Editing Planetary nebula (section)

{{Short description|Type of emission nebula created by dying red giants}}
{{Infobox astronomical formation|name=Planetary nebula|image=File:N1535s.jpg|caption=[[NGC 1535]]|Mass=0.1{{solar mass}}-1{{solar mass}}<ref name=Osterbrock>{{citation
 | title = Astrophysics of gaseous nebulae and active galactic nuclei
 | last1 = Osterbrock
 | first1 = Donald E.
 | last2 = Ferland
 | first2 = G. J.
 | editor = Ferland, G. J.
 | publisher = University Science Books
 | date = 2005
 | isbn = 978-1-891389-34-4
 | url-access = registration
 | url = https://archive.org/details/astrophysicsofga0000oste
 }}</ref>|commonscat=Planetary nebulae|thing=[[Emission nebula]]|size=~1 ly<ref name=Osterbrock/>|density=100 to 10,000 particles per cm{{sup|3}}<ref name=Osterbrock/>|qid=Q13632|discover=1764, [[Charles Messier]]<ref>{{Cite web |title=Messier 27 (The Dumbbell Nebula) |date=19 Oct 2017|url=https://www.nasa.gov/feature/goddard/2017/messier-27-the-dumbbell-nebula |website=nasa.gov}}</ref> }}
[[File:NGC6543.jpg|thumb|alt=The image's organization is similar to that of a cat's eye. A bright, almost pinpoint, white circle in the center depicts the central star. The central star is encapsulated by a purple and red irregularly edged, elliptically shaped area which suggests a three-dimensional shell. This is surrounded by a pair of superimposed circular regions of red with yellow and green edges, suggesting another three-dimensional shell.|X-ray/optical composite image of the [[Cat's Eye Nebula]] (NGC 6543)]]
[[File:Southern Ring Nebula by Webb Telescope (2022).jpg|alt=Two cameras aboard Webb Telescope captured the latest image of this planetary nebula, cataloged as NGC 3132, and known informally as the Southern Ring Nebula. It is approximately 2,500 light-years away.|thumb|Two cameras aboard [[James Webb Space Telescope|Webb Telescope]] captured the latest image of this planetary nebula, cataloged as [[NGC 3132]], and known informally as the Southern Ring Nebula. It is approximately 2,500 light-years away.]]
[[File:NGC 6326 by Hubble Space Telescope.jpg|thumb|[[NGC 6326]], a planetary nebula with glowing wisps of outpouring gas that are lit up by a binary<ref name="Miszalski2011">{{harvnb|Miszalski|Jones|Rodríguez-Gil|Boffin|2011}}</ref> central star]]

A '''planetary nebula''' is a type of [[emission nebula]] consisting of an expanding, glowing shell of [[ionization|ionized]] gas ejected from [[red giant]] stars late in their lives.<ref name="Frankowskietal2009">{{harvnb|Frankowski|Soker|2009|pp=654–8}}</ref>

The term "planetary nebula" is a [[misnomer]] because they are unrelated to [[planet]]s. The term originates from the planet-like round shape of these [[nebula]]e observed by astronomers through early telescopes. 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".<ref name=Darquier>{{cite book
|last1=Darquier
|first1=A.
|date=1777
|title=Observations astronomiques, faites à Toulouse (Astronomical observations, made in Toulouse)
|publisher=Avignon: J. Aubert; (and Paris: Laporte, etc.)
|url=https://archive.org/details/BUSA077-240-_126}}
</ref><ref name ="Olsen2017">{{cite magazine
|last1=Olson
|first1=Don
|last2=Caglieris
|first2=Giovanni Maria
|date=June 2017
|title=Who Discovered the Ring Nebula?
|magazine=Sky & Telescope
|pages= 32–37}}</ref><ref name="Steinicke2018">{{cite web
|title=Antoine Darquier de Pellepoix
|author=Wolfgang Steinicke 
|url=http://www.klima-luft.de/steinicke/ngcic/persons/darquier.htm
|access-date=9 June 2018}}</ref>
Though the modern interpretation is different, the old term is still used.

All planetary nebulae form at the end of the life of a star of intermediate mass, about 1-8 solar masses. It is expected that the [[Sun]] will form a planetary nebula at the end of its life cycle.<ref>{{Cite web |last=Daley |first=Jason |date=May 8, 2018 |title=The Sun Will Produce a Beautiful Planetary Nebula When It Dies |url=https://www.smithsonianmag.com/smart-news/sun-will-produce-beautiful-planetary-nebula-when-it-dies-180969028/ |access-date=30 March 2020 |website=Smithsonian Magazine |language=en}}</ref> They are relatively short-lived phenomena, lasting perhaps a few tens of millennia, compared to considerably longer phases of [[stellar evolution]].<ref name="FrewParker2010">They are created after the red giant phase, when most of the outer layers of the star have been expelled by strong [[stellar wind]]s {{harvnb|Frew|Parker|2010|pp=129–148}}</ref> 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 (P.N.N.), ionizes the ejected material.<ref name="Frankowskietal2009" /> Absorbed ultraviolet light then energizes the shell of nebulous gas around the central star, causing it to appear as a brightly coloured planetary nebula.

Planetary nebulae probably play a crucial role in the [[chemistry|chemical]] [[Galaxy formation and evolution|evolution of the Milky Way]] by expelling [[chemical element|element]]s into the [[interstellar medium]] from stars where those elements were created. Planetary nebulae are observed in more distant [[galaxy|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 star|binary central stars]], stellar winds and [[magnetic field]]s may play a role.