Sierra Buttes 2007 (Two southern HII complexes)

by Steve Gottlieb

While I was observing at the Sierra Buttes following the Lassen party, I took a look at two interesting HII regions in southern Scorpius -- NGC 6334 ("Cat's Paw Nebula") and NGC 6357 ("Lobster Nebula" or "War and Peace Nebula"). These massive star-formation complexes are just two degrees apart, but seem to get neglected as they are located fairly far south near the stinger of Scorpius. John Gleason captured both of these regions from Coonabarabran ( ). These are both going to be high on my list when I return to Australia hopefully next year. If you explore this region, make sure to continuing further SW and SE to two remarkable planetaries -- NGC 6302 (Bug Nebula) and NGC 6337 (Cheerio Nebula).


NGC 6334 = Cat's Paw Nebula = RCW 127 = Sh 2-8 = Gum 62
17 20 53 -36 04 21
Size 40'x30'

18" (7/17/07): The "Cat's Paw Nebula" is a fascinating HII complex and molecular cloud with several distinct sections. At 73x and OIII or UHC filter, the brightest section is on the SE side and consists of a 4'-5' glow extending mostly north of a mag 8.5 star (HD 156738) at 17 20.9 -36 04 (2000). Appears weaker on the SW side of the star and slightly brighter wrapping around the eastern side of the star. John Herschel's description applies to only this section.

A second large section forming the SW component (VdBH 86 = Gum 61) lies 13' to the west and consists of a faint, 5' glow involving a 17" pair (HD 319703). This piece is asymmetric and appears as a broad fan sweeping N to SE from the central stars and is very weak or nonexistent to the SW of the stars.

A group of smaller pieces forming the NE component (identified in SIMBAD as Gum 64b) is 12'-15' N of the brighter SE section. First is an obvious 2' glow surrounding HD 319702 at 17 20.8 -35 52 (2000). A small, faint knot of nebulosity lies 3.5'-4' W, no more than 1' in diameter. This knot is also situated 2' SSE of a mag 9.5 star that is free from nebulosity. But on the NW side of this star another few arc minutes is a third detached piece of nebulosity in this group, ~2' in diameter. Very weak nebulosity appears to connect the NE with the SE section.

Finally, midway between these smaller pieces and the large SW section, a small extremely faint detached glow (Gum 64a) was glimpsed close SE of a star.

NGC 6357 = Gum 66 = RCW 131 = Sh 2-11 = War and Peace Nebula
17 24 44 -34 12.1
Size 50'x40'

18" (7/16/07): at 115x a faint elongated hazy glow was visible just north of a nice 14" pair of mag 11/12 stars. Adding an OIII filter dramatically improves this HII region and shows a bright, elongated nebulosity oriented WSW-ENE, ~5'x2'. Appears brighter in the middle just north of the double star. A faint star is off the north side, oppositely placed from the double. At 174x the nebula is slightly brighter and clumpy in the middle on the south side and a couple of very small slightly brighter knots are occasionally visible. The group of stars to the south (including the double) is catalogued as Pismis 24. Only the brightest portion of this huge HII complex was noticed. Located 8' WNW of mag 7 HD 157528. This star is the northermost of a 27' string of four mag 6-7 stars that extends to the south. NGC 6334 (Cat's Paw Nebula) lies two degrees SW. The nebula is associated with the Wolf-Rayet star HD 157504 = WR 93 which is located east of the bright section.

Observing Reports Observing Sites GSSP 2010, July 10 - 14
Frosty Acres Ranch
Adin, CA

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