# Messier Index/M27

The Dumbbell Nebula (also known as Messier 27, M 27, or NGC 6853) is a w:planetary nebula (PN) in the w:constellation w:Vulpecula, at a distance of about 1,360 w:light years.
This object was the first w:planetary nebula to be discovered; by w:Charles Messier in 1764. At its brightness of w:visual magnitude 7.5 and its diameter of about 8 w:arcminutes, it is easily visible in binoculars, and a popular observing target in amateur telescopes.

## Structure

This PN appears to be shaped like an w:prolate spheroid and is viewed from our perspective along the plane of its w:equator. In 1992, Moreno-Corral et al. computed that the rate of expansion in the plane of the sky of this PN 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 w:semi-minor axis w:radius of 1.01 ly, this implies that the kinematic age of the nebula is some 9,800 years.

### Knots

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

### Central star

The central star, a w:white dwarf, is estimated to have a radius which is 0.055 ± 0.02 R$_☉$ which gives it a size larger than any other known white dwarf. The central star mass was estimated in 1999 by Napiwotzki to be 0.56 ± 0.01 M$_☉$.

## Notes

    ^a Radius = distance × sin(angular size / 2) = 1,240$^{+180}$$_{−140}$ * sin(8′.0 / 2) = 1.44$^{+0.21}$$_{−0.16}$ ly
    ^b Semi minor axis = distance × sin(minor axis size / 2) = 1,240$^{+180}$$_{−140}$ * sin(5′.6 / 2) = 1.01$^{+0.15}$$_{−0.11}$ ly
    ^c Kinematic age = semi-minor axis / expansion rate = 1.01$^{+0.15}$$_{−0.11}$ ly / 31 km/s = 9.56$^{+1.42}$$_{−1.04}$×10$^{12}$ km / 31 km/s = 3.08$^{+0.46}$$_{−0.34}$×10$^{11}$ s = 9,800$^{+1,500}$$_{−1,100}$ yr
    ^d 7.5 apparent magnitude - 5 * (log$_{10}$(420$^{+50}$$_{−70}$ pc distance) - 1) = -0.6$^{+0.4}$$_{−0.3}$ absolute magnitude

## References

* 1 2 3 4 5 6 7 "SIMBAD Astronomical Database". Results for M 27. Retrieved 2007-01-03.
* 1 2 3 Benedict, G. Fritz; McArthur, B. E.; Fredrick, L. W.; Harrison, T. E.; Skrutskie, M. F.; Slesnick, C. L.; Rhee, J.; Patterson, R. J.; Nelan, E.; Jefferys, W. H.; van Altena, W.; Montemayor, T.; Shelus, P. J.; Franz, O. G.; Wasserman, L. H.; Hemenway, P. D.; Duncombe, R. L.; Story, D.; Whipple, A. L.; Bradley, A. J. (2003). "Astrometry with The Hubble Space Telescope: A Parallax of the Central Star of the Planetary Nebula NGC 6853". The Astronomical Journal. 126 (5): 2549–2556. doi:10.1086/378603.{{cite journal}}: CS1 maint: multiple names: authors list (link)
* 1 2 3 Harris, Hugh C.; Dahn, Conard C.; Canzian, Blaise; Guetter, Harry H.; Leggett, S. K.; Levine, Stephen E.; Luginbuhl, Christian B.; Monet, Alice K. B.; Monet, David G.; Pier, Jeffrey R.; Stone, Ronald C.; Tilleman, Trudy; Vrba, Frederick J.; Walker, Richard L. (February 2007). "Trigonometric Parallaxes of Central Stars of Planetary Nebulae". The Astronomical Journal. 133 (2): 631–638. doi:10.1086/510348.{{cite journal}}: CS1 maint: date and year (link) CS1 maint: multiple names: authors list (link)
* 1 2 3 O'Dell, C. R.; Balick, B.; Hajian, A. R.; Henney, W. J.; Burkert, A. (2002). "Knots in Nearby Planetary Nebulae". The Astronomical Journal. 123 (6): 3329–3347. doi:10.1086/340726.{{cite journal}}: CS1 maint: multiple names: authors list (link)
* 1 2 O'dell, C. R.; Balick, B.; Hajian, A. R.; Henney, W. J.; Burkert, A. (2003). "Knots in Planetary Nebulae". Winds, Bubbles, and Explosions: a conference to honor John Dyson, Pátzcuaro, Michoacán, México, September 9-13, 2002 (Eds. S. J. Arthur & W. J. Henney) Revista Mexicana de Astronomía y Astrofísica (Serie de Conferencias) (http://www.astroscu.unam.mx/~rmaa/). 15: 29–33. {{cite journal}}: External link in |journal= (help)CS1 maint: multiple names: authors list (link)

## External links

* SEDS Messier page on M27
* M27 Dumbbell Nebula
* M27 image taken by Stargazer Observatory
* M27