LMC 8 Supergiant Shell

Two enormous and utterly gorgeous star clouds reside in LMC 8

Image credit & copyright: Team Ciel Austral

RA: 05h 03m Dec: -70° 30′

Diameter: 2,900 light-years

OB Associations: LH 18, 23, 24, 26

NGC Objects: NGC 1813, 1815, 1823, 1833, 1837, 1845

Supergiant Shell LMC 8

LMC 8 is located in the southwestern corner of the Large Magellanic Cloud and its shell is open to the southwest, with nebulous filaments to the southeast and northwest, and significant amounts of internal diffuse emission in the east of the shell (alas, not visible to us).

The SGS contains four OB associations, two of which are vast star clouds, LH 24 and LH 26 (together they comprise NGC 1845). Smaller LH 18 flows off the northwest end of LH 26 in a north-northwest direction and its trio of brighter clusters gives it an odd boomerang shape. Very small LH 23, embedded in N191, lies some distance off LH 24’s southern end and its small, bright glow contains a great little treasure – N191A, a low excitation blob. N186, a large but very ghostly superbubble, lies in the northeast of the SGS.

Low magnification overview

LMC 8 is dominated by NGC 1845 which comprises the two beautiful and enormous star clouds, LH 24 and LH 26. Together they stretch ~20′ x 10′ in a NNE-SSW direction. Small, fuzzy SL 232 marks the NNE end, and the small brightish glow of emission nebula NGC 1833 marks the south-southwest end. And between them, the clouds are filled with a multitude of mag 12+ stars which, like all the LMC’s large star clouds are arranged in beautiful stellar patterns and chains. (The four bright mag ~9.5 stars that form a noticeable rectangle are Milky Way stars superimposed on the star clouds.) LH 18 appears as a delightful, albeit faint, boomerang shape thanks to the haze of its clusters. The superbubble, N186, is invisible without a filter, and with the UHC filter appears as nothing more than a couple of tendril-thin, almost-transparent strands of nebulosity; just visible. With the UHC filter, the nebulosity in the star clouds is restricted to the faint nebulous glow of NGC 1833 at the southern end of the clouds. N191 at the southern end of the supergiant shell, appears as a tiny, faintly glowing shard of nebulosity.

N186 Superbubble

A threadbare superbubble

N186 Superbubble

A threadbare superbubble

N186 Superbubble

SL 158 (Open Cluster)

RA 04 59 14.0 Dec -70 15 18 Mag 11.9 Size 1.3’

16″ at 228x: Lying just off the southwestern rim of superbubble N186, SL 158 appears beautifully bright, round, ~20” in diameter, no stars resolved.

SL 158

SL 160 (Open Cluster)

RA 04 59 27.0 Dec -70 25 00 Mag – Size 1.0′

16″ at 228x: SL 160 appears as a very faint, very small, round haze.

SL 160

NGC 1815 (Open Cluster)

RA 05 02 26.7 Dec -70 37 19 Mag 12.4 Size 1.2′

16″ at 228x: NGC 1815 appears as a relatively bright, round, smooth and even glow, 20″ in diameter. No stars are resolved. What looks like a mag 12.6 star lying 1′ SSE, is actually a cluster, BSDL 470.

NGC 1815

LH 18 (OB Association)

RA 05 03 39.0 Dec -70 20 54 Size 8′ x 4′

16″ at 228x: LH 18 is a large association with a delightful boomerang shape owing to the arrangement of the trio of clusters, NGC 1813, NGC 1823, and SL 200. The field is scattered with mag 12-13 stars and a large number of fainter stars (and three additional, very small clusters), along with the beguiling background haze of unresolved stars. Like all associations, it is very interesting to look at the whole of the association – the arrangement of the clusters among the stars – before inspecting the clusters as individuals (HS 94, NGC 1813, 1823, SL 200 KMHK 493, 494 – below).

LH 18

HS 94 (Open Cluster)

RA 05 02 28.8 Dec -70 17 20 Mag – Size 0.7′

16″ at 228x: The westernmost of the LH 18’s clusters, HS 94 appears as a very faint, very small, round droplet; its pale light all but lost in the maze of stars.

HS 94

NGC 1813 (Open Cluster)

RA 05 02 42.8 Dec -70 19 13 Mag 12.8 Size 0.8′

16″ at 228x: NGC 1813 appears as a relatively bright, hazy, irregular glow, 30″ in diameter. A mag 14 star lying on its southern end is resolved.

NGC 1813

NGC 1823 (Open Cluster)

RA 05 02 42.8 Dec -70 19 13 Mag 12.8 Size 0.8′

16″ at 228x: NGC 1823 appears as a fairly faint, hazy, irregularly shaped glow, ~35″ in diameter. Three small stars are resolved on the edges of the glow.

NGC 1823

SL 200 (Open Cluster)

RA 05 03 46.7 Dec -70 24 01 Mag 12.8 Size –

16″ at 228x: This is the largest of the three clusters that contribute to LH 18’s boomerang shape. It appears as a fairly bright, hazy, narrow oval shaped glow, ~55″ x 20″ in size, elongated N-S. No stars are resolved. Picked up with averted vision, a very small and very faint stellar glow lies off its southern edge; this is a tiny cluster, BSDL 500.

SL 200

KMHK 493 + KMHK 494 (Open Clusters)

KMHK 493: RA 05 03 45.0 Dec -70 21 12 Mag – Size 0.5′

KMHK 494: RA 05 03 50.7 Dec -70 22 23 Mag – Size 0.5′ x 0.4′

16″ at 228x: These two extremely small clusters are separated by 1.1′, and both appear as nothing more than very faint, stellar beads of dim light set among the lovely field of stars, best seen with averted vision.

KMHK 493, 494

HS 104 (Open Cluster)

RA 05 04 02.0 Dec -70 37 38 Mag – Size 0.5′

16″ at 228x: Lying on the outskirts of the star cloud, HS 104 appears as a very faint, very small, round smudge of palest light.

HS 104

N191 (Low Excitation Blob)

RA 05 04 34.0 Dec -70 54 18 Mag – Size 1.5′ x 1.0′

16″ at 228x: N191 is an enchanting little object: a bright low excitation blob wrapped in a larger mist of nebulosity and the whole framed within a lovely triangle of stars. It appears as a brightish slash of nebulosity, ~1’ in size and elongated NNW-SSE . Four of OB association LH 23’s stars are resolved in the glow. The nebulosity appears as two distinctly different glows – N191B to the NNW is a very faint and diffuse round glow and N191A on the SSE end is subtly bright… as one feels it should be… for it’s a LEB! What a delight!! The mag 12.7 blob responds well to the UHC filter, a ~10” brightish silky glow, very slightly elongated N-S, and with edges that melt rapidly into the faint, roundish glow that surrounds it and that itself rapidly melts away into the sky. With and without the filter everything that comprises exquisite little N191 makes one realise that things really are the sum of all their parts.

N191

N190 = NGC 1833 (Emission Nebula)

RA 05 04 23.5 Dec -70 44 07 Mag 11.7 Size 4.0′

16″ at 228x + UHC filter: NGC 1833 appears as a moderately bright nebulous crescent oriented NNE-SSW, 1.2′ in diameter, and whose opening to the SE is filled with fainter nebulosity. It has nicely defined edges. Unfiltered, a mag 13.4 star is resolved within the crescent shaped section of nebulosity, along with 3 more fainter stars. The nebulous glow forms an attractive pair with the starry-string cluster NGC 1837 that lies 3′ ENE.

NGC 1833

LH 24 + LH 26 = NGC 1845 (Star Cloud)

LH 24: RA 05 04 48 Dec -70 43 00 Size 16′ x 10

LH 26: RA 05 06 19 Dec -70 28 50 Size 17′ x 10′

16″ at 228x: NGC 1845 comprises the two beautiful and enormous star clouds, LH 24 and LH 26. Together they stretch ~20′ x 10′ in a NNE-SSW direction with a slightly less-starry nibble out of the western side which divides the two star clouds. The open cluster SL 232 (which is often taken as NGC 1845) marks the northeast end, and the two open clusters NGC 1833 and 1837, mark the southwest end. The two star clouds are filled with a stunning mix of mag 11+ stars, too many to count – a beautiful assemblage of stars whose stellar patterns and chains, small gatherings and small open clusters are a delight to explore! Faintish patches of unresolved stars lie around here and there like small glowing puddles among the stars. Four bright mag ~9.5 stars that form a noticeable trapezium (trapezoid in North American English) are Milky Way stars superimposed on the star clouds. (They are a lovely quartet and it’s always nice to bump into friends from home in the Cloud!)

LH 24 + LH 26

N189 (HII Region)

RA 05 04 55.1 Dec-70 07 41 Mag – Size 1.5′ x 1.2′

16″ at 228x + UHC filter: N189 appears as a faint, off-round mistiness, ~30″ in diameter and with no discernible edges; it simply melts away into the sky.

N189

NGC 1837 (Open Cluster)

RA 05 04 56.9 Dec -70 42 56 Mag 10.6 Size 1.3′

16″ at 228x: An unusual looking cluster, fairly bright NGC 1837 is a 1.2′ long string of stars extending N-S with half a dozen resolved mag 12.2-14 stars immersed in a faint haze of unresolved stars. The northern end of the string is a slightly bulbous, very irregular ~20″ knot of unresolved stars attached to the string by a mag 12.3 star. The starry-string cluster forms an attractive pair with the glowing nebulous NGC 1833 that lies 3′ WSW.

NGC 1837

BSDL 579 (Open Cluster)

RA 05 04 58.0 Dec -70 31 06 Mag – Size –

16″ at 228x: BSDL 579 appears as a very faint, very small, smudge of stellar light.

BSDL 579

SL 224 (Open Cluster)

RA 05 05 42.8 Dec -70 19 30 Mag 13.4 Size 0.9′

16″ at 228x: SL 224 appears as a relatively bright, round glow, 20″ in diameter, with a very slightly brighter centre. No stars are resolved.

SL 224

BSDL 635 (Open Cluster)

RA 05 06 15.0 Dec -70 29 36 Mag – Size 0.6′

16″ at 228x: This cluster lies just off SL 232’s southwest end and appears as a pretty bright, small and narrow slash of stellar light, elongated NNW-SSE.

BSDL 635

SL 232 (Open Cluster)

RA 05 06 19.8 Dec -70 28 50 Mag 10.2 Size 1.30′

16″ at 228x: SL 232 is often taken as NGC 1845. It appears as a moderately bright glow, 25″ in diameter, and just slightly off-round. No stars are resolved.

SL 232

SL 249 (Open Cluster)

RA 05 07 35.5 Dec -70 44 56 Mag 12.8 Size 0.8′ x 0.7′

16″ at 228x: SL 249 appears as a relatively bright, round glow, ~15” in diameter, with no stars resolved.

SL 249

SL 252 (Open Cluster)

RA 05 07 51.0 Dec -70 23 18 Mag – Size 0.6”

16″ at 228x: Averted vision picked up this tiny little cluster, nothing more than a very small and very faint, round pale glow.

SL 252

KHMK 581 (Open Cluster)

RA 05 08 18.0 Dec -70 34 30 Mag – Size 1.7′ x 1.5′

16″ at 228x: KMHK 581 appears as a very faint, round mistiness against the starry background, ~20″ in diameter. I would have passed right over it had I not known to stop and search for it.