Ring Nebula

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Ring Nebula
Emission nebula
Planetary nebula
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The Ring Nebula as seen in infrared and visible light by a multiple exposure of images from the James Webb Space Telescope's NIRCam, showing an outer layer of hydrogen that is very faint in visible light
Observation data: J2000 epoch
Right ascensionTemplate:RA[1]
DeclinationTemplate:DEC[1]
Distance2,570±90[1] ly   (790±30[1] pc)
Apparent magnitude (V)8.8[2]
Apparent dimensions (V)230″ × 230″[3]
ConstellationLyra
Physical characteristics
Radius1.3+0.8
−0.4Page Template:Citation/styles.css has no content.[a] ly
Absolute magnitude (V)−0.2+0.7
−1.8Page Template:Citation/styles.css has no content.[b]
DesignationsM 57, NGC 6720,[4] GC 4447.
See also: Lists of nebulae

The Ring Nebula is a planetary nebula in the northern constellation of Lyra,[5] about mid-way between the prominent stars Beta and Gamma Lyrae.[6] It is also catalogued as Messier 57, M57 and NGC 6720. The nebula was discovered by Charles Messier in 1779. It has an apparent visual magnitude of 8.8, which is too faint to be visible with the naked eye, but it can be readily observed with a small telescope.

File:The Ring Nebula M57 Goran Nilsson & The Liverpool Telescope.jpg
HaRGB image of the Ring Nebula (M57) showing the faint outer shells. The spiral galaxy IC 1296 can also be seen in the top left. Data from the Liverpool Telescope on La Palma, Islas Canarias (Canary Islands), Spain.

A planetary nebula is formed when a star, during the last stages of its evolution before becoming a white dwarf, expels a vast luminous envelope of ionized gas into the surrounding interstellar space. The progenitor star for the ring nebula is now a carbon-oxygen white dwarf with an apparent visual magnitude of +15.75. Based on parallax measurements, this star is located at a distance of approximately 2,570 light-years (790 pc) from the Sun. After expanding for 1,610 years, the nebula currently has a diameter of 4.6 ly.

History

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 persistent "planetary nebula" terminology).[7] 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.[8][9]

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.[10] 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.[11][12] The nebula was first photographed by the Hungarian astronomer Eugene von Gothard in 1886.[10]

Observation

File:M57-v2.png
Location of the Ring Nebula in the constellation Lyra

M57 is found 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.[13]

The nebula disk has an angular size of 1.5 × 1 arcminutes, making it too small to be resolved with 10×50 binoculars.[13] 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.[14] Using a UHC or OIII filter greatly enhances visual observation, particularly in light polluted areas. The interior hole can be resolved by a 10 cm (4 in) instrument at a magnification of 100×.[13] Larger instruments will show a few darker zones on the eastern and western edges of the ring and some faint nebulosity inside the disk.[15] The central star, at magnitude 14.8, is difficult to spot.[14]

Properties

M57 is 0.787 kpc (2,570 light-years) from Earth.[4] It has a visual magnitude of 8.8. Photographs taken over a period of 50 years show the rate of nebula expansion is roughly 1 arcsecond per century.[16] Spectroscopic observations show that the expansion velocity along the line of sight is 20–30 km/s. M57 is illuminated by a central white dwarf with an apparent magnitude of 15.75.[17]

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 emission lines are so-called "forbidden lines" which occur only in regions of very low density containing no more than a few thousand 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 contribute to the reddishness at 654.8 and 658.3 nm.[16]

Nebula structure

M57 is thought 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 estimated to be expanding for approximately 1,610 ± 240 years.[citation needed]

Central star

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

The central star 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 about 300 times more luminous than the Sun,[18] but its apparent magnitude is only +15.75.[17]

In 2025 JWST observed a dust disk around the central star.[18]

See also

Notes

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  1. Page Template:Citation/styles.css has no content.^ Radius = distance × sin(angular size / 2) = 2.3+1.5
    −0.7     kly     * sin(230″ / 2) = 1.3+0.8
    −0.4     ly
  2. Page Template:Citation/styles.css has no content.^ 8.8 apparent magnitude − 5 × (log10(700+450
    −200     pc     distance / 10 pc)) = −0.2+0.7
    −1.8     absolute magnitude

References

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  1. ^ a b c d Template:Cite Gaia DR3
  2. ^ Page Module:Citation/CS1/styles.css has no content.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. ^ Page Module:Citation/CS1/styles.css has no content.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. ^ a b Page Module:Citation/CS1/styles.css has no content."M 57". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2006-12-19. {{cite web}}: Invalid |mode=Script error: No such module "Citation mode". (help)
  5. ^ Page Module:Citation/CS1/styles.css has no content.Coe, Steven R. (2007). Nebulae and how to observe them. Astronomers' observing guides. Springer. p. 111. ISBN 978-1-84628-482-3.
  6. ^ Page Module:Citation/CS1/styles.css has no content.Plotner, Tammy (2009). The Night Sky Companion: A Yearly Guide to Sky-Watching 2009. The Patrick Moore Practical Astronomy Series. Springer Science & Business Media. p. 98. ISBN 978-0-387-79509-6.
  7. ^ Page Module:Citation/CS1/styles.css has no content.Olson, Don; Caglieris, Giovanni Maria (June 2017). "Who Discovered the Ring Nebula?". Sky & Telescope. pp. 32–7.
  8. ^ Page Module:Citation/CS1/styles.css has no content.Garfinkle, Robert A. (1997). Star-hopping: Your Visa to Viewing the Universe. Cambridge University Press. ISBN 978-0-521-59889-7. OCLC 37355269.
  9. ^ Page Module:Citation/CS1/styles.css has no content.Messier, Charles (1780). "Catalogue des Nébuleuses & des amas d'Étoiles". Connoissance des Temps for 1783. pp. 225–249.
  10. ^ a b Page Module:Citation/CS1/styles.css has no content.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.
  11. ^ Page Module:Citation/CS1/styles.css has no content.Frommert, Hartmut; Kronberg, Christine. "William Huggins (February 7, 1824 – May 12, 1910)". SEDS. Retrieved 2008-04-11.
  12. ^ Page Module:Citation/CS1/styles.css has no content.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.
  13. ^ a b c Page Module:Citation/CS1/styles.css has no content.Crossen, Craig; Rhemann, Gerald (2004). Sky Vistas: Astronomy for Binoculars and Richest-field Telescopes. Springer. p. 261. ISBN 978-3-211-00851-5.
  14. ^ a b Page Module:Citation/CS1/styles.css has no content.Dunlop, Storm (2005). Atlas of the Night Sky. Collins. ISBN 978-0-00-717223-8.
  15. ^ Page Module:Citation/CS1/styles.css has no content."M 57". Messier Objects Mobile — Charts, Maps & Photos. 2016-10-16.
  16. ^ a b Page Module:Citation/CS1/styles.css has no content.Karttunen, Hannu (2003). Fundamental Astronomy. Springer. pp. 314. ISBN 978-3-540-00179-9.
  17. ^ a b Page Module:Citation/CS1/styles.css has no content.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.
  18. ^ a b Page Module:Citation/CS1/styles.css has no content.Sahai, Raghvendra; Griet Van de Steene; Peter van Hoof; Zijlstra, Albert; Volk, Kevin; Dinerstein, Harriet L.; Barlow, Michael J.; Peeters, Els; Manchado, Arturo; Matsuura, Mikako; Cami, Jan; Cox, Nick L. J.; Aleman, Isabel; Bernard-Salas, Jeronimo; Clark, Nicholas; Justtanont, Kay; Kaplan, Kyle F.; Kavanagh, Patrick J.; Wesson, Roger (2025). "JWST observations of the Ring Nebula (NGC 6720): III. A dusty disk around its Central Star". The Astrophysical Journal. 985 (1): 101. arXiv:2504.01188. Bibcode:2025ApJ...985..101S. doi:10.3847/1538-4357/adc91c.

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