LMC 4 Supergiant Shell

Southern Periphery

A region of fiery star birth and death

Image credit & copyright: Team Ciel Austral

RA: 05h 32m Dec: -66° 10′

Diameter: –

OB Associations: LH 70, 75, 78, 79, 86, 92

NGC Objects: 2004, 2011, 2020, 2021, 2053

LMC 4 is so enormous that its colossal cavity is on a separate page:

LMC 4 Cavity

Supergiant Shell LMC 4 Southern Periphery

The southern periphery of the supergiant shell LMC 4 is arguably one of the Cloud’s most complicated and diverse regions. It has three magnificent complexes and an exotic object, all within a celestial stone’s throw from each other: the Sextant, Superbubble N57A, the Seagull Nebula, and NGC 2020, a rare Wolf-Rayet bubble, along with stars, clusters, stellar associations and great drifts of nebulosity.

Low magnification overview

The Sextant is one of the most beautiful objects in the Cloud with its arc of glittering young stars and clusters forming a perfect sixth of a circle, and its two nebulous superbubbles, one at either end. Without a filter it is a graceful arc of mixed magnitude stars intertwined with the beautiful glow of nebulosity. With the UHC filter it is flooded with nebulosity, and the superbubble on the western side (N51D) stands out boldly, while the eastern side superbubble (N51A) only shows a partial bubble with some faint nebulosity on the northeast side and a few scraggles along the southeast side.

N57A (a superb Wolf-Rayet bubble) and N57C (a superbubble) are a most intriguing (but unrelated) pair of neighbours, and their glowing nebulosity is superb at low magnification with the UHC filter; the perfect ring of the bubble blown by a single star contrasting with the beautiful pearly haze of nebulosity of the strangely shaped superbubble, blown by the lives and deaths of the massive members of OB 76. And the dusty N59 Seagull Nebula is certainly one of the Cloud’s masterpieces. Luminous nebulosity, dark dusty areas, and sparkling stars… it is superb both with and without a UHC filter. North of these complexes lies a swathe of OB associations and clusters leading the eye northwards to the Quadrant and thus into the supergiant shell’s cavity.

N51 Sextant

A spectacular complex

N51 Sextant

A spectacular complex

N51 Sextant

N57A Superbubble

The Cosmic Reef superbubble

N57A Superbubble

The Cosmic Reef superbubble

N57A Superbubble

N57C Wolf-Rayet Bubble

NGC 2020, a dazzling Wolf-Rayet bubble

N57C Wolf-rayet Bubble

N57C Wolf-Rayet Bubble

NGC 2020, a dazzling Wolf-Rayet bubble

N57C Wolf-rayet Bubble

N59 Seagull Nebula

A dusty, glowing seagull

N59

N59 Seagull Nebula

A dusty, glowing seagull

N59

SL 497 (Open Cluster)

RA 05 28 23.4 Dec -67 38 33 Mag – Size 0.9′

16″ at 228x: This cluster appears as a faint, off-round haze, ~18″ in diameter, with a very slightly brighter centre.

SL 497

SL 498 (Open Cluster)

RA 05 28 34.8 Dec -67 13 35 Mag 12.0 Size 1.2′

16″ at 228x: SL 498 appears as a fairly bright, off-round cluster, ~30″ in diameter. It has a slightly gritty looking appearance and only one small star is resolved, lying at its southwestern edge.

SL 498

SL 522 (Open Cluster)

RA 05 30 37.4 Dec -67 11 08 Mag 12.1 Size 1.0′ x 0.9′

16″ at 228x: This cluster appears as a fairly faint, round, glow, ~25′ in diameter.

SL 522

NGC 2004 (Young Globular Cluster)

RA 05 30 41.3 Dec -67 17 22 Mag 9.6 Size 3.0′ x 2.8′ Age ~16 million years

16″ at 228x: A spectacular young globular cluster lying in a rich, starry field! And at 16 million years of age, it is a mere fledgling of a young globular cluster. It appears bright, ~3′ in diameter, with a small, dazzling core. Its halo is gorgeous with stars spiraling out like a celestial fireworks Catherine wheel, with around two dozen stars resolved. A mag 12 star, blue supergiant R109, lies just beyond the northern edge.

NGC 2004

HS 338 (Open Cluster)

RA 05 31 44.9 Dec -66 11 07 Mag – Size 0.9′

16″ at 228x: HS 338 is a very faint cluster, a mere dab of stellar light, ~10″ in diameter.

HS 338

LH 70 (OB Association)

RA 05 31 59.0 Dec -67 22 06 Mag – Size 7′ x 4′

16″ at 228x: LH 70 is a very attractive, oval-shaped stellar association, 5′ x 2′, oriented E-W and consisting of half a dozen mag 13 and fainter stars set against a rich glow of unresolved stars. Exotically, the brightest object in LH 70 is a background galaxy shining through the Cloud. LEDA 3700089 appears as a bright, round glow, ~25″ in diameter. The small cluster, HS 341 lies to the SE of the galaxy, and it appears as a fairly bright streak, ~12″ in size, oriented N-S.

LH 70

LH 75 + NGC 2011 (OB Association + Binary Cluster)

LH 75: RA 05 32 19.0 Dec -67 31 18 Mag – Size 3′

NGC 2011 : RA 05 32 19.8 Dec -67 31 17 Mag 10.6 Size 1.0′ Sep 0.47′ PA 163°

BRHT 14b: RA 05 32 20.0 Dec -67 31 42 0.45 mag – Size –

16″ at 228x: LH 75 is a bright little 3′ association, roundish in shape, that stands out well against its starry and nebulous background. It is dominated by NGC 2011 which appears as a very bright, tight knot of stars in which three stars are resolved, hemmed in by a bright glow of unresolved stars that is almost triangle-shaped and 1.5′ in diameter. A 3′ line of LH 75’s brighter stars, oriented E-W, passes through the south end of the glow, and NGC 2011’s binary companion, BRHT 14b is part of them – it appears as the bigger and fuzzier star lying due south of NGC 2011. The easternmost star of the line is the cluster KMHK 1050 and increasing the magnification to 333x shows it is encased in a faint fuzziness of unresolved stars.

LH 75 + NGC 2011 + BRHT 14b

N56 (Emission Nebula)

RA 05 32 38.7 Dec -67 32 56 Mag – Size –

16″ at 228x + UHC filter: N56 is a large swathe of faint nebulosity. N57 sweeps north-northeast from the superbubble N57A and merges into N56, which continues to sweep north-northeast before dramatically streaming east, flowing north of the Seagull Nebula and a little further east of it before petering out. The tapestry of nebulosity looks like an Impressionist’s softest brush strokes of faintest pearl-coloured light: pale, wraith-like smudges and tendrils against the rich starry background. And in the way of faint nebulae, there are no discernible edges; they simply dissolve into each other and into the starry sky.

N56

LH 78 (OB Association)

RA 05 33 18.1 Dec -67 31 20.4 Mag – Size 4′

16″ at 228x: Standing out well against the starry and nebulous background, LH 78 is lovely – a round, loose group of a dozen mag 12-13.5 stars set against a backdrop of soft, glowing unresolved stars, 3′ in diameter. The association appears attached to the southern end of the long, narrow, N-S oriented association LH 79.

LH 78

LH 79 + NGC 2021 (OB Association + Open Cluster)

RA 05 33 30.1 Dec -67 27 18 Mag – Size 7′ x 3′

NGC 2021: RA 05 33 30.3 Dec -67 27 11 Mag 12.1 Size 0.9′

16″ at 228x: LH 79 is a striking stellar association, elongated N-S ~5′ x 3′, and consisting of a mix of brighter and fainter stars of which around a dozen are resolved. The association stands out well against the starry and nebulous background. NGC 2021 lies just north of centre in LH 79 and appears as a bright, compact knot, slightly off-round, ~25″ in diameter. No stars are resolved. LH 79’s narrow stream of stars flows south for 3′ and they appear to attach to LH 78 at the southern end.

LH 79 + NGC 2021

BRHT 63a,b (Binary Cluster)

BRHT 63a: RA 05 34 29.0 Dec -67 27 12 Size 0.22′ Sep 0.53′ PA 151°

16″ at 228x: This binary pair looks like a pair of very faint and very small glows, elongated NNW-SSE, almost like a pair of smudgy and curiously stretched stars.

BRHT 63a,b

Brey 52 (Wolf-Rayet Star)

RA 05 34 52.1 Dec -67 21 28 Mag 14.9

16″ at 228x: Brey 52 has a stunning location – it lies just south of a brilliant pair of blue supergiants that dominate the scene – mag 10.9 HD 269797 (the westernmost star) and mag 10.3 HD 269801! Unfortunately, their brilliance washes out their exotic neighbour, but what a glorious pair of sparklers in the eyepiece.

Brey 52

LH 86 (OB Association)

RA 05 34 31.1 Dec -67 07 27 Mag – Size 0.95′ x 0.85′

16″ at 228x: LH 86 is a pretty, 5′ x 3′ oval stellar association, oriented NNW-SSE, and consisting of a dozen mag 12 and fainter stars scattered against the faint glow of unresolved stars.

LH 86

SL 582 (Open Cluster)

RA 04 55 53.0 Dec -69 42 54 Mag – Size –

16″ at 228x: SL 582 appears as a bright, drop of fuzzy stellar light, 20″ in diameter. It forms a nice “pair” with mag 10.4 HD 269789 that lies 1′ SE.

SL 582

KMHK 1098 (Open Cluster)

RA 05 34 40.3 Dec -67 30 14 Mag – Size 0.9′ x 0.8′

16″ at 228x: This cluster appears as a bright, narrow streak, ~20″ in size, elongated NNW-SSE with a small star lying off its southwestern edge.

KMHK 1098

LH 92 (OB Association)

RA 05 36 39.0 Dec -67 27 06 Mag – Size 2.5′

16″ at 228x: LH 92 appears as a pretty little 1.2′ row of four small stars, oriented N-S; the northernmost star being the brightest. The southern end has a small, faint roundish gathering of unresolved stars.

LH 92

NGC 2053 (Open Cluster)

RA 05 37 41.6 9 Dec -67 24 4 Mag 12.5 Size 1.5′ x 1.3′

16″ at 228x: NGC 2053 appears as a relatively bright, oval glow, 1.0′ x 40″ elongated NNE-SSW. It is enticingly gritty, especially in its halo, but with no stars resolved.

NGC 2053

N66 (Planetary Nebula)

RA 05 36 20.7 Dec -67 18 07 Mag – Size 0.13

Hubble’s 1991 image of planetary nebula N66. Credit: J.C. Blades/NASA/ESA

This is a very special planetary nebula. On June 26, 1991, Hubble Space telescope imaged N66 – it was the first time a planetary nebula had ever been seen so clearly in a galaxy beyond our own Milky Way. The image reveals complex structures and details as small as 0.08 light-years across (0.1 arcsecond resolution). Not only that, but it’s also a fascinating planetary nebula because according to Pena et al (2004), it is the only confirmed planetary nebula where the central star is a Wolf-Rayet star of the nitrogen sequence (WN). They went on to say: “The object presents a complex multipolar structure, dominated by very bright lobes located at both sides of the central star and separated by a narrow waist. In addition there is a pair of very extended and twisted loops, also pointing in opposite directions; their symmetry axis and collimation angle differs from those of the bright lobes.” The star brightened dramatically in 1993 and 1994, but returned to its previous brightness level within four years. What an amazing planetary nebula to observe! But alas, (as I expected) it remained invisible to my eyes and telescope, but it was wonderful searching for it among the multitude of stars. (Note: some sources muddle N66 in the LMC with N66A in the SMC.)