N105 Superbubble

A beautifully bright superbubble

Image credit Robert Gendler

Central Coordinates:

RA: 05h 09m Dec: -68° 53′

Diameter: 290 x 195 light-years

OB Associations: LH 31

NGC Objects: NGC 1855, 1858

N105, lying against the rich lustre of the northwestern outskirts of the bar

N105 is the second of the pair of neighbouring superbubbles made magnificent by their dazzling inhabitants, the other being N103 so brilliantly highlighted by the blazing young globular cluster, NGC 1850.

LH 31 + N105A = NGC 1858 (OB Association + Emission Nebula)

RA 05 09 56.0 Dec -68 54 06 Mag 9.9 Size 4 x 2′

16″ at 228x: LH 31 = NGC 1858 is a beautiful assemblage of stars, 3.5′ x 1.5′ elongated NNW-SSE, in which a dozen or so stars lie tangled up in the exquisite glow of unresolved stars and nebulosity. Mag 12 HD 269116 lies on the south side and on the western side of the association lies mag 13.7 Brey 16, a rare eclipsing binary, consisting of a Wolf-Rayet WN4 star and an O5-class blue supergiant. Another Wolf-Rayet star, mag 13.9 Brey 16a, lies embedded in a bright little patch of nebulosity that lies at the northern end of the complex. The binary cluster, BRHT 48a + b, lie off the glow’s northwest side. Separated by ~1′, they appear remarkably similar in size, shape, and brightness – both ~10′, fairly faint, and round. No stars resolved.

N105A’s nebulosity without a filter is bright and patchy. It has a strong response to the UHC filter and appears quite unusual in that it is brightest along both its eastern and western edges, fading to faint in the centre. The patch lying at the north end is irregularly round and beautifully bright. The edges of the nebula dissolve away into the background sky in a rapid fade-out.

The stars within NGC 1858 are at different phases of their evolution. Researchers have detected a protostar, a very young, emerging star, indicating that star formation within the cluster may still be active or has stopped very recently. Credit: NASA, ESA and G. Gilmore (University of Cambridge)

NGC 1854/55 + BSDL 748 (Young Globular Cluster + Binary Cluster)

NGC 1854/55: RA 05 09 21.1 Dec -68 50 39 Mag 10.4 Size 2.3 Age ~80 million years

BSDL 748: RA 05 09 28.4 Dec -68 51 01 Mag – Size 0.8′ x 0.7′

16″ at 228x: This is a stunning young globular cluster. It appears beautifully bright, 1′ in diameter, and slightly elongated N-S. It has a rich even glow brightening to a very bright core (NGC 1854). The surrounding halo is much fainter, and a few small, faint stars are resolved in it at 333x. A very small, bright knot is attached to its north end. The small companion, BSDL 748, lying east-southeast of the young globular, appears as a small, round, faint knot of stars.