Editing Ring Nebula

{{short description|Planetary nebula in Lyra}}
{{for|another object|Ring Nebula (NGC 6822)}}
{{Infobox Planetary nebula
|type= Planetary
| name = Ring Nebula
| image = Webb captures detailed beauty of Ring Nebula (NIRCam image) (weic2320b).jpg
| caption = The Ring Nebula as seen in [[infrared]] and [[visible light]] by a [[multiple exposure]] of images from the [[w:James Webb Space Telescope|James Webb Space Telescope]]'s [[NIRCam]], showing an outer layer of [[w:hydrogen|hydrogen]] that is very faint in visible light
| credit = [[NASA]]/[[STScI]]/[[Association of Universities for Research in Astronomy|AURA]]
| epoch = [[J2000]]
| ra = {{RA|18|53|35.079}}<ref name="simbad">
{{cite simbad
  | title=M 57
  | access-date=2006-12-19 |df=ymd
}}</ref>
| dec = {{DEC|+33|01|45.03}}<ref name="simbad" />
| dist_ly = {{val|2567|115}}<ref name="simbad" />
| dist_pc = {{val|787|35}}<ref name="simbad" />
| radius_ly = {{val|1.3|+0.8|-0.4}}{{Ref label|A|a|none}}
| appmag_v = 8.8<ref name="Murdin2000">
{{cite book
  | author=Murdin, P.
  | date=2000
  | chapter=Ring Nebula (M57, NGC 6720)
  | editor=Paul Murdin
  | title=Encyclopedia of Astronomy and Astrophysics
  | id = Article ID #5323
  | publisher=[[Institute of Physics Publishing]]
  | bibcode=2000eaa..bookE5323.
  | doi=10.1888/0333750888/5323
  | isbn=978-0-333-75088-9
}}</ref>
| size_v = 230″ × 230″<ref name="ODelletal2002" />
| constellation = [[Lyra]]
<!-- invalid parameter | diameter_ly = 0.9 ly -->
| absmag_v = {{val|-0.2|+0.7|-1.8}}{{Ref label|B|b|none}}
| names = [[Messier object|M]] 57,<ref name="simbad" /> [[New General Catalogue|NGC]] 6720,<ref name="simbad" /> [[Boss General Catalogue|GC]] 4447.
}}

The '''Ring Nebula''' (also catalogued as '''Messier 57''', '''M57''' and '''NGC 6720''') is a [[planetary nebula]] in the northern [[constellation]] of [[Lyra]].<ref name=coe2007/>{{Ref label|C|C|none}} Such a [[nebula]] is formed when a star, during the last stages of its [[stellar evolution|evolution]] before becoming a [[white dwarf]], expels a vast luminous envelope of ionized gas into the surrounding [[interstellar space]]. [[File:The Ring Nebula M57 Goran Nilsson & The Liverpool Telescope.jpg|thumb|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]].]]

==History==
This nebula was discovered by the French astronomer [[Charles Messier]] while searching for [[comet]]s 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).<ref>
{{cite magazine
| last1        = Olson
| first1       = Don
| last2        = Caglieris
| first2       = Giovanni Maria
| date         = June 2017
| title        = Who Discovered the Ring Nebula?
| magazine     = Sky & Telescope
| pages        = 32–7
}}</ref> It would be entered into [[Messier object|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.<ref>
{{cite book
 | first=Robert A. | last=Garfinkle
 | date=1997
 | title=Star-hopping: Your Visa to Viewing the Universe
 | publisher=[[Cambridge University Press]]
 | isbn=978-0-521-59889-7
 | oclc=37355269
}}
</ref><ref>
{{cite book
 | first=Charles | last=Messier
 | date=1780
 | chapter=Catalogue des Nébuleuses & des amas d'Étoiles
 | title=Connoissance des Temps for 1783
 | pages=225–249
}}</ref>

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.<ref name=steinicke2010/> In 1864, English [[Amateur astronomy|amateur astronomer]] [[William Huggins]] examined the spectra of multiple nebulae, discovering that some of these objects, including M57, displayed the spectra of bright [[emission line]]s 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.<ref>
{{cite web
 | last=Frommert | first=Hartmut
 |author2=Kronberg, Christine
  | url=http://messier.seds.org/xtra/Bios/huggins.html
 | title=William Huggins (February 7, 1824 – May 12, 1910)
 | publisher=[[Students for the Exploration and Development of Space|SEDS]]
 | access-date=2008-04-11 |df=ymd
}}</ref><ref>
{{cite journal
 | last=Huggins | first=W.
 |author2=Miller, W. A.
  | title=On the Spectra of Some of the Nebulae. And On the Spectra of Some of the Fixed Stars
 | journal=[[Proceedings of the Royal Society of London]]
 | date=1863–1864 | volume=13
 | pages=491–493
 | jstor=112077
 | doi=10.1098/rspl.1863.0094
| doi-access=free
 }}</ref> The nebula was first photographed by the Hungarian astronomer [[Eugene von Gothard]] in 1886.<ref name=steinicke2010/>

==Observation==
[[File:M57-v2.png|thumb|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 Lyrae|Beta]] (β) to [[Gamma Lyrae|Gamma]] (γ) Lyrae, making it an easy target for [[Amateur astronomy|amateur astronomers]] to find.<ref name=crossen_rhemann2004/>

The nebula disk has an angular size of {{nowrap|1.5 × 1 [[Minute and second of arc|arcminutes]]}}, making it too small to be resolved with 10×50 [[binoculars]].<ref name=crossen_rhemann2004/> It is best observed using a [[telescope]] with an [[aperture]] of at least {{Convert|20|cm|abbr=on|sigfig=1}}, but even a {{Convert|7.5|cm|abbr=on|sigfig=1}} telescope will reveal its elliptical ring shape.<ref name="nightsky">
 {{cite book
  | last = Dunlop
  | first = Storm
  | author-link = Storm Dunlop
  | title = Atlas of the Night Sky
  | url = https://archive.org/details/collinsatlasofni0000dunl
  | url-access = registration
  | publisher = [[HarperCollins|Collins]]
  | date = 2005
  | isbn = 978-0-00-717223-8
}}
</ref> Using a UHC or OIII filter greatly enhances visual observation, particularly in [[Light pollution|light polluted]] areas. The interior hole can be resolved by a {{Convert|10|cm|abbr=on|sigfig=1}} instrument at a magnification of 100×.<ref name=crossen_rhemann2004/> Larger instruments will show a few darker zones on the eastern and western edges of the ring and some faint nebulosity inside the disk.<ref>{{cite web |url=https://messierobjects101.com/messier-object-m57-ring-nebula/ |title=M 57 |website=Messier Objects Mobile — Charts, Maps & Photos |df=ymd|date=2016-10-16 }}</ref> The central [[star]], at magnitude 14.8, is difficult to spot.<ref name="nightsky" />

==Properties==
M57 is {{Convert|0.787|kpc|ly|abbr=in|lk=on}} from [[Earth]].<ref name="simbad" /> It has a [[Apparent magnitude|visual magnitude]] of 8.8 and a dimmer [[photographic magnitude]], of 9.7. Photographs taken over a period of 50 years<ref name=karttunen/> show the rate of nebula expansion is roughly 1&nbsp;[[Minute and second of arc|arcsecond]] per century, which corresponds to spectroscopic observations as 20–{{val|30|u=km/s}}. M57 is illuminated by a central [[white dwarf]] of 15.75v [[Apparent magnitude|visual magnitude]].<ref name=apj134/>

All the interior parts of this nebula have a blue-green tinge that is caused by the doubly ionized [[oxygen]] [[emission line]]s at 495.7 and 500.7&nbsp;[[nanometer|nm]]. These observed so-called "[[forbidden line]]s" 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&nbsp;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&nbsp;nm.<ref name=karttunen>
{{cite book
 | first=Hannu | last=Karttunen
 | date=2003
 | title=Fundamental Astronomy
 | url=https://archive.org/details/fundamentalastro00kart_973 | url-access=limited | pages=[https://archive.org/details/fundamentalastro00kart_973/page/n315 314]
 | publisher=[[Springer (publisher)|Springer]]
 | isbn=978-3-540-00179-9
}}</ref>

===Nebula structure===
M57 is of the class of such starburst nebulae known as [[Bipolar nebula|bipolar]], 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 nebula 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 central star; 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 (constellation)|Lupus]] planetary [[IC 4406]]. Some of the knots do exhibit well-developed tails which are often detectable in optical thickness from the visual spectrum.<ref name="ODelletal2002">
{{cite journal
  | author=O'Dell, C. R.
  | author2=Balick, B.
  | author3=Hajian, A. R.
  | author4=Henney, W. J.
  | author5=Burkert, A.  | date=2002
  | title=Knots in Nearby Planetary Nebulae
  | journal=[[Astronomical Journal]]
  | volume=123 | issue=6 | pages=3329–3347
  | bibcode=2002AJ....123.3329O
  | doi=10.1086/340726
| doi-access=free
  }}</ref><ref name="ODelletal2003">
{{cite journal
  | last1=O'Dell | first1=C. R.
  | last2=Balick | first2=B.
  | last3=Hajian | first3=A. R.
  | last4=Henney | first4=W. J.
  | last5=Burkert | first5=A.
  | date=2003
  | title=Knots in Planetary Nebulae
  | journal=Revista Mexicana de Astronomía y Astrofísica, Serie de Conferencias
  | volume=15  | pages=29–33
  | bibcode=2003RMxAC..15...29O
}}</ref>

===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]] after exhausting its supply of [[hydrogen]] fuel. Thus it no longer produces its energy through [[nuclear fusion]] and, in [[stellar evolution|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 {{Solar mass|0.61–0.62}}, with a surface temperature of {{val|fmt=commas|125,000|5,000|ul=K}}. Currently it is 200 times more luminous than the [[Sun]], but its [[apparent magnitude]] is only +15.75.<ref name=apj134>
{{cite journal
 | last=O'Dell | first=C. R.
 |author2=Sabbadin, F. |author3=Henney, W. J.
  | date=2007
 | title=The Three-Dimensional Ionization Structure and Evolution of NGC 6720, The Ring Nebula
 | journal=[[Astronomical Journal]]
 | volume=134 | issue=4 | pages=1679–1692
 | bibcode=2007AJ....134.1679O
 | doi=10.1086/521823
| doi-access=free| url=https://www.openaccessrepository.it/record/99251/files/fulltext.pdf| archive-url=https://web.archive.org/web/20240220232803/https://www.openaccessrepository.it/record/99251/files/fulltext.pdf| url-status=dead| archive-date=February 20, 2024}}</ref>

In 2025 [[James Webb Space Telescope|JWST]] observed a dust disk around the central star.<ref>{{cite arXiv |eprint=2504.01188 |last1=Sahai |first1=Raghvendra |author2=Griet Van de Steene |author3=Peter van Hoof |last4=Zijlstra |first4=Albert |last5=Volk |first5=Kevin |last6=Dinerstein |first6=Harriet L. |last7=Barlow |first7=Michael J. |last8=Peeters |first8=Els |last9=Manchado |first9=Arturo |last10=Matsuura |first10=Mikako |last11=Cami |first11=Jan |last12=Cox |first12=Nick L. J. |last13=Aleman |first13=Isabel |last14=Bernard-Salas |first14=Jeronimo |last15=Clark |first15=Nicholas |last16=Justtanont |first16=Kay |last17=Kaplan |first17=Kyle F. |last18=Kavanagh |first18=Patrick J. |last19=Wesson |first19=Roger |title=JWST observations of the Ring Nebula (NGC 6720): III. A dusty disk around its Central Star |date=2025 |class=astro-ph.SR }}</ref>

==See also==
* [[List of planetary nebulae]]
* [[Messier object]]
* [[New General Catalogue]]
* [[List of Messier objects]]
* [[NGC 6565]], which is undergoing a similar process and is of the same type

== Notes ==
{{refbegin}}
<ol type="a">
<li>{{Note label|A|a|none}}Radius = distance × sin(angular size / 2) = {{val|2.3|+1.5|-0.7|u=kly}} * sin(230″ / 2) = {{val|1.3|+0.8|-0.4|u=ly}}</li>
<li>{{Note label|B|b|none}}8.8 apparent magnitude − 5 × (log<sub>10</sub>({{val|700|+450|-200|u=pc}} distance / 10 pc)) = {{val|-0.2|+0.7|-1.8}} absolute magnitude</li>
<li>{{Note label|C|c|none}}Specifically in the north of Lyra which makes it visible from everywhere above about the [[47th parallel south]]. However the Sun passes through Sagittarius far to the south (or technically the Earth orbits so as to make the Sun seem to do so) throughout December. This also makes the cluster mostly risen during day, not night, in the nearest months but will never impede pre-dawn and post-sunset views from the upper half of northerly latitudes.</li>
</ol>
{{refend}}

==References==
{{reflist|30em|refs=
<ref name=coe2007>{{Cite book | first1=Steven R. | last1=Coe | title=Nebulae and how to observe them | series=Astronomers' observing guides | publisher=Springer | date=2007 | isbn=978-1-84628-482-3 | page=111 | url=https://books.google.com/books?id=roXyxpcc9MsC&pg=PA111}}</ref>

<ref name=crossen_rhemann2004>{{Cite book | first1=Craig | last1=Crossen | first2=Gerald | last2=Rhemann | title=Sky Vistas: Astronomy for Binoculars and Richest-field Telescopes | publisher=Springer | date=2004 | isbn=978-3-211-00851-5 | page=[https://archive.org/details/springer_10.1007-978-3-7091-0626-6/page/n310 261] | url=https://archive.org/details/springer_10.1007-978-3-7091-0626-6}}</ref>

<ref name=steinicke2010>{{Cite book | first1=Wolfgang | last1=Steinicke | title=Observing and Cataloguing Nebulae and Star Clusters: From Herschel to Dreyer's New General Catalogue | publisher=Cambridge University Press | date=2010 | isbn=978-0-521-19267-5 | pages=42–43 | url=https://books.google.com/books?id=wyWjVWYWoO8C&pg=PA43}}</ref>
}}

==External links==
{{Commons category|Ring Nebula}}
* [[WorldWide Telescope]]
** [http://www.worldwidetelescope.org/wwtweb/goto.aspx?object=M57&ra=18.8933&dec=33.0333&zoom=1 M57 (The Ring Nebula)]
* [https://web.archive.org/web/20130712214658/http://www.caha.es/the-ring-nebula.html M57] ''Calar Alto Observatory''
* [http://messier.seds.org/m/m057.html Messier 57] ''SEDS''
* [[Astronomy Picture of the Day]]
** [https://apod.nasa.gov/apod/ap050311.html Infrared Ring Nebula] (2005 March 11)
** [https://apod.nasa.gov/apod/ap091106.html Ring Nebula Deep Field] (2009 November 6)
** [https://apod.nasa.gov/apod/ap091115.html M57: The Ring Nebula] (2009 November 15)
** [https://apod.nasa.gov/apod/ap120312.html The Scale of the Universe – Interactive] (2012 March 12)
* [http://www.nightskyinfo.com/archive/ring_nebula M57 – Planetary Nebula in Lyra] ''NightSkyInfo''
* [http://www.spacetelescope.org/bin/images.pl?searchtype=freesearch&string=M57 M57] {{Webarchive|url=https://web.archive.org/web/20070313101824/http://www.spacetelescope.org/bin/images.pl?searchtype=freesearch&string=M57 |date=2007-03-13 }} ''ESA/Hubble''
* [http://www.constellation-guide.com/ring-nebula-m57-in-lyra/ Ring Nebula (M57) in Lyra] ''Constellation Guide'' (May 26, 2013)
* {{cite web|title=M57 – Ring Nebula|url=http://www.deepskyvideos.com/videos/messier/M57_ring_nebula.html|work=Deep Sky Videos|publisher=[[Brady Haran]]|author=Szymanek, Nik|author-link=Nik Szymanek|author2=Lawrence, Pete |df=ymd}}{{WikiSky|name=The Ring Nebula}}

{{Portal bar|Astronomy|Stars|Outer space}}
{{Messier objects}}
{{catalogs|M=57|NGC=6720|GC=4447}}
{{NGC objects: 6001-7000}}
{{Sky|18|53|35.079|+|33|01|45.03|2300}}

[[Category:Planetary nebulae]]
[[Category:Lyra]]
[[Category:Messier objects]]
[[Category:NGC objects]]
[[Category:Orion–Cygnus Arm]]
[[Category:Astronomical objects discovered in 1779]]
[[Category:Discoveries by Charles Messier]]