Editing Planetary nebula (section)

=== Discovery ===

The first planetary nebula discovered (though not yet termed as such) was the [[Dumbbell Nebula]] in the constellation of [[Vulpecula]]. It was observed by [[Charles Messier]] on July 12, 1764 and listed as M27 in his [[Messier object|catalogue]] of nebulous objects.<ref name=Kwok1>{{harvnb|Kwok|2000|pp=1–7}}</ref> To early observers with low-resolution telescopes, M27 and subsequently discovered planetary nebulae resembled the giant planets like [[Uranus]].  As early as January 1779, the French astronomer [[Antoine Darquier de Pellepoix]] described in his observations of the [[Ring Nebula]], "a very dull nebula, but perfectly outlined; as large as Jupiter and looks like a fading planet".<ref name=Darquier/><ref name="Olsen2017"/><ref name="Steinicke2018"/> 

The nature of these objects remained unclear. In 1782, [[William Herschel]], discoverer of Uranus, found the [[Saturn Nebula]] (NGC 7009) and described it as "A curious nebula, or what else to call it I do not know". He later described these objects as seeming to be planets "of the starry kind".<ref>{{Cite journal|last=Zijlstra|first=A.|date=2015|title=Planetary nebulae in 2014: A review of research|url=http://www.astroscu.unam.mx/rmaa/RMxAA..51-2/PDF/RMxAA..51-2_azijlstra.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://www.astroscu.unam.mx/rmaa/RMxAA..51-2/PDF/RMxAA..51-2_azijlstra.pdf |archive-date=2022-10-09 |url-status=live|journal=Revista Mexicana de Astronomía y Astrofísica|volume=51|pages=221–230|arxiv=1506.05508|bibcode=2015RMxAA..51..221Z}}</ref>  As noted by Darquier before him, Herschel found that the disk resembled a planet but it was too faint to be one. In 1785, Herschel wrote to [[Jérôme Lalande]]:

<blockquote>These are celestial bodies of which as yet we have no clear idea and which are perhaps of a type quite different from those that we are familiar with in the heavens. I have already found four that have a visible diameter of between 15 and 30 seconds. These bodies appear to have a disk that is rather like a planet, that is to say, of equal brightness all over, round or somewhat oval, and about as well defined in outline as the disk of the planets, of a light strong enough to be visible with an ordinary telescope of only one foot, yet they have only the appearance of a star of about ninth magnitude.<ref>Quoted in {{cite journal|last1=Hoskin|first1=Michael|year=2014|title=William Herschel and the Planetary Nebulae|journal=Journal for the History of Astronomy|volume=45|issue=2|pages=209–225|bibcode=2014JHA....45..209H|doi=10.1177/002182861404500205|s2cid=122897343}}</ref></blockquote>

He assigned these to Class IV of his catalogue of "nebulae", eventually listing 78 "planetary nebulae", most of which are in fact galaxies.<ref>p. 16 in {{cite book|last1=Mullaney|first1=James|title=The Herschel Objects and How to Observe Them|year=2007|isbn=978-0-387-68124-5|series=Astronomers' Observing Guides|bibcode=2007hoho.book.....M|doi=10.1007/978-0-387-68125-2}}</ref>

Herschel used the term "planetary nebulae" for these objects. The origin of this term not known.<ref name="Kwok1" /><ref name="Moore2007">{{harvnb|Moore|2007|pp=279–80}}</ref> The label "planetary nebula" became ingrained in the terminology used by astronomers to categorize these types of nebulae, and is still in use by astronomers today.<ref name="seds2013">{{harvnb|SEDS|2013}}</ref><ref name="hubbleSite1997">{{harvnb|Hubblesite.org|1997}}</ref>