Английская Википедия:Dumbbell Nebula

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Шаблон:Short description Шаблон:Infobox Planetary nebula The Dumbbell Nebula (also known as the Apple Core Nebula, Messier 27, and NGC 6853) is a planetary nebula (nebulosity surrounding a white dwarf) in the constellation Vulpecula, at a distance of about 1360 light-years. It was the first such nebula to be discovered, by Charles Messier in 1764. At its brightness of visual magnitude 7.5 and diameter of about 8 arcminutes, it is easily visible in binoculars and is a popular observing target in amateur telescopes.

Shape and size

The Dumbbell Nebula appears 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 angularly was, viewed from our distance, no more than Шаблон:Val (″) per century. From this, an upper limit to the age of 14,600 years may be determined. In 1970, Bohuski, Smith, and Weedman found an expansion velocity of Шаблон:Val. Given its semi-minor axis radius of Шаблон:Val, this implies that the kinematic age of the nebula is 9,800 years.

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.

Central star

The central star, a white dwarf progenitor, is estimated to have a radius which is Шаблон:Val (0.13 light seconds) which gives it a size larger than most other known white dwarfs. Its mass was estimated in 1999 by Napiwotzki to be Шаблон:Val.

Appearance

Файл:Vulpecula IAU.svg Located in the faint constellation Vulpecula, within the Summer Triangle.

Файл:Messier27-starmap.png 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.

• Dumbbell Nebula, north is diagonal left-up

  Dumbbell Nebula, north is diagonal left-up

• Dumbbell Nebula (Messier 27) imaged by the Very Large Telescope

  Dumbbell Nebula (Messier 27) imaged by the Very Large Telescope

• Blend of UHC and RGB exposures of M27 taken with moderate level amateur equipment in the center of a capital city

  Blend of UHC and RGB exposures of M27 taken with moderate level amateur equipment in the center of a capital city

• M27 with 5.5" telescope from city suburbs

  M27 with 5.5" telescope from city suburbs

• Skywatcher 120mm ED APO

  Skywatcher 120mm ED APO

See also

• Messier object
• List of Messier objects
• List of planetary nebulae
• New General Catalogue

Notes

1. Шаблон:Note labelRadius = distance × sin(angular size / 2) = Шаблон:Val * sin(8′.0 / 2) = Шаблон:Val ly
2. Шаблон:Note labelSemi minor axis = distance × sin(minor axis size / 2) = Шаблон:Val × sin(5′.6 / 2) = Шаблон:Val ly
3. Шаблон:Note labelKinematic age = semi-minor axis / expansion rate = Шаблон:ValШаблон:Ref label ly / 31 km/s = Шаблон:Val / 31 km/s = Шаблон:Val s = Шаблон:Val yr
4. Шаблон:Note label7.5 apparent magnitude - 5 × (log₁₀(Шаблон:Val distance) - 1) = Шаблон:Val absolute magnitude

External links

• SEDS: Messier Object 27
• Шаблон:WikiSky
• M27 on astro-pics.com
• Шаблон:Cite web
• M27

Шаблон:Messier objects Шаблон:Ngc70 Шаблон:Vulpecula Шаблон:Portal bar Шаблон:Sky Шаблон:Authority control