by Steve Gottlieb
During a 5-year period in the 1840's this unstable beast brightened from 1.5 to -1 (peaking in 1843) and was temporarily the second brightest star in the sky, nearly rivalling Sirius. The blowouts from 1843 are now known as the "Homunculus Nebula" (due to a resemblance to a stubby mannequin), and have been expanding into space at 1-5 million km/hr ever since. The nebula was first reported in 1944 by Argentine astronomer Enrique Gaviola using a 61-inch reflector — "Using a power of 1200 diameters and stars images not larger than 1", a shape resembling a "homunculus" with its head pointing northwest, legs opposite, and arms folded over a fat body, could be clearly seen". After the HST imaged the bipolar blow-outs in exquisite detail (http://antwrp.gsfc.nasa.gov/apod/ap041128.html), this probably sparked amateur interest in observing the Homunculus, although with a total size of only 16"x12", this object requires high power and good seeing to resolve much detail.
My best view of the Homunculus on this trip was on July 4th - in fact, it was first object I turned the 18-inch scope to after viewing the comet Tempel impact! In steady seeing, a wealth of detail was visible at 293x. The bright 6" lobe to the SE of Eta was split by a dark lane (forming the two "legs" of the Homuculus). This lane actually consists of two darker "holes" with the outer dark hole more prominent. In moments of good seeing the outer periphery of the lobe had a slightly tattered or scalloped structure and was flattened on the SE end. Jutting out a few arcseconds to the NE was a small, thin spike that was visible continuously with averted vision. On the opposite SW side, only a small, brighter extension or oval nodule bulged out slightly from the SE lobe. The fainter NW lobe had a more translucent appearance with a pinched "key" or "bust" outline as the nebulosity is very weak or absent in the middle of the sides (this lobe forms the "head" of the Homunculus). At the center of this remarkable sight was the bright, quasi-stellar, reddish-orange Eta Carinae.
For comparison on another steady night, here are notes from February '04 in Costa Rica with Ray Cash's 13.1-inch travelscope: at 200x, the Homunculus Nebula was remarkable in excellent seeing on the last evening of observing. Both Eta and the nebula were a uniquely vivid color - an amazing fluorescent orange-tangerine. Extending to the SE of Eta is the brighter lobe, perhaps 6" in diameter with a sharp outline that was flattened along the southern edge in a mushroom shape. There appeared to be a partial darker lane in the interior. Extending to the NW was a smaller (4"-5") and much fainter lobe that faded with increased magnification. A tiny spike of nebulosity jutted out along to the NE between the two lobes. A couple of very close and faint companions lie just NE of Eta.
Posted on sf-bay-tac Aug 13, 2005 19:53:07 PT
Converted by report.pm 1.2 Mar 07, 2006 20:03:14 PT