Ursa Minor
From Wikipedia, the free encyclopedia
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| List of stars in Ursa Minor | |
| Abbreviation: | UMi |
| Genitive: | Ursae Minoris |
| Symbolism: | The Little Bear |
| Right ascension: | 15 h |
| Declination: | +75° |
| Area: | 256 sq. deg. (56th) |
| Main stars: | 7 |
| Bayer/Flamsteed stars: | 23 |
| Stars with known planets: | 1 |
| Bright stars: | 2 |
| Nearby stars: | 0 |
| Brightest star: | Polaris (2.02m) |
| Nearest star: | π1 UMi (70.8 ly) |
| Messier objects: | 0 |
| Meteor showers: | Ursids |
| Bordering constellations: | Draco Camelopardalis Cepheus |
| Visible at latitudes between +90° and −10° Best visible at 21:00 (9 p.m.) during the month of June | |
Ursa Minor (pronounced /ˌɝːsə ˈmaɪnɚ/) is a constellation in the northern sky. Its name is Latin for 'little bear', contrasting with Ursa Major, the Great Bear. It was one of the 48 constellations listed by the 1st century astronomer Ptolemy, and remains one of the 88 modern constellations. Ursa Minor is notable as the location of the north celestial pole, although this will change after some centuries due to the precession of the equinoxes.[1]
Contents[hide] |
[edit] Notable features
[edit] Stars
Ursa Minor is colloquially known as the Little Dipper because its seven brightest stars seem to form the shape of a dipper (ladle or scoop). The star at the end of the dipper handle is Polaris, the North Star. Polaris can also be found by following a line through the two stars which form the end of the "bowl" of the Big Dipper, a nearby asterism found in the constellation Ursa Major.
Polaris (α UMi), the brightest star in the constellation, is a yellow supergiant shining at 2.02 apparent magnitude . It belongs to the rare class of Cepheid variable stars. Only a bit less bright is β UMi (Kochab), a 2.08 orange giant star.
The four stars in the "bowl" of the little dipper are unusual in that they are of second, third, fourth and fifth magnitude. Hence they provide an easy guide to determining what magnitude stars are visible, useful for city dwellers or testing your eyesight.
[edit] Named stars
| Proper Name | Bayer Designation | Apparent Magnitude | Distance (LY) |
|---|---|---|---|
| Polaris | α UMi | 2.02 | 430 |
| Kochab | β UMi | 2.07 | 126 |
| Pherkad | γ UMi | 3.00 | 480 |
| Yildun | δ UMi | 4.85 | 185 |
| Urodelus | ε UMi | 4.21 | 347 |
| Alifa al Farkadain | ζ UMi | 4.32 | 376 |
| Anwar al Farkadain | η UMi | 4.95 | 97 |
[edit] Deep sky objects
Ursa Minor Dwarf, a dwarf galaxy, is located in the area of the constellation.
[edit] History and mythology
Ursa Minor is commonly visualized as a baby bear with an unusually long tail. The tail was said to have been lengthened from that usually expected for a bear, due to its being held by the tail and spun around the pole.(The center of the sky)
Ursa Minor and Ursa Major were related by the Greeks to the myth of Callisto and Arcas. However, in a variant of the story, in which it is Boötes that represents Arcas, Ursa Minor was considered to represent a dog. This is the older tradition which sensibly explains both the length of the tail and the obsolete alternate name of Cynosura (the dog's tail) for Polaris, the North Star.[2]
Previously, Ursa Minor was considered to be just seven close stars, mythologically regarded as sisters. In early Greek mythology, the seven stars of the Little Dipper were considered to be the Hesperides, daughters of Atlas. Together with the nearby constellations of Boötes, Ursa Major, and Draco, it may have formed the origin of the myth of the apples of the Hesperides, which forms part of the Labours of Hercules.[original research?]
In earliest times, Ursa Minor was named the Dragon's wing, and was considered a part of Draco. The dragon's wing as an asterism is now long forgotten.[citation needed]
In other cultures, Ursa Minor was the hole in which the earth's axle found its bearing. In Hindu mythology, the Pole Star is Dhruva (the word means pole today), and there is a story behind him becoming a star.[citation needed]
Ursa Major
From Wikipedia, the free encyclopedia
 | |
| List of stars in Ursa Major | |
| Abbreviation: | UMa |
| Genitive: | Ursae Majoris |
| Symbolism: | the Great Bear |
| Right ascension: | 10.67 h |
| Declination: | +55.38° |
| Area: | 1280 sq. deg. (3rd) |
| Main stars: | 7, 20 |
| Bayer/Flamsteed stars: | 93 |
| Stars with known planets: | 8 |
| Bright stars: | 6 |
| Nearby stars: | 12 |
| Brightest star: | ε UMa (Alioth) (1.7124m) |
| Nearest star: | Lalande 21185 (8.29 ly) |
| Messier objects: | 7 |
| Meteor showers: | Alpha Ursa Majorids Leonids-Ursids |
| Bordering constellations: | Draco Camelopardalis Lynx Leo Minor Leo Coma Berenices Canes Venatici Boötes |
| Visible at latitudes between +90° and −30° Best visible at 21:00 (9 p.m.) during the month of April | |
 | |
Ursa Major (IPA: /ˈɜrsə ˈmeɪdʒər/) is a constellation visible throughout the year in most of the northern hemisphere. Its name means the Great Bear in Latin. It is dominated by the widely recognized asterism known as the Big Dipper or Plough, which is a useful pointer toward north, and which has mythological significance in numerous world cultures.
Contents[hide] |
[edit] Asterisms
The seven brightest stars of Ursa Major form the well-known asterism known as the Big Dipper in the United States and Canada, or the Plough in the United Kingdom and Ireland.
Another asterism is recognized in Arab culture, a series of three pairs of stars:
- ν and ξ Ursae Majoris, Alula Borealis and Australis, the "first leap";
- λ and μ Ursae Majoris, Tania Borealis and Australis, the "second leap";
- ι and κ Ursae Majoris, Talitha Borealis and Australis, the "third leap".
These stars are found along the southwest border of the constellation.
[edit] Notable features
[edit] Stars
Except for Dubhe and Alkaid, the stars of the Big Dipper all have proper motions heading towards a common point in Sagittarius. A few other such stars have been identified, and together they are called the Ursa Major Moving Group.
Mizar, a star in the Big Dipper, forms the famous optical double star with Alcor.
The stars Merak (β Ursae Majoris) and Dubhe (α Ursae Majoris) are known as the "pointer stars" because they are helpful for finding Polaris, also known as the North Star. By visually tracing a line from Merak through Dubhe and continuing, one's eye will land on Polaris, accurately indicating true north.
W Ursae Majoris is the prototype of a class of contact binary variable stars, and ranges between 7.75m and 8.48m.
47 Ursae Majoris has a planetary system with two confirmed planets, 2.54 times and 0.76 times the mass of Jupiter.
Several bright galaxies are found in Ursa Major, including the pair Messier 81 (one of the brightest galaxies in the sky) and Messier 82 above the bear's head, and Pinwheel Galaxy (M101), a beautiful spiral northwest of η Ursae Majoris. The other notable spiral galaxies Messier 108 and Messier 109 may also be found in this other constellation. Altogether, the constellation contains about 50 galaxies observable through amateur telescope. The bright planetary nebula Owl Nebula (M97), named for its appearance, can be found along the bottom of the bowl of the Big Dipper. Of note as a curiosity more than an interesting deep sky object is Messier 40, a double star that Messier nonetheless included in his catalogue.
The Hubble Deep Field is located to the northeast of δ Ursae Majoris.
[edit] History
Ursa Major was one of the 48 constellations listed by the 1st century astronomer Ptolemy. It is mentioned by such poets as Homer, Spenser, Shakespeare, Tennyson and Bertrand Cantat. The Finnish epic Kalevala mentions it, and Vincent Van Gogh painted it.
[edit] Mythology
The constellation of Ursa Major has been seen as a bear by many distinct civilizations.[1]
In Greek mythology, Zeus lusts after a young woman named Kallisto, a nymph of Artemis. Hera, Zeus's wife, turns Kallisto into a bear because of her jealousy. Kallisto, while in bear form later encounters her son Arcas. Arcas almost shoots the bear, but to avert the tragedy, Zeus sweeps them both into the sky, forming Ursa Major.[2] In another tale, Ursa Major was associated with the Hesperides. With Ursa Minor, Boötes, Draco, and Hercules it may have inspired the myth of the Apples of the Hesperides, one of The Twelve Labours of Hercules.[original research?]
One of the few star groups mentioned in the Bible (Job 9:9; 38:32; Amos 5:8 — Orion and the Pleiades being others), Ursa Major was also pictured as a bear by the Jewish peoples. ("The Bear" was mistranslated as "Arcturus" in the Vulgate and the error persisted in the KJV. Later translations have corrected this.)[citation needed]
The Iroquois Native Americans interpreted Alioth, Mizar, and Alkaid as three hunters pursuing the Great Bear. According to one version of their myth, the first hunter (Alioth) is carrying a bow and arrow to strike down the bear. The second hunter (Mizar) carries a large pot — the star Alcor — on his shoulder in which to cook the bear while the third hunter (Alkaid) hauls a pile of firewood to light a fire beneath the pot.
In Burmese, Pucwan Tārā (pronounced "bazun taja") is the name of a constellation comprising stars from the head and forelegs of Ursa Major; pucwan is a general term for prawn, shrimp, crab, lobster, etc.
[edit] Graphic visualisation
In European star charts, the constellation was visualized with the 'square' of the Big Dipper forming the bear's body and the chain of stars as a long tail. However, bears do not have long tails, and Jewish astronomers considered Alioth, Mizar, and Alkaid instead to be either three cubs following their mother, and the Native Americans as three hunters.
Noted children's book author H. A. Rey, in his 1952 book The Stars: A New Way to See Them, (ISBN 0-395-24830-2) instead had the "bear" image of the constellation, much as Johannes Hevelius had done (as far as the figure of the bear facing "left"), oriented with Alkaid as the tip of the bear's nose, and the "handle" of the Big Dipper part of the constellation forming the outline of the top of the bear's head and neck, rearwards to the shoulder, and because of Rey's book, many amateur astronomers have come to accept Rey's star chart interpretation of Ursa Major, dropping the idea of the Big Dipper's "handle" as being the hind end of the bear, with a non-natural "tail" extending rearwards.
 Book plate by Sidney Hall depicting Ursa Major |  Johannes Hevelius drew Ursa Major as if being viewed from outside the celestial sphere. |
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