Ursa Major, a constellation
also known as the GREAT BEAR, known also as the GREAT DIPPER. This is a large constellation, but only the seven stars composing the "dipper" are conspicuous, and we confine our notice to
[hide][top]Finding the Big Dipper Constellation or Ursa Major in the Night Sky
The Great Dipper figure is too well known to need description. However we should write something here - read more in About Ursa Major below :)
Directly north of Leo Minor
is one of the great figures of uranography, and one of the most familiar to ordinary observation of all the constellations Ursa Major, the Greater Bear. Indeed, in the northern hemisphere because of its situation within about forty degrees of the north polar star, Ursa Major is probably seen and recognized in the heavens more than any other group of stars.
It is especially known by the celebrated figure of the Great Dipper, formed by seven stars in the flank and tail of the Bear. In the latitude of New York the Great Dipper never sets, the star in the extreme end of the long handle just skimming the horizon in the evenings of November and December, while in May and June it is almost overhead.
Ursa Major, the Great Bear, known also as the Great or Big Dipper and is a large constellation, but only the seven stars composing the "dipper" are conspicuous, and we confine our notice to them.
Depending on what season you are viewing, you will find the Great Bear changes in its orientation and it was thought by the ancients that this was a dance of the bear.
The idea of dancing was connected with Ursa Major, as well as with the other circumpolar constellations
, by the ancients. Sir G. C. Lewis says that this was derived from the circular dances of the Greeks. The two bears (Ursa Major and Ursa Minor
) were imagined reeling round the pole like a pair of waltzers.
Do note from the diagram below that the orientation of this constellation varies with the season. Moreover, you may see it in one position as you go out to dinner and in a different one as you return from a dance late the same night.
The Big Dipper Ursa Major Throughout the Seasons in the Northern Hemisphere
[hide][top]Myth of Big Dipper Constellation or Ursa Major
Calisto was the daughter of Lycaon, King of Arcadia, and was an attendant of the goddess Diana. Jupiter
fell in love with the beautiful princess Calisto, and his wife Juno became enraged with jealousy and changed the
princess into a bear.
Calisto, however, had borne to Jupiter a son named Areas, who became a famous hunter. One day while hunting in the Arcadian forest he came upon a bear, and was about to slay it, not knowing that it was his mother. Jupiter then interfered and changed Areas into a bear also and translated both to heaven. Calisto became Ursa Major andArcas Ursa Minor. When Juno learned of this she was greatly displeased, and she went to Tethys, wife of Oceanus, the Ocean, and begged her to promise never to receive these bears beneath her waves. Tethys promised, and as a result these constellations never set, but whirl forever round the pole.
[hide][top]About Ursa Major or Big Dipper Constellation
Facing north one will find the 7 stars that make up Ursa Major, the Great bear or big dipper.
Four of these stars form a trapezium; the three others which make the tail, are nearly a prolongation of the diagonal of the trapezium, formed by joining the stars.
The names of these seven stars beginning with the end of the handle are Alkaid y Mizar, Alioth, Megrez, Phecda, Merak and Dubhe. These are all second magnitude except Megrez, which is third magnitude.
Dubhe is twenty-nine degrees from the Polar Star ; the top of the dipper is ten degrees in length and the bottom eight degrees ; the two pointers
are 5 apart. These distances should be , carefully remembered for future use.
[hide][top]Telescopic Objects in Ursa Major
Four stars form the bowl and three the handle; and the resemblance is the more perfect since all but one of the stars are of the same magnitude.
In this dipper the second star from the end of the handle is an object that carries us back to the days of the early Arabs. This is the star Mizar and its faint companion Alcor which form a naked-eye double. So difficult is it to see Alcor that this was the standard eyesight test given to recruits for the Arabian army. Although to the casual observer the bowl of the dipper may seem almost devoid of stars, a careful count with the naked eye on a clear night will reveal ten or twelve faint ones. In this area are located several famous telescopic objects.
Also look closely, on any clear night, at the star Mizar, at the break in the handle of the Dipper. You can see a faint star very near it. The Arabians call it Alcor, "the Test," perhaps meaning that it required a good eye to see it. An ordinary eye can see it now, which leads some astronomers to suppose that the star Alcor is gradually becoming brighter.
The individual names of these stars, beginning with the northwestern corner of the bowl of the imaginary dipper, are Dubhe, Merak, Phaed, Megrez (the faint one), Alioth, Mizar (before mentioned with its companion, Alcor), and Benetnasch. Their Greek letter names, in the same order, are Alpha, Beta, Gamma, Delta, Epsilon, Zeta, and Eta.
Alpha and Beta, the pair in the outer side of the bowl, are often called the Pointers, because an imaginary line drawn through them and extended pole wards nearly hits the pole-star at a distance of about thirty degrees. These seven stars differ in color, al though the fact may not be apparent to hasty observation. Alpha and Gamma are yellow. Beta is greenish, and Zeta and Eta are brilliant white. Delta, now so much fainter than its sisters that one feels a certain disappointment over the irregularity which it introduces into an otherwise perfect array of equal stars, seems formerly to have been as bright as any of them, and, in his time, Tycho Brahe, the famous Danish astronomer, estimated it of the second magnitude, like the others. It is probably a long-period variable.
The names of these seven stars beginning with the end of the handle are Ajkaid, Mizar, Alioth, Megrez, Ptiecda, Merak and Dubhe. These are all second magnitude except Megrez, which is third magnitude.
In the middle of the handle is a famous naked-eye double, Mizar, whose companion, close by on the northeast, is named Alcor. These stars are sometimes called the Horse and Rider. Any good eye can easily separate them, and yet they were at one time regarded as a test of naked-eye seeing
Dubhe is twenty-nine degrees from the Polar Star ; the top of the dipper is ten degrees in length and the bottom eight degrees; the two pointers are 5 degrees apart. These distances should be carefully remembered for future use.
Lastly, the observer may turn to the pair Mizar and Alcor
, the former the middle star in the Great Bear s tail, the latter 15 off. It seems quite clear, by the way, that Alcor has increased in brilliancy of late, since among the Arabians it was considered an evidence of very good eyesight to detect Alcor, whereas this star may now be easily seen even in nearly full moonlight. Mizar is a double star
, and a fourth star is seen in the same field of view with the others. The distance between Mizar and its companion is about 14 degrees; the magnitude of Mizar 3, of the companion 5 ; their colors white and pale green, respectively.
[hide][top]Double Stars in Ursa Major
Zeta (Mizar) Magnitudes 3 and 5 Pw. 140°; Dist 14".5.
Xi The Bonthem one of the pair which mark the left hind paw.
Two nebulae, one fairly bright, about half a degree apart - M81, M82 M97
- A. R. 11* 07°, Dec 55° 43' — 2" south-following beta. A planetary nebula