Big Dipper
| Big Dipper | |
|---|---|
 View of the constellation | |
| Designation | |
| Latin Name | Ursa Major |
| Genitive | Ursae Majoris |
| Abbreviation | UMa |
| Observation | |
| (Epoch J2000.0 ) | |
| Right ascension | Between 119.5 and 216.25 |
| Declination | Between 29 and 73.5 |
| Observable size | 1280 deg 2 ( 3 ) |
| Visibility | Between 90 N and 30 S |
| Meridian | April 20 , 21:00 |
| Stars | |
| Bright ( m 3.0) | 6 ( , , , , , ) |
| To the naked eye | 216 |
| Bayer / Flamsteed | 92 |
| Close ( d 16 s. ) | 3 |
| The brightest | Alioth (1.76) |
| Nearest | Lalande 21185 (8.29 s. ) |
| Objects | |
| Messier objects | 7 ( M40 , M81 , M82 , M97 , M101 , M108 , M109 ) |
| Meteor swarm | Alpha ursa majorides Leonids-Ursids |
| Neighboring constellations | Cowherd Coma Berenices Hunting Dogs Dragon Giraffe Lion Lynx Little Lion |
change  | |
Ursa Major is the third largest constellation in the sky. It contains the "Big Dipper" or "large pot", one of the constellations the best known of the northern hemisphere. It is easily recognizable by the form of pan that make up its seven brightest stars. The Big Dipper is a constellation circumpolar for observers located above 41 latitude north and it never seems to sleep. In Greek , the word bears arktos said it was one of 48 constellations identified by Ptolemy.
Summary |
History
According to Greek mythology , this constellation represents Callisto , a nymph loved by Zeus. When Hera , the wife of Zeus , discovered their relationship, she changed Callisto into Ursa Major and her son Arcas as Ursa Minor. Outraged by this affront to her honor, Hera demanded justice in the ocean, and the bears were then condemned to perpetually rotate around the North Pole , never allowed to rest under the sea
According to another version, the nymph Callisto was the daughter of Lycaon, a king of Arcadia. Zeus saw her while she was hunting in company with Artemis and he prit. Hera, jealous, the girl changed into a bear after she gave birth to a son, Arcas. The child grew and became a man, and one day he was participating in a hunt, the goddess Callisto walked to where he stood, hoping to see him shoot an arrow to his mother, in complete ignorance. But Zeus took the bear and placed him among the stars. Later, her son Arcas joined him. They took the names respectively of Big Dipper and Little Dipper.
According to another version, Callisto was a nymph of Artemis in the service. She vowed to remain a virgin as Artemis. One day while she was picking flowers, Zeus saw her and fell in love with her. As he knew she was a virgin, he had to play the big game he had the idea to make the appearance of his mistress, and returned from her walk, she was surprised by so much need for tenderness. Time passed and felt her belly swell nymph and when she undressed to take a bath with Artemis and other nymphs in the Dead Sea, she saw her big belly felt guilty for not immediately notice that n was not the goddess. And when the goddess saw him, she went into a rage and turned Callisto into a bear before she gives birth. And the goddess said to the other nymphs: "Kill it before it escapes, WE WILL MAT AND DINNER!" At these words, the nymph ran, pursued by hunters. When all this was finished, Zeus picked up the carcass of the bear that was condemned to exile and put it in heaven. There she will give birth and Arcas , who joined her and follows her all the time.
The Big Dipper is the origin of the term "North": the Romans called this constellation September triones is to say "seven oxen plowing "which always revolve around the north. In the UK it is called the Plough (plow), the United States , the Big Dipper (large spoon), in Scandinavia , Karlavgen (the car of Charles, possibly Charlemagne ) in Britain kamm Karr (trolley twisted), Karr Arzhur (carriage of King Arthur ) or Lost-arar (the tip of the plow). In astronomy Hindu , it is also called Sapta Rishi (seven sages), and Persian , Haft Awrang (the seven thrones ). In Chinese astronomy , the seven main stars correspond to the asterism Beidou , one of the oldest constellations used (except the lunar mansions , whose orientation was used to follow the seasons.
Some Indians of North America ( Algonquin , Micmac , Narragansett , Cherokee ) also consider this group of stars like a bear chased by three hunters.
An Arabic version says that the constellation represents a father's coffin pulled by her three daughters (the rectangle formed by the four stars represent his coffin). They have worn since the dawn of time and try to catch her killer (Little Dipper). The day they will catch the murderer, that's the end of ikhan.
Stargazing
The Big Dipper is the most famous constellation, it is learned first widely recognized in the northern hemisphere. Seven stars stand out clearly from the others and form the trolley (or casserole). This training wagon is visible throughout the year in cities above 40 degrees latitude north, as an indication New York , Rome and Beijing are very close to this latitude. For cities farther south, the trolley disappears below the horizon for the fall.
- Identification of the constellation
The "large pot" can be spotted by direct observation. Dubhe ( UMa) Merak ( UMa) Phecda ( UMa), Megrez ( UMa) Alioth ( UMa), Mizar ( UMa) and Alkaid ( UMa) are one of the constellations of the most famous: "Chariot" or the "pan" (or sometimes the "Spoon") of the Big Dipper. This asterism is so characteristic and bright as Johann Bayer from the tip (Dubhe) and ascended (Alkaid) to denote the stars of the constellation, instead of sorting magnitude as was his practice to do so.
- Shape of the constellation
Another asterism comes from the culture Arabic. These "leaps of the gazelle", a series of three pairs of stars:
- Alula Borealis ( UMa) and Alula Australis ( UMa), the "first leap";
- Tania Borealis ( UMa) and Tania Australis ( UMa), the "second leap";
- Talitha Borealis ( UMa) and Talitha Australis ( UMa), the "third leap".
These stars are located along the southwestern border of the constellation, the "toe" of the Bear.
- Mizar and Alcor
Mizar ( UMa) is the middle star in the series of three which form the "neck" of the pan. It is known to have a companion - Alcor (80 UMa) - which is discernible to the naked eye (you can guess the illustration). To distinguish them was indeed challenging traditional acuity of vision in many cultures, Genghis Khan would have been one of the criteria for selection of archers.
- Featured from the constellation
These stars are visible particularly useful for finding other major stars, the Big Dipper playing the role of a true celestial signpost.
- A well known method to determine the location of Polaris ( Ursae Minoris) by drawing a line from Merak to Dubhe, and the following five times the distance between these two stars, we fall on the Star Polar after thirty degrees.
- In the other direction, by extending the line to Dubhe Merac, this alignment begins with UMa after ~ 10 , then UMa (first jump of the Gazelle, and front leg of the Bear) even after ~ 10 , and after a final jump of ~ 10 we fall on Zosma ( Leo) (visible in the illustration). The pair of stars that form the front leg is almost in alignment, thereby confirming its identification.
- If we start from the inside edge of the pan, you can follow the alignment Megrez ( UMa) Phecda ( UMa). This alignment also depends on UMa after ~ 10 ~ 15 and then after a fainter star between the first two jumps of gazelle, which is Praecipua ( 46 Leonis Minoris ). By continuing this alignment we fall into the Lion ), first on Leo (shown in the illustration) and its extension on Regulus , after a total distance of ~ 45.
- In another sense, the same alignment Phecda ( UMa) Megrez ( UMa) crosses the guardians of the Little Dipper , and the feet of the dragon , and finally arrives in the axis of the wings of the swan.
- Another well known method of tracking is to follow the curve of the tail of the pan, turning left along the arc of a circle to Bootis (Arcturus), then continue along the same distance and with the same curvature to Virginis (Spica).
- In the other direction, the diagonal of the pot that goes through Megrez ( UMa) and Merak ( UMa) extends through UMa and the pair of stars that marks the third "leap of Gazelle ( and UMa), and the end of the constellation. In addition, in the same alignment, we found a small star of Lynx (without interest), and after ~ 30 in the same extension you fall on Castor and Pollux (a little right of center), of Gemini , always in the same alignment Rigel and Betelgeuse in the constellation of Orion.
- The "back" of the Big Dipper form an alignment between Megrez ( UMa) and Dubhe ( UMa), which extends through 23 UMa and UMa (end of the constellation, the "butt" of the Bear). This alignment extends through the Lynx on about thirty degrees to fall on Capella 's Check.
- In another sense, the alignment of the "back" Dubhe ( UMa) to Megrez ( UMa) through Alkaid ( UMa), the "nose" of the Bear, crosses the head of the tick and allows identify Gemma in the Northern Crown.
- If we extend the axis-Phecda Dubhe by plotting the same distance, it falls just below the two galaxies M81 and M82 (not always easy to find otherwise)
toiles principales
Alioth ( Ursae Majoris)
Alioth ( UMa), right in the middle of the tail of the "trolley" is the brightest star in the constellation Ursa Major, and indeed, the 34 th of the celestial dome.
Alioth is a distant white star of 81 light years , about four times larger than the Sun and three times more massive. Its spectral type denotes a particular star (A0 p): it has certain parts of its atmosphere enriched in certain elements ( oxygen , europium , chromium , ect.) while they are in deficit of other areas. Alioth is classified as a star of type variables 2 Canum Venaticorun , including 2 Canum Venaticorum or Cor Caroli, is in fact the prototype).
Dubhe ( Ursae Majoris)
Dubhe ( UMa), the second star of the constellation, is a supergiant orange, about 30 times larger than the Sun. It is also a double star because it has a remote companion of 23 AU , which orbit around it in 44 years. Later, at 9000 AU, is another binary system.
Mizar ( Ursae Majoris)
Mizar (without Alcor) is a complex stellar system of four stars: two pairs of stars (one orbiting in 20.5 days, the other 180 days) rotate around each other. She holds a place of first rank in the history of double stars : Mizar with its rider Alcor is a visual binary known since time immemorial, the first telescopic double ( Mizar A and B, discovered by Giovanni Riccioli in 1650 ), the first double shot (by GP Bond in 1857), and Mizar Aa and Ab, the first spectroscopic binary (announced by Edward Charles Pickering in 1889).
Other stars
Merak Phecda, Megrez, Alioth and Mizar, all five of the hot stars of class A, part of a remote group of stars about 80 light years and moving cans into space. This group of stars called the current stars of the Big Dipper
Celestial Objects
Many galaxies are found in Ursa Major, the pair M81 (one of the brightest galaxies in the sky) and M82 over the "head" of the Bear, M101 , a beautiful spiral galaxy north-west 'Alkaid ( UMa) and the spiral galaxies M108 and M109. The constellation contains about 50 galaxies, most of which are less brilliant than the 10th magnitude.
There is also the planetary nebula M97.
See also
Internal Links
- List of stars in Ursa Major
- List of celestial objects of the Big Dipper
- Current stars of the Big Dipper
- Flag of Alaska
External Links
- Ursa Major long exposure view from Saintes.
(1 votes, average: 4.00 out of 5, rated)
Loading ...