Deep Sky Object of the Month

(left) Open cluster NGC 2818 in Pyxis. (right) Detailed photo of the planetary nebula.

This pair of objects is reminiscent of M46/NGC 2438 in northern Puppis, only fainter and much further south. In spite of its southerly declination and faintness, it is a worthy target for six-inch and larger scopes--proof that an object doesn't have to be bright to be interesting.

The cluster, NGC 2818, is about nine arc-minutes across with 60 or so stars visible in a 12.5" scope. The stars appear to be evenly distributed, with little central condensation. The cluster stands out well from the background, although there are no bright cluster members.

The planetary nebula, NGC 2818A is listed at photographic magnitude 13, though visually it comes in at 11.6. The nebula is a bit like M27 in that the brighter sections have a dumbbell or hourglass shape. The hourglass is oriented north-south; faint outer extensions to the east and west give it the overall oval shape shown in the photo above. In smaller scopes, the extensions may not be seen.

What makes this pair interesting is that the two objects are related--NGC 2818A is indeed a member of the open cluster. Currently this is the only known example of an open cluster and a planetary nebula being physically related. M46 and NGC 2438 on the other hand are a chance alignment; the planetary nebula is a foreground object. The distance to NGC 2818/2818A is about 11,400 light years. This would make the nebula rather large for a planetary, about 7 x 3 light years.

How to get there:

Unfortunately, these objects present a challenge for naked-eye star hopping as they lie in an area devoid of bright stars. A good finder or setting circles will make the job easier. Try using Epsilon Antliae (mag. 4.5) to the east of the objects or Psi Velorum (mag. 3.5) to the south as a starting point.

Finder chart for NGC 2818/2818A