Dumbbell Nebula The
Dumbbell Nebula is a
planetary nebula (nebulosity surrounding a white dwarf) in the
constellationVulpecula, at a distance of about 1360
light-years. It was the first such nebula to be discovered, by
Charles Messier in 1764. At its brightness of
visual magnitude 7.5 and diameter of about 8
arcminutes, it is easily visible in binoculars[6] and is a popular observing target in
amateur telescopes.
Shape and sizeThe Dumbbell Nebula appears shaped like a
prolate spheroid and is viewed from our perspective along the plane of its equator. In 1992, it was computed that its rate of expansion angularly was, viewed from our distance, no more than 2.3
arcseconds per century. From this, an upper limit to the age of 14,600 years may be determined. In 1970 it was found to have an expansion velocity of 31
km/s. This implies that the kinematic age of the nebula is 9,800 years.
StructureLike many nearby planetary nebulae, the Dumbbell contains knots. Its central region is marked by a pattern of dark and bright cusped knots and their associated dark tails (see picture). The knots vary in appearance from symmetric objects with tails to rather irregular tail-less objects.
Central starThe central star, a
white dwarf , is estimated to have a radius which is 0.13 light seconds which gives it a size larger than most other known white dwarfs.
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