1 and 3 Feb 2003 (Blowing Bubbles in the Wind)

by Steve Gottlieb


With the sky clearing this past weekend, I took advantage of quite transparent conditions on both Saturday, 1 Feb with Matt Marcus and Shneor Sherman and on Monday evening, 3 Feb with Robert Leyland and David Silva. Seeing was a bit soft on Saturday night at Grey Pine, but humidity was low and the transparency excellent and conditions were even better on Monday night (excellent seeing, very calm, no dew).

Here are a few of the highlights:

Sextans B (UGC 5373) is dwarf irregular galaxy which is often included in lists of local group galaxy, but recent research shows it probably lies just outside the dynamical system (4.3 million l.y.) in a small group which includes NGC 3109, Sextans B and the Antlia Dwarf.

Sextans B = UGC 5373 = MCG +01-26-005 = CGCG 036-012 10 00 00.0 +05 19 56 V = 11.3; Size 5.1x3.5; SB = 14.3; PA = 110d

17.5" (2/1/03): Picked up without difficulty at 100x, 8' NE of mag 7.7 SAO 118040 (middle of three on a line with two mag 11 stars). At 140x, Sextans B appeared as a large, oval glow, elongated 3:2 WNW-ESE, ~3.5'x2.2', with a low surface brightness and broad, weak concentration. The surface seems slightly irregular or mottled and four fainter stars are near the periphery. This galaxy was surprisingly easy in excellent conditions.

I've been slowly working through the brightest quasars (about a dozen observed) and had no trouble with this Eridanus QSO. With a redshift of z = .573, this object is roughly 6 billion l.y distant (for comparison 3C 273 checks in with z = .158)

PKS 0405-12 = MSH 04-12 04 07 48.4 -12 11 36 V = 14.9

17.5" (2/3/03): identified immediately at 220x in an uncrowded star field. Appears as a mag 14.5-15 "star" (V = 14.86) 2.3' SSW of a mag 11 star and 3.3' NE of a mag 12.5 star. Visible with direct vision without difficult.

I had lost interest on my Hickson Compact Group survey (10 nasties to go), but after Randy Muller reported success with 99 of the 100), I felt compelled to dust off my finder charts of the remaining 10 and finish up this list! So, I took a look at one new one -- HCG 33, which revealed a close pair of faint galaxies:

CGCG 469-002n = HCG 33B 05 10 47.3 +18 01 49 Size 0.5x0.3

17.5" (2/3/03): HCG 33B is the northern of a close pair of galaxies with HCG 33A 40" S. Appears faint, very small, elongated 3:2 N-S, 20"x13". A mag 13.5 star 0.8' SW for the SW vertex of a small triangle with HCG 33A and 33B. This galaxy appears slightly brighter and larger than HCG 33A.

CGCG 469-002s = HCG 33A

05 10 47.7 +18 01 11 V = 14.2; Size 0.4x0.3

17.5" (2/3/03): HCG 33A is the southern member of a close pair with HCG 33B 40" N. Appears very faint, very small, probably elongated 4:3 SW-NE, 16"x12". A mag 13.5 star is just 36" W. This galaxy seems slightly less prominent than HCG 33B.

In excellent transparency conditions, I enjoy tracking down faint, large, emission nebulae. The Sharpless catalogue has a large number of obscure HII regions - and some of these are little-known gems.

Sh 2-309 = LBN 1053 07 31 47 -19 21.9 Size 12

17.5" (2/1/03): At 100x, I immediately noticed a small clump of four stars which seemed weakly nebulous but there was no responses using an OIII, UHC or H-beta filters. At 140x, a very small knot was visible on the following side of this small group of stars, but there still was no filter response. 220x increased the contrast further on the nebulous knot and the small clump of stars (~1.5' diameter) seemed encased in a weak nebulous glow, perhaps a couple of arcmin in size (the listed diameter for Sh 2-309 is 12'). Located 22' WNW of a mag 5.6 HD 60341 and 10' NNE of mag 7.5 SAO 153009.

The surprise of the weekend was Sh 2-308 in Canis Major -- an amazing 40' circular bubble which shows up at very low power (I used a 31 Nagler) with an OIII filter. On Monday night, we had David Silva's 14" GOTO Starmaster along with Robert Leyland's and my 17.5" aimed at this object:

Sh 2-308 = LBN 1052 = HD 50896 = EZ CMa = W-R 6 06 54 13.0 -23 55 42 Size 35

17.5" (2/1/03 and 2/3/03): this huge, obscure, Wolf-Rayet ring was a surprise at 100x at appeared as a faint, roughly circular 35'-40' glow just north of naked-eye 16 CMa! Although faintly visible without a filter, it is quite distinct with an OIII filter with a very high contrast 20' nearly straight border running ~N-S along the western border. This edge is the only portion which shows some scalloped structure and irregularities in surface brightness but it does have a dramatic edge (front) with the dark sky to the west using an OIII filter. On the south end, the nebula bends east, crossing through the middle of a trio of mag 7.5-8.5 stars and then passing just south of naked-eye mag 3.9 16 CMa. The eastern border fades in brightness and it's difficult to trace the edge. On the northern side there is a locally brighter patch which involves a small group of stars. The NW corner is sharply angled between the N-S running western edge and the northern edge. Near the center (offset a bit west) is mag 6.7 EZ CMa (mag 6.71-6.95), also catalogued as WR (Wolf-Rayet) 6. This object responds dramatically to an OIII filter at 63x (31 Nagler) as in fact is barely visible without a filter.

The illuminating star EZ CMa (small amplitude variable) is a massive Wolf-Rayet type losing mass from its outer layers through a strong stellar wind.

Wolf-Rayet rings are among my favorite objects - there are only a dozen or so known objects. The outer shell is an expanding envelope of shocked ionized gas being pushed outward by a high-mass Wolf-Rayet star into a circumstellar envelope. The strong stellar wind from the massive star sweeps up ambient gas forming the bubble. Here's the rest of the gallery of Wolf-Rayet rings:

N2359 = Thor's Helmet = LBN 1041 = Sh 2-298 07 18 31 -13 13.5 Size 8x6

17.5" (12/28/00): "Thor's Helmet" is a remarkably bright, detailed nebulosity at 100x using an OIII filter. The central region is 5' bubble (illuminated by a Wolf-Rayet star) with a brighter rim along the west side giving a "C" appearance with irregular knots, filamentary wisps of nebulosity and areas of thinner nebulosity in the interior. A number of fainter stars are superimposed in the central region along with some brighter mag 11 stars on the north portion of the rim. Attached at the south end is a brighter 4' extension elongated towards the west with a mag 9 star at its SE side. This section then thins out into a long 10' streamer which precedes the main section and forms the southern "horn" of the helmet. A second long, thicker streamer is attached at the north end of the central mass and extends out to the NW (this piece is also catalogued as IC 468). A fainter strip of nebulosity also begins on the north end and extends 10' due west while weak nebulosity is also west of the central helmet off the south side. Illuminated by the Wolf-Rayet star HD 56925 = WR 7.

N3199 = E127-EN014 = RCW 48

10 17.1 -57 55 Size 22x22

18" (7/8/02): this is an amazing HII region with a 20 Nagler and UHC filter at 103x. It appears as a fairly bright, thick crescent opening towards the east, roughly 10'x6'! The surface brightness is very irregular but noticeably brighter on the south end with a couple of brighter stars embedded at this end. Off the bright portion of the south end, much lower surface brightness haze extends the curve further SW for several arcmin and spreads out somewhat increasing the length to ~15'. The main mass has a curdled, mottled appearance and dark lanes appear to intrude into the nebulosity. The illuminating star HD 89358 is a Wolf-Rayet star (WR 18) and this nebulosity is reminiscent of the Crescent Nebula in Cygnus (should be dubbed the "Southern Crescent").

N6164/6165 = E226-EN012 = PK 336-0.1 = Ced 135a/b

16 33 52.4 -48 06 40 Size 6

18" (7/8/02): this Wolf-Rayet shell was a startling sight at 171x and UHC filter! A bright illuminating star (HD 148937 at V = 6.8) is surrounded by two lobes or loops to the NW (N6164) and SE (N6165). Both loops contain brighter arcs symmetrically placed at the opposite ends. This is a large object, ~6' diameter, with the SE knot a bit brighter. A mag 9 star is 3' NE, outside the nebulosity. Located near the midpoint of mag 4.5 Epsilon Normae 1.3 NW and N6188/6193 a similar distance SE.

This object is listed as a planetary nebula (PK 336-0.1) in several older sources. The illuminating star is a massive Wolf-Rayet type losing mass from its outer layers through a strong stellar wind (similar mechanism with the Crescent and Thor's Helmet).

N6888 = Crescent Nebula = LBN 203 = Sh 2-105

20 12 06.5 +38 21 17 Size 20x10

17.5" (6/30/00): Stunning view at 100x (20mm Nagler) using an OIII filter. The outline appears as a huge, irregular cosmic egg sitting in a very rich Cygnus star field, ~18'x11', with the complete annulus easily visible. The brightest section is along the north side and passes through a mag 7.2 star at the north edge. This piece is shows much structure with several knots and wispy tendrils. An isolated bright knot is within the weakly glowing interior which has an irregular surface brightness and is on a line with the mag 7.2 star and the mag 7.4 central star. There are interior wispy striations which appear to radiate from the central star towards the NW rim at the end of the bright arc. The rim is widest on the SW end with more nebulosity filling in towards the center. The fine texture and structure of the nebulosity creates a 3-dimensional feel and an "electric" effect.