N4 Complex

An eye-catching arrangement of stars, clusters, nebulae and a SNR

Image credit Robert Gendler

RA: 04h 53m 15s Dec: -66° 55′ 36″

Diameter: –

OB Associations: LH 4

NGC Objects: NGC 1714, 1715, 1731

N4 is very eye-catching with the scattered stars of NGC 1731 to the east wrapped in a soft and patchy mist of nebulosity, and a lovely 6′ arc of stars, oriented NW-SE, lying ~3′ to its west and whose open curve showcases the small, mismatched pair of emission nebula, NGC 1714 and 1715

LH 4 = NGC 1731 (OB Association)

RA 04 53 15.0 Dec -66 55 36 Mag 9.9 Size 8′

16″ at 228x: Easily two dozen faint stars are resolved in NGC 1731, scattered over a 4′ area elongated somewhat E-W. Its centrepiece is the double star HJ 3710 with its beautiful bright mag 10.7 blue supergiant and mag 12.7 companion at 12.9″. The double star lies in the binary cluster SL 82 and the rest of the cluster appears as a very small and faint haze to the immediate west of the double stars. To the east of the double stars one can see the very faint, very small, hazy smudge of the other member of the binary pair, cluster KMHK 212.

HS 51 (Open Cluster)

RA 04 52 44.5 Dec -66 52 55 Mag – Size 0.7′

16″ at 228x: There is a nice star hop to reach the small cluster HS 51 – one simply follows the irregularly spaced arc of stars that begin at the orangey mag 11.5 star, and diminish in magnitude as they curve to the NW, and there at the end, appearing like the faintest star of them all, although it’s a bit smudgy, is the very small, very faint cluster.

N4A = NGC 1714 (Emission Nebula)

RA 04 52 08.4 Dec -66 55 23 Mag 11.6 Size 1.1′

16″ at 228x + UHC filter: NGC 1714 and NGC 1715, separated by a mere 1′ form a very unusual and close pair. NGC 1714 appears as a beautifully bright, round knot, ~30″ in diameter, with a brighter core off-centre to the north. A brightish wisp extends to the west and a very much fainter one to the south. The nebula has crisp edges expect for the two wisps which have edges that simply fade out. Mag 11.0 WOH S 53, an M2-class supergiant, lies 1′ NW.

N4B = NGC 1715 (Emission Nebula)

RA 04 52 11.7 Dec -66 54 29 Mag 0- Size 1.1′ x 0.9′

16″ at 228x + UHC filter: Forming a lovely pair with NGC 1714 just 1′ SSW, NGC 1715 appears as a faint, diffuse glow, ~40″ in diameter. The soft round nebulosity has no edges and simply fades away into the surrounding sky. Without the filter the nebula looks deceptively like a bubble with a faint star dead centre. Mag 10.8 mag K-type star, HD 268261, lies 2.5′ NNW.

N4C (Emission Object)

RA 04 52 23.0 Dec -66 55 18 Mag – Size –

16″ at 228x + UHC filter: This tiny object, lying almost midway between two stars, remained invisible.

N4D (SNR)

RA 04 53 21.0 Dec -66 56 19 Size 3.7′ x 1.1′ Age –

16″ at 228x: The supernova remnant J0453-6655 is clearly visible in Henize’s Hα emission catalogue as a bright arc of optical filaments surrounding a cavity. For us observers, it’s not so beautifully obvious, but on a night of excellent transparency it appears, unfiltered, as a few smudges of very faint mist. It has a good response to the O III filter, appearing as a faint and very mistily patchy, nebulosity that has no edges but just fades away.