A number of features exist that are of interest to astronomers. Taurus hosts two of the nearestopen clusters to Earth, thePleiades and theHyades, both of which are visible to the naked eye. At first magnitude, thered giantAldebaran is the brightest star in the constellation. In the northeast part of Taurus isMessier 1, more commonly known as the Crab Nebula, asupernova remnant containing apulsar. One of the closest regions of active star formation, the Taurus-Auriga complex, crosses into the northern part of the constellation. Thevariable starT Tauri is the prototype of a class ofpre-main-sequence stars.
Taurus is a large and prominent constellation in thenorthern hemisphere's winter sky, betweenAries to the west andGemini to the east; to the north liesPerseus andAuriga, to the southeastOrion, to the southEridanus, and to the southwestCetus. 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.[4]
This constellation forms part of the zodiac and hence is intersected by theecliptic. This circle across thecelestial 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.[4] Thegalactic plane of theMilky Way intersects the northeast corner of the constellation and thegalactic 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 asGould's Belt passes through the constellation.[5]
The recommended three-letter abbreviation for the constellation, as adopted by theInternational Astronomical Union in 1922, is "Tau".[6] The official constellation boundaries, as set by Belgian astronomerEugène Delporte in 1930, are defined by a polygon of 26 segments. In theequatorial coordinate system, theright ascension coordinates of these borders lie between03h 23.4m and05h 53.3m, while thedeclination coordinates are between 31.10° and −1.35°.[7] Because a small part of the constellation lies to the south of thecelestial equator, this can not be a completelycircumpolar constellation at any latitude.[8]
The brightest member of this constellation is Aldebaran, an orange-hued,spectral class K5 IIIgiant star.[10] Its name derives fromالدبرانal-dabarān,Arabic for "the follower", probably from the fact that it follows thePleiades during the nightly motion of thecelestial sphere across the sky.[11][12][13] Forming the profile of a Bull's face is aV orK-shapedasterism of stars. This outline is created by prominent members of theHyades,[14] the nearest distinct openstar cluster after theUrsa Major Moving Group.[15] In this profile, Aldebaran forms the bull's bloodshot eye, which has been described as "glaring menacingly at the hunter Orion",[16] a constellation that lies just to the southeast. Aldebaran has around 116% the mass of the Sun.[17] It also hosts a candidate exoplanet.[17]
The Hyades span about 5° of the sky, so that they can only be viewed in their entirety with binoculars or the unaided eye.[18] It includes a naked eye double star,Theta Tauri (the proper name of Theta2 Tauri isChamukuy),[19] with a separation of 5.6 arcminutes.[20]
In the northwestern quadrant of the Taurus constellation lie the Pleiades (M45), one of the best known open clusters, easily visible to the naked eye. The seven most prominent stars in this cluster are at least visualmagnitude six, and so the cluster is also named the "Seven Sisters". However, many more stars are visible with even a modest telescope.[21] Astronomers estimate that the cluster has approximately 500–1,000 stars, all of which are around 100 million years old. However, they vary considerably in type. The Pleiades themselves are represented by large, bright stars; also many smallbrown dwarfs andwhite dwarfs exist. The cluster is estimated to dissipate in another 250 million years.[22] The Pleiades cluster is classified as a Shapley class c and Trumpler class I 3 r n cluster, indicating that it is irregularly shaped and loose, though concentrated at its center and detached from the star-field.[23]
To the east, the two horns of the bull are formed byBeta (β) Tauri andZeta (ζ) Tauri; two star systems that are separated by 8°. Beta is a white, spectral class B7 III giant star known asEl Nath, which comes from the Arabic phrase "the butting", as in butting by the horns of the bull.[24] At magnitude 1.65, it is the second brightest star in the constellation, and shares the border with the neighboring constellation of Auriga. As a result, it also bears the designation Gamma Aurigae. Zeta Tauri (the proper name isTianguan[19]) is aneclipsing binary star that completes an orbit every 133 days.[10]
The starLambda (λ) Tauri is an eclipsing binary star. This system consists of a spectral class B3 star being orbited by a less massive class A4 star. Theplane of their orbit lies almost along the line of sight to the Earth. Every 3.953 days the system temporarily decreases in brightness by 1.1 magnitudes as the brighter star is partially eclipsed by the dimmer companion. The two stars are separated by only 0.1astronomical units, so their shapes are modified by mutual tidal interaction. This results in a variation of their net magnitude throughout each orbit.[25]
Central area of constellation Taurus, showing Aldebaran at the lower left.
Located about 1.8° west ofEpsilon (ε) Tauri isT Tauri, the prototype of a class ofvariable stars calledT Tauri stars. This star undergoes erratic changes in luminosity, varying betweenmagnitude 9 to 13 over a period of weeks or months.[4] This is a newly formed stellar object that is just emerging from its envelope of gas and dust, but has not yet become amain sequence star.[26] The surroundingreflection nebulaNGC 1555 is illuminated by T Tauri, and thus is also variable in luminosity.[27] To the north liesKappa Tauri, a visualdouble star consisting of two A7-type components. The pair have a separation of just 5.6 arc minutes, making them a challenge to split with the naked eye.[28]
In the northern part of the constellation to the northeast of the Pleiades lies the Crystal Ball Nebula, known by its catalogue designation ofNGC 1514. Thisplanetary nebula is of historical interest following its discovery by German-born English astronomerWilliam Herschel in 1790. Prior to that time, astronomers had assumed thatnebulae were simply unresolved groups of stars. However, Herschel could clearly resolve a star at the center of the nebula that was surrounded by a nebulous cloud of some type. In 1864, English astronomerWilliam Huggins used the spectrum of this nebula to deduce that the nebula is a luminous gas, rather than stars.[29]
North-west of ζ Tauri by 1.15 degrees is theCrab Nebula (M1), a supernova remnant. This expandingnebula was created by aType II supernova explosion, which was seen from Earth on July 4, 1054. It was bright enough to be observed during the day and is mentioned in Chinese historical texts. At its peak, the supernova reached magnitude −4, but the nebula is currently magnitude 8.4 and requires a telescope to observe.[32][33]North American peoples also observed the supernova, as evidenced from a painting on a New Mexican canyon and various pieces of pottery that depict the event. However, the remnant itself was not discovered until 1731, whenJohn Bevis found it.[22]
This constellation includes part of the Taurus-Auriga complex, or Taurus dark clouds, a star-forming region containing sparse, filamentary clouds of gas and dust. This spans a diameter of 98light-years (30parsecs) and contains 35,000 solar masses of material, which is both larger and less massive than theOrion Nebula.[34] At a distance of 490 light-years (150 parsecs), this is one of the nearest active star forming regions.[35] Located in this region, about 10° to the northeast of Aldebaran, is an asterismNGC 1746 spanning a width of 45arcminutes.[31]
During November, theTauridmeteor shower appears to radiate from the general direction of this constellation. TheBeta Taurid meteor shower occurs during the months of June and July in the daytime, and is normally observed using radio techniques.[36] Between 18 and 29 October, both theNorthern Taurids and theSouthern Taurids are active; though the latter stream is stronger.[37] However, between November 1 and 10, the two streams equalize.[37]
Taurus as depicted inUrania's Mirror, a set of constellation cards published in London c.1825.
The identification of theconstellation of Taurus with a bull is very old, certainly dating to theChalcolithic, and perhaps even to theUpper Paleolithic. Michael Rappenglück of theUniversity of Munich believes that Taurus is represented in acave painting at the Hall of the Bulls in the caves atLascaux (dated to roughly 15,000 BC), which he believes is accompanied by a depiction of the Pleiades.[38][39] The name "seven sisters" has been used for the Pleiades in the languages of many cultures, including indigenous groups ofAustralia,North America andSiberia. This suggests that the name may have a common ancient origin.[40]
Taurus marked the point ofvernal (spring) equinox in theChalcolithic and theEarly Bronze Age, from about 4000 BC to 1700 BC, after which it moved into the neighboring constellation Aries.[41] The Pleiades were closest to the Sun at vernal equinox around the23rd century BC. InBabylonian astronomy, the constellation was listed in theMUL.APIN asGU4.AN.NA, "TheBull of Heaven".[42] Although it has been claimed that "when the Babylonians first set up their zodiac, the vernal equinox lay in Taurus,"[43] there is a claim that the MUL.APIN tablets indicate[42] that the vernal equinox was marked by the Babylonian constellation known as "the hired man" (the modern Aries).[44]
In theOld BabylonianEpic of Gilgamesh, the goddessIshtar sends Taurus, theBull of Heaven, to kill Gilgamesh for spurning her advances.[45] Enkidu tears off the bull's hind part and hurls the quarters into the sky where they become the stars we know as Ursa Major and Ursa Minor. Some locate Gilgamesh as the neighboring constellation of Orion, facing Taurus as if in combat,[46] while others identify him with the sun whose rising on the equinox vanquishes the constellation. In early Mesopotamian art, the Bull of Heaven was closely associated withInanna, theSumerian goddess of sexual love, fertility, and warfare. One of the oldest depictions shows the bull standing before the goddess' standard; since it has 3 stars depicted on its back (the cuneiform sign for "star-constellation"), there is good reason to regard this as the constellation later known as Taurus.[47]
The same iconic representation of the Heavenly Bull was depicted in theDendera zodiac, anEgyptian bas-relief carving in a ceiling that depicted thecelestial hemisphere using aplanisphere. In these ancient cultures, the orientation of the horns was portrayed as upward or backward. This differed from the later Greek depiction where the horns pointed forward.[48] To the Egyptians, the constellation Taurus was a sacred bull that was associated with the renewal of life in spring. When the spring equinox entered Taurus, the constellation would become covered by the Sun in the western sky as spring began. This "sacrifice" led to the renewal of the land.[49] To the earlyHebrews, Taurus was the first constellation in their zodiac and consequently it was represented by the first letter in their alphabet,Aleph.[50]
InGreek mythology, Taurus was identified withZeus, who assumed the form of a magnificent white bull to abductEuropa, a legendary Phoenician princess. In illustrations of Greek mythology, only the front portion of this constellation is depicted; this was sometimes explained as Taurus being partly submerged as he carried Europa out to sea. A second Greek myth portrays Taurus asIo, a mistress of Zeus. To hide his lover from his wifeHera, Zeus changed Io into the form of a heifer.[51] Greek mythographerAcusilaus marks the bull Taurus as the same that formed the myth of theCretan Bull, one ofThe Twelve Labors ofHeracles.[52]
Taurus became an important object of worship among theDruids. Their Tauric religious festival was held while the Sun passed through the constellation.[41] Among the arctic people known as theInuit, the constellation is called Sakiattiat and the Hyades is Nanurjuk, with the latter representing the spirit of thepolar bear. Aldebaran represents the bear, with the remainder of the stars in the Hyades being dogs that are holding the beast at bay.[53]
InBuddhism, legends hold thatGautama Buddha was born when thefull moon was inVaisakha, or Taurus.[54] Buddha's birthday is celebrated with the Wesak Festival, orVesākha, which occurs on the first or second full moon when the Sun is in Taurus.[55]
In 1990, due to theprecession of the equinoxes, the position of the Sun on the first day of summer (June 21) crossed the IAU boundary of Gemini into Taurus.[56] The Sun will slowly move through Taurus at a rate of 1° east every 72 years until approximately 2600 AD, at which point it will be in Aries on the first day of summer[citation needed].
As of 2008[update], the Sun appears in the constellation Taurus from May 13 to June 21.[57] Intropical astrology, the Sun is considered to be in the signTaurus from April 20 to May 20.[58]
Thespace probePioneer 10 is moving in the direction of this constellation, though it will not be nearing any of the stars in this constellation for many thousands of years, by which time its batteries will be long dead.[59]
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