Southern Specialties and a List of Nebulae
The sparse open cluster NGC 2818 in southern Pyxis contains the 12th-magnitude planetary nebula NGC 2818a. This blue-light image from the the Digitized Sky Survey
is ½° wide. Click on the image for a closer view of the cluster and nebula.
Courtesy Palomar Observatory Sky Survey.
The far-southern Milky Way offers several outstanding examples of the variety and complexity of the bipolar class. Easiest to view is NGC 2818a
in southern Pyxis near Vela. It is one of the very few planetaries located within an open cluster (NGC 2818). The cluster is nothing very special, with 40 stars of magnitude 11.5 and fainter scattered across 7', but the nebula is an interesting sight 0.6' wide in the cluster's western side. It is a beautiful example of the bipolar class, with extensive lobes connected by a very thin waist.
Much older, larger, and more evolved is NGC 2899 deep in Vela. It's nearly as large as M76, but due to its far-southern location and its relatively low surface brightness, it's much less well known. At the 1993 Winter Star Party I observed its large, ghostly, somewhat twisted bipolar shape in a 15-inch telescope through an O III filter.
Only the bright, oblong inner region of NGC 2346 is visible in most telescopes. But a large aperture and a nebula filter reveal the big, bipolar wings to the upper right and lower left. NGC 3132 is nearly half a light year in diameter, and at a distance of about 2000 light years is one of the nearer known planetary nebulae.
Courtesy Hubble Heritage Project and NASA.
Saving the best for last, NGC 3132
at the Vela-Antlia border is known as the Eight-Burst or Southern Ring Nebula. At first glance it looks like a rough clone of the more famous M57 in Lyra, and like that Ring it has recently been classified as a "diabolo bipolar," a normal bipolar that we observe down its long axis. Even the central star is deceptive. The true central star is a very faint (16th-magnitude) companion to the 10th-magnitude star that's easily visible in the center of the planetary. The companion is beyond amateur reach, being just 1.6" southwest of the primary. The ring shape is easy in almost any telescope, but as with most of these objects, you'll need high magnification and a nebula filter to pick out more elusive details.
|Some Bipolar Planetary Nebulae |
|Name ||(2000.0) |
|M76 ||01h 42.1m ||+51° 34.1' ||160 x 110 ||10.1 || 17.6|
|J320 ||05h 05.6m ||+10° 42.0' ||22 x 22 ||11.9 || 14.3 |
|J900 ||06h 25.9m ||+17° 47.2' ||12 x 10 ||11.7 || 16.5 |
|Mink 1-7 ||06h 37.4m ||+24° 00.4' ||29 ||13.0 || |
|NGC 2346 ||07h 09.4m ||+00° 38.6' ||60 x 50 ||11.8 || 11-14 (var) |
|NGC 2371/2 ||07h 25.6m ||+29° 29.0' ||130 x 54 ||11.3 || 14.9 |
|NGC 2440 ||07h 41.9m ||-18° 12.5' ||72 x 42 ||9.4 || 17.5 |
|NGC 2818a ||09h 16.0m ||-36° 37.8' ||35 x 35 ||11.9 || 18.5 |
|NGC 2899 ||09h 27.0m ||-56° 06.5' ||125 x 65 ||12.2 || 15.9 |
|NGC 3132 ||10h 07.0m ||-41° 12.0' ||84 x 53 ||9.2 || 10.0 |
* Includes outer extensions and halos.