Interesting Facts About Ursa Major

Interesting Facts About Ursa Major
The Big Dipper by Bob King

The Great Bear

In Latin, “ursus” means bear, while in Greek the word is “arktos”, hence the name Arctic (“bearish”) which describes the far northern region of the earth where the constellation of Ursa Major (“greater she-bear”) dominates. Together with the adjoining constellation of Ursa Minor (“the smaller she-bear”), these two conspicuous northern constellations are circumpolar, and so are visible throughout the year in the northern hemisphere.

Contains The Dipper Star Asterism

Ursa Major is the 3rd largest constellation in the night sky and is readily distinguished by means of a remarkable cluster of seven bright stars in the northern heavens, forming what is familiarly termed “The Dipper”. It is also referred to as the “the Plough” or “Frying Pan”, with four of its stars forming a pan shape, and the other three a handle. However, this beautiful arrangement of stars forms less than half of the entire constellation known as Ursa Major.

Seven Brightest Stars

Ursa Major’s seven brightest stars in order of brightest are as follows:

Alioth, a 1.75 magnitude white star, 127 times brighter than our own sun, and located 81 light-years distant.

Dubhe, a 1.81 magnitude orange star, 415 times brighter than our own sun, and located 124 light-years distant.

Alkaid, a 1.85 magnitude blue star, 255 times brighter than our own sun, and located 101 light-years distant.

Mizar, a 2.23 magnitude white star, 73 times brighter than our own sun, and located 78 light-years distant.

Merak, a 2.34 magnitude white star, 70 times brighter than our own sun, and located 79 light-years distant.

Phad, a 2.41 magnitude white star, 71 times brighter than our own sun, and located 84 light-years distant.

Psi Ursae Majoris, a 3 magnitude orange star, 225 times brighter than our own sun, and located 147 light-years distant.

ursa major star guideInteresting Objects

Ursa Major is a remarkable constellation containing Bode’s Galaxy (M81), a dense spiral galaxy with an incredible 250 billion suns, as well as the Cigar Galaxy (M82), the Pinwheel Galaxy (M101), and the Barred Spiral Galaxies of M108 and M109, both of which are 12 million light years away. The planetary Owl Nebula (M97) is also found in Ursa Major, 1,630 light-years from Earth.

Ursa Major As A Star Clock

In the Northern hemisphere Ursa Major never sets below the horizon, and is visible the whole year round. It is also circumpolar in the UK and Northern USA and is seen to complete a whole counterclockwise rotation every 24 hours around the ‘North Star’ (Polaris) located in neighboring Ursa Minor. This motion has been used as an excellent star clock throughout history.

Ursa Major As A Directional Compass

Polaris is located very close to the north celestial pole and has also been extremely useful as a directional compass, as well as determining location. The North Star is always elevated as many degrees above the horizon as the observer is north of the equator. The stars Merak and Dubhe in ‘The Dipper’ are called the pointers, because they always point toward Polaris. Note the second star from the end of the Dipper’s handle actually consists of Mizar, and its fainter companion Alcor. These stars appear close together and being able to distinguish one from the other was used by many ancient armies as a test for those wishing to become an archer, including the Persian and Romans. The Arabs also used them as a test of good eyesight.

Mythology of Ursa Major

One version of the legend goes that Callisto’s beauty surpassed that of Hera, which so infuriated the goddess that she turned her into a bear. Years later, Arcas, Callisto’s son, was out hunting and was about to kill the bear unwittingly when Zeus intervened and swung both Callisto and Arcas, now transformed into a bear, up into the sky as Ursa Major and Ursa Minor respectively. Hera was annoyed the pair were given so much honor and so convinced Poseidon to forbid them from bathing. It is for this reason that these constellations are circumpolar and never dip below the horizon when viewed from Northern latitudes.

Next Step: Mapping the night sky using Ursa Major