NGC 2818 A planetary within a cluster within the Compass
Target: NGC 2818, NGC2818A
Camera: Canon 350d modified, CLS clip filter
Exposure Capture: DLSR Focus,
Scope: GSO CF RC200
EFR: f/8
Mount: EQ6 Pro
Exposure Setting: Prime focus, @ ISO800 ICNR off Custom WB
Exposures: 10 @ 360s lights taken between 8:00 and 12:00pm total 60 min 12/02/2010
Seeing: no moon, slight wind,
Guiding: Orion Starshoot Autoguider using PHD with ED80
Focus: DSLR Focus Bahitov mask
Stacking: DSS 5 darks no flats
Processing: PS CS3,
NGC 2818 Observation data
(Epoch J2000.0 [1]) Right ascension 09h 16m 01.656s [1] Declination -36° 37′ 38.76″ [1] Distance 10,400 ly [2] Apparent dimensions (V) 2' [2] Constellation Pyxis Physical characteristics Radius 3.25 ly [2] Other designations NGC 2818[1], PLN 261+8.1[2] See also: Planetary nebula, Lists of nebulae
NGC 2818 is a planetary nebula located in the southern constellation Pyxis (The Compass). This spectacular nebula 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 carry on as a white dwarf. [3]
It is often cited as a member of the open cluster framing it, however, radial velocity differences between the planetary nebula and open cluster suggest a chance alignment. The case is yet another example of a superposed pair, joining the famed case of NGC 2438 and M46.
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. To date, no true association has been established between open clusters and planetary nebulae.
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