Dumbbell Nebula

Dumbbell Nebula

ESO image showing extended structure and central star
Observation data
(Epoch J2000)
Right ascension 19h 59m 36.340s[1]
Declination +22° 43′ 16.09″[1]
Distance 1360+160
−212 ly (417+49
−65 pc)[2][3]
Apparent magnitude (V) 7.5[1]
Apparent dimensions (V) 8′.0 × 5′.6[4]
Constellation Vulpecula
Physical characteristics
Radius 1.44+0.21
−0.16 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]
Diabolo Nebula,[1]
Dumb-Bell Nebula,[1]

The Dumbbell Nebula (also known as Apple Core Nebula, Messier 27, M 27, or NGC 6853) is a planetary nebula in the constellation Vulpecula, at a distance of about 1,360 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.

M27. This picture was processed and combined using IRAF and MaxIm DL by Mohamad Abbas.

Structure

The Dumbbell Nebula 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 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.[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 Helix Nebula and the Eskimo Nebula, the heads of the knots have bright cusps which are local photoionization fronts.[5]

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]

See also

Wikimedia Commons has media related to Dumbbell Nebula.

Notes

  1. ^ Radius = distance × sin(angular size / 2) = 1240+180
    −140    [3] * sin(8′.0 / 2) = 1.44+0.21
    −0.16     ly
  2. ^ Semi minor axis = distance × sin(minor axis size / 2) = 1240+180
    −140    [3] × sin(5′.6 / 2) = 1.01+0.15
    −0.11     ly
  3. ^ Kinematic age = semi-minor axis / expansion rate = 1.01+0.15
    −0.11    [b] ly / 31 km/s = 9.56+1.42
    −1.04    ×1012 km     / 31[4] km/s = 3.08+0.46
    −0.34    ×1011     s = 9800+1500
    −1100     yr
  4. ^ 7.5 apparent magnitude - 5 × (log10(420+50
    −70     pc     distance) - 1) = −0.6+0.4
    −0.3     absolute magnitude

References

  1. 1 2 3 4 5 6 7 "SIMBAD Astronomical Database". Results for M 27. Retrieved 2007-01-03.
  2. 1 2 3 Benedict, G. Fritz; McArthur, B. E.; Fredrick, L. W.; Harrison, T. E.; et al. (2003). "Astrometry with The Hubble Space Telescope: A Parallax of the Central Star of the Planetary Nebula NGC 6853". Astronomical Journal 126 (5): 2549–2556. arXiv:astro-ph/0307449. Bibcode:2003AJ....126.2549B. doi:10.1086/378603.
  3. 1 2 3 Harris, Hugh C.; Dahn, Conard C.; Canzian, Blaise; Guetter, Harry H.; et al. (2007). "Trigonometric Parallaxes of Central Stars of Planetary Nebulae". Astronomical Journal 133 (2): 631–638. arXiv:astro-ph/0611543. Bibcode:2007AJ....133..631H. doi:10.1086/510348.
  4. 1 2 3 O'Dell, C. R.; Balick, B.; Hajian, A. R.; Henney, W. J.; et al. (2002). "Knots in Nearby Planetary Nebulae". Astronomical Journal 123 (6): 3329–3347. Bibcode:2002AJ....123.3329O. doi:10.1086/340726.
  5. 1 2 O'dell, C. R.; Balick, B.; Hajian, A. R.; Henney, W. J.; et al. (2003). "Knots in Planetary Nebulae". Revista Mexicana de Astronomía y Astrofísica, Serie de Conferencias 15: 29–33. Bibcode:2003RMxAC..15...29O.

External links

Coordinates: 19h 59m 36.340s, 22° 43′ 16.09″

This article is issued from Wikipedia - version of the Monday, February 29, 2016. The text is available under the Creative Commons Attribution/Share Alike but additional terms may apply for the media files.