NGC 2818 [SEP] constellation
NGC 2818
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.
It is often cited as a member of the open cluster NGC 2818A framing it, however, radial velocity differences between the planetary nebula and open cluster suggest a chance
NGC 2438
NGC 2438 is a planetary nebula about 3,000 light years away in the constellation Puppis. It was discovered by William Herschel on March 19, 1786.
NGC 2438 appears to lie within the cluster M46, but it is most likely unrelated since it does not share the cluster's radial velocity. The case is yet another example of a superposed pair, joining the famed case of NGC 2818.
Long exposures have shown that this planetary nebula has an extended double halo, while the more easily visible portion probably