Ring Nebula

The Ring Nebula (also catalogued as Messier 57, M57 or NGC 6720) is a planetary nebula in the northern constellation of Lyra.[4] Such objects are formed when a shell of ionized gas is expelled into the surrounding interstellar medium by a star at the end of its asymptotic giant branch phase, in the last stages of its evolution before becoming a white dwarf.

The Ring Nebula M57 Goran Nilsson & The Liverpool Telescope
HaRGB image of the Ring Nebula (M57) showing the faint outer shells. Data from the Liverpool Telescope on La Palma.
The Ring Nebula
M57 The Ring Nebula
M57, The Ring Nebula (Hubble Space Telescope)
Observation data: J2000 epoch
Right ascension 18h 53m 35.079s[1]
Declination+33° 01′ 45.03″[1]
Distance2567±115[1] ly   (787±35[1] pc)
Apparent magnitude (V)8.8[2]
Apparent dimensions (V)230″ × 230″[3]
Physical characteristics
[a] ly
Absolute magnitude (V)−0.2+0.7
Notable features-
DesignationsM 57,[1] NGC 6720,[1] GC 4447.


This nebula was discovered by the French astronomer Charles Messier while searching for comets in late January 1779. Messier's report of his independent discovery of Comet Bode reached fellow French astronomer Antoine Darquier de Pellepoix two weeks later, who then independently rediscovered the nebula while following the comet. Darquier later reported that it was "...as large as Jupiter and resembles a planet which is fading" (which may have contributed to the use of the "planetary nebula" terminology).[5] It would be entered into Messier's catalogue as the 57th object. Messier and German-born astronomer William Herschel speculated that the nebula was formed by multiple faint stars that were unresolvable with his telescope.[6][7]

In 1800, German Count Friedrich von Hahn announced that he had discovered the faint central star at the heart of the nebula a few years earlier. He also noted that the interior of the ring had undergone changes, and said he could no longer find the central star.[8] In 1864, English amateur astronomer William Huggins examined the spectra of multiple nebulae, discovering that some of these objects, including M57, displayed the spectra of bright emission lines characteristic of fluorescing glowing gases. Huggins concluded that most planetary nebulae were not composed of unresolved stars, as had been previously suspected, but were nebulosities.[9][10] The nebula was first photographed by the Hungarian astronomer Eugene von Gothard in 1886.[8]


Vega in lyra
Location of M57 in the constellation Lyra.

Messier 57 is located south of the bright star Vega, which forms the northwestern vertex of the Summer Triangle asterism. The nebula lies about 40% of the distance from Beta (β) to Gamma (γ) Lyrae, making it an easy target for amateur astronomers to find.[11]

The nebula disk has an angular size of 1.5 × 1 arcminutes, making it too small to be resolved with 10×50 binoculars.[11] It is best observed using a telescope with an aperture of at least 20 cm (8 in), but even a 7.5 cm (3 in) telescope will reveal its elliptical ring shape.[12] The interior hole can be resolved by a 10 cm (4 in) instrument at a magnification of 100×.[11] Larger instruments will show a few darker zones on the eastern and western edges of the ring, and some faint nebulosity inside the disk.[13] The central star, at magnitude 14.8, is difficult to spot.[12]


M57 is 0.787 kpc (2,570 light-years) from Earth.[1] It has a visual magnitude of 8.8v and photographic magnitude of 9.7p. Photographs taken over a period of 50 years[14] show the rate of nebula expansion is roughly 1 arcsecond per century, which corresponds to spectroscopic observations as 20–30 km s−1. M57 is illuminated by a central white dwarf or planetary nebula nucleus (PNN) of 15.75v visual magnitude.[15]

All the interior parts of this nebula have a blue-green tinge that is caused by the doubly ionized oxygen emission lines at 495.7 and 500.7 nm. These observed so-called "forbidden lines" occur only in conditions of very low density containing a few atoms per cubic centimeter. In the outer region of the ring, part of the reddish hue is caused by hydrogen emission at 656.3 nm, forming part of the Balmer series of lines. Forbidden lines of ionized nitrogen or [N II] contributes to the reddishness at 654.8 and 658.3 nm.[14]

Nebula structure

M57 is an example of the class of planetary nebulae known as bipolar nebulae, whose thick equatorial rings visibly extend the structure through its main axis of symmetry. It appears to be a prolate spheroid with strong concentrations of material along its equator. From Earth, the symmetrical axis is viewed at about 30°. Overall, the observed nebulosity has been currently estimated to be expanding for approximately 1,610 ± 240 years.

Structural studies find this planetary exhibits knots characterized by well developed symmetry. However, these are only silhouettes visible against the background emission of the nebula's equatorial ring. M57 may include internal N II emission lines located at the knots' tips that face the PNN; however, most of these knots are neutral and appear only in extinction lines. Their existence shows they are probably only located closer to the ionization front than those found in the Lupus planetary IC 4406. Some of the knots do exhibit well-developed tails which are often detectable in optical thickness from the visual spectrum.[3][16]

Planetary nebula nucleus (PNN)

The central PNN was discovered by Hungarian astronomer Jenő Gothard on September 1, 1886, from images taken at his observatory in Herény, near Szombathely (now part of Szombathely). Within the last two thousand years, the central star of the Ring Nebula has left the asymptotic giant branch after exhausting its supply of hydrogen fuel. Thus it no longer produces its energy through nuclear fusion and, in evolutionary terms, it is now becoming a compact white dwarf star.

The PNN now consists primarily of carbon and oxygen with a thin outer envelope composed of lighter elements. Its mass is about 0.61–0.62 M, with a surface temperature of 125,000 ± 5,000 K. Currently it is 200 times more luminous than the Sun, but its apparent magnitude is only +15.75.[15]


Hubble reveals the Ring Nebula’s true shape

Hubble image of the Ring Nebula

The Ring Nebula M57

The Ring Nebula captured with a DSLR camera


The Ring Nebula in infrared

See also


  1. ^ Radius = distance × sin(angular size / 2) = 2.3+1.5
    * sin(230″ / 2) = 1.3+0.8
  2. ^ 8.8 apparent magnitude − 5 × (log10(700+450
    distance / 10 pc)) = −0.2+0.7
    absolute magnitude


  1. ^ a b c d e f g "M 57". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2006-12-19.
  2. ^ Murdin, P. (2000). "Ring Nebula (M57, NGC 6720)". In Paul Murdin (ed.). Encyclopedia of Astronomy and Astrophysics. Institute of Physics Publishing. Bibcode:2000eaa..bookE5323.. doi:10.1888/0333750888/5323. ISBN 978-0-333-75088-9. Article ID #5323.
  3. ^ a b O'Dell, C. R.; Balick, B.; Hajian, A. R.; Henney, W. J.; Burkert, A. (2002). "Knots in Nearby Planetary Nebulae". Astronomical Journal. 123 (6): 3329–3347. Bibcode:2002AJ....123.3329O. doi:10.1086/340726.
  4. ^ Coe, Steven R. (2007). Nebulae and how to observe them. Astronomers' observing guides. Springer. p. 111. ISBN 978-1-84628-482-3.
  5. ^ Olson, Don; Caglieris, Giovanni Maria (June 2017). "Who Discovered the Ring Nebula?". Sky & Telescope. pp. 32–7.
  6. ^ Garfinkle, Robert A. (1997). Star-hopping: Your Visa to Viewing the Universe. Cambridge University Press. ISBN 978-0-521-59889-7. OCLC 37355269.
  7. ^ Messier, Charles (1780). "Catalogue des Nébuleuses & des amas d'Étoiles". Connoissance des Temps for 1783. pp. 225–249.
  8. ^ a b Steinicke, Wolfgang (2010). Observing and Cataloguing Nebulae and Star Clusters: From Herschel to Dreyer's New General Catalogue. Cambridge University Press. pp. 42–43. ISBN 978-0-521-19267-5.
  9. ^ Frommert, Hartmut; Kronberg, Christine. "William Huggins (February 7, 1824 – May 12, 1910)". SEDS. Retrieved 2008-04-11.
  10. ^ Huggins, W.; Miller, W. A. (1863–1864). "On the Spectra of Some of the Nebulae. And On the Spectra of Some of the Fixed Stars". Proceedings of the Royal Society of London. 13: 491–493. doi:10.1098/rspl.1863.0094. JSTOR 112077.
  11. ^ a b c Crossen, Craig; Rhemann, Gerald (2004). Sky Vistas: Astronomy for Binoculars and Richest-field Telescopes. Springer. p. 261. ISBN 978-3-211-00851-5.
  12. ^ a b Dunlop, Storm (2005). Atlas of the Night Sky. Collins. ISBN 978-0-00-717223-8.
  13. ^ "M 57". Messier Objects Mobile — Charts, Maps & Photos. 2016-10-16.
  14. ^ a b Karttunen, Hannu (2003). Fundamental Astronomy. Springer. p. 314. ISBN 978-3-540-00179-9.
  15. ^ a b O'Dell, C. R.; Sabbadin, F.; Henney, W. J. (2007). "The Three-Dimensional Ionization Structure and Evolution of NGC 6720, The Ring Nebula". Astronomical Journal. 134 (4): 1679–1692. Bibcode:2007AJ....134.1679O. doi:10.1086/521823.
  16. ^ O'Dell, C. R.; Balick, B.; Hajian, A. R.; Henney, W. J.; Burkert, A. (2003). "Knots in Planetary Nebulae". Revista Mexicana de Astronomía y Astrofísica, Serie de Conferencias. 15: 29–33. Bibcode:2003RMxAC..15...29O.

External links


73P/Schwassmann–Wachmann, also known as Schwassmann–Wachmann 3, is a periodic comet in the Solar System that is in the process of disintegrating. Starting the 2011 perihelion passage the primary component 73P-C was recovered on 28 November 2010 near apparent magnitude 21.3; it came to perihelion (closest approach to the Sun) on 16 October 2011.Comet Schwassmann–Wachmann 3 was one of the comets discovered by astronomers Arnold Schwassmann and Arno Arthur Wachmann, working at the Hamburg Observatory in Bergedorf, Germany. It began disintegrating on its re-entry to the inner Solar System in 1995, in a reaction triggered by the Sun's heating of the comet as it emerged from the colder regions of the outer Solar System.

Comet 73P is a parent body of meteor shower Tau Herculids.

The comet was discovered as astronomers were exposing photographic plates in search of minor planets for a minor planet survey, on May 2, 1930. The comet was lost after its 1930 apparition, but was observed several more times.

73P/Schwassmann–Wachmann has an orbital period of slightly less than 5 1/3 years so that it comes nearest to the Earth every 16 years. The primary fragment 73P-C has an Earth-MOID of 0.04 AU (6,000,000 km; 3,700,000 mi). 73P was originally estimated to have a core diameter of 1100 meters.

Antoine Darquier de Pellepoix

Antoine Darquier de Pellepoix (23 November 1718, in Toulouse – 18 January 1802, in Toulouse) was a French astronomer. He has usually been credited with the discovery of the Ring Nebula in 1779, but in fact he independently rediscovered it upon reading a report of Charles Messier regarding Messier's own observations of Comet Bode. His description that the object was "...as large as Jupiter and resembles a planet which is fading" led to the terminology "planetary nebula".

Bubble Nebula (NGC 6822)

The Bubble Nebula in Barnard's Galaxy has the official designation of Hubble 1925 I as it was the first (Roman numeral 1) object recorded in a paper by E. Hubble 1925. It includes areas of bright H II emission. It is located north-west of the larger Hubble 1925 III.

Cometary knot

Cometary knots are structures observed in several nearby planetary nebulae, including the Helix Nebula (NGC 7293), the Ring Nebula (NGC 6720), the Dumbbell Nebula (NGC 6853), the Eskimo Nebula (NGC 2392), and the Retina Nebula (IC 4406). It is believed that they are a common feature of the evolution of planetary nebulae, but can only be resolved in the nearest examples. They are generally larger than the size of the Solar system (i.e. the orbit of Pluto), with masses comparable to that of the Earth.The knots represent "the ionized 'skin' of a dense, dusty molecular globule" that forms a crescent-shaped structure where it is ionized and illuminated by the central star, with a trailing spoke or tail. The central globule is at least 1000 times denser than the surrounding material that streams past it. The appearance is analogous to the tail of a comet that faces away from its star, but comets are solid bodies and much smaller in overall size and mass.

On the near side of the Helix Nebula, the central dusty globule of each cometary knot appears dark against the background of a central spherical shell that emits [O III] 5007 Angstrom light. Those on the far side do not obstruct this light source and so do not have this dark appearance.

Diamond ring nebula

Diamond ring nebula may refer to:

Abell 33

Abell 70

Emission nebula

An emission nebula is a nebula formed of ionized gases that emit light of various wavelengths. The most common source of ionization is high-energy photons emitted from a nearby hot star. Among the several different types of emission nebulae are H II regions, in which star formation is taking place and young, massive stars are the source of the ionizing photons; and planetary nebulae, in which a dying star has thrown off its outer layers, with the exposed hot core then ionizing them.

Friedrich von Hahn

Friedrich II. Graf von Hahn (July 27, 1742 – October 9, 1805) was a German nobleman, a philosopher and astronomer. He suggested the Doppler effect before Doppler.Von Hahn was born in Neuhaus, Holstein. In 1793 he started the construction of a private observatory, the first in Mecklenburg, which was well equipped.

He owned some of the largest mirrors made by William Herschel and precision instruments for determining the position of stars. In 1800, he discovered the central star in M57, the Ring Nebula in the constellation Lyra.

He died in Remplin, Mecklenburg. After his death, his son, the "theatrical count" and father of author Ida, Countess von Hahn-Hahn, squandered his fortune and all books and instruments were sold. The best instruments were bought by Friedrich Wilhelm Bessel for the new observatory in Königsberg. One instrument is on display in the Deutsches Museum in Munich. His herschelian telescope was acquired in 1812 by the Neapolitan astronomer, Federigo Zuccari, for the new Capodimonte Observatory . Now the mirror of this telescope is part of the Observatory Museum collection.

He is honoured together with Otto Hahn by the lunar crater Hahn.

Helix Nebula

The Helix Nebula, also known as The Helix, NGC 7293, is a large planetary nebula (PN) 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 distance, having now been measured by GAIA, is 655±13 light-years. It is similar in appearance to the Cat's Eye Nebula and the Ring Nebula, whose size, age, and physical characteristics are similar to the Dumbbell Nebula, varying only in its relative proximity and the appearance from the equatorial viewing angle. The Helix Nebula has sometimes been referred to as the "Eye of God" in pop culture, as well as the "Eye of Sauron".

Hubble Heritage Project

The Hubble Heritage Project was founded by a group of astronomers in 1998. The team releases on an almost monthly basis pictures of celestial objects like planets, stars, galaxies and galaxy clusters.

A team of astronomers and image processing specialists selects images from the Hubble Space Telescope's public data archive, which are usually only shared within the astronomical community. Because most of the photos were taken for scientific reasons they often lack sufficient exposure across a range of colors. A small amount of observation time with the Hubble Space Telescope has been granted to the team to fill in the gaps in these images.

The Project has been recognized for its contribution to public inspiration in producing some of the most aesthetically pleasing images ever produced in astronomy. Achievements for the team include the Astronomical Society of the Pacific 2003 Klumpke-Roberts Award for "outstanding contributions to the public understanding and appreciation of astronomy." In 2002, two Heritage images were selected in the Rochester Institute of Technology's "Images From Science" traveling gallery exhibit. Several images have been selected by the US and UK postal systems. In 2000, a first-class US postage stamp showing the Ring Nebula was one of five Hubble images selected to be part of a commemorative series of stamps honoring astronomer Edwin P. Hubble.

The website of the project contains a lot of information about the NASA/ESA Hubble Space Telescope, including a lot of interesting images taken by the Hubble, and information about the future of Hubble. The images on the site are the most notable ones taken by Hubble, and are specifically enhanced with color for release to the public. They are available in different formats, including as computer wallpapers.

List of planetary nebulae

The following is an incomplete list of known planetary nebulae.

Little Dumbbell Nebula

The Little Dumbbell Nebula, also known as Messier 76, NGC 650/651, the Barbell Nebula, or the Cork Nebula, is a planetary nebula in the constellation Perseus. It was discovered by Pierre Méchain in 1780 and included in Charles Messier's catalog of comet-like objects as number 76. It was first recognised as a planetary nebula in 1918 by the astronomer Heber Doust Curtis. However, there is some contention to this claim, as Isaac Roberts in 1891 did suggest that M76 might be similar to the Ring Nebula (M57), being instead as seen from the side view. The structure is now classed as a bipolar planetary nebula (BPNe).

Distance to M76 is currently estimated as 780 parsecs or 2,500 light years, making the average dimensions about 0.378 pc. (1.23 ly.) across.The total nebula shines at the apparent magnitude of +10.1 with its central star or planetary nebula nucleus (PNN) at +15.9v (16.1B) magnitude. The UV-light from the PNN is expanding outer layers that form the present nebula, and has the surface temperature of about 88,400 K. The whole planetary nebula is approaching us at 19.1 km/s.The Little Dumbbell Nebula derives its common name from its resemblance to the Dumbbell Nebula (M27) in Vulpecula. It was originally thought to consist of two separate emission nebulae and was thus given two catalog numbers in the NGC 650 and 651. Some consider this object to be one of the faintest and hardest to see objects in Messier's list.


Lyra (; Latin for lyre, from Greek λύρα) is a small constellation. It is one of 48 listed by the 2nd century astronomer Ptolemy, and is one of the 88 constellations recognized by the International Astronomical Union. Lyra was often represented on star maps as a vulture or an eagle carrying a lyre, and hence is sometimes referred to as Vultur Cadens or Aquila Cadens ("Falling Vulture" or "Falling Eagle"), respectively. Beginning at the north, Lyra is bordered by Draco, Hercules, Vulpecula, and Cygnus. Lyra is visible from the northern hemisphere from spring through autumn, and nearly overhead, in temperate latitudes, during the summer months. From the southern hemisphere, it is visible low in the northern sky during the winter months.

Vega, Lyra's brightest star, is one of the brightest stars in the night sky, and forms a corner of the famed Summer Triangle asterism. Beta Lyrae is the prototype of a class of stars known as Beta Lyrae variables. These binary stars are so close to each other that they become egg-shaped and material flows from one to the other. Epsilon Lyrae, known informally as the Double Double, is a complex multiple star system. Lyra also hosts the Ring Nebula, the second-discovered and best-known planetary nebula.

NGC 3132

NGC 3132, also known as the Eight-Burst Nebula, the Southern Ring Nebula, is a bright and extensively studied planetary nebula in the constellation Vela. Its distance from Earth is estimated at about 613 pc. or 2,000 light-years.

NGC 6822

NGC 6822 (also known as Barnard's Galaxy, IC 4895, or Caldwell 57) is a barred irregular galaxy approximately 1.6 million light-years away in the constellation Sagittarius. Part of the Local Group of galaxies, it was discovered by E. E. Barnard in 1884 (hence its name), with a six-inch refractor telescope. It is one of the closer galaxies to the Milky Way. It is similar in structure and composition to the Small Magellanic Cloud. It is about 7,000 light-years in diameter.

Planetary nebula

A planetary nebula, abbreviated as PN or 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 arguably a misnomer because they are unrelated to planets or exoplanets. The true origin of the term was likely derived from the planet-like round shape of these nebulae as observed by astronomers through early telescopes, and although the terminology is inaccurate, it is still used by astronomers today. The first usage may have occurred during the 1780s with the English astronomer William Herschel who described these nebulae as resembling planets; however, as early as January 1779, the French astronomer Antoine Darquier de Pellepoix described in his observations of the Ring Nebula, "... very dim but perfectly outlined; it is as large as Jupiter and resembles a fading planet."All planetary nebulae form at the end of intermediate massed star's lifetimes. They are a relatively short-lived phenomenon, lasting perhaps a few tens of thousands of years, compared to considerably longer phases of stellar evolution. Once all of the red giant's atmosphere has been dissipated, energetic ultraviolet radiation from the exposed hot luminous core, called a planetary nebula nucleus (PNN), ionizes the ejected material. Absorbed ultraviolet light then energises the shell of nebulous gas around the central star, causing it to appear as a brightly coloured planetary nebula.

Planetary nebulae likely play a crucial role in the chemical evolution of the Milky Way by expelling elements into the interstellar medium from stars where those elements were created. Planetary nebulae are observed in more distant galaxies, yielding useful information about their chemical abundances.

Starting from the 1990s, Hubble Space Telescope images revealed that many planetary nebulae have extremely complex and varied morphologies. About one-fifth are roughly spherical, but the majority are not spherically symmetric. The mechanisms that produce such a wide variety of shapes and features are not yet well understood, but binary central stars, stellar winds and magnetic fields may play a role.

Ring Nebula (NGC 6822)

The Ring Nebula in Barnard's Galaxy has the official designation of Hubble 1925 III as it was the third (Roman numeral 3) object recorded in Hubble's 1925 paper, N.G.C. 6822, A Remote Stellar System. It includes areas of bright H II emission. In Paul W. Hodge's 1977 paper it was designated Hodge 4.

Its appearance is very similar to the filamentary nebula found in the Large Magellanic Cloud (see Meaburn 1981). It most resembles the circular ring-like nebula N70 in the LMC.

Shapley 1

Shapley 1 (Sp 1 or PLN 329+2.1) is an annular planetary nebula in the constellation of Norma with a magnitude of +12.6. As viewed from Earth, it is peculiar in that it seems to be a non-bipolar, torus-shaped planetary nebula. However, it is thought that this is due to the viewpoint of looking directly down on a binary system whose orbit is perpendicular to Earth.Discovered in 1936 by Harlow Shapley, it is approximately 4900 light years from Earth, and is around 8700 years old. At the center of the nebula is a magnitude 14 white dwarf star. It has an angular diameter of 1.1 arc minutes, which makes it about one-third (.32) of a light year across.

WR 124

WR 124 is a Wolf–Rayet star in the constellation of Sagitta surrounded by a ring nebula of expelled material known as M1-67. It is one of the fastest runaway stars in the galaxy with a radial velocity around 200 km/s. It was discovered by Paul W. Merrill in 1938, identified as a high velocity Wolf–Rayet star. It is listed in the General Catalogue of Variable Stars as QR Sagittae with a range of 0.08 magnitudes.

WR 7

WR 7 (HD 56925) is a Wolf–Rayet star in the constellation of Canis Major. It lies at the centre of a complex bubble of gas which is shocked and partially ionised by the star's radiation and winds.

The distance is uncertain, with estimates between 3.5 kiloparsecs (11,410 light-years) and 6.9 kiloparsecs (22,500 light-years). Assuming a distance of 4.8 kiloparsecs (15,600 light-years), this star is calculated to be 280,000 times brighter than our Sun] 16 times more massive, and 1.41 times larger with a surface temperature of 112,000 K.

Stars of its kind are characterised by a rapid loss of stellar mass, driven by chemically enriched high-speed stellar winds. It is estimated that it loses mass at the rate of 7x10−5 solar masses each year through winds of 1,545 km/s.The ring nebula NGC 2359 is excited by the ionising radiation of WR7. It is also known as Thor's Helmet or the Duck Nebula. The ring is approximately 4pc across and prominent at wavelengths from radio to X-ray.

See also

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