NGC 2818

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title: "NGC 2818" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["planetary-nebulae", "ngc-objects", "pyxis", "eso-objects", "astronomical-objects-discovered-in-1826"] description: "Planetary nebula in the constellation Pyxis" topic_path: "general/planetary-nebulae" source: "https://en.wikipedia.org/wiki/NGC_2818" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::summary Planetary nebula in the constellation Pyxis ::

::data[format=table title="Infobox Planetary nebula"]

Field	Value
name	NGC 2818
type	Planetary
image	NGC 2818 by the Hubble Space Telescope.jpg
caption	Hubble Space Telescope image of NGC 2818
(red: nitrogen, green: hydrogen, blue: oxygen)
epoch	J2000.0
ra
dec
dist_ly	10,400
size_v	2'
constellation	Pyxis
radius_ly	3.25
names	NGC 2818, PLN 261+8.1 ESO 372-PN13
::

|name = NGC 2818 | type = Planetary |image = NGC 2818 by the Hubble Space Telescope.jpg |caption = Hubble Space Telescope image of NGC 2818 (red: nitrogen, green: hydrogen, blue: oxygen) |epoch = J2000.0 |ra = |dec = |dist_ly = 10,400 |appmag_v = |size_v = 2' |constellation = Pyxis |radius_ly = 3.25 |absmag_v = |notes = |names = NGC 2818, PLN 261+8.1 ESO 372-PN13 NGC 2818 is a planetary nebula located in the southern constellation Pyxis (The Compass). It consists largely of glowing gases from the star's outer layers ejected during the final stages of its life when it had run out of the fuel necessary to sustain its core fusion processes. The remnants of its core will remain as a white dwarf.

NGC 2818 presents a complex morphology, and overall has bipolar structure, making it a bipolar nebula. The two lobes are somewhat broken and irregular. There are also filamentary structures radiating from the center, and near the center of the nebula, several cometary knots. The mass of the nebula is estimated at 0.6 solar masses. It is about 11,000 years old.

The progenitor star was likely about 2.3 times the mass of the Sun. The central star is very hot, with an effective temperature of 130 kK.

Open cluster membership

NGC 2818 appears very close to the open cluster NGC 2818A. Whether it is a member of the open cluster has been controversial: earlier papers found the radial velocity differences between the planetary nebula and open cluster to a chance alignment. name=mermilliod2001 name=majaess2007 However, more recent studies suggest that NGC 2818 is indeed a member of NGC 2818A.

Partly because of their small total mass, open clusters have relatively poor gravitational cohesion. Consequently, open clusters tend to disperse after a relatively short time, typically some 10 million years, because of external gravitational influences amid other factors. Under exceptional conditions, open clusters can remain intact for up to 100 million years.

Theoretical models predict that planetary nebulae can form from main-sequence stars of between 8 and 1 solar masses, which puts their age at 40 million years and older. Although there are a few hundred known open clusters within that age range, a variety of reasons limit the chances of finding a member of an open cluster in a planetary nebula phase. One such reason is that the planetary nebula phase for more massive stars belonging to younger clusters is on the order of thousands of years - a blink of the eye in cosmic terms. Only one association has been established between open clusters and nearby nebulae, the extremely distant nebula PHR 1315-6555.

References

References

1. SIMBAD, [http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=NGC+2818&submit=SIMBAD+search NGC 2818] (accessed 1 March 2009)
2. ScientificBlogging.com, [http://www.scientificblogging.com/news_releases/ngc_2818_nebula_within_cluster_inside_compass NGC 2818 - A Nebula Within a Cluster Inside A Compass] {{webarchive. link. (2013-02-02 , ''staff writer'', 2009 January 15th 01:00 AM (accessed 1 March 2009))
3. "HubbleSite - NewsCenter - Hubble Snaps a Splendid Planetary Nebula (01/15/2009) - Release Images". hubblesite.org.
4. (2024). "Planetary Nebula NGC 2818: Revealing its complex 3D morphology". Monthly Notices of the Royal Astronomical Society.
5. (2001). "Red giants in open clusters". Astronomy & Astrophysics.
6. (2007). "In Search of Possible Associations between Planetary Nebulae and Open Clusters". Publications of the Astronomical Society of the Pacific.
7. (2025). "The physical association of planetary nebula NGC 2818 with open cluster NGC 2818A". Astronomy & Astrophysics.
8. (September 16, 2010). "First planetary nebula associated with an open cluster discovered".

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