Taurus (Latin for ‘the Bull’) is one of the constellations of the zodiac. It is a large and prominent constellation in the northern hemisphere’s winter sky. It is one of the oldest constellations, dating back to at least the Early Bronze Age when it marked the location of the Sun during the spring equinox. In the equatorial coordinate system, the right ascension coordinates of the constellation lie between 03h 23.4m and 05h 53.3m, 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.
Taurus lies between Aries to the west and Gemini to the east; to the north lie Perseus and Auriga, to the southeast Orion, to the south Eridanus, and to the southwest Cetus. In September and October, Taurus is visible in the evening along the eastern horizon. The most favorable time to observe Taurus in the night sky is during the months of December and January. By March and April, the constellation will appear to the west during the evening twilight.
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 the Gould's Belt passes through the Taurus constellation.
Taurus is the second astrological sign in the present Zodiac. It spans the 30-60th degree of the zodiac. The Sun is in the sign of Taurus from about April 21 until about May 21 (Western astrology) or from about May 16 to June 16 (sidereal astrology). People born between these dates, depending on which system of astrology they subscribe to, may be called Taureans. The symbol of the bull is based on the Cretan Bull, the white bull that fathered the Minotaur who was killed by Theseus. The Sun transits the constellation of Taurus from May 14 to June 19.
[https://en.wikipedia.org/wiki/Taurus_(astrology)]
Alexander Jamieson’s Celestial Atlas (1822)
[http://www.astronomytrek.com/taurus-the-bull/]
The identification of the constellation of Taurus with a bull is very old, certainly dating to the Chalcolithic, and perhaps even to the Upper Paleolithic. Michael Rappenglück believes that Taurus is represented in a cave painting at the Hall of the Bulls in the caves at Lascaux (dated to roughly 15,000 BCE), which he believes is accompanied by a depiction of the Pleiades. The name ‘seven sisters’ has been used for the Pleiades in the languages of many cultures, including indigenous groups of Australia, North America and Siberia. This suggests that the name may have a common ancient origin.
Taurus marked the point of vernal (spring) equinox in the Chalcolithic and the Early Bronze Age, from about 4000 BCE to 1700 BCE, after which it moved into the neighboring constellation Aries. The Pleiades were closest to the Sun at vernal equinox around the 23rd century BCE. In Babylonian astronomy, the constellation was listed in the MUL.APIN as GU4.AN.NA, ‘The Bull of Heaven.’ As this constellation marked the vernal equinox, it was also the first constellation in the Babylonian zodiac and they described it as ‘The Bull in Front.’ The Akkadian name was Alu.
In the Mesopotamian Epic of Gilgamesh, one of the earliest works of literature, the goddess Ishtar sends Taurus, the Bull of Heaven, to kill Gilgamesh for spurning her advances. Some locate Gilgamesh as the neighboring constellation of Orion, facing Taurus as if in combat, 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 with Inanna, the Sumerian 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.
The same iconic representation of the Heavenly Bull was depicted in the Dendera zodiac, an Egyptian bas-relief carving in a ceiling that depicted the celestial hemisphere using a planisphere. 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. 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. To the early Hebrews, Taurus was the first constellation in their zodiac and consequently it was represented by the first letter in their alphabet, Aleph.
In Greek mythology, Taurus was identified with Zeus, who assumed the form of a magnificent white bull to abduct Europa, a legendary Phoenician princess. In illustrations of Greek mythology, only the front portion of this constellation are depicted; this was sometimes explained as Taurus being partly submerged as he carried Europa out to sea. A second Greek myth portrays Taurus as Io, a mistress of Zeus. To hide his lover from his wife Hera, Zeus changed Io into the form of a heifer. Greek mythographer Acusilaus marks the bull Taurus as the same that formed the myth of the Cretan Bull, one of The Twelve Labors of Heracles.
Taurus became an important object of worship among the Druids. Their Tauric religious festival was held while the Sun passed through the constellation.
Among the arctic people known as the Inuit, the constellation is called Sakiattiat and the Hyades is Nanurjuk, with the latter representing the spirit of the polar bear. Aldebaran represents the bear, with the remainder of the stars in the Hyades being dogs that are holding the beast at bay.
In Buddhism, legends hold that Gautama Buddha was born when the Full Moon was in Vaisakha, or Taurus. Buddha’s birthday is celebrated with the Wesak Festival, or Vesākha, which occurs on the first or second Full Moon when the Sun is in Taurus.
According to traditional Chinese uranography, the modern constellation Taurus is located within the western quadrant of the sky, which is symbolized as the White Tiger of the West (Xī Fāng Bái Hǔ). The name of the western constellation in modern Chinese ‘jīn niú zuò,’ meaning ‘the golden bull constellation.’
[https://en.wikipedia.org/wiki/Taurus_(Chinese_astronomy)]
The constellations Orion (center), Taurus (upper right) and Canis Major (lower left). If you can find Orion, finding Taurus is easy. Just extend the line of Orion’s belt to the northwest until you find a bright orange star nestled in a V-shaped cluster of stars. The bright star is Aldebaran, a swollen giant star some 45x the diameter of our own sun. The ‘V’ which marks the head of the bull, is the nearby Hyades star cluster. It’s remarkably beautiful in dark sky, with several close star pairs to challenge your visual acuity. Just northwest of the ‘V,’ the Pleiades is perhaps the most famous of all star groupings.
[http://astronomer.wpengine.netdna-cdn.com/wp-content/uploads/2011/01/Taurus-Orion.jpg]
[http://astropixels.com/constellations/charts/Tau.html]
At first magnitude, the red giant Aldebaran is the brightest star in the constellation:
Aldebaran
[http://skylightsblog.blogspot.gr/2014/12/an-new-deep-sky-object-outshined-by.html]
Alpha Tauri (Aldebaran) is an orange giant star located about 65 light years away. It is the brightest star of Taurus and the fourteenth brightest star in the nighttime sky. The name Aldebaran is Arabic (al-dabarān) and means ‘the Follower,’ presumably because it rises near and soon after the Pleiades.
Aldebaran is classified as a type K5 III star, which indicates it is an orange-hued giant star that has evolved off the main sequence after exhausting the hydrogen at its core. This has caused it to expand to 44.2 times the diameter of the Sun, equivalent to approximately 61 million kilometers. Stellar models predict it only has about 50% more mass than the Sun, yet it shines with 425 times the Sun’s luminosity due to the expanded radius. Aldebaran is a slightly variable star, of the slow irregular variable type LB. It varies by about 0.2 in apparent magnitude from 0.75 to 0.95. With a near-infrared J band magnitude of −2.1, only Betelgeuse (−2.9), R Doradus (−2.6), and Arcturus (−2.2) are brighter.
The three medium-bright stars of Orion’s Belt point to reddish Aldebaran
[http://earthsky.org/brightest-stars/aldebaran-is-taurus-bloodshot-eye]
Aldebaran is one of the easiest stars to find in the night sky, partly due to its brightness and partly due to its spatial relation to one of the more noticeable asterisms in the sky. If one follows the three stars of Orion’s belt from left to right (in the Northern Hemisphere) or right to left (in the Southern), the first bright star found by continuing that line is Aldebaran. Since the star is located (by chance) in the line of sight between the Earth and the Hyades, it has the appearance of being the brightest member of the more scattered Hyades open star cluster that makes up the bull’s-head-shaped asterism; however, the star cluster is actually more than twice as far away, at about 150 light years.
Aldebaran disappears behind the Moon (Rome, 29 Oct. 2015, 10:41 PM)
[http://www.virtualtelescope.eu/2015/10/15/29-oct-2015-the-moon-occults-aldebaran/]
Aldebaran is close enough to the ecliptic to be occulted by the Moon. Such occultations occur when the Moon’s ascending node is near the autumnal equinox. A series of 49 occultations occur starting at 29 Jan 2015 and ending at 3 Sep 2018. Each event is visible from a different location on Earth, but always in the northern hemisphere or close to the equator. That means that people in e.g. Australia or South Africa can never observe an Aldebaran occultation. This is due to the fact that Aldebaran is slightly too far south of the ecliptic. A reasonably accurate estimate for the diameter of Aldebaran was obtained during the September 22, 1978 occultation. Aldebaran is in conjunction with the Sun around June 1 of each year.
On March 11, of 509 AD, a lunar occultation of Aldebaran was observed in Athens, Greece. English astronomer Edmund Halley studied the timing of this event, and in 1718 concluded that Aldebaran must have changed position since that time, moving several minutes of arc further to the north. This, as well as observations of the changing positions of stars Sirius and Arcturus, led to the discovery of proper motion. Based on present day observations, the position of Aldebaran has shifted 7′ in the last 2000 years; roughly a quarter the diameter of the full Moon.
In 1993, radial velocity measurements of Aldebaran, Arcturus and Pollux showed that Aldebaran exhibited a long-period radial velocity oscillation, which could be interpreted as a substellar companion. The measurements for Aldebaran implied a companion with a minimum mass 11.4 times that of Jupiter in a 643-day orbit at a separation of 2.0 AU (300 Gm) in a mildly eccentric orbit.In 2015 a study showed stable longterm evidence for both a planetary companion and stellar activity.
The planetary exploration probe Pioneer 10 is currently heading in the general direction of the star and should make its closest approach in about two million years.
[https://en.wikipedia.org/wiki/Aldebaran]
Beta Tauri (Elnath) is the second brightest star in the constellation Taurus, with an apparent magnitude of 1.68. The star’s traditional name Elnath (Arabic an-naţħ) is a reference to ‘the butting’ of the bull’s horns. Elnath’s absolute magnitude is -1.34, similar to another Taurean star, Maia in the Pleiadian star cluster. Like Maia, Elnath is a B class giant with a luminosity 700 times solar. However being approximately 130 light years distant compared to Maia’s estimated 360 light years, Elnath ranks as the second brightest star in the constellation.
Uniquely positioned along the plane of our Milky Way Galaxy a few degrees west of the galactic anticenter, Elnath heralds a rich collection of nebulae and star clusters. This star can be occulted by the moon. Such occultations occur when the moon’s ascending node is near the vernal equinox, as was the case in 2007. Most occultations are visible only in parts of the Southern Hemisphere, because the star lies at the northern edge of the lunar occultation zone. Rarely, it may be occulted as far north as southern California.
There is a faint star that appears close enough to Elnath for astronomers to consider it a double star. Its visual companion, known as BD+28 795B, has a position angle of 239 degrees and is separated from the main star by 33.4 arcseconds.
[https://en.wikipedia.org/wiki/Beta_Tauri]
Alcyone (Eta Tauri)
[https://stargazerslounge.com/topic/199104-alcyone-eta-tauri/]
Alcyone (Eta Tauri) is a star system in the constellation Taurus. It is the third brightest star in Taurus and the brightest star in the Pleiades cluster. Alcyone is approximately 440 light years from Earth. It is named after the mythological figure Alcyone, one of the mythological Pleiades. It has an apparent magnitude of +2.87 (absolute magnitude −2.39), and a radius almost 10 times that of the Sun. Its temperature is approximately 13,000 K giving it a total luminosity that is 2,400 times solar. The spectral type of B7IIIe indicates that emission lines are present in its spectrum.
The main star of the system, Alcyone A, consists of three components, the brightest being a B-type giant star. The closest companion has a very low mass and is less than 1 milli-arcsecond away, with a likely orbital period just over four days. The other star is about half the mass of the giant and they are separated by 0.031 arcseconds, or about the distance from the Sun to Jupiter, orbiting in about 830 days. Further four companions are all fainter than 11th magnitude, and component D is itself double with two nearly equal components separated by 0.30".
[https://en.wikipedia.org/wiki/Alcyone_(star)]
To the west, the two horns of the bull are formed by Beta Tauri and Zeta Tauri; Zeta Tauri is a binary star with an apparent visual magnitude of 3.0, which is bright enough to be seen with the naked eye. It lies at a distance of roughly 440 light-years from the Earth. This is a single-lined spectroscopic binary system, which means the two components are orbiting so close to each other that they cannot be resolved with a telescope. The two components are separated by an estimated distance of about 1.17 Astronomical Units, or 117% of the distance from the Earth to the Sun. They are following circular orbits with a period of nearly 133 days.
Compared to the Sun, the primary is an enormous star with more than 11 times the mass and 5-6 times the radius. It is rotating rapidly with a projected rotational velocity of 125 km s−1. The companion has about 94% the mass of the Sun, although it is unknown whether this is a main sequence star, a neutron star, or a white dwarf. If it is a main sequence star, then the mass indicates it may have a stellar classification of G4.
The spectrum of the primary component has a stellar classification of B2 IIIpe. A luminosity class of ‘III’ indicates this is a giant star that has exhausted the hydrogen at its core and evolved away from the main sequence. The ‘e’ suffix is used for stars that show emission lines in their spectrum. For Be stars such as this, the emission lines are produced by a rotating circumstellar disk of gas, made of material that has been ejected from the star’s outer envelope. An oscillatory pattern in this spectrum is being caused by a single-armed spiral density wave in the disk. The disk may be precessing from the gravitational influence of the secondary component.
[https://en.wikipedia.org/wiki/Zeta_Tauri]
Theta Tauri is a double star in the constellation Taurus and the brightest member of the Hyades open cluster. It dominated by two 3rd magnitude stars, θ1 Tauri and θ2 Tauri, which are separated by 5.62 arcminutes (0.094°) on the sky. The first component, θ1 Tauri, is located at a distance of 154.4 ly (47.3 pc), while the second component, θ2 Tauri is at a distance of 150.4 light-years (46.1 parsecs). If these estimates are correct, then the two components are separated by about four light years and hence are unlikely to form a binary star system.
θ1 Tauri is the dimmer star, an orange K-type giant with an apparent magnitude of +3.84. θ2 Tauri is a white A-type giant with a mean apparent magnitude of +3.40. θ2 Tauri is classified as a Delta Scuti type variable star and its brightness varies from magnitude +3.35 to +3.42 with a period of 1.82 hours. Both bright stars are spectroscopic binaries and have at least one closer companion. Θ1 Tauri has a 7th magnitude companion 0.082 arcseconds, or at least 4 astronomical units (AU), away from the primary. θ2 has a 6th magnitude companion 0.005 arcseconds, or at least 2 AU, distant. It completes an orbit once every 141 days.
[https://en.wikipedia.org/wiki/Theta_Tauri]
Lambda Tauri is an eclipsing binary star, with an 11th magnitude companion 182 arcseconds from the primary. This system consists of a spectral class B3 star being orbited by a less massive class A4 star. The plane 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 0.1 astronomical units, so their shapes are modified by mutual tidal interaction. This results in a variation of their net magnitude throughout each orbit.
Epsilon Tauri is an orange giant star located approximately 45 parsecs (147 light-years) from the Sun. It has the traditional name Ain (Arabic for ‘eye’) and was given the name Oculus Boreus (Latin for ‘Northern eye’) by John Flamsteed. It is a member of the Hyades open cluster. It is claimed to be the heaviest among planet-harboring stars with reliable initial masses, although the star HD 13189 is potentially more massive. Given its large mass, this star, though presently of spectral type K0 III, was formerly of spectral type A that has now evolved off the main sequence into the giant phase. It is regarded as a red clump giant; that is, a core-helium burning star.
Since Epsilon Tauri lies near the plane of the ecliptic, it is sometimes occulted by the Moon and (very rarely) by planets. In 2007 a massive extrasolar planet was reported orbiting the star with a period of 1.6 years in a somewhat eccentric orbit. Its discoverers claimed it was the first planet ever discovered in an open cluster.
[https://en.wikipedia.org/wiki/Epsilon_Tauri]
T Tauri is located about 1.8° west of Epsilon Tauri. This star undergoes erratic changes in luminosity, varying between magnitude 9 to 13 over a period of weeks or months. It is a newly formed stellar object that is just emerging from its envelope of gas and dust, but has not yet become a main sequence star. The surrounding reflection nebula NGC 1555 is illuminated by T Tauri, and thus is also variable in luminosity:
T Tauri and Hind’s Variable Nebula
The yellowish star near center in this dusty telescopic skyview is T Tauri, prototype of the class of T Tauri variable stars. Just next door is the yellow cosmic cloud historically known as Hind’s Variable Nebula (NGC 1555). Over 400 light-years away, at the edge of an otherwise invisible molecular cloud, both star and nebula are seen to vary significantly in brightness but not necessarily at the same time, adding to the mystery of the intriguing region. T Tauri stars are now generally recognized as young (less than a few million years old), sun-like stars still in the early stages of formation. To further complicate the picture, infrared observations indicate that T Tauri itself is part of a multiple system and suggest that the associated Hind’s Nebula may also contain a very young stellar object. The naturally colored image spans about 7 light-years at the estimated distance of T Tauri.
[http://apod.nasa.gov/apod/ap140503.html]
Taurus hosts two of the nearest open clusters to Earth, the Pleiades and the Hyades, both of which are visible to the naked eye:
Pleiades to Hyades
This cosmic vista stretches almost 20 degrees across the gentle constellation Taurus. It begins at the Pleiades and ends at the Hyades, two of the best known star clusters in planet Earth’s sky. At left, the lovely Pleiades star cluster is about 400 light-years away. In a familiar celestial scene, the cluster stars shine through dusty clouds that scatter blue starlight. At right, the V-shaped Hyades cluster looks more spread out compared to the compact Pleiades and lies much closer, 150 light-years distant. Of course, the Hyades cluster stars seem anchored by bright Aldebaran, a red giant star with a yellowish appearance. But Aldebaran actually lies only 65 light-years away, by chance along the line of sight to the Hyades cluster. Faint dust clouds found near the edge of the Taurus Molecular Cloud are also evident throughout the remarkable 12 panel mosaic. The wide field of view includes the youthful star T Tauri and Hind’s variable nebula about four degrees left of Aldebaran on the sky.
[https://apod.nasa.gov/apod/ap111117.html]
Forming the profile of a Bull’s face, the ‘V’-shaped asterism of stars 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. 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 their brightest star, a naked eye double star, Theta Tauri, with a separation of 5.6 arcminutes:
Hyades for the Holidays
Recognized since antiquity and depicted on the shield of Achilles according to Homer, stars of the Hyades cluster form the head of the constellation Taurus the Bull. Their general V-shape is anchored by Aldebaran, the eye of the Bull and by far the constellation’s brightest star. Yellowish in appearance, red giant Aldebaran is not a Hyades cluster member, though. Modern astronomy puts the Hyades cluster 151 light-years away making it the nearest established open star cluster, while Aldebaran lies at less than half that distance, along the same line-of-sight. Along with colorful Hyades stars, this stellar holiday portrait locates Aldebaran just below center, as well as another open star cluster in Taurus, NGC 1647 at the left, some 2,000 light-years or more in the background. The central Hyades stars are spread out over about 15 light-years. Formed some 800 million years ago, the Hyades star cluster may share a common origin with M44 (Praesepe), a naked-eye open star cluster in Cancer, based on M44’s motion through space and remarkably similar age.
[http://apod.nasa.gov/apod/ap121224.html]
In the northeastern 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 visual magnitude six, and so the cluster is also named the ‘Seven Sisters.’ However, many more stars are visible with even a modest telescope:
M45 (The Pleiades)
[https://www.spacetelescope.org/projects/fits_liberator/fitsimages/davidedemartin_5/]
Find the Pleiades cluster by facing east and looking 2-3 fists above the eastern horizon in late October around 10 p.m. local time.
They’re called the Seven Sisters, but can you see all seven? Better known as the Pleiades star cluster, this lovely group in the shape of a miniature Big Dipper enchants the eye on autumn nights. There’s nothing quite like it in the heavens. Most stars are single and separate from each other, but the Pleiades packs more than a handful into a compact bunch that stands apart from nearly everything else in the sky.
The Pleiades star cluster is located in Taurus and dominated by hot blue stars that formed within the past 100 million years. It is one of brightest star clusters in the sky. It contains some 3,000 stars and lies about 444 light-years from Earth. Side to side the group spans 13 light-years, or about halfway from Earth to the bright star Vega. Like a school of fish, its members move together as a gravitationally-bound swarm through space.
In late October the group clears the treetops around 9:30 p.m. local time and remains visible the rest of the night.
When asked how many stars they see in the cluster, beginning observers will usually say five. That’s what most of us see at a glance, and it makes sense because the five brightest Pleiades- Alcyone, Atlas, Electra, Maia, and Merope- range from magnitude 2.9 to 4.2, well within the grasp of most observers from a reasonably dark sky site. But can we do better?
The brighter of the Pleiades stars with names are shown along with their magnitudes. After spotting the five easy ones, try Taygeta and then Pleione to make seven.
According to Agnes Clerke, a late 19th-century/early 20th-century astronomer and writer, Carrington and Denning (British amateur astronomers) counted fourteen. Robert Burnham, in his 3-volume Celestial Handbook, writes that ‘there are at least 20 stars in the group which might be glimpsed under the finest conditions.’
Wow! Really? Let’s start with the next two easier targets. Extend a line from Alcyone through Maia to find Taygeta. Most amateur astronomers can spot this one with ease. A touch of averted vision, a technique of looking ‘around’ the object of interest instead of directly at it, should make this a snap. It’s the next one, Pleione, that gives many observers trouble. Not only is it dimmer, but the star nestles against brighter Atlas. For me, seeing it requires good dark adaption, patience, and a mix of averted and direct vision.
This view shows the bright central cluster plus additional fainter members and several unrelated but helpful guide stars nearby along with their magnitudes. In addition to the core cluster, stars circled in red are Pleiades members.
That’s seven. Ready to move on to the challenge round? We now go deep, pinging stars ranging from magnitude 5.4 to the inky sky limit of 6.5. Fully dark-adapted eyes and a moonless, transparent sky are musts. The dim Asterope duo and Celaeno beckon near the Pleiades core, but that’s the problem. They’re so close to other member stars, they’re difficult to distinguish on their own.
I’ve caught tantalizing hints of both with averted vision when the cluster’s high in the sky. Asterope presents a special challenge as the pair is separated by only 2.4 arc minutes- more than one arc minute closer than the famous Double-Double Epsilon Lyrae, itself no easy split, and nearly two magnitudes fainter. At best, you might see them as a single elongated star.
Once we move beyond the distraction of the central cluster, hunting gets easier. The magnitude 5.4 star (HD 23753) below the ‘dipper handle’ is relatively easy, but the 6.0 (HD 23950) will place greater demands on your visual cortex. 18 Tauri likewise is relatively easy with averted vision, but beware of the 6.1 and 6.5 members south of Atlas. They’ll push your vision to the limit. But that’s where you want to be, right? Limits tempt us to go that extra step.
By the way, I keep a pair of binoculars at my side to not only verify Pleiades star sightings, but to help me know just where to look if I’m having difficulty finding a star. They also provide a splendid and visually refreshing look at the cluster after straining to see its fainter members.
So let’s add up our starry gems. The bright five plus two not-so-difficult core cluster stars make seven. Add in seven more faint hanger-ons (we’ll count Asterope as one) and you’ve got 14. Not bad, not bad at all.
[http://www.skyandtelescope.com/astronomy-news/observing-news/many-pleiades-can-see10222014/]
In the northern part of the constellation to the northwest of the Pleiades lies the Crystal Ball Nebula, known by its catalogue designation of NGC 1514. This planetary nebula is of historical interest following its discovery by German-born English astronomer William Herschel in 1790. Prior to that time, astronomers had assumed that nebulae 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 astronomer William Huggins used the spectrum of this nebula to deduce that the nebula is a luminous gas, rather than stars. The distance to this nebula is 700 pc (2200 light years):
This image composite shows two views of a puffy, dying star, or planetary nebula, known as NGC 1514. The view on the left is from a ground-based, visible-light telescope; the view on the right shows the object in infrared light, as seen by NASA’s Wide-field Infrared Survey Explorer, or WISE.
A new image from NASA’s Wide-field Infrared Survey Explorer shows what looks like a glowing jellyfish floating at the bottom of a dark, speckled sea. In reality, this critter belongs to the cosmos- it’s a dying star surrounded by fluorescing gas and two very unusual rings.
The object, known as NGC 1514 and sometimes the ‘Crystal Ball’ nebula, belongs to a class of objects called planetary nebulae, which form when dying stars toss off their outer layers of material. Ultraviolet light from a central star, or in this case a pair of stars, causes the gas to fluoresce with colorful light. The result is often beautiful- these objects have been referred to as the butterflies of space.
NGC 1514 was discovered in 1790 by Sir William Herschel, who noted that its ‘shining fluid’ meant that it could not be a faint cluster of stars, as originally suspected. Herschel had previously coined the term planetary nebulae to describe similar objects with circular, planet-like shapes.
Planetary nebulae with asymmetrical wings of nebulosity are common. But nothing like the newfound rings around NGC 1514 had been seen before. Astronomers say the rings are made of dust ejected by the dying pair of stars at the center of NGC 1514. This burst of dust collided with the walls of a cavity that was already cleared out by stellar winds, forming the rings.
WISE was able to spot the rings for the first time because their dust is being heated and glows with the infrared light that WISE can detect. In visible-light images, the rings are hidden from view, overwhelmed by the brightly fluorescing clouds of gas.
Infrared light has been color-coded in the new WISE picture, such that blue represents light with a wavelength of 3.4 microns; turquoise is 4.6-micron light; green is 12-micron light; and red is 22-micron light. The dust rings stand out in orange. The greenish glow at the center is an inner shell of material, blown out more recently than an outer shell that is too faint to be seen in WISE’s infrared view. The white dot in the middle is the central pair of stars, which are too close together for WISE to see separately.
[https://www.nasa.gov/mission_pages/WISE/news/wise20101117.html]
A degree to the northwest of ζ Tauri is the Crab Nebula (M1), a supernova remnant. This supernova explosion 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. 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, when John Bevis found it:
The Crab Nebula
The Crab Nebula, the result of a supernova noted by Earth-bound chroniclers in 1054 A.D., is filled with mysterious filaments that are are not only tremendously complex, but appear to have less mass than expelled in the original supernova and a higher speed than expected from a free explosion. The Crab Nebula spans about 10 light-years. In the nebula’s very center lies a pulsar: a neutron star as massive as the Sun but with only the size of a small town. The Crab Pulsar rotates about 30 times each second.
[https://www.nasa.gov/multimedia/imagegallery/image_feature_1604.html]
NGC 1409 and NGC 1410 are a set of colliding galaxies in Taurus constellation:
[http://www.constellation-guide.com/constellation-list/taurus-constellation/]
NGC 1410/1409: Intergalactic Pipeline
These two galaxies are interacting in a surprising way, connected by a ‘pipeline’ of obscuring material that runs between them over 20,000 light-years of intergalactic space. Silhouetted by starlight, the dark, dusty ribbon appears to stretch from NGC 1410 (the galaxy at the left) and wrap itself around NGC 1409 (at right). A mere 300 million light-years distant in the constellation of Taurus, the pair's recent collision has likely drawn out this relatively thin lane of material which is only about 500 light-years wide. Though the Hubble Space Telescope image dramatically illustrates how galaxies exchange matter when they collide, it also presents challenges to current pictures of galaxy evolution. The titanic collision has triggered star formation in NGC 1410 as evidenced by its blue star forming regions, yet NGC 1409 remains devoid of hot, young blue stars even though observations indicate that material is flowing into it. Bound by gravity, these two galaxies are doomed to future collisions, merging over time into one.
[http://apod.nasa.gov/apod/ap010112.html]
Taurus 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 98 light-years (30 parsecs) and contains 35,000 solar masses of material, which is both larger and less massive than the Orion Nebula. At a distance of 490 light-years (150 parsecs), this is one of the nearest active star forming regions. Located in this region, about 10° to the northeast of Aldebaran, is the asterism NGC 1746 spanning a width of 45 arcminutes:
Dusty Nebulae in Taurus
This complex of dusty nebulae linger along the edge of the Taurus molecular cloud, a mere 450 light-years distant. Stars are forming on the cosmic scene, including extremely youthful star RY Tauri prominent toward the upper left of the 1.5 degree wide telescopic field. In fact RY Tauri is a pre-main sequence star, embedded in its natal cloud of gas and dust, also cataloged as reflection nebula vdB 27. Highly variable, the star is still relatively cool and in the late phases of gravitational collapse. It will soon become a stable, low mass, main sequence star, a stage of stellar evolution achieved by our Sun some 4.5 billion years ago. Another pre-main sequence star, V1023 Tauri, can be spotted below and right, embedded in its yellowish dust cloud adjacent to the striking blue reflection nebula Ced 30.
[https://apod.nasa.gov/apod/ap130711.html]
X-rays may provide valuable information about whether a star may have planets, like the star GJ 176:
X-rays reveal temperament of possible planet-hosting stars
X-rays may provide valuable information about whether a star system will be hospitable to life on planets. Stellar X-rays mirror magnetic activity, which can produce energetic radiation and eruptions that could impact surrounding planets. Researchers used Chandra and XMM-Newton to study 24 stars like the Sun that were at least one billion years old. The latest study indicates older Sun-like stars settle down relatively quickly, boosting prospects for life to develop on planets around them.
A new study using data from NASA’s Chandra X-ray Observatory and ESA’s XMM-Newton suggests X-rays emitted by a planet’s host star may provide critical clues to just how hospitable a star system could be. A team of researchers looked at 24 stars similar to the Sun, each at least one billion years old, and how their X-ray brightness changed over time.
Since stellar X-rays mirror magnetic activity, X-ray observations can tell astronomers about the high-energy environment around the star. In the new study the X-ray data from Chandra and XMM-Newton revealed that stars like the Sun and their less massive cousins calm down surprisingly quickly after a turbulent youth.
This artist’s illustration depicts one of these comparatively calm, older Sun-like stars with a planet in orbit around it. The large dark area is a ‘coronal hole, ‘a phenomenon associated with low levels of magnetic activity. The inset box shows the Chandra data of one of the observed objects, a two billion year old star called GJ 176, located 30 light years from Earth.
To understand how quickly stellar magnetic activity level changes over time, astronomers need accurate ages for many different stars. This is a difficult task, but new precise age estimates have recently become available from studies of the way that a star pulsates using NASA’s Kepler and ESA’s CoRoT missions. These new age estimates were used for most of the 24 stars studied here.
Astronomers have observed that most stars are very magnetically active when they are young, since the stars are rapidly rotating. As the rotating star loses energy over time, the star spins more slowly and the magnetic activity level, along with the associated X-ray emission, drops.
Although it is not certain why older stars settle down relatively quickly, astronomers have ideas they are exploring. One possibility is that the decrease in rate of spin of the older stars occurs more quickly than it does for the younger stars. Another possibility is that the X-ray brightness declines more quickly with time for older, more slowly rotating stars than it does for younger stars.
[http://chandra.harvard.edu/photo/2017/gj176/index.html]
During November, the Taurid meteor shower appears to radiate from the general direction of this constellation. The Beta Taurid meteor shower occurs during the months of June and July in the daytime, and is normally observed using radio techniques. In October, between the 18th and the 29th, both the Northern Taurids and the Southern Taurids are active; though the latter stream is stronger. However, between November 1 and 10, the two streams equalize.
C/2016 R2 (PANSTARRS) is a comet, discovered using the Pan-STARRS telescopes on September 7, 2016. The comet has recently attracted attention from many astronomers as it approaches its closest point to the sun in May 2018. It has been observed to have a very complex tail, which has been suggested to be due to a fast rotation period of the nucleus:
[https://en.wikipedia.org/wiki/C/2016_R2_(PANSTARRS)]
Blue Comet in the Hyades
Stars of the Hyades cluster are scattered through this mosaic spanning over 5 degrees on the sky toward the constellation Taurus. Presently cruising through the Solar System, the remarkably blue comet C/2016 R2 PanSTARRS is placed in the wide field of view using image data from January 12. With the apex of the V-shape in the Hyades cluster positioned near the top center, bright Aldebaran, alpha star of Taurus, anchors the frame at the lower right. A cool red giant, Aldebaran is seen in orange hues in the colorful starfield. While the stars of the Hyades are gathered 151 light-years away, Aldebaran lies only 65 light-years distant and so is separate from the cluster stars. On January 12 (2018), C/2016 R2 was over 17 light-minutes from planet Earth and nearly 24 light-minutes from the Sun. Its blue tinted tail largely due to CO+ gas fluorescing in sunlight, the head or coma of the comet appears with a slightly greenish hue, likely emission from diatomic carbon.
[https://apod.nasa.gov/apod/ap180118.html]
[https://en.wikipedia.org/wiki/Taurus_(constellation)]
No comments:
Post a Comment