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Bode’s Galaxy

Bode’s Nebula, M81, NGC 3031

When it was discovered by Johann Bode in 1774, the distinction between nebulae and galaxies was still unclear, and this object was therefore at one time known as 'Bode's Nebula'. It was added independently to the Messier Catalogue in 1779, and so is also known as M81 its number in that catalogue.

Bode's 'Nebula' is in fact a spiral galaxy, and at a distance of some twelve million light years, it is - in galactic terms - a relatively close neighbour to the Milky Way. Because of this, it is one of the brightest galaxies in the skies of Earth, and its visual magnitude of +6.9 makes it detectable with even a modest telescope.

The galaxy is angled so that its spiral form is clearly visible, with two long symmetrical spiral arms arcing out from its core and through the disc of the galaxy. These arms are dense with interstellar dust, and are the site of intense stellar formation.

Bode's Galaxy is the most significant member of a small galactic group, to which the galaxy gives its name: the M81 Group. Gravitational forces within the group cause its members to interact with one another, and this effect is clearly seen between Bode's Galaxy and the neighbouring irregular galaxy M82. These two galaxies, along with others in the group, exchange tenuous threads of material across intergalactic space, and these interactions are thought to lie behind the high levels of stellar formation within the group.

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