Messier Index/M27

Dumbbell Nebula
Observation data
(Epoch w:J2000)
Right ascension 19h 59m 36.340s[1]
Declination +22° 43′ 16.09″[1]
Distance 1,360+160−212 ly (417+49−65 pc)[2][3]
Apparent magnitude (V) 7.5[1]
Apparent dimensions (V) 8′.0[citation needed] × 5′.6[4]
Constellation w:Vulpecula
Physical characteristics
Radius 1.44+0.21−0.16 lya
Absolute magnitude (V) -0.6+0.4−0.3d
Notable features Central star radius is largest
known for a white dwarf.
Other designations NGC 6853,[1] M 27,[1]

Diabolo Nebula,[1]

Dumb-Bell Nebula,[1]

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

w:ESO image showing extended structure and central star
Credit: ESO

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.[4][5]

Knots

HST closeup of knots in M 27
Credit: C.R. O'Dell (Vanderbilt University)

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.[5]

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.[2] The central star mass was estimated in 1999 by Napiwotzki to be 0.56 ± 0.01 M.[2]

Notes

^a Radius = distance × sin(angular size / 2) = 1,240+180−140[3] * 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[3] * sin(5′.6 / 2) = 1.01+0.15−0.11 ly
^c Kinematic age = semi-minor axis / expansion rate = 1.01+0.15−0.11b ly / 31 km/s = 9.56+1.42−1.04×1012 km / 31[4] km/s = 3.08+0.46−0.34×1011 s = 9,800+1,500−1,100 yr
^d 7.5 apparent magnitude - 5 * (log10(420+50−70 pc distance) - 1) = -0.6+0.4−0.3 absolute magnitude

References

  1. a b c d e f g "SIMBAD Astronomical Database". Results for M 27. http://simbad.u-strasbg.fr/Simbad. Retrieved 2007-01-03. 
  2. a b c 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. http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2003AJ....126.2549B. 
  3. a b c 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. http://adsabs.harvard.edu/abs/2007AJ....133..631H. 
  4. 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. doi:10.1086/340726. http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2002AJ....123.3329O. 
  5. 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. http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2003RMxAC..15...29O. 

External links

Last modified on 28 April 2010, at 03:20