M81 - BODE'S GALAXY

Bode's Galaxy (M81, NGC 3031) is a grand-design spiral galaxy located approximately 11.8 million light-years from Earth in the constellation Ursa Major. It was discovered by Johann Elert Bode in 1774, and Charles Messier cataloged it in 1781. M81 is one of the brightest galaxies in the night sky at visual magnitude 6.9 and is the largest member of the M81 Group, one of the nearest galaxy groups to the Local Group that contains the Milky Way. The galaxy spans about 90,000 light-years in diameter and features beautifully defined spiral arms that can be traced from the bright, yellowish central bulge outward through the disk. The spiral arms contain prominent dust lanes, blue regions of active star formation, and reddish HII regions. M81 is currently engaged in a gravitational interaction with its neighbor M82 (the Cigar Galaxy) and the fainter galaxy NGC 3077. This interaction, which reached its closest approach about 300 million years ago, has created bridges and streams of hydrogen gas connecting the three galaxies, observable in radio wavelengths. The tidal forces from this encounter triggered the intense starburst activity seen in M82. At the center of M81 lies a supermassive black hole with a mass of approximately 70 million solar masses, which has been precisely measured using observations of the orbiting gas disk. M81 is one of the premier targets for amateur astronomers in the northern hemisphere. Binoculars reveal it as a bright, elongated fuzzy patch, and it can be seen in the same field as M82. A 6-inch telescope shows the bright core and the extent of the disk, while 10-inch and larger instruments can trace spiral arm structure under dark, transparent skies.

M81 spans approximately 90,000 light-years in diameter, contains a 70 million solar mass central black hole, and lies about 11.8 million light-years from Earth.