Little Dumbbell Nebula (M 76)

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About this Image

The appearance of the quite faint M76 resembles to some degree that of the Dumbbell Nebula M27. Most probably, the main body (the bar, or cork) is a bright and slightly elliptical ring we see edge-on, from only a few degrees off its equatorial plane. This ring seems to expand at about 42 km/sec.

Along the axis perpendicular to this plane, the gas expands significantly more rapidly to form the lower surface brightness "wings" of the butterfly. This nebula is surrounded by a faint bipolar halo covering a region of 290 arc seconds in diameter; this material was probably ejected in the form of stellar winds from the central star when it was still in the Red Giant phase of evolution.

Today the central star is of mag 16.6 and a high temperature of some 60,000 K, which will probably cool down as a white dwarf over the coming tens of billions of years. The nice colorsare emitted both in blue-green (O-III) and in red color (H-alpha).
North is to the right.

Below you see a crop on the center of the above image in 50/100% size.

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Technical Details


16" cassegrain in secondary focus at f/10

Mount MK-100 GEM
Camera SBIG STL-11000M at -30C, internal filter wheel; AO-L
Filters Astronomik Ha + LRGB
Date Dec 07, 2005 and Jan 07, 2007.
Location Wildon/Austria
Sky Conditions 2005: mag 5 sky, seeing unstable, temperature 0 C,
2007: mag 5.5 sky, raw FWHM 1.9" deconvolved to 1.5", temperature 0C,
Exposure 2005: Ha:R:G:B = 60:60:50:60 min (10 min resp. 30 min sub-exposures) binned 2x2
2007: L:Ha = 180:120 min (20 min resp. 60 min sub-exposures) 1x1 bin
Processing Image aquisition, registration and color combine in Maxim;
synthetic luminance from RGB, H-alpha blended into red channel, curves, unsharp mask, color balance in Photoshop; Noise reduction by Neatimage for dark areas;
2007: L incorporated, Ha as red and L; wavelet filtering for bright parts; color balance in Photoshop CS2,