Taurus the Bull
As ever with these incredibly old constellations, many stories are attached to them. In the best known of the classical myths the bull is the god Zeus, who took on many guises for his seductions. To Europa, the beautiful daughter of the king of Tyre, he appeared as a splendid and friendly white bull. Europa was so taken with him that she draped him with flowers and climbed on his back. Whereupon Zeus swam out to sea and took her to Crete.
Taurus is a zodiac constellation. It lies on the ecliptic, the apparent path of the Sun during Earth's annual journey around it. It's also where we would see the Moon and other planets during the year. In Babylonian astronomy Taurus was the first constellation of the zodiac, because the year began at the spring equinox and the Sun was in Taurus at that time. The equinox had passed to Aries by the time of Ptolemy, and is now in Pisces because of precession induced by the wobble in Earth's axis.
An easy way to find Taurus in the sky is to start with Orion, since the three belt stars are easily recognized. In the northern hemisphere, follow them to the northwest. They point towards Aldebaran (al-DEB-uh-run) and the Pleiades star cluster. The best time to observe Taurus is in December and January.
Aldebaran, also known as Alpha Tauri, is the brightest star of Taurus. The eye of the bull is an orange giant some 65 light years away and a noticeably reddish color. It's some 500 times brighter than the Sun and nearly 45 times bigger across. If Aldebaran were where the Sun is, it would reach to the orbit of Mercury.
Beta Tauri (Elnath or Alnath) is the constellation's second brightest star, a white giant that marks one of the bull's horns. It's more than 700 times brighter than the Sun, even more luminous than Aldebaran. From Earth it doesn't seem as bright as Aldebaran only because it's twice as far away. It used also to be known as Gamma Aurigae and represented the charioteer Auriga's foot. However in the officially-defined modern constellations, every part of the sky is uniquely defined. When the boundaries were set, the bull kept his horn and the charioteer lost a foot.
An interesting star is the variable Lambda Tauri which is 480 light years away. It's actually a triple star system and the main reason for its variability is that two of the three stars form an eclipsing binary. The binary is almost edge on to us, so as the stars circle each other about every four days, we see them taking turns to block each other's light from us. Lambda Tauri A is nearly six thousand times brighter than the Sun and its companion over a hundred times as luminous as the Sun. The third star Lambda Tauri C is smaller than the Sun and orbits the binary every 33 days.
Tauri contains two prominent star clusters that can be seen with the unaided eye: The Hyades and the Pleiades.
Aldebaran looks as though it's a member of the Hyades. However the Hyades cluster is well over twice as far away as Aldebaran. Aldebaran just happens to be in the same line of sight. The Hyades is an open star cluster with several hundred members. Some of the bright stars make up the V-shape of the bull's head. The Hyades were rain nymphs, daughters of Atlas the Titan, who in Greek mythology, held up the world. In the myths the number of Hyades and their names vary from source to source. Unlike those representing their half sisters the Pleiades, the bright stars of the Hyades aren't named.
The Pleiades are probably the best known star cluster in the world. Like the Hyades, they're the daughters of Atlas and an oceanic nymph. In English they're commonly known as the Seven Sisters. There are supposed to be seven of them, but it's very difficult to see more than six without binoculars. Many cultures represent the Pleiades with six stars and some have myths about a missing Pleiad. In fact there are at least a thousand stars in the cluster, but we only see some of the brightest ones.
The Crystal Ball Nebula (NGC 1514) is a planetary nebula discovered by William Herschel in 1790. In his survey of nebulae, Herschel had found that some of them were clusters of stars that couldn't be resolved without a large telescope. But this one wasn't. He could see one bright central star surrounded by some nebulous material. Some nebulae of this type looked like planets in eighteenth century telescopes. However they are true nebulae formed from the material of the outer layers of dying sunlike stars.
I've saved the most spectacular object in Taurus for last, the Crab nebula. It was discovered in 1731, though the event that created it had been seen nearly seven hundred years previously by Chinese observers. The nebula is a supernova remnant containing a pulsar. A pulsar is a spinning neutron star. It's what is left of the core of a massive star following the collapse and convulsive explosion in which it blows off its outer layers. The gas cloud is now twelve light years across – that's about 120 trillion kilometers or 72 trillion miles – and still expanding.
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