N120

A fascinating complex containing a wind-blown bubble and a SNR

Image credit Robert Gendler

RA: 05h 19m 04s Dec: -69° 38′ 56″

Diameter: 429 x 326 light-years

Local OB Associations: LH 42

NGC Objects: NGC 1918

SNR N120, together with several H II regions and a wind-blown bubble forms a large nebular complex (which is also called N120) whose shape forms a bright, incomplete ring open to the south

Low magnification observation

At low magnification and without a filter, N120 = NGC 1918 is a beautifully soft collection of hazy nebulae, whose semicircular shape is embedded in the glorious star-dust haze of the LMC’s bar. The scene is dominated by the two gloriously bright mag 11 stars, and studded with a scattering of stars. Like all these wonderful complexes lying in the bar, the UHC filter really makes it stand out from the haze. The largest nebula, N120C, lying on the east side appears as a brightish, roundish glow and the rest of the complex’s nebulosity extends westwards from it as an elongated glow of ~5′ length. The OIII filter, aided by averted vision, reveals the SNR as a haze so faint, it is almost like an impression rather than a sighting… which somehow seems fitting when I consider that I am looking at the leftovers of the explosive end of a massive star’s life.

LH 42 (OB Association)

RA 05 18 58.0 Dec -69 39 30 Size 2′ x 1.5′

16″ at 228x: The bright stars of OB association LH 42 are immersed in the beautifully uneven and diffuse nebulous glows. (Is there anything as pretty as the brights sparks of stars lying against a nebulous haze?) A striking pair of stars dominate the scene: Mag 11.6 Brey 22 (Wolf-Rayet star (Brey 22) and mag 11.1 HD 269382 (O-type star) side-by-side, separated by a mere 9″. A wonderful sight! In all, close to 20 mag 14 and fainter stars are resolved.

N120A (Wind-blown Bubble)

RA 05 19 16.0 Dec -69 38 12 Mag – Size –

16″ at 228x: N120A surrounds mag 12.7 blue supergiant BI 141 (type B3Iab) that lies embedded in the nebulosity and without a filter the nebulosity appears as a faint, round mist of nebulosity with no edges. The star appears to lie towards the western side. The nebulosity has a good response to the UHC filter, appearing ~20″ in diameter, round, uneven and with fairly well-defined edges. The star now appears more towards the centre of the nebulosity.

N120B (Open Cluster)

RA 05 19 05.0 Dec -69 38 48 Mag – Size –

16″ at 228x + UHC filter: N120B is the smallest and the brightest of the nebulae; appearing as a very small, bright knot of light with crisp edges.

N120C (Emission Object)

RA 05 19 05.0 Dec -69 38 48 Mag – Size –

16″ at 228x + UHC filter: This is the complex’s biggest section, a bright, even glow, just off-round and around 45″ in diameter. Its edges are quite well-defined and fade away rapidly. The rest of the complex’s nebulosity extends from N120C as an elongated glow of ~5′ length.

N120D (Emission Nebula)

RA 05 18 27.8 Dec -69 39 50 Mag – Size –

16″ at 228x + UHC filter: N120D appears as a small, faint misty smudge of nebulosity that simply fades away at the edges. Without the filter a star is involved in the nebulosity.

SNR N120 (Supernova Remnant)

RA 05 19 04.5 Dec -69 38 56 Size 1.4′ × 1.7′ Age 7,300 years

16″ at 128x + OIII filter: A dark sky, superb transparency, and not a little time is required to examine this incredibly faint SNR, lying between N120B and N150D. Under ideal conditions it is just barely visible as a very diffuse haze. A slightly brighter, but still very faint, and narrow arc-like sliver lies on the haze’s SE edge. It is also very diffuse and has no edges, just a narrow sliver fading away into the surrounding haze.

No matter how many times I look at a SNR, be it in the LMC or our own galaxy, and no matter how small a portion of the SNR I can see, I cannot describe the sense of wonder I experience at seeing the little smudge of light that represents the life of the universe past, present and future.