Gottlieb's Wicked Adventures in Oz (III)

by Steve Gottlieb

NGC 5189 in eastern Musca has to be one of the strangest looking planetaries you're ever going to meet up with. In fact, when John Herschel took his first look back in 1835 from the Cape of Good Hope with his father's 18.5-inch reflector, his first words were "very strange object"! You'd think that this object would have merited some serious research papers, but by the time of Burnham's Celestial Handbook it was mistakenly thought to be a bright emission nebula (same story in Hartung's "Astronomical Objects for Southern Telescopes") and as recently as the Sky Atlas 2000.0 it was plotted as an emission nebula. Such was the sad case until recently with a number of deep southern objects.

Though admittedly, based on physical appearance you would never guess that this was a planetary. If you take a look at http://www.rcopticalsystems.com/gallery/ngc5189.html or the Angle-Australian Observatory image at http://www.ast.cam.ac.uk/AAO/images/captions/aat083.html you'll see why it has been dubbed the "Spiral Planetary", though to be more precise I would have named it the "Barred-Spiral Planetary". Large scopes reveal much of the detail visible in these two images. I guarantee if this spectacular bi-polar planetary was located in the northern sky, it would be right up there in popularity with the Ring, the Dumbbell and the Saturn Nebula (and shows a ton more detail), but at -66 degrees dec, I'm guessing not many here have heard of it.

In the eyepiece, varying magnifications reveal a wealth of detail crammed into 2' of sky and a number of superimposed stars add to its weird appearance. I first took a look at NGC 5189 three years ago through Don Whiteman's 12-inch reflector from a rural site just 90 minutes outside of Sydney and was fascinated. So, it was high on my observing list for this trip and did not disappoint...

18" (7/6/05 - Magellan Observatory, Australia): the "Spiral Planetary" is certainly one of the most remarkably structured planetaries and would be famous if located in the northern hemisphere. At 128x using a UHC filter, a high surface brightness "bar" at least 1' in length, elongated SW-NE forms the main body of the planetary. The bar is slightly curved and has an irregular surface brightness. On the NE end is a prominent bright knot, roughly 6" in size. Nebulosity hooks below this knot, extending below the bar. Above the SW end of the bar is the brightest superimposed star and a hook of nebulosity sweeps up to the NW, wrapping above this star. The entire structure is encased in a much fainter oval envelope. A total of five stars are superimposed including a very close double which is just south of the SW end of the bar and the 14th magnitude central star situated SE of the center of the bar.

Posted on sf-bay-tac Jul 30, 2005 15:14:19 PT
Converted by report.pm 1.2 Mar 06, 2006 21:28:52 PT