Polaris is called the North Star because it is the closest star to the north celestial pole. This means that as the Earth rotates, Polaris appears to remain stationary in the sky while all of the other stars rotate around it. Because the Earth wobbles slightly as it rotates on its axis, Polaris will not always be the North Star. In about 14, years the north celestial pole will point away from Polaris and toward Vega. This process is known as procession.
Polaris is an important star for navigation, allowing mariners to easily identify their latitude. Ursa Minor is one of the 48 constellations identified by the Greek astronomer Ptolemy in the second century.
It is an ancient constellation with roots in many cultures. To the ancient Babylonians it was known as the Wagon of Heaven. They have quasar-like nuclei with very high surface brightness.
The Ursids are a prominent meteor shower whose radiant appears to be Ursa Minor. The Ursids peak between December 18 and Ursa Minor is associated with two different myths.
In the first myth, the constellation represents Ida, the nymph who took care of Zeus on the island of Crete when he was young, along with Adrasteia, the nymph who is associated with the larger Ursa Major constellation. Zeus would eventually free his brothers and sisters and become the supreme god of the Olympians. In the second myth, the constellation represents Arcas, son of Zeus, and the nymph Callisto.
Callisto then roamed the forests for years until she came face to face with her son, Arcas. Arcas was scared of the great bear in front of him and drew his spear, but Zeus quickly intervened to prevent a tragedy. Arcas is frequently more associated with the Bootes constellation, the celestial herdsman. In an older myth, the seven stars that form the Little Dipper were said to represent the Hesperides, the seven daughters of Atlas. Home » Constellations » Ursa Minor Constellation.
Ursa Minor remains among the 88 modern constellations where it holds the 56 th place in terms of size, covering around square degrees.
Polaris is the brightest star in Ursa Minor. Another star, Kochab, is slightly fainter than Polaris, being the second-brightest star in Ursa Minor. Kochab also held the title of the North Pole Star several thousands of years ago. The constellation of Ursa Minor, just like its grander counterpart, Ursa Major, is marked by the famous asterism, the Little Dipper.
The Little Dipper asterism can be seen as the handle of a ladle, hence the North American name. There are no Messier objects present in the constellation of Ursa Minor.
Currently, around 4 stars have been discovered to host planets in Ursa Minor. The Ursids meteor shower is associated with Ursa Minor. There is one meteor shower associated with the constellation: the Ursids. Ursa Minor contains five named stars. Ursa Minor is usually associated with two different myths. In one, the constellation represents Ida, the nymph who took care of Zeus on the island of Crete when he was small, along with Adrasteia, the nymph represented by the larger constellation Ursa Major.
Cronus, fearful of an old prophecy that said that one of his children would overthrow him, swallowed five of his children after they were born. When Zeus was born, Rhea tricked Cronus into swallowing a stone instead, and Zeus eventually fulfilled the prophecy. He freed his brothers Poseidon and Hades and sisters Hera, Hestia and Demeter, and became the supreme god of the Olympians.
In a different myth, the constellation represents Arcas, son of Zeus and the nymph Callisto. Callisto spent the next 15 years wandering in the woods and avoiding hunters.
One day, she came face to face with her son. Scared, Arcas drew a spear, ready to do away with the bear. Luckily, Zeus saw the scene and intervened before it was too late. He sent a whirlwind that scooped the mother and son up to the heavens, where Callisto became Ursa Major and Arcas, Ursa Minor.
In a slightly different version of the myth, it is the goddess Artemis who turns Callisto into a bear for breaking her chastity vow. Bond STScI. In addition, their handles appear to extend in opposite directions.
The Big Dipper is by far the brighter of the two, appearing as a long-handled pan, while the Little Dipper resembles a dim soup ladle. However, the late Ken Franklin, former chief astronomer of New York's Hayden Planetarium, used to tell his audiences that the Little Dipper looked more like a meat cleaver to him. Astronomy neophytes sometimes mistake the Pleiades star cluster for the Little Dipper because the brightest Pleiades stars resemble a tiny skewed dipper.
But in reality, most people have never seen the Little Dipper, because most of its stars are too dim to be seen through light-polluted skies. If you ever wanted to judge the quality of your night sky , you need only look to the bowl of the Little Dipper. The four stars that comprise the bowl run in brightness from second to fifth magnitude. The magnitude system has its origins in the classification by brightness of about 1, stars carried out by the Greek astronomer Hipparchus in the second century B.
The average of the 21 brightest stars in the sky is defined as first magnitude, while the faintest stars normally visible to the unaided eye on a clear, dark night are said to be of sixth magnitude.
0コメント