Dumbbell Nebula
Encyclopedia
The Dumbbell Nebula is a planetary nebula
(PN) 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
.
and is viewed from our perspective along the plane of its 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 semi-minor axis
radius
of 1.01 ly, this implies that the kinematic age of the nebula is some 9,800 years.
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.
, 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. The central star mass was estimated in 1999 by Napiwotzki to be 0.56 ± 0.01 M☉
.
Planetary nebula
A planetary nebula is an emission nebula consisting of an expanding glowing shell of ionized gas ejected during the asymptotic giant branch phase of certain types of stars late in their life...
(PN) in the constellation
Constellation
In modern astronomy, a constellation is an internationally defined area of the celestial sphere. These areas are grouped around asterisms, patterns formed by prominent stars within apparent proximity to one another on Earth's night sky....
Vulpecula
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 .-Stars:There are no stars brighter than 4th magnitude in...
, at a distance of about 1,360 light years.
This object was the first planetary nebula
Planetary nebula
A planetary nebula is an emission nebula consisting of an expanding glowing shell of ionized gas ejected during the asymptotic giant branch phase of certain types of stars late in their life...
to be discovered; by Charles Messier
Charles Messier
Charles Messier was a French astronomer most notable for publishing an astronomical catalogue consisting of deep sky objects such as nebulae and star clusters that came to be known as the 110 "Messier objects"...
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
Amateur astronomy
Amateur astronomy, also called backyard astronomy and stargazing, is a hobby whose participants enjoy watching the night sky , and the plethora of objects found in it, mainly with portable telescopes and binoculars...
.
Structure
This PN appears to be shaped like an prolate spheroidProlate spheroid
A prolate spheroid is a spheroid in which the polar axis is greater than the equatorial diameter. Prolate spheroids stand in contrast to oblate spheroids...
and is viewed from our perspective along the plane of its equator
Equator
An equator is the intersection of a sphere's surface with the plane perpendicular to the sphere's axis of rotation and containing the sphere's center of mass....
. 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 semi-minor axis
Semi-minor axis
In geometry, the semi-minor axis is a line segment associated with most conic sections . One end of the segment is the center of the conic section, and it is at right angles with the semi-major axis...
radius
Radius
In classical geometry, a radius of a circle or sphere is any line segment from its center to its perimeter. By extension, the radius of a circle or sphere is the length of any such segment, which is half the diameter. If the object does not have an obvious center, the term may refer to its...
of 1.01 ly, this implies that the kinematic age of the nebula is some 9,800 years.
Knots
Helix Nebula
The Helix Nebula is a large planetary nebula located in the constellation Aquarius. Discovered by Karl Ludwig Harding, probably before 1824, this object is one of the closest to the Earth of all the bright planetary nebulae. The estimated distance is about 215 parsecs or 700 light-years...
and the Eskimo Nebula
Eskimo Nebula
The Eskimo Nebula , also known as the Clownface Nebula or Caldwell 39, is a bipolar double-shell planetary nebula . It was discovered by astronomer William Herschel in 1787. The formation resembles a person's head surrounded by a parka hood. It is surrounded by gas that composed the outer layers of...
, the heads of the knots have bright cusps which are local photoionization fronts.
Central star
The central star, a white dwarfWhite dwarf
A white dwarf, also called a degenerate dwarf, is a small star composed mostly of electron-degenerate matter. They are very dense; a white dwarf's mass is comparable to that of the Sun and its volume is comparable to that of the Earth. Its faint luminosity comes from the emission of stored...
, 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. The central star mass was estimated in 1999 by Napiwotzki to be 0.56 ± 0.01 M☉
Solar mass
The solar mass , , is a standard unit of mass in astronomy, used to indicate the masses of other stars and galaxies...
.
See also
- Messier objectMessier objectThe Messier objects are a set of astronomical objects first listed by French astronomer Charles Messier in 1771. The original motivation of the catalogue was that Messier was a comet hunter, and was frustrated by objects which resembled but were not comets...
- List of Messier objects
- List of planetary nebulae
- New General CatalogueNew General CatalogueThe New General Catalogue of Nebulae and Clusters of Stars is a well-known catalogue of deep sky objects in astronomy. It contains 7,840 objects, known as the NGC objects...