View source for NGC 246

{{Short description|Planetary nebula in the constellation Cetus}}
{{Planetary nebula
| image = [[Image:NGC 246.jpg|300px]]
| caption=An [[infrared]] [[Spitzer Space Telescope]] image of NGC 246.<br>Credit: [[NASA]]/[[JPL]].
| name = [[New General Catalogue|NGC]] 246
| type = Planetary
| epoch = [[J2000]]
| ra = {{RA|00|47|03.338}}<ref name="simbad" />
| dec = {{DEC|-11|52|18.94}}<ref name="simbad" />
| dist_ly = {{Val|{{convert|1080|pc|ly|disp=number}}|{{convert|220|pc|ly|disp=number}}|{{convert|260|pc|ly|disp=number}}|fmt=commas}}<ref name=Löbling2018/>
| appmag_v = 8<ref name="seds"/> / 11.8 (central star)<ref name="simbad" />
| size_v = 3.8{{prime}}<ref name="seds">{{cite web
  | title=SEDS NGC Catalog Online
  | work=Results for NGC 246
  | url=http://spider.seds.org/ngc/ngc.cgi?NGC+246
  | access-date=2010-11-29}}</ref>
| constellation = [[Cetus]]
| radius_ly = 2-3<ref name=jumk>{{cite web
  | title=NGC 246
  | work=Astronomy: Stars & Planets
  | url=http://jumk.de/astronomie/special-stars/ngc-246.shtml
  | access-date=2013-01-07}}</ref>
| absmag_v =
| notes =
| names = Skull Nebula,<ref name="Astronow-10-08" /> Pac-Man Nebula,<ref name="Levy" /> [[Caldwell catalogue|Caldwell]]&nbsp;56, [[Hipparcos Catalogue|HIP]] 3678, PMN J0047-1152, 2E 178, PN VV 4, [[IRAS]] 00445-1207, MCT 0044-1208<ref name="simbad" />
}}

'''NGC 246''' (also known as the '''Skull Nebula'''<ref name="Astronow-10-08">"The Night Sky", ''[[Astronomy Now]]'', Oct 2008.</ref> or '''Caldwell 56''') is a [[planetary nebula]] in the [[constellation]] [[Cetus]]. It was discovered in 1785 by [[William Herschel]]. The nebula and the stars associated with it are listed in several catalogs, as summarized by the [[SIMBAD]] database.<ref name="simbad">{{cite simbad
  | title=NGC 246
  | access-date=2006-12-22}}</ref> 

The nebula is roughly {{Val|{{convert|1080|pc|ly|disp=number}}|{{convert|220|pc|ly|disp=number}}|{{convert|260|pc|ly|disp=number}}|fmt=commas|u=[[light-year]]s}} away.<ref name=Löbling2018>{{Cite journal |last=Löbling |first=Lisa |date=2018-06-01 |title=Sliding along the Eddington Limit—Heavy-Weight Central Stars of Planetary Nebulae |journal=Galaxies |volume=6 |issue=2 |pages=65 |arxiv=1806.07279 |doi=10.3390/galaxies6020065|doi-access=free |bibcode=2018Galax...6...65L }}</ref> NGC 246's central star is the 12th magnitude<ref name="omeara">Stephen James O'Meara, ''The Caldwell Objects'', Sky Publishing Corporation, {{ISBN|0-933346-97-2}}, p 223.</ref> [[white dwarf]] HIP 3678 A.<ref>{{Cite journal |last1=Adam |first1=C. |last2=Mugrauer |first2=M. |date=2014-11-01 |title=HIP 3678: a hierarchical triple stellar system in the centre of the planetary nebula NGC 246 |journal=Monthly Notices of the Royal Astronomical Society |volume=444 |issue=4 |pages=3459–3465 |doi=10.1093/mnras/stu1677 |doi-access=free |issn=0035-8711|arxiv=1409.5339 |bibcode=2014MNRAS.444.3459A }}</ref> In 2014, astronomers discovered a second companion to NGC 246's central star, which has a comoving companion star called HIP 3678 B. The second companion star, a red dwarf known as HIP 3678 C, was discovered using the [[European Southern Observatory]]'s [[Very Large Telescope]]. This makes NGC 246 the first planetary nebula to have a [[Hierarchical trinary star|hierarchical triple star system]] at its center.<ref name=":0">{{Cite web |last=information@eso.org |title=Stars and Skulls: new ESO image reveals eerie nebula |url=https://www.eso.org/public/news/eso2019/ |access-date=2023-03-09 |website=www.eso.org |language=en}}</ref> 

NGC 246 is not to be confused with the [[Rosette Nebula]] (NGC 2237), which is also referred to as the "Skull."<ref>{{cite web | url=https://www.cnn.com/2018/02/14/world/rosette-nebula-heart/index.html | title=A hole in the heart of the Rosette Nebula | website=[[CNN]] | date=14 February 2018 }}</ref> Among some amateur astronomers, NGC 246 is known as the "Pac-Man Nebula" because of the arrangement of its central stars and the surrounding star field.<ref name="Levy">David H. Levy, ''Deep Sky Objects'', Prometheus Books, 2005, {{ISBN|1-59102-361-0}}, p 129.</ref>
==Image gallery==
<gallery>
File:The Skull Nebula NGC246 Goran Nilsson & The Liverpool Telescope.jpg|HaRGB image of The Skull Nebula (NGC 246). Data from the [[Liverpool Telescope]], processed by Göran Nilsson. Total exposure time 1.1 hours.
File:n246s.jpg|NGC 246 acquired using the Schulman 0.8m Telescope atop Mount Lemmon, AZ. This is a full color (visual) image.
</gallery>

==References==
{{Reflist}}

==External links==
* {{commonscat-inline}}
{{WikiSky}}

{{Catalogs|NGC=246|C=56}}
{{Caldwell catalogue}}
{{Ngc5}}
{{Cetus}}

{{DEFAULTSORT:NGC 0246}}
[[Category:Planetary nebulae]]
[[Category:Cetus]]
[[Category:NGC objects|0246]]
[[Category:Caldwell objects|056b]]
[[Category:Astronomical objects discovered in 1785|17841127]]
[[Category:Discoveries by William Herschel]]
[[Category:Hipparcos objects|3678]]
[[Category:IRAS catalogue objects|00445-1207]]