Star Names:

Ursa Major


Map of The Constellation of Ursa Major
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Ursa Major is a prominent constellation in the northern hemisphere. It is the third largest constellation in the sky. Its name is Latin for the Great Bear. The constellation is also often referred to as the Big Dipper or the Plough, after the well-known asterism that dominates it.

Ursa Major is one of the oldest and most widely recognized constellations in the sky. It holds significance in many cultures, many of which identify it with a bear. The constellation was listed by the Greek astronomer Ptolemy in the 2nd century. Before Ptolemy, it was mentioned in such ancient texts as the works of Homer and the Bible.

In Greek mythology, Ursa Major is identified with Callisto, a beautiful young nymph Zeus fell in love with. His jealous wife Hera subsequently turned her into a bear. Many years later, still in bear form, Callisto met her and Zeus' son Arcas in the woods and advanced toward him, but he didn't recognize her. Zeus stepped in and, to avoid tragedy, he placed them both in the sky, forming the constellations Ursa Major and Bootes.

In a different myth, Ursa Major is associated with Adrasteia, one of the nymphs who nursed Zeus as an infant, while the other nymph, Ida, is identified with the constellation Ursa Minor, the Little Bear. In different cultures, Ursa Major has been identified with a number of different forms in the sky: camel, canoe, skunk, sickle, shark and bushel among others.

Ursa Major and Ursa Minor are called the Great and Small Wagon in most Slavic cultures, with the constellation Bootes representing the driver, because they circle the north pole. Ancient Greek navigators used Ursa Major for orientation at sea. The stars [8316] alpha and [8319] beta Ursae Majoris are sometimes called the Pointers because they point to the north pole. Similarly, Germans call Ursa Major Großer Wagen, or the Great Cart. The Dutch name for the constellation is Steelpannetje, the Saucepan.

Arabs visualised the constellation as a coffin with a line of mourners. The star on the tip of the bear's tail, [8317] eta Ursae Majoris, has the traditional Arabic names Alkaid (from "al-qa'id," meaning "the leader") and Benetnasch (from "banat na'sh," meaning "daughters of the bier"). The Chinese identified the Plough asterism with Beidou, the Northern Dipper, or as the Emperor's Chariot. Arabs associated the three pairs of stars marking the bear's feet – [8328] nu and [8335] xi, [8327] lambda and [8322] mu, [8323] iota and [8329] kappa Ursae Majoris – with the tracks of a gazelle, while the Chinese called them Santai, which means "three steps to heaven."

The seven brightest stars are known as the Seven Gods in Mongolia. The Iroquois saw the three stars marking the tail as three hunters in pursuit of the Great Bear. In India, the constellation is known as Sapta Rishi, the Seven Sages, with each of the brightest stars representing one of the sages.

The constellation Ursa Major occupies an area of 1280 square degrees and contains nine stars with known planets. It can be seen at latitudes between +90° and -30° and is best visible at 9 p.m. during the month of April.

The brightest seven stars in the constellation form a well-known asterism, the Big Dipper or the Plough, one of the most familiar shapes in the night sky. The three brightest stars in Ursa Major are [8315] epsilon, [8316] alpha and [8317] eta Ursae Majoris.

[8316] alpha Ursae Majoris or Dubhe ("bear") is the second brightest star in Ursa Major and one of the Pointers, two stars that point toward Polaris, the North Star. Dubhe is a red giant approximately 124 light-years distant. It was the northern pole star itself around 5,100 BC and will reclaim the status around the year 20,500 AD. Dubhe is orbited by a main sequence companion and a close pair of stars. The Chinese call it the Celestial Pivot or the First Star of the Northern Dipper.

[8319] beta Ursae Majoris or Merak ("the loins") is the other star in the constellation that points to Polaris, along with [8316] alpha Ursae Minoris. About 79 light-years distant, Merak is part of the Ursa Major moving group of stars, also known as Collinder 285, a stellar group that shares common velocities and is believed to have a common origin. The group’s core lies approximately 80 light-years away. Merak is a main sequence dwarf that emits excess infrared radiation and has a disk of hot gas and dust surrounding it. It is slightly larger than the Sun.

[8320] gamma Ursae Majoris, also known as Phad or Phecda ("the thigh"), is also part of the Ursa Major moving group. It is another main sequence dwarf, 84 light-years distant.

[8325] delta Ursae Majoris or Megrez ("the base") is a bluish-white dwarf, approximately 81 light-years away. It marks the base of the bear’s tail. It has two companion stars and also belongs to the Ursa Major moving group.

[8315] epsilon Ursae Majoris or Alioth ("tail") is the brightest star in Ursa Major and the 31st brightest star in the sky. It has an apparent visual magnitude of 1.76 and is approximately 81 light-years distant. The Chinese know it as the Star of Jade Sighting-tube or the Fifth Star of the Northern Dipper. It is one of the 57 navigational stars, used for orientation because of its luminosity and position in the sky. It is a white main sequence star, 108 times more luminous than the Sun.

[8318] zeta Ursae Majoris or Mizar ("the girdle" or "the waistband") is the fourth brightest star in the constellation. It is a multiple star system and the first binary star ever discovered. Mizar has a faint visual companion, [8334] Alcor (80 Ursae Majoris). Both stars are in fact binary systems and all the four stars involved are main sequence white dwarfs. Both Mizar and Alcor belong to the Ursa Major moving group.

[8317] eta Ursae Majoris, also known as Alkaid ("the leader") and Benetnash ("the daughters of the bier"), is the third brightest star in the constellation and the 35th brightest star in the sky. It is a hot bluish-white main sequence dwarf. It lies approximately 100 light-years away and marks the tip of the bear’s tail. The Chinese call it the Star of Twinkling Brilliance or the Seventh Star of the Northern Dipper. Like [8315] Alioth, Alkaid does not belong to the Ursa Major moving group.

Another notable star in Ursa Major is W Ursae Majoris (HD 83950), which serves as the prototype of a class of stars known as the contact binary variable stars or W Ursae Majoris variables. The star is an eclipsing binary star whose two components are so close that they touch each other and even share a common outer layer. Both stars are yellow main sequence dwarfs.

[8402] 47 Ursae Majoris is a yellow dwarf 46 light-years distant, notable for being a solar twin, a star very similar to our Sun. It is one of the top target stars for NASA’s Terrestrial Planet Finder project. It has two confirmed extrasolar planets in its orbit.

Winnecke 4, also known as Messier 40, is a double star included among the notable deep sky objects in Charles Messier’s catalogue, one of the few mistakes Messier made. The star is approximately 510 light-years-distant.

Ursa Major is also home to several interesting deep sky objects. These include the galaxies Messier 81, Messier 82, Messier 101, Messier 108 and Messier 109, to mention just a few of the brightest ones in the constellation. There are about 50 galaxies in Ursa Major in total.

Messier 81 (NGC 3031) is also known as Bode’s Galaxy. It is one of the best examples of a grand design spiral galaxy, lying approximately 12 million light-years from Earth. It is a large galaxy with an active nucleus harbouring a supermassive black hole. It has near-perfect spiral arms. It was discovered by the German astronomer Johann Elert Bode in 1774. Messier 81 is the largest of the 34 galaxies in the M81 Group, one of the nearest groups of galaxies to the Local Group, approximately 11.7 million light-years away. Bode’s Galaxy can be found 10 degrees northwest of [8316] alpha Ursae Majoris.

Messier 82 (NGC 3034) is also called the Cigar Galaxy. Approximately 12 million light-years distant, it is a prototype starburst galaxy, one that is five times as bright as our own galaxy, the Milky Way, and about a hundred times brighter than the Milky Way’s centre. In the core of the Cigar Galaxy, stars are being born 10 times faster than those in our galaxy. The Cigar Galaxy is visibly distorted by its larger neighbor, Bode’s Galaxy.

The Pinwheel Galaxy, or Messier 101 (NGC 5457), is another spiral galaxy, approximately 27 million light-years distant. It is a large galaxy, almost twice the size of the Milky Way. It can be seen face-on near [8317] eta Ursae Minoris. It was discovered by the French astronomer Pierre Méchain, who called it a "nebula without a star, very obscure and pretty large, 6’ to 7’ in diameter, between the left hand of Bootes and the tail of the great Bear." The Pinwheel Galaxy has five prominent satellite galaxies. The gravitational interaction between them may have been what triggered the grand design pattern formation in Messier 101.

Two other notable galaxies in Ursa Major are Messier 108 (NGC 3556), a barred spiral galaxy that can be seen almost edge-on, and Messier 109, another barred spiral galaxy located near [8320] gamma Ursae Majoris, approximately 46 million light-years distant. Messier 109 has at least three satellite galaxies of its own.

The Owl Nebula, or Messier 97 (NGC 3587), is a bright planetary nebula named for its resemblance to a pair of owl-like eyes. It can be spotted at the lower end of the bowl of the Big Dipper.

Ursa Major belongs to the Ursa Major family of constellations, along with Ursa Minor, Draco, Canes Venatici, Bootes, Coma Berenices, Corona Borealis, Camelopardalis, Leo Minor and Lynx.

Constellations directly bordering Ursa Major are Draco, Camelopardalis, Leo Minor and Lynx, Leo, Coma Berenices, Canes Venatici and Bootes.

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