Dumbbell Nebula


The Dumbbell Nebula is a planetary nebula in the constellation Vulpecula, at a distance of about 1227 light-years. This object was the first planetary nebula to be discovered; by Charles Messier in 1764. At its brightness of visual magnitude 7.5 and its diameter of about 8 arcminutes, it is easily visible in binoculars, and a popular observing target in amateur telescopes.

Shape and size

The Dumbbell Nebula appears to be shaped like a prolate spheroid and is viewed from our perspective along the plane of its equator. In 1992, Moreno-Corral et al. computed that its rate of expansion in the plane of the sky was no more than 2.3" per century. From this, an upper limit to the age of 14,600 yr may be determined. In 1970, Bohuski, Smith, and Weedman found an expansion velocity of 31 km/s. Given its semi-minor axis radius of 1.01 ly, this implies that the kinematic age of the nebula is some 9,800 years.

Structure

Like 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. The knots vary in appearance from symmetric objects with tails to rather irregular tail-less objects. Similarly to the Helix Nebula and the Eskimo Nebula, the heads of the knots have bright cusps which are local photoionization fronts.

Central star

The central star, a white dwarf progenitor, is estimated to have a radius which is which gives it a size larger than most other known white dwarfs. The central star mass was estimated in 1999 by Napiwotzki to be.

Appearance

The Dumbbell nebula can be easily seen in binoculars in a dark sky, just above the small constellation of Sagitta.
As seen in amateur telescopes: