, and the Latin letters A through u. Later designated three stars as Delta and two stars as Theta, Kappa, Sigma, Omega, and the Latin letter A. The star g Tauri was dropped after it was found to be a duplicate of Kappa Ceti (Kappa¹ and Kappa²)

There are four stars above magnitude 3 in Taurus. The brightest member of this constellation is Aldebaran, an orange-hued, spectral class K5 III giant star. Its name derives from الدبران al-dabarān, Arabic for "the follower", probably from the fact that it follows the Pleiades during the nightly motion of the celestial sphere across the sky. Forming the profile of a Bull's face is a V or K-shaped asterism of stars. This outline is created by prominent members of the Hyades, the nearest distinct open star cluster after the Ursa Major Moving Group. In this profile, Aldebaran forms the bull's bloodshot eye, which has been described as "glaring menacingly at the hunter Orion", a constellation that lies just to the southeast. Aldebaran has around 116% the mass of the Sun. It also hosts a candidate exoplanet.

The Hyades span about 5° of the sky, so that they can only be viewed in their entirety with binoculars or the unaided eye. It includes a naked eye double star, Theta Tauri (the proper name of Theta² Tauri is Chamukuy), with a separation of 5.6 arcminutes.