Dumbbell Nebula

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 1227 light-years.[1] 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,[5] and a popular observing target in amateur telescopes.

Dumbbell Nebula
Emission nebula
Planetary nebula
Image of the Dumbbell Nebula (Messier 27, M 27) by the Very Large Telescope
Observation data: J2000 epoch
Right ascension 19h 59m 36.340s[1]
Declination+22° 43′ 16.09″[1]
Distance417+49
−65 pc[2][3]
376.3±6.2[1] pc
Apparent magnitude (V)7.5[1]
Apparent dimensions (V)8.0′ × 5.6′[4]
ConstellationVulpecula
Physical characteristics
Radius1.44+0.21
−0.16[a] ly
Absolute magnitude (V)−0.6+0.4
−0.3[d]
Notable featuresCentral star radius is among the largest
known for a white dwarf.
DesignationsNGC 6853,[1] M 27,[1]
Diabolo Nebula,[1]
Dumb-Bell Nebula,[1]

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.[4][6]

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 (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.[6]

Central star

The central star, a white dwarf progenitor, is estimated to have a radius which is 0.055±0.02 R☉ (0.13 light seconds) which gives it a size larger than most other known white dwarfs.[2] The central star mass was estimated in 1999 by Napiwotzki to be 0.56±0.01 M☉.[2]

Appearance

It is located in the faint constellation Vulpecula, between Cyngus and Aquila, within the Summer Triangle.

It can be located in the sky a few degrees north of γ Sagittae, near the star 14 Vulpeculae.

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:

  • North is diagonal left-up
  • North is left
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See also

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. "M 27". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2007-01-03.
  2. 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. 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. 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. "M 27". 2016-10-15.
  6. 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.

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