Spiral Galaxy M-81 ( NGC 3031)
"Bode's Nebula"

Click here to see a full size version of this image.

This is a 40 minute exposure with an STL-1301E CCD camera thru Kopernik's 20-inch telescope. By using a focal reducing lens we cut the normal F/8.1 focal ratio down to F/5. The field of view is about 20x21 arc minutes.

M-81 is one of the most magnificent spirals in the heavens, remarkable for its strikingly symmetrical structure and dynamic appearance. The spiral whorls enclose a bright ovoid central mass composed of millions of faint stars. This bright central region surrounds an almost stellar nuclear condensation. Narrow dust lanes border the well defined spiral arms on their inside edges; the arms themselves are well resolved into star clouds and bright patches of nebulosity. In stellar content M81 seems to resemble the great galaxy M31 in Andromeda.

The long dimension corresponds to about 36,000 light years at the accepted distance, and the actual luminosity is equal to about 20 billion suns. E. Holmberg estimated the total mass to be about 250 billion suns, somewhat exceeding the mass of our own Milky Way system.

• M-81, NGC 3031
• Magnitude: 7.1
• Constellation: Ursa Major
• RA: 9h 55m 11.0s
• Dec: +69d 5m 19s Epoch 2000
• Size (mins) 26.7 x 14.2
• Classification: SA(s)ab I-II
                          Spiral, S-shaped, Luminosity class I-II
  
  

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George Normandin, KAS

March 2nd, 2005