Ursa Major - the Great Bear

This circumpolar constellation, when seen in diagrammatic form, is a passable representation of a bear, except that (it seems to me!) the tail is too long! But in reality many of the stars are very faint, and are seriously outshone by the seven stars of the asterism known as The Plough.

The constellation's greatest claim to fame, perhaps, is that the stars Merek and Dubhe point to Polaris, the pole star, in Ursa Minor.

Dubhe, (alpha Ursae Majoris), is a yellow giant, with a close 4.8 magnitude companion which orbits every 44.7 years. Despite being designated the alpha star, Dubhe is not, according to some authorities, the brightest star in the constellation. That distinction goes to Alioth, (epsilon Ursae Majoris), the nearest star in the "tail" to the bear's body, but in reality there is little if any naked-eye difference in brightness between them.

The star that represents the bend in the tail is Mizar, (zeta Ursae Majoris), a visual double with Alcor, and can (easily?) be split with the naked eye. A small telescope will reveal that Mizar has another star twinned with it. Mizar is particularly interesting historically as, in 1650, it was the first double ever to be identified.

The star at the end of the tail is the blue-white Alkaid (eta Ursae Majoris), sometimes called Benetnasch.

Ursa Major has a number of Messier objects. The most interesting ones from an observation point of view are M81, M82, and M97.

M81 (NGC 3031) is a superb spiral galaxy. It and M82 form a spectacular pair. M81 is one of the most dense of galaxies, containing some 250 billion stars. A large telescope is required to resolve the fine detail.

M82 is best described as spindle shaped. It is thought that an explosion at its centre created its shape.

M97 (NGC 3587). The two dark central areas, visible only using a very large telescopes, resemble an owl's eyes. Consequently M97 is known as the "Owl Nebula".