Selasa, 26 Oktober 2010

The Bear's realm
The dominant constellation on this map is Ursa Major the Great Bear. Because this region is far from the Milky Way — where star clusters and nebulae abound — most of the great deep-sky objects here are galaxies. If you don't have a go-to telescope, the seven stars of the Big Dipper can help you find these objects.
The dominant constellation on this map is Ursa Major the Great Bear. Because this region is far from the Milky Way — where star clusters and nebulae abound — most of the great deep-sky objects here are galaxies. If you don't have a go-to telescope, the seven stars of the Big Dipper can help you find these objects.Start with the galaxies on Messier's list: Bode's Galaxy (M81), the Cigar Galaxy (M82), M101, M108, and M109. An eyepiece/telescope combination that provides a field of view wider than ½° will catch both M81 and M82. Higher magnifications will reveal a large core and tight, graceful spiral arms in M81, and a wide, dark lane and splotchy bright areas in M82.

Many large spiral galaxies have up to a dozen nearby galaxies that, with the primary object, form a group. The M81 Group lies 11 million light-years away and counts about a dozen galaxies. To see them, use an 8-inch or larger scope from a dark site. On the other side of M81 from M82 is NGC 3077, a 10th-magnitude spiral.

It's worth finding the Owl Nebula (M97), a bright planetary nebula in Ursa Major. Under a dark sky, a 4-inch or larger telescope will show the Owl's face, which contains two round, dark areas (the "eyes"). The Owl is a low-surface-brightness object that, except for a bit of a mottled surface, doesn't have a lot of detail.

The most famous double star in the sky lies at the bend of the Big Dipper's handle, and you don't need a telescope to see it. Alcor (80 Ursae Majoris) and Mizar (Zeta Ursae Majoris) once were a vision test for Roman soldiers. Mizar itself, however, is a much closer double star with a separation of only 14".
Spiral galaxy M101 is located in the constellation Ursa Major.
George Jacoby, Bruce Bohannan, Mark Hanna/NOAO/AURA/NSF

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