Anne’s Picture of the Day: The Little Dumbbell Nebula

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April 12, 2013

Messier 76, a planetary nebula in Perseus

Image Credit & Copyright: Adam Block/NOAO/AURA/NSF (http://www.caelumobservatory.com/obs/bestofaop.shtml)

Messier 76 (also known as The Little Dumbbell Nebula or NGC 650/651) is a rather faint bipolar planetary nebula of about 1.23 light-year across, located some 2,500 light-years from Earth in the Eastern part of the constellation of Perseus, while it is approaching us at approximately 19.1 kilometers per second.

Planetary nebulae represent the final brief stage in the life of a medium-sized star like our Sun. While consuming the last of the fuel in its core, the dying star expels a large portion of its outer envelope. This material then becomes heated by the radiation from the stellar remnant and radiates, producing glowing clouds of gas that can show complex structures, as the ejection of mass from the star is uneven in both time and direction.

Over the next several thousand years, the nebula will gradually disperse into space, and then the white dwarf will cool and fade away for billions of years. Our own Sun is expected to undergo a similar fate, but fortunately this will not occur until some 5 billion years from now.

The nebula derives its nickname from its resemblance to the brighter Dumbbell Nebula (M27) in the constellation of Vulpecula. It was originally thought to consist of two separate emission nebulae and was thus given two catalog numbers in the New General Catalogue of Nebulae and Clusters of Stars (abbreviated as NGC): NGC 650 (the upper part in this image and NGC 651 (the lower part).

Its main body (known as the “cork”) is most probably a bright and slightly elliptical donut-shaped ring we see edge-on, from only a few degrees off its equatorial plane. This ring seems to expand at about 42 kilometers per second. Along the axis perpendicular to this plane, the gas expands significantly more rapidly to form the fainter “wings” of the nebula. A faint halo is surrounding the cork and the wings, consisting of material that was probably ejected in the form of stellar winds from the central star when it was still in its red giant phase.

Messier 76 has a surface temperature of about 88,400 K, while the central dying star (HD 10346) has a temperature of some 60,000 K, and will cool down as a white dwarf over the coming tens of billions of years.

This image is showing emission from hydrogen atoms in red and oxygen atoms in complementary blue hues. The nebula’s dying star can be picked out as the blue-tinted star near the center of the cork.

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