The Dumbbell Nebula (also known as the Apple Core Nebula, Messier 27, and NGC 6853) is a

planetary nebula A planetary nebula (PN, plural PNe) is a type of emission nebula consisting of an expanding, glowing shell of ionized gas ejected from red giant stars late in their lives. The term "planetary nebula" is a misnomer because they are unrelated to ...

(nebulosity surrounding a white dwarf) in the

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The origins of the e ...

Vulpecula Vulpecula is a faint constellation in the northern sky. Its name is Latin for "little fox", although it is commonly known simply as the fox. It was identified in the seventeenth century, and is located in the middle of the Summer Triangle (an ...

, at a distance of about 1360

light-year A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distances and is equivalent to about 9.46 trillion kilometers (), or 5.88 trillion miles ().One trillion here is taken to be 1012 ...

s. It was the first such nebula to be discovered, by

Charles Messier Charles Messier (; 26 June 1730 – 12 April 1817) was a French astronomer. He published an astronomical catalogue consisting of 110 nebulae and star clusters, which came to be known as the ''Messier objects''. Messier's purpose f ...

in 1764. At its brightness of

visual magnitude Apparent magnitude () is a measure of the brightness of a star or other astronomical object observed from Earth. An object's apparent magnitude depends on its intrinsic luminosity, its distance from Earth, and any extinction of the object's ...

7.5 and diameter of about 8

arcminute A minute of arc, arcminute (arcmin), arc minute, or minute arc, denoted by the symbol , is a unit of angular measurement equal to of one degree. Since one degree is of a turn (or complete rotation), one minute of arc is of a turn. The na ...

s, 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 A spheroid, also known as an ellipsoid of revolution or rotational ellipsoid, is a quadric surface obtained by rotating an ellipse about one of its principal axes; in other words, an ellipsoid with two equal semi-diameters. A spheroid has circu ...

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 (″) 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 . Given its

semi-minor axis In geometry, the major axis of an ellipse is its longest diameter: a line segment that runs through the center and both focus (geometry), foci, with ends at the two most widely separated points of the perimeter. The semi-major axis (major wikt: ...

radius of , 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 The Helix Nebula (also known as NGC 7293 or Caldwell 63) is a planetary nebula (PN) located in the constellation Aquarius. Discovered by Karl Ludwig Harding, probably before 1824, this object is one of the closest of all the bright planetary neb ...

and the

Eskimo Nebula The Eskimo Nebula (NGC 2392), also known as the Clown-faced Nebula, Lion Nebula, or Caldwell 39, is a bipolar double-shell planetary nebula (PN). It was discovered by astronomer William Herschel in 1787. The formation resembles a person's head s ...

, the heads of the knots have bright cusps which are local

photoionization Photoionization is the physical process in which an ion is formed from the interaction of a photon with an atom or molecule. Cross section Not every interaction between a photon and an atom, or molecule, will result in photoionization. The prob ...

fronts.

Central star

The central star, a

white dwarf A white dwarf is a stellar core remnant composed mostly of electron-degenerate matter. A white dwarf is very dense: its mass is comparable to the Sun's, while its volume is comparable to the Earth's. A white dwarf's faint luminosity comes fro ...

progenitor, is estimated to have a radius which is (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 .

Appearance

The Dumbbell nebula can be easily seen in binoculars in a dark sky, just above the small constellation of

Sagitta Sagitta is a dim but distinctive constellation in the northern sky. Its name is Latin for 'arrow', not to be confused with the significantly larger constellation Sagittarius 'the archer'. It was included among the 48 constellations listed by t ...

. Dumbbell Nebula from NA.jpg, Dumbbell Nebula, north is diagonal left-up M27 - Dumbbell Nebula.jpg, Dumbbell Nebula (Messier 27) imaged by the

Very Large Telescope The Very Large Telescope (VLT) is a telescope facility operated by the European Southern Observatory on Cerro Paranal in the Atacama Desert of northern Chile. It consists of four individual telescopes, each with a primary mirror 8.2 m across, ...

File:M27 Bortle9+FMoon ASI2400 RC10 UHC+RGB.jpg, Blend of UHC and RGB exposures of M27 taken with moderate level amateur equipment in the center of a capital city File:M27 from Scottsdale AZ.jpg, M27 with 5.5" telescope from city suburbs File:Dumbell nebula in NH.jpg, Skywatcher 120mm ED APO

Notes

Radius = distance × sin(angular size / 2) = * sin(8′.0 / 2) = ly
Semi minor axis = distance × sin(minor axis size / 2) = × sin(5′.6 / 2) = ly
Kinematic age = semi-minor axis / expansion rate = ly / 31 km/s = / 31 km/s = s = yr
7.5 apparent magnitude - 5 × (log₁₀( distance) - 1) = absolute magnitude

References

External links

SEDS: Messier Object 27
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Dumbbell Nebula (M27) at Constellation Guide
{{DEFAULTSORT:Dumbbell Nebula Planetary nebulae Vulpecula Messier objects NGC objects Orion–Cygnus Arm 17640712