Star cluster M46 and planetary nebula NGC 2438 - Open cluster M46 and planetary nebula...

Star cluster M46 and planetary nebula NGC 2438 - Open cluster M46 and planetary nebula NGC 2438 - M46 (NGC 2437) is an age cluster located at 5400 years - light. It contains about 500 stars, 150 of which are brilliant. It is about 300 million years old. The planetary nebula NGC 2438 does not appear to belong to this cluster, and must be closer although its distance is unknown. Image obtained by Siding Spring's 3.9m telescope The open cluster NGC 2437 (M46) has an angular diameter of almost half a degree and is quite beautiful in even quite a modest telescope. It has an integrated magnitude of about 6 and so is on the threshold of naked - eye visibility. The cluster is quite old as these things go, about 300 million light years. It is about 5000 light years distant, in the northern part of the constellation of Puppis. Although planetary nebula distances are notoriously difficult to measure, NGC 2438 seems to be in the foreground and is not connected to the cluster. Planetaries are in any case the result of the demise of an old, low mass stars and are thus not seen in relatively young open clusters