OR 12/28/13: Resolving the Brightest Star in M33
by Steve Gottlieb
On December 28, 2013 (Saturday) I met Carter Scholz at Lake Sonoma during an unusual stretch of clear, dry winter weather. There were two other participants, Matt Marcus and Caroline Scolari. The transparency was predicted by the CSC to be excellent as well as no cloud cover, though the jet stream was running right down the coast, so seeing was expected to be poor. But the seeing was fine, especially for the first several hours, though I often kept to 260x. Observing started close to 6:40 and I stopped a little before 1:00, so there was a good 6 hours to explore a number of lesser known targets and some eye-candy. I ended up logging about 50 objects and some of the highlights are below.
B324, a highly luminous hypergiant, is the brightest individual star
in M33. It appeared as a mag 15 star at the north edge of IC 142, a
luminous HII region to the north of the core. Humphreys (1980) classified
B324 as an A5-type star but it is considered to be a post-red supergiant
on a blue loop to warmer temperatures and eventually a supernova. Globular
Cluster U49 lies 3.3' NW. It was visible as a very faint mag 16.2 "star".
The position was easy to pinpoint as the cluster forms the northern
vertex of a right triangle with a mag 11.3 star (at the right angle)
1.3' S and a mag 13.5 star 1.5' SSE. Visible ~75% of the time once identified.
I also looked globular cluster C39 on the southeast end of the galaxy.
This cluster also appeared as a very faint 16th magnitude "star",
which was not visible continuously in soft seeing. Although the listed
mag of C39 is a few tenths brighter than U49, I didn't find this cluster
KTG 8 = NGC 672/IC 1727/NGC 684
This trio consists of the 8' physical pair NGC 672 and IC 1727, which
reside at a distance of ~25 million l.y., along with NGC 684 (up to
10x the distance). IC 1727 = KTG 8A appeared fairly faint, very large,
very elongated 3:1 NW-SE, low surface brightness, ~2.5'x0.8' though
the outer halo fades into the background gradually so the dimensions
are difficult to estimate. Contains a slightly brighter "bar"
that is extended 4:1 or 5:1 NW-SE, ~45"x10". The halo is more
extensive NW of this bar, so the appearance is asymmetric. NGC 672 =
KTG 8B lies 8' NE and appeared very bright, very large, elongated 5:2
WSW-ENE, mottled appearance. Contains a brighter, elongated "bar"
that is slightly angled (roughly 7:2 E-W) to the major axis of the halo.
Slightly brighter "patches" were visible just beyond the bar
(on both the east and west side), probably where spiral arms attach
to the bar. NGC 684, another 34' NE, appeared as a fairly bright, beautiful
edge-on 7:1 E-W, 1.8'x0.25', sharply concentrated with a very small,
very bright core and a faint stellar nucleus.
At 375x, IC 161 = VV 54a appeared moderately bright, fairly small,
elongated 3:2 ~E-W, 0.4'x0.25', well concentrated with a very bright
core than increases to a stellar nucleus. An extremely faint companion
off the SE side (the pair forming VV 54) was not seen. Forms a 2.5'
pair with IC 162 = VV 55a = Arp 228. IC 162 appeared moderately bright,
fairly small, round, 30" diameter, fairly well concentrated with
a small bright core. The halo increases in size to at least 0.8' with
averted vision. MCG +02-05-039, a close companion just 1.0' SE is situated
just outside the halo, and appeared very faint, small, elongated 2:1
N-S, 24"x12". UGC 1268, 4' N of IC 162, appeared very faint,
elongated 5:2 SW-NE, low even surface brightness, 30"x12".
A mag 12 star just 24" NE detracts from viewing. Located 4' N of
IC 162 = Arp 228. Arp placed IC 162 in his category of "concentric
KTS 15 = ESO 543-021/-022/-023
KTS 15, a trio of ESO galaxies in Cetus, consists of a close pair and
a thin edge-on ~14' SE. ESO 543-021 = KTS 15A appeared very faint, fairly
small, round, 25" diameter, low even surface brightness [face-on
Sc]. A mag 13.5-14 star is 1.6' NE. ESO 543-022 = KTS 15B, situated
2.6' ESE, appeared faint, fairly small, slightly elongated ~N-S, 25"x20",
fairly low even surface brightness but higher surface brightness than
ESO 543-021. ESO 543-023 = KTS 15C lies 12.5' SE and noted as a faint,
thin edge-on, at least 5:1 NNW-SSE, 0.8'x0.15', low even surface brightness.
The redshift-based distances of the 3 galaxies are ~250 million l.y.,
650 million l.y. and 125 million l.y., so the galaxies are not physically
KTS 28 = NGC 1721/1725/1728
KTS 28 consists of three prominent NGC galaxies forming an E-W chain. NGC 1721 = KTS 28A appeared moderately to fairly bright, fairly small, high surface brightness, elongated 3:2 NW-SE, ~45"x30". Contains a small, bright irregular core. A mag 14 star is 0.8' NE of center. NGC 1725 = KTS 28B, just 1.6' SE, also appeared moderately to fairly bright, fairly small, slightly elongated SSW-NNE, well concentrated with a very small bright core. Initially logged as 25" diameter, but the low surface brightness halo increases in size to 35"-40". Finally, NGC 1728, just 1.3' NE, also appeared moderately to fairly bright, elongated 5:2 or 3:1 N-S, 0.6'x0.2', sharp concentration with a small bright core and bright stellar nucleus. MCG -02-13-031, a very thin edge-on, lies 9.5' SSE and NGC 1725, a barred spiral, lies 8.5' N. NGC 1725 is fairly bright, moderately large, well concentrated with a bright elongated core or bar oriented E-W that increases to a small, rounder nucleus. The halo is much fainter and elongated 2:1 NW-SE, ~1.8'x0.9'. The galaxy is bracketed by mag 10 stars 2' N and 2.9' E, with a mag 11 star 1.4' S.
UGCA 128 = KTS 32A dominates this trio as a moderately bright and large
glow, round, irregular surface brightness, 1.0' diameter, contains a
bright 20" core. Several stars are involved or nearby including
a mag 12.5 star off the NW end, 1.4' from center and a mag 13 star at
the SSE side, 40" from center. In addition a mag 15 star is at
the north edge, along with another mag 15 star right at the NW end.
ESO 556-18 = KTS 32B lies 10' ESE and appeared extremely faint, small,
round, 15" diameter, possible very faint stellar nucleus. A mag
15.5 star is at the north edge and perhaps my comment about a faint
stellar nucleus refers to this star. The image is from the Carnegie-Irvine
Atlas of southern galaxies.
At 200x, NGC 7452 (labeled as UGC 12304 in Megastar) appeared fairly
faint, fairly small, elongated ~5:3 SW-NE, 0.8'x0.5', brighter core.
At 282x, the core appeared double [post merger system?], with the two
extremely small nuclei just resolved at 10" separation and oriented
along the major axis! The northeast component appeared quasi-stellar.
A mag 13.2 star is 1.2' E of center. NGC 7452, just 3.1' W, is faint,
very small, round, 12" diameter, extremely small or stellar nucleus.
NGC 7674, the brightest member of HCG 96, appeared fairly bright, fairly
small, round, 0.8' diameter, sharply concentrated with a small, very
bright core. CGCG 406-113 = HCG 96C is just off the NE edge [33"
from center] and was easily seen as fairly faint, very small, round,
15" diameter. HCG 96D (faintest member) lies 1.1' SE, and was extremely
faint and small, round, 6" diameter. Finally, NGC 7675 = HCG 96B
appeared moderately bright, fairly small, elongated 4:3 or 5:4 SSW-NNE,
0.6'x0.45', well concentrated with a small. very bright core.
Using 200x and an OIII filter, this small Abell planetary appeared
fairly faint, round, 0.4' diameter, crisp-edged and uniform surface
brightness. Better view unfiltered at 375x, as the disc appeared to
have a slightly irregular surface brightness (though not clearly annular).
Abell 4 lies just 38' ESE of the center of M34. PGC 2201858, PGC 2201006
and PGC 2202835, three 16th magnitude (B) galaxies, were tracked down
6.8' WNW, 6.7' E and 11' NE, respectively. All appeared as 8"-12"
fuzzballs, but PGC 2201006 was the brightest.
NGC 1530 in Camelopardalis is fairly bright, large, elongated nearly 3:2 N-S, ~3.5'x2.2'. Contains a large, brighter circular core within a very large, elongated halo. A low contrast, thin spiral arm is attached on the west side of the core and sweeps north at the edge of the halo and a similar enhancement is visible on the east side extending due south. Two mag 15 stars [22" separation] are superimposed on the NW side [1.1' from center] and a mag 12.8 star lies 2.5' N.
NGC 2146, the "Dusty Hand", is a highly distorted (post-merger?) galaxy, with a dusty spiral arm that has looped in front of the galaxy's core. NGC 2146 appeared very bright, very large, elongated 5:2 NW-SE, ~5'x2', with a very asymmetric structure. Contains a very bright, elongated core, ~1.2'x0.5' NW-SE, but with no distinct nucleus. A low contrast dust lane cuts through the core unevenly, with the main section on the north side, so the lane initially appears to run parallel to the core on the southwest side. But a fainter, elongated section of the core extending NW-SE is just beyond the dust lane on the southwest side. To the southeast of the core, the outer halo is diffuse with a low surface brightness and is not aligned with the major axis of the core, extending more towards the east. On the NW side of the core, the halo has a higher and irregular surface brightness with a slightly brighter curving arc (arm) along its eastern side.