M81/M82 |
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Deep Sky Object Chart
| Stars in Ursa Major
| M40
| M81/M82
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M81 is a beautiful, highly regular "Sb" type spiral system, with two well defined arms that wind out into the darkness. In larger instruments, the dark dust lanes swirling around M81's core can be glimpsed. A genuine neighbor, M82 lies within the same telescopic field - and is clearly not a twin. First, M81 is oval in outline, but M82 is a somewhat irregular fat streak of light, its face crossed by blotches and streaks of dark material. Classified sometimes as an irregular system, M82 is also envisioned as an "Sd" spiral, a dusty fat disk with a small nucleus - in this case, seen edge-on. Regardless of the exact nomenclature, M82 shows ample evidence for frantic bursts of star formation in it's hidden central regions; arcs of gas are flung out from here, emitting radio and other wavelengths, and photographs show glimpses of huge clusters of hit blue stars hiding amid the dust. M81 and M82 are among the brighter galaxies, and can even be glimpsed in binoculars if the sky is dark. The M81-82 pair is merely the center of a small cluster of galaxies rather like the "local group" that contains our galaxy, the Andromeda galaxy, and a dozen others. The M81 group is among the nearest galactic families beyond the local group; the distance may be about 8 million light years. Other members include the fainter NGC 2976 (type Sd spiral, magnitude 10.8), NGC 3077 (elliptical, magnitude 11), and the odd IC 2574 (irregular with possible spiral pattern, magnitude 13). For clarity, these galaxies are not plotted on our chart this month; all lie within a few degrees of M81/82 and can be located on most good charts. In all, about a dozen galaxies are now thought to be members of the M81 group.
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