Showpiece regions in the LMC (3)

[Steve Gottlieb]

3) LMC-N158/159/160

LMC-N158
NGC 2074 (24"): this prominent HII region (LMC-N158C) and cluster (OB-association LH 101) appeared as a very bright, very large "C" shaped nebula surrounding a semi-circular chain or crown of stars open to the SW. Two bright mag 10.4 and 11 stars oriented SW-NE (50" separation) lie on the northwest end of this crown. The northeastern luminary is a very close pair of OB-stars (TDS 3273 = 11.4/11.8 at 2") and the star at the southwest end (HD 269923) is the brightest in the cluster. On the opposite southeast end of the chain is a brighter mag 12.5 star (O3-class supergiant). A small bright knot, ~35" diameter, is superimposed on the general glow in the northeast side of the "C". At 216x at least 20 fainter stars were resolved in the chain besides the brighter stars at the ends. NGC 2074 is part of a huge complex (LMC-N158) stretching 11' SW-NE with NGC 2081, a bright HII region that lies just 8' NE. LMC-N158 is located roughly 20' SSE of the center of the Tarantula Nebula.

NGC 2081 (24"): At 214x, this is a gorgeous star cloud consisting of two dozen stars in a 5' region (stellar association LH 104 dominated by B-class supergiants), including many mag 13-14 stars as well as mag 12.2 star HD 38489 (an extreme luminous blue variable) on the northeast side. Adding a UHC filter enhances a fairly bright HII glow that nearly surrounds the entire cluster in a triangular wreath (weak in the center)! The brightest portion is a ribbon with a bright region (identified in SIMBAD as BSDL 2722) at one end just south of the cluster and extending due east. With closer inspection BSDL 2722 actually consists of a couple of knots and fainter streaks intersecting! Just beyond the east end of this ribbon is NGC 2091, a slightly elongated cluster that is collinear with the streamer. HDE 269936, a mag 11 "star" (found to be an extremely compact cluster) is just off the SW side and NGC 2074, a bright HII region and cluster (part of the same complex LMC-N158), lies 8' SW.

LMC-N159
NGC 2078 (24"): this is the northwest component of an impressive 4' emission nebula filled with bright knots (LMC-N159), several of which form a curving "S" shape. At 200x and UHC filter it appeared as a fairly bright, moderately large glow surrounding a mag 12 star (B5 supergiant R148) and two fainter stars. This knot is elongated ~E-W, ~1.2'x0.8' and is encased in a fainter outer halo that extends perhaps 1.5', mostly to the north. NGC 2079, an extremely bright isolated patch, lies 1.7' S, NGC 2083 is a similar distance to the east, and NGC 2084 is 2.5' SE.

R148 forms a 6" pair - not logged - with the optical counterpart (V~14.8) of LMC X-1, a 10 solar-mass black hole and variable X-ray source. Nearby is the impressive LMC-N160 complex with NGC's 2077 and 2080, another very bright patch of nebulosity, 6' N and NGC's 2085 and 2086, a smaller bright pair, a similar distance to the NE. This complex along with LMC-N159 is within the O-association LH 105.

NGC 2079 (24"): this is the brightest section of an impressive 4' collection of perhaps 8 different emission knots (collectively LMC-N159) that are encased in a diffuse glow and carry four separate NGC designations. NGC 2079 (LMC-N159A) is situated on the southwest end of the complex and appeared extremely bright, ~1' diameter,with a uniform very high surface brightness. The outline has an unusual triangular shape (one vertex at the north end) with a well-defined border and appears detached from the the main section. Without a filter, a faint star and ionizing source (DD 13, an unresolved pair of O-stars) is located at the center of the glow.

NGC 2079 is collinear with two mag 12 stars 1.7' N (at the center of 2078) and another mag 12 star 3.5' N. The main section of the complex to the northeast forms a large "S" shaped group of multiple knots with NGC 2078 1.7' N, 2084 to the east and 2083 to the NE.

NGC 2083 (24"): at 214x and UHC filter, NGC 2083 appeared as a bright, large, slightly elongated glow ~1.8' diameter, surrounding a mag 12.5 star (O-class supergiant). A brighter knot is embedded within the glow on the west side (LMC-N159I) on a line with NGC 2078. Removing the filter, the bright central star has a companion at ~7" and several other mag 14 stars are embedded in the periphery of the glow. On the southeast side is the 15th magnitude "star" N159-5, known as the LMC "Papillon Nebula". This very compact object (not resolved) is classified as a Young Stellar Object (YSO) and High Excitation Blob (HEB).

NGC 2083 is situated in the northeast section of the curving "S" shaped NGC 2078/79/83/84 complex (LMC-N159 and OB-association LH 105). This complex shares the same field with two additional bright emission regions - NGC 2085/86 4' N and NGC 2077/80 ~5.5' NNW (LMC-N160), and the combined complex forms a superb field of bright HII regions ~35' SSE of the center of the Tarantula Nebula. Although Herschel assigned 4 NGC numbers within LMC-N159, I logged at least 7 different brighter knots (see NGC 2084 for more).

NGC 2084 (24"): NGC 2084 forms the SE region of the complex and it's composed of several nearby components. At the NE end of this extended region is a moderately bright, round knot, ~45" diameter (N159G). Without a filter a star is involved with N159G (sketched by John Herschel but not catalogued). A second, brighter embedded "glow" is close WSW on a direct line with NGC 2079. This knot corresponds with John Herschel's position for NGC 2084 and is catalogued by Henize as N159C-east. It appeared very bright, fairly large, elongated, ~1.2'x1.0'. Removing the filter a couple of stars are involved (with one brighter star). Finally, N159C-west (also sketched by Herschel) lies 1.5' W of NGC 2084 = N159C-east in the center of the entire complex and is connected to NGC 2084 by a faint bridge of nebulosity. N159C-west appeared fairly bright, moderately large, round, 45" diameter.

LMC-N160 Complex
NGC 2077 (24"): this is the southwest component of a very bright, impressive 2' emission patch with NGC 2080. At 200x and UHC filter, NGC 2077 appeared bright, moderately large, elongated 2:1 E-W, ~1.2'x0.6'. Without a filter, three fainter stars are involved in the glow (one is a massive Wolf-Rayet star). Forms a close pair of with NGC 2080 (Ghost Head Nebula) 1.1' NE.

NGC 2085 and 2086, a smaller pair of bright HII glows, lie 3' and 4' ESE, and the entire collection forms LMC-N160. In addition, a bright complex of HII knots including NGC 2078, 2079, 2083 and 2084 (LMC-N159 and O-association LW 105) lies 5' S. Together these groups form a stunning field about 35' SSE of the Tarantula Nebula.

NGC 2080 = Ghost Head Nebula (24"): at 200x and UHC filter, this emission nebula is very impressive, appearing as an extremely bright nebulous glow with an irregular shape, ~1.5' diameter, slightly elongated. The brightest section is encased in a larger, fainter nebulous glow that extends mostly to the south. NGC 2077, a bright HII glow, is attached on the SW side with their centers just 1' apart. At 350x the view was fascinating with 3 or 4 "stars" embedded (the brightest one or two appear to be quasi-stellar knots) and NGC 2080 had a curdled texture. A couple of brighter mag 13/14 stars are off the NW side and a number of stars trail off to the east and NE (part of the O-association LH 103). Located 30' SSE of the center of the Tarantula Nebula.

Along with NGC 2085 and 2086, another pair of knots ~3' SE, this group forms LMC-N160. Roughly 6' S is LMC-N159, another stunning group of nebulous glows consisting of NGC 2078, 2079, 2083 and 2084. NGC 2080 is the brightest region in the LMC-N159/160 complex and is nicknamed the "Ghost-Head Nebula" from a 2000 HST image. The two "eyes" of the Ghost (noted as quasi-stellar above) are rare, compact "high excitation blobs" (HEBs) discovered in 1986.

NGC 2085 (24"): this HII knot is part of an amazing field of nebulous glows located ~35' SSE of the Tarantula Nebula. At 200x using a UHC filter, NGC 2085 appears bright, fairly small, ~25" diameter. A mag 10.0 star (supergiant HDE 269953) is just off the NE end (23" from the center). NGC 2085 forms a close pair with NGC 2086 = IC 2145, a similar knot just 1.2' E. Both of these knots are immersed in small, much fainter nebulous halos but the bright star itself does not appear to be involved. Viewing with the filter, the field is divided up into three main groups with NGC 2085 and 2086 forming a close E-W pair separated by a mag 10 star. NGC 2080 (brightest section in the LMC-N159/160 complex) and NGC 2077 lies ~2.5' NW and an impressive cluster of nebulous knots (NGC 2078, 2079, 2083 and 84) is roughly 6' SSW.

NGC 2086 = IC 2145 (24"): this is the eastern component of a close pair of nebulous glows with NGC 2085 just 1.2' W. This pair is part of a fascinating group of numerous emission nebulae (LMC-N160 and LMC-N159) just 35' S of the Tarantula nebula. At 200x with a UHC filter, this knot appears very bright (slightly brighter than NGC 2085), fairly small, round, ~30" diameter. Without a filter a faint star is near the center. Mag 10 supergiant HD 269953 (misidentified as NGC 2086 in the ESO catalogue), which is nearly attached to the NE side of NGC 2085, lies 1' W.

[Ivan Maly]

Another memorable region indeed. Here are my notes from the observation made with a 5.5", followed by a scan from Dunlop's catalog (I assume it is not in copyright) and some additional notes I made after returning home.

Dunlop 152 is hypothesized (SEDS “??”) to be the brightest (S-most) knot in the “lucky shamrock” complex NGC 2078, 2079, 2083, 2084 – namely NGC 2079. This complex lies S of the Tarantula, past the nicely resolved (“grainy crescent”) NGC 2074 and the “double double” complex of NGC 2077, 2080, 2085, and 2086, whose members display their highly unequal brightness at low power. Photo chart 79-11 in NSOG vol. 3 is very helpful, and there is a separate one for [the complex of NGC 20-] 78-79-83-84. All four of its members are discernible without difficulty at low power, and the fainter ones form a nebulous semicircle around more deeply separated and brighter -79. These objects are in the “arm” of the LMC, running toward the bar from 30 Dor.

797

[Above is Dunlop’s drawing of his #152 (inverted). His note reads: “A cluster of six or seven small nebulae, forming a square figure 5’ or 6’ diameter, with several minute stars mixt. This is a very pretty group of nebulae.” Almost undoubtedly it is not NGC 2079 alone but the entire group involved with it, which I saw as the “lucky shamrock”.]

[Steve Gottlieb]

John Herschel was the one who added the "??" to the identification of NGC 2079 = Dunlop 152, though if he had seen the sketch you would think that would have nailed the identification with the entire complex. Unfortunately, Dunlop's positions were typically pretty poor -- in this case about 15' too far SE -- and Herschel was often frustrated trying to match the correct identification.

Here's John Herschel's sketch for comparison -- cut out from his wonderful map of the LMC with north up

798

[Ivan Maly]

That's a great-looking map. What publication is it from?

In some cases I found that Dunlop's objects not in the NGC may be far from the coordinates given but quite unambiguously described. Also it seems that a number of neighboring objects may be offset from the coordinates given in an identical way, which makes their collective identification unambiguous. Naturally I would not spend my time on this kind of identification work were I in South Africa with an 18.5" ;)

[Steve Gottlieb]

That's a great-looking map. What publication is it from?

Herschel modestly titled the map "First Approximation to a chart of the Nubecula Major, or greater Magellanic Cloud", but he did a wonderful job mapping the positions of the main stars with a 5-inch apochromat. This work began on 2 Nov 1836 and was completed on 26 Mar 1837. He worked across the LMC in 34 different zones with his refractor, taking down the positions of all stars down to roughly 10th-magnitude.

The completed catalogue of LMC stars and nebulae was published in his 1847 CGH catalogue -- "Results of astronomical observations made during the years 1834 to 1838 at the Cape of Good Hope". The drawings of all nebulae proved an overwhelming task, but you can download the map here (https://www.repository.cam.ac.uk/handle/1810/226363)

[Ivan Maly]

Thank you, Steve. Indeed he was well equipped on that trip, with a refractor as well... surely not an "apochromat" though ;) Wonderful map, I wish I had it before.

[Steve Gottlieb]

Oops, he may have journeyed to the Cape with state of the art equipment but not with an apochromat:D

By the way, his 5-inch equatorial achromatic refractor had a 7-foot focal length (previously used at Slough to measure double stars)

[FaithJ]

Thanks Steve, these are now on my list for my trip to Australia in March/April. :)

[Steve Gottlieb]

I wish I could join you, Faith, but I'll probably wait another year to return (visited last November). If you spent any time with the LMC in your earlier visit to Australia, you know how easy it is to get overwhelmed trying to identify objects in the LMC as there are often multiple clusters/nebulae in field after field. So best to prepare as much as possible in advance!

Have you seen Mati Morel's "LMC Visual Atlas 2000"? It includes 31 charts using the GSC (down to mag 15), creating very detailed maps in an 11" x 8.5" spiral-bound notebook. I've found it pretty helpful in my trips, though I don't know if it's still available.

[FaithJ]

Hi Steve, no I've not seen it but I've heard of it. I have just looked it up on Amazon (UK) and it's currently unavailable. However, I do have Jenni Kay's softback guide to the Magellanic Clouds, which is published by the Webb Deep-Sky Society, and have downloaded some charts from Patrick Kavanagh's website Clouds of Magellan (http://www.cloudsofmagellan.net.au/)

[Marko]

Have added a chart with all what is being discussed by Steve above having labels. This comes from my selected charts done for a week long trip in 3/2010. We see both the 1955 area, the 2014 area and the 2032 area which I consider a fantastic local area to explore with globular 2004 thrown in 'for free'.

Also of note near the bottom of this chart is a group of clusters that has been called 'The Grapes' locally by experienced observer Albert Highe.

806 (Please excuse that this one is not a negative format)

For an extensive set of charts you may visit my site here:
http://www.astrospotter.com/SouthernSkyAllCharts

[Ivan Maly]

Kay was also one of the lead authors of the third ("southern") volume of the Night Sky Observer's Guide. I found the chapters on the Magellanic Clouds in this volume exceptionally helpful on both of my trips. It seemed to me that a lot of globular clusters mentioned and plotted there are considered open now - actually almost all of them. With that in mind, however, their classification as "globular" certainly hits the nail on the head as far as their visual appearance, so it is actually useful.

[FaithJ]

I am thinking of taking the Night Sky Observers Guide Vol 3 with me, even though it is quite a large and heavy book. That said, I carried it from Texas back to the UK in 2010 (I bought it at TSP).

[Ivan Maly]

Those of you who are fully computerized will laugh but on both of my trips a separate, huge Rubbermaid-style clamshell was carrying pretty much only astronomy books and atlases (such as this NSOG volume) and the tripod... this arrangement actually saved the books when two 1.2-liter bottles of Australian rum clanked hard against each other in the other clamshell and only one of the bottles survived. N.B. travelers: Canon IS binoculars are not only waterproof but also rum-proof. Highly recommended for trips to Oz ;)

[FaithJ]

I remember reading about the rum incident on your blog. I had a similar incident - sort of similar in that it involved copious amounts of liquid - when my bag, in company with all the rest from the flight, was left on the tarmac by the brains trust that is the baggage handlers at Bangkok Suvarnabhum Airport during a tropical downpour and all my stuff got soaked. Fortunately there was nothing that was valuable or easily damaged in there and my Sky and Telescope Pocket Sky Atlas is waterproof anyway. I had to spread everything out in my hotel room to dry. The less said about that trip - not a pure observing trip, fortunately - the better, it was a bit of a disaster (http://www.fjastronomy.com/washout-down-under-a-tale-of-woe/) from start to finish for various reasons.
Next time, I will put my stuff inside a bin liner.