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Dumbbell Nebula
Dumbbell Nebula
Dumbbell Nebula
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Dumbbell Nebula
Emission nebula
Planetary nebula
Dumbbell Nebula (Messier 27) in Vulpecula
Observation data: J2000 epoch
Right ascension19h 59m 36.319s[1]
Declination+22° 43′ 16.312″[1]
Distance389+15
−6[1] pc
Apparent magnitude (V)7.4[2]
Apparent dimensions (V)8.0′ × 5.6′[3]
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]
See also: Lists of nebulae

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.[1] 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[4] and is a popular observing target in amateur telescopes.

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 2.3 arcseconds (″) 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 31 km/s. Given its semi-minor axis radius of 1.01 ly, this implies that the kinematic age of the nebula is 9,800 years.[3][5]

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]

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.[6] Its mass was estimated in 1999 by Napiwotzki to be 0.56±0.01 M☉.[6]

Appearance

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Constellation Vulpecula

Location map

The Dumbbell nebula is located in the faint constellation Vulpecula, within the Summer Triangle. It is located in the sky a few degrees north of γ Sagittae, near the star 14 Vulpeculae. It is bright enough to be seen in binoculars.

See also

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Notes

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References

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Revisions and contributorsEdit on WikipediaRead on Wikipedia

Dumbbell Nebula

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from Grokipedia
The Dumbbell Nebula (Messier 27 or NGC 6853) is a bipolar in the northern constellation of , approximately 1,270 light-years from Earth. Discovered by French astronomer on July 12, 1764, it was the first planetary nebula identified. The nebula is named for its hourglass or dumbbell shape, consisting of two expanding lobes of ionized gas and dust ejected from its central star. With an of 7.4, it spans about 8 by 5.7 arcminutes and is visible to the under very or easily with and small telescopes, best in late summer from the . Composed mainly of , oxygen, , and , it glows in colors including blue from oxygen, green from , and red from and , excited by ultraviolet radiation from the central . images reveal its prolate structure viewed equatorially, offering insights into the evolution of Sun-like stars.

Discovery and History

Discovery

The Dumbbell Nebula, designated as Messier 27 (M27), was discovered on July 12, 1764, by the French astronomer while he was systematically searching for comets in the constellation . Messier described the object in his notes as a "new and singular nebula; no star is at its center, it is of an oval form, and the center is brighter than the extremities," noting its faint and diffuse appearance without recognizing its true nature. This observation marked the first recorded identification of a , though at the time, such objects were not yet understood as the ejected shells of dying stars. Messier included the nebula as the 27th entry in his famous catalog of non-cometary celestial objects, compiled to aid comet hunters in distinguishing true from fixed "nebulae and star clusters." In the , the Dumbbell Nebula appeared comet-like due to its hazy, elongated form, fitting into Messier's broader effort to map deceptive sky features that could be confused with transient . Subsequent observations refined its classification; in 1784, British astronomer examined it and designated it as a based on its disk-like appearance resembling a planet.

Naming and Early Observations

The Dumbbell Nebula was first noted by on July 12, 1764, during his search for comets, and cataloged as M27 for its oval, starless appearance. In 1784, observed the object through his reflector telescope and described it as a bright of irregular round form with a diameter of about 3 or 4 arcseconds, much brighter in the middle, resembling a planet due to its uniform glow and lack of resolvable stars. The nebula's distinctive name originated from observations by , who in August 1828 viewed it with his 18.5-inch reflector and noted its hourglass or dumbbell shape, likening the bipolar lobes to a double-headed shot or exercise weight; this description was published in his 1833 catalog, where he designated it h 2001 and compared the form to a "dumb-bell." Alternative nicknames include the Apple Core Nebula, reflecting its compact, rounded central appearance in some views. In 1888, J. Louis Emil Dreyer included it in the as NGC 6853, standardizing its position at 19h 59m 35s and +22° 43'. Further details emerged in 1848 when William Parsons, 3rd Earl of Rosse, sketched the nebula using his newly operational 72-inch Leviathan telescope at , revealing a clear bipolar structure with elongated lobes extending from a brighter central bar, enhancing understanding of its non-spherical form beyond earlier disk-like impressions. By the , spectroscopic advancements confirmed its nature; in 1864, William Huggins applied to M27 and identified bright emission lines indicative of ionized gases, distinguishing it from stellar or true planetary objects and solidifying its classification as a —a term originally coined by for similar disk-shaped emissions.

Observational Characteristics

Location and Visibility

The Dumbbell Nebula resides in the constellation , the Fox, positioned near the prominent asterism formed by the stars , , and . Its precise celestial coordinates are 19h 59m 36.0s and +22° 43′ 16″ in the J2000 epoch. The nebula's location places it conveniently close to brighter stars such as in the neighboring constellation Cygnus, aiding in its identification during stargazing sessions. With an apparent magnitude of 7.5, the Dumbbell Nebula is bright enough to be glimpsed by the naked eye under exceptionally dark skies, though it is far more readily visible using basic optical aids. In the Northern Hemisphere, optimal viewing occurs during summer evenings, when Vulpecula rises high in the sky, with prime visibility spanning from July through October. Amateur astronomers often locate it by drawing an imaginary line from Gamma Lyrae through Beta Cygni (Albireo) and extending it equally beyond, or by moving northward about 3° from Gamma Sagittae. For observation, 50mm reveal the as a compact, fuzzy patch of light, providing an accessible entry point for beginners. Small telescopes with a 4-inch enhance the view, allowing resolution of the prominent central bar that hints at its distinctive shape, especially under clear, moonless conditions.

Appearance in Telescopes and

The Dumbbell Nebula presents a striking or shape in visual observations, featuring two symmetric lobes connected by a bright rectangular central bar that dominates the inner structure. In amateur telescopes with apertures around 8 inches, the nebula appears as a compact apple-core form, with the two lobes clearly defined against the central bar, while larger instruments reveal intricate filaments and dense knots scattered across the lobes, adding texture to the overall structure. Iconic imaging from the , taken in 2001, highlighted the detailed structure of the lobes and surrounding halo, showcasing the nebula's complex gaseous features in high resolution. A 2011 image from NASA's further illuminated cooler dust components, revealing intricate lanes of dust and molecular material encircling the central regions. Across multiple wavelengths, the nebula's appearance varies significantly: in optical light, it displays glowing ionized gas forming the prominent lobes and bar; observations emphasize the cooler and molecular remnants; and radio studies detect emissions from molecular , tracing the nebula's outer molecular envelope.

Physical Properties

Distance and Dimensions

The Dumbbell Nebula lies at a distance of approximately 1,350 light-years (413 parsecs) from , based on a statistical distance scale for planetary nebulae calibrated using astrometric data from the DR3 catalog of their central stars. Trigonometric measurements of the nebula's central star from DR3 yield a distance of about 1,260 light-years (387 parsecs), with uncertainties reflecting the challenges of precise for such objects. Earlier ground-based and observations provided a similar estimate of around 1,370 light-years (420 parsecs), confirming the nebula's proximity within the Galactic disk. The apparent of the nebula's bright central region measures 8 by 5.6 arcminutes, encompassing the prominent dumbbell-shaped structure visible in optical images. A faint outer halo extends the total to about 15 arcminutes, revealing diffuse ejected during the star's late evolutionary phases. At its established , these angular dimensions correspond to physical sizes of roughly 3.1 by 2.2 light-years for the main body and up to 5.9 light-years including the halo, highlighting the nebula's compact scale compared to larger interstellar structures. These linear extents are derived directly from the angular measurements scaled by the . Distance determinations for the Dumbbell Nebula rely on multiple complementary techniques to account for systematic uncertainties inherent in individual methods. Trigonometric parallax, the gold standard for nearby astronomical objects, measures the annual shift in the central star's position against background stars, with Gaia providing high-precision data across billions of sources. Expansion parallax offers an independent kinematic approach, utilizing proper motions of ionized knots traced via Hubble Space Telescope imaging combined with radial expansion velocities from spectroscopic observations, yielding consistent results within 10-20% of parallax-based values. Spectroscopic methods further refine estimates by analyzing line-of-sight velocities of emission features, such as those from [O III] lines, to model the nebula's three-dimensional expansion and constrain its depth along the line of sight.

Central Star Properties

The central star of the Dumbbell Nebula is a classified as spectral type DAO, characterized by prominent Balmer lines alongside absorption lines from He II. This reflects its status as a hot, -rich remnant in the post-asymptotic giant branch phase. The of the star is approximately 85,000 K, positioning it among the hottest known central stars of planetary nebulae and driving intense ultraviolet emission. With a visual magnitude of 13.5, it appears faint from but dominates the nebula's illumination. The star's mass is estimated at 0.56 ± 0.01 solar masses, and its radius measures 0.055 ± 0.02 solar radii, yielding an absolute bolometric magnitude of approximately -0.6—equivalent to roughly 150 times the Sun's luminosity, predominantly in the ultraviolet spectrum that ionizes the ejected envelope. Photometric observations reveal statistically significant variability in the star's brightness over timescales of years, though no clear periodic components have been identified. The central star may have a faint companion at magnitude 17.

Structure and Composition

Morphological Features

The Dumbbell Nebula exhibits a distinctive bipolar morphology, characterized by two prominent lobes of ionized gas extending along a symmetry axis inclined approximately 15° from the plane of the sky, separated by a dense equatorial that creates the characteristic or dumbbell shape. This structure arises from collimated outflows that have sculpted the nebula into multiple pairs of bipolar lobes, with opening angles around 30°, suggesting a multipolar configuration rather than a simple bipolar form. The central region features a cavity surrounding the progenitor , carved by fast stellar winds interacting with earlier remnants, which confines the bipolar expansions. Key morphological components include numerous cometary knots, which are dense globules of gas and dust with elongated tails pointing radially away from the central star, often displaying bright cusps on their ionization fronts facing the star. These knots, varying in size from about 17 billion to 56 billion kilometers and containing roughly three masses of material each, form at the interface between ionized and neutral regions, where stellar smaller particles and leave trailing structures. An inner shell of ionized gas delineates the bright lobes, while an outer halo of neutral material extends faintly beyond, contributing to the nebula's overall envelope. The nebula displays slight asymmetry, with the southern lobe appearing brighter and more elongated than the northern counterpart, evidenced by fan-shaped nebulosities and radial streamers that indicate non-uniform density distributions. This bipolar architecture is interpreted through models invoking binary interactions during the common-envelope phase of the or rapid rotation inducing equatorially enhanced mass loss, both mechanisms promoting the collimation observed in such planetary nebulae. In amateur telescopes, the dumbbell shape is readily apparent as two bright lobes, highlighting its accessibility for morphological study.

Chemical Makeup

The Dumbbell Nebula (M27) is primarily composed of ionized gas, with (H II) and (He II) as the dominant elements, alongside significant contributions from oxygen (O III), , and carbon. Spectroscopic analysis reveals helium abundance by number as approximately 0.12 relative to , while oxygen is enhanced at 12 + log(O/H) ≈ 8.6; and carbon are also present at notable levels, consistent with its classification as a Type I . These abundances reflect the chemical enrichment from the star's , ionized by radiation from the central . Dust content in the nebula includes both and carbon-rich grains, detected through observations that show emission features indicative of these materials. Molecular (H₂) is observed in the outer regions, particularly within dense globules of lower , suggesting remnants of the progenitor's envelope. Key spectroscopic features include strong forbidden emission lines, such as [O III] at 500.7 nm, which dominates the nebula's apple-green visual appearance and indicates low-density conditions in the ionized gas ( densities around 10³–10⁴ cm⁻³). Other prominent lines include [O II] at 372.7 nm, Hα, and Hβ, highlighting the stratified structure.

Formation and Evolution

Age and Expansion Dynamics

The Dumbbell Nebula displays a layered kinematic structure revealed through spectroscopic observations, with distinct expansion velocities across its shells. The central He II-emitting region remains nearly stationary, expanding at ≤7 km/s, while an inner [O III]-emitting shell expands at 13 km/s. The main outer [O III] shell reaches 31 km/s, and the surrounding [N II] shell extends to 35 km/s, with velocities increasing outward in a pattern indicative of ballistic expansion where material ejects at constant speeds proportional to . These velocities reflect the nebula's dynamical evolution, with the main shell's average expansion rate ranging from approximately 17 to 27 km/s based on integrated spectroscopic profiles across the bright bipolar structure. In the protruding lobes, velocities rise to as high as 40 km/s, driven by the bipolar morphology that channels faster material along the axis. proper motion studies from the 1990s and 2000s measured the central star's motion at 19.2 mas/yr, confirming the overall ballistic and supporting models of uniform ejection without significant . The nebula's age is derived from dynamical expansion, using the formula t = θ * d / v_exp, where θ is the angular radius, d is the distance, and v_exp is the expansion velocity, yielding estimates of 9,500 to 12,000 years since the onset of shell ejection. This range accounts for variations in measured velocities and distances, with a 1970 study reporting 31 km/s for the primary shell and an age of about 9,800 years at a then-assumed distance. Recent Gaia astrometry refines the central star's distance to 372 pc and proper motions, providing expansion parallax confirmation that aligns with or slightly lowers prior age estimates by improving distance precision.

Role in Planetary Nebula Research

The Dumbbell Nebula (Messier 27) is recognized as a prototypical due to its status as the first such object discovered, by on July 12, 1764, which facilitated early and ongoing comparative studies of these structures across the field. Its classic bipolar morphology has made it a benchmark for classifying and modeling aspherical , with detailed kinematic and structural analyses serving as references for understanding the diversity of shapes in this class. Key observational studies have advanced knowledge of the nebula's central and envelope. Far Ultraviolet Spectroscopic Explorer (FUSE) observations in the early 2000s detected hot molecular at approximately 2500 K surrounding the central , offering insights into the interaction between stellar and the ejected envelope during the post-asymptotic giant branch (AGB) phase. These spectra also revealed velocity stratification in atomic and molecular outflows, challenging models of nebular excitation and supporting the role of shocks from line-driven in shaping the structure. NASA's imaging in 2011 captured infrared emission from dust features, including radial spokes of molecular material, which helped quantify the remnants of AGB mass loss and test predictions for dust grain survival in ionized environments. The nebula has contributed significantly to broader research. Its well-resolved bipolar lobes have been used to validate hydrodynamical and magnetohydrodynamical models of asymmetric ejection, demonstrating how and binary interactions can produce point-symmetric features observed in many . Abundance studies, such as those measuring densities and states across its extent, have informed chemical evolution models, revealing enhancements in elements like and oxygen that trace AGB and mixing processes. Recent developments underscore its enduring value. A 2024 review of planetary nebulae evolution highlights Messier 27 as a key example in population synthesis models, integrating its and chemistry to refine estimates of progenitor masses and the fraction of bipolar forms among low- to intermediate-mass stars. As of November 2025, no major new observations have superseded these foundational contributions.

References

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  2. http://www.messier.seds.org/m/m027.html
  3. https://www.constellation-guide.com/dumbbell-nebula-messier-27/
  4. https://www.nasa.gov/image-article/dumbbell-nebula-hydrogen-oxygen/
  5. https://adsabs.harvard.edu/full/2002JHA....33...57H
  6. https://www.scifac.hku.hk/kwok/publication_reprint/kwok283.pdf
  7. https://science.nasa.gov/solar-system/skywatching/night-sky-network/the-summer-triangles-hidden-treasures/
  8. https://www.deepskycorner.ch/obj/m27.en.php
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  10. https://www.astronomy.com/observing/101-must-see-cosmic-objects-the-dumbbell-nebula/
  11. https://science.nasa.gov/asset/hubble/close-up-of-m27-the-dumbbell-nebula/
  12. https://esahubble.org/images/opo0306d/
  13. https://www.astro-photo.nl/deepsky/nebulae/m27-dumbbell-nebula-including-its-halo
  14. https://www.spitzer.caltech.edu/images/4409-sig11-011-Weighing-in-on-the-Dumbbell-Nebula
  15. https://www.messier-objects.com/messier-27-dumbbell-nebula/
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  18. https://academic.oup.com/mnras/article/543/3/3035/8266508
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  28. https://noirlab.edu/public/images/noao0121a/
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  33. https://ui.adsabs.harvard.edu/abs/1970ApJ...162...27B
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