Dumbbell Nebula
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| Planetary nebula | Lists of nebulae |
|---|---|
 Image of the Dumbbell Nebula taken by Robert J. Vanderbei, Princeton University |
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| Observation data (Epoch J2000) |
|
| Right ascension | 19h 59m 36.340s[1] |
| Declination | +22° 43′ 16.09″[1] |
| Distance | 1,360+160−210 ly (420+50−70 pc)[2] |
| Apparent magnitude (V) | 7.5[1] |
| Apparent dimensions (V) | 8′.0[citation needed] × 5′.6[3] |
| Constellation | Vulpecula |
| Physical characteristics | |
| Radius | 1.58+0.19−0.24 ly[a] |
| Absolute magnitude (V) | -0.6+0.4−0.3[d] |
| Notable features | Central star radius is largest known for a white dwarf. |
| Other designations | NGC 6853,[1] M 27,[1] |
The Dumbbell Nebula (also known as Messier 27, M 27, or NGC 6853) is a planetary nebula (PN) in the Vulpecula constellation, at a distance of about 1360 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 great observing target in amateur telescopes.
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[edit] Structure
This PN appears to be shaped like an prolate spheroid and is viewed from our perspective along the plane of its 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. Is 1970, Bohuski, Smith, & Weedman found an expansion velocity of 31 km/s. Given the semi-minor axis radius of 1.11+0.13−0.17 ly,[b] this implies that the kinematic age of the PN is 10,700+1,300−1,600 [c] years old.[3][4]
[edit] Knots
Credit: C.R. O'Dell (Vanderbilt University)
Like many nearby planetary nebulas, 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 Helix Nebula and the Eskimo Nebula, the heads of the knots have bright cusps which are local photoionization fronts.[4]
[edit] Central star
The central star, a 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.[2] The central star mass was estimated in 1999 by Napiwotzki to be 0.56 ± 0.01 M☉.[2]
[edit] See also
[edit] Notes
- ^ Radius = distance × sin(angular size / 2) = 1,360+160−210[2] * sin(8′.0 / 2) = 1.58+0.19−0.24 ly
- ^ Semi minor axis = distance × sin(minor axis size / 2) = 1,360+160−210[2] * sin(5′.6 / 2) = 1.11+0.13−0.17 ly
- ^ Kinematic age = semi-minor axis / expansion rate = 1.11+0.13−0.17[b] ly / 31 km/s = 1.05+0.12−0.16×1013 km / 31[3] km/s = 3.39+0.4−0.5×1011 s = 10,700+1,300−1,600 yr
- ^ 7.5 apparent magnitude - 5 * (log10(420+50−70 pc distance) - 1) = -0.6+0.4−0.3 absolute magnitude
[edit] References
- ^ a b c d e f g SIMBAD Astronomical Database. Results for M 27. Retrieved on January 3, 2007.
- ^ a b c d e 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.
- ^ a b c 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.
- ^ a b 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.
