Discovered by William Herschel in 1786.
Planetary nebula NGC 2438 appears superimposed over the open star cluster M46,
although it is almost certainly no member of the cluster, but a foreground
object (see M46 for details). It is one of the discoveries of William Herschel,
who cataloged it as H IV.39
Planetary nebulae have been detected in several globular star clusters
in our Galaxy. These densely-packed, gravitationally-bound groups of
100,000s to millions of stars are far older than their open cluster
counterparts.
