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RA: 00h 59m 4.2s
Dec: −72° 10′ 42″
Ch: MSA:501, U2:441, SA:24
Ref: SIMBAD, Skiff20080430-s
Type: open cluster
Mag: B=?, V=?
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observed it from Paramatta, New South Wales, and included it as No. 25 in his catalogue of 1827. Using a 9-inch f/12 telescope, he described it as "A pretty large, pretty bright nebula, about 2.25' diameter, irregular round figure, resolvable, very slight condensation, not well defined at the edges." He observed it on 7 occassions.
Observed by Sir John Herschel at the Cape of Good Hope with an 18-inch f/13 speculum telescope. He recorded it as "B, L, pmE, pgmbM, 5', resolvable (ill seen, below the pole)." On a second occassion he called it "Cluster, imperfectly resolved; rather irregular figure; 5' diameter. Not equally condensed about centre; fades imperceptibly; has a double star (12th mag) in centre." His third observation was recorded as "B, L, irregularly round, gmbM, 3' or 4' in extent, fades away insensibly." His next observation was recorded as "B, L, neb with resolvable centre; irregularly extended into a kind of broad train as in figure, gently graduating away to the borders. 6' diameter." His final observation was recorded as "B, L, irregular figure, with a star 13th mag in most compressed part."
Recorded in "Observations of the Southern Nebulae made with the Great Melbourne Telescope".
See the discussion of Lithograph M.1.4 for the details.
"Dun 25; diam 3'; cluster, fairly condensed, inv in and surrounded by neb; SMC."
Bailey, S.I. (1908) A catalogue of bright stars and nebulae. Ann.Harv.Coll.Obs., 60(8), 199.
Remarks, p.216: "This object is fairly typical of many which occur in the Magellanic Clouds. It consists of a few stars involved n a more or less irregular nebuosity. There appears to be every gradation from a cluster of stars with only a suspicious of nebulosity, to a nebula in which a few stars are involved. At the end of this series is NGC 2070, 30 Dor, the brightest and most interesting of them all. In this case, the irregular nebulosity is the important feature, but this invovles a coarse cluster of stars. The scale of the Cooke plates is too small to show more than a few of the brightest objects which occur in th Magellanic Clouds."
Kron, G. E. (1956) Star Clusters in the Small Magellanic Cloud: I. Identification of 69 Clusters. PASP, Vol. 68. [1956PASP...68..125K]
Describes it as a blue cluster, noting the presence of nebulosity as well as very bright blue stars, probably blue supergiants. He notes that it is loosely concentrated towards the centre, is bright and exhibits nitrogen and hydrogen emission nebulosity.
(Catalogues of Hydrogen Alpha Emission Stars and Nebulae in the Magellanic Clouds, Astrophysical Journal Supplement 2, 1956, p315) notes that his nebula LH N 115-66 is "NGC 346. Nail 101. Excited by HD 5980." The nebula measures 9.7' x 8.2', is round with considerably irregular borders and exhibits very marked structural detail.
("Clusters in the Small Magellanic Cloud", Irish Astronomical Journal, Vol. 4, 1956) classifies it as an open cluster. He notes that "the stars are embedded in nebulosity and some are of sufficiently high temperature to excite the nebular spectrum."
("UBV photometry of star clusters in the Magellanic Clouds", Astronomical Journal, Vol. 73, 1968) find that the integrated V magnitude through a 60'' diaphragm is 10.3. They note that it is also known as Kron 39 and Lindsay 60. They remark that it is "embedded in bright emission nebulosity. This nebula is N 66 in Henize."
catalogue gives the size as 14', which is the size of the associated nebulosity. The cluster itself is only 5.2'.
(Sulentic and Tifft 1973) notes that this is a cluster+nebulosity in the SMC.
"A very young component in the pre-eminent starburst region of the Small Magellanic Cloud". A&A 517, A39.
"LHA115-N66, or in short N66 (Henize 1956), is the largest and the most luminous HII region in the Small Magellanic Cloud (SMC). It is also known as DEM S 103 and NGC346, the latter referring to the bright OB association located at its center. … N66 is considered to be the scaled-down counterpart of the Large Magellanic Cloud starburst 30 Doradus. It indeed hosts the largest sample of young, massive stars in the whole SMC with 33 O-type stars among which 11 are of type O6.5 or earlier. It contains at least one W-R star in the massive binary or maybe triple system HD5980. An age of ∼3 Myr has been estimated for NGC346 from evolutionary models in the H-R diagram.HD5980 lies behind a SNR which has no known optical counterpart. Compared to the Orion Nebula, N66 has an H-alpha luminosity almost 60 times higher. This radiant flux is also reminiscent of those of giant HII regions in distant metal-poor galaxies, such as regions A1 and A2 in IC 4662 lying 2.44 Mpc away. Therefore, N66 offers a valuable template for studying these kinds of distant galaxies with high resolution.
"Apart from its recently formed massive star population mentioned above, NGC346 also has a large population of low-mass, pre-main-sequence stars covering a mass range down to the subsolar regime. The PMS population is found to be mainly concentrated in a number of subclusters away from the massive star association. The typical ages of the PMS population derived from models appear to suggest that low-mass star formation events occurred at two different epochs about 4 and 10 Myr ago.
"The present study is concerned with massive star formation in the N66 complex. Clustered mainly in NGC346, as mentioned above, massive stars dominate the central part of the whole HII region with their strong UV radiation field. Twenty two of the above-mentioned 33 O stars are contained in the central cluster. The hottest star, W3, is reclassified as O2 III(f*). The most massive star,W1, of the central cluster, classified O4 III(n)(f) , has multiple components and the mass of the brightest component is at most 85 M_solar. The cluster has disrupted the bulk of the natal molecular cloud, and therefore not much CO emission is detected towards N66, except for two positions which are mapped in the (1–0) and (2–1) transitions.
"One of these CO peaks is associated with a remarkable feature of the whole landscape, a compact HII region, called N66A, according to Henize (1956). The HII region apparently lies at the south-eastern end of an absorption lane that runs over some 60 pc from north-west to south-east below the NGC 346 cluster. This paper is mainly devoted to this compact HII region. Despite extensive research on various components of the N66/NGC346 complex, few studies have so far dealt with this HII region. We attempt to demonstrate that this region represents the youngest episode of massive star formation in N66.
"A word of caution seems necessary about the name of this object. From their observations of H2 emission line and the ISOCAM LW2 band, Contursi et al. and Rubio et al. detected several embedded sources towards N66, which they alphabetically designated from "A" to "I". The IR source A should not be confused with the Henize N66A HII component, which corresponds to the IR source "H". In a similar way, NGC346 corresponds to "C"."
Their Figure 1 presents a "composite three-color image of the SMC HII region N66. The star cluster above the curling absorption lane is the OB association NGC 346. N66A is the brightest compact HII region lying at the eastern end of the dark lane. Note the wind-driven bubble centered on the brightest star HD 5980. The other bright star lying towards the field center is Sk 80. The image, taken with the ESO NTT/SuSI2, results from the coaddition of narrow-band filters H-alpha (red), [OIII] (green), and H-beta (blue). The field size is 336″ x 350″ corresponding to 100 x 103 pc. North is up and east to the left. … The NGC 346 cluster appears to be at the center of an HII bowl, the southern border of which is delineated by a compressed ionized gas front and an absorption lane running over some 60pc. In particular, N66A stads out as the most compact HII nebula of the whole region, with coordinates (J2000.0) RA = 00:59:14.8, decl = -72:11:01. The compact HII region is apparently associated with the compressed gas front and the absorption lane.
"The field of view of the NTT image is larger than that of HST ACS. It also displays a turbulent environment in the eastern side of N66 with many indications of shocked gas. In particular, the wind-driven bubble centered on HD 5980 is quite impressive. A narrow ridge can also be discerned towards the southern outer boundary of the complex. This feature is also affectedby stellar shock winds, as indicated by its remarkable [SII] emission."
Figure 2: "A composite three-color image of SMC N66A created using the HST ACS images in H-alpha (red), filter I, F814W (green), and filter V, F555W (blue). Field size 512 x 512 pixels, or 26″ x 26″ (approx 7.5 x 7.5 px). North is up and east to the left. … Figure 2 presents a high-resolution composite image of the N66A HII region … The compact HII region is about 10arcsec in diameter, corresponding to about 3 pc. It contains a strong absorption lane. Interestingly, two bright stars, labelled #1 and #2, are located towards the central part of the region, above the dust lane (see also Fig. 3.). Separated by 0.7 arcsec (about 0.2 pc) they are the main exciting stars of the HII region."
"N66A is clearly the most compact HII region of the N66 complex in the optical. Its relative compactness, brightness, and location suggest that it is probably a relatively younger generation in the N66 complex. It should belong to a distinct and rare class of HII regions in the Magellanic Clouds (MCs) called High-Excitation "Blobs", or HEBs. In contrast to the typical HII regions of the MCs, which are extended structures with sizes of several arc minutes corresponding to physical scales of more than 50pc and powered by a large number of exciting stars, HEBs are relatively dense and small regions of about 5 arcsec to 10 arcsec in diameter in the optical, corresponding to about 1.5 to 3.0 pc and excited by a much smaller number of massive stars. … These compact HII regions are also heavily affected by local dust compared to other ionized features of the complex in which they are hosted. This is also the case for N66A, which is marked by a prominent absorption lane of local dust crossing the whole nebula. The two other known examples of HEBs in the SMC are N88A and N81, which were also observed with HST.
"HEBs are usually located adjacent to ordinary giant HII regions or seen lying across them. This implies that they form as a consequence of triggering by a previous generation of massive stars in the complex. Simple reasoning suggests that HEBs and their small exciting clusters are formed from the material remaining after a preceding massive-star formation event. More specifically, the apparent association of N66A with the compressed ionized front and the absorption lane, both centered on the NGC 346 cluster, suggests that N66A is a secondary, younger generation of stars."
by Jim Lucyk: Burnhams V3 p1917.
writes: "In the Cloud's northern sector four objects fit within a wide telescopic field of view. NGC 346 is a large, nebulous star cluster, about as bright as the Trifid nebula, and has a conspicuous, elongated ridge of stars."
Vol 24 No 3 June 1971: "stars immersed in nebula in 12.5-inch."
15cm - by far the brtst feature in the SMC. lg br neb 10'x4' in pa35, brtr on NE side of cen cl. cl surrounded by bar-shaped neb 4'x2' perpendicular to lgr surrounding env. in cen of this is 1' region that is *ry and of hisfcbr. about six m13 *s res, plus additional ones at threshold in br neb. BS, 9Nov1993, LCO.
A 10-inch f/5 reflector at about 30x shows it as a pretty bright milky patch which is elongated roughly west-east, having a star involved on its eastern side.
1994-12-04, Die Boord, 6-inch f/8.6 Newtonian. Easy as a triangular glowing patch with a prominent star. Averted vision at 217x shows the patch as mottled with a couple of stars imagined.
1997-09-20, Sutherland (Karoo), SAAO plateau. 11x80 tripod-mounted binoculars. Skies excellent.
The brightest knot in the SMC, looks like a typical globular cluster. In these glasses, it appears as a lower surface-brightness version of NGC 362 nearby.
11x80: 1997-10-09, 02:30, Jonkershoek, seeing 3, transparency 3, darkness 3 "Bright knot in the SMC. Like a 8.5 mag globular cluster with no nucleus. Lies at the northern tip of the most nebulous portion of the SMC."
16-inch f/10 SCT (127x 290x)
The cluster is quite compressed with faint stars resolve and a outstanding double star on its north-eastern edge but easily picked out. The cluster displays a slightly north-east to south-west impression with hints of nebulosity. The south-eastern edge might be more define.
12-inch f/10 SCT (95x, 218x, 346x)
The wide field of view 95x shows several objects bathed in nebulosity. NGC 346 appears to be a soft roundish nebula with a slightly elongated E-W granular bar more or less 1.5' in diameter, embedded in stardust and nebulosity. High power 218x reveals a few splinter stars and an obvious double star in the brighter hazy star-point bar. With averted vision a dark nebula around 6' can be seen to the close west of NGC 346. Between NGC 346 and NGC 330 a string of faint stars show a very faint knot of nebulosity, which is most probably IC 1611, and part of the string. NGC 330 which can be seen in low power 95x seems to be a relatively bright granular patch with splinter stars in nebulosity barely an arc minute in size situated about 20' towards the SW from NGC 346. In higher power 218x the knot of stars in NGC 330, resolve into star points and mingle well with the surrounding nebulosity with a few faint stars on the top north edge. Towards the NE more or less 20' from NGC 346, NGC 371 can be seen as a lovely fully resolved splash of stars and well intervened with nebulosity, which extends slightly more to the west with fainter members running into the NGC 395 cluster, which shows the two cluster parts well. There are pieces of faint nebulosity that wisps throughout the star members of NGC 395, although the core of shows a bright uneven dense middle part, probably faint unresolved stars. With averted vision there seems to be a faint elongated NW-SE piece of nebulosity more or less 3' just NW of NGC 395. Just about 3' SE of NGC 395 a faint stringy patch of very faint stars can be seen I guess it could be NGC 1624. In a 0111 filter the rich complex field of view turns into a network of nebulosity and clumps of faint stars, which is just awesome.
Alldays (22.50S, 20.12E, 770m).
12-inch f/10 SCT (218x, 346x)
Situated about 20' North East of NGC 330, NGC 346 in contrast is covered in nebulosity and displays a large, elongated (NW-SE) very granular cluster embedded in stardust and nebulosity. A band of faint stars sprinkled in haze cuddle the area between the two clusters (52x). Take your time to discover a harvest of delightful objects in the SMC, there are just to many to deal with right now.
Instrument:12-inch Dobsonian Reflector Telescope.
Eyepieces:26mm Super Wide Field Eyepiece.
20mm Ultra Wide Angle Eyepiece.
Sky Conditions:Whole Milky Way is visible.
Transparency of the Sky:The sky is clean.
Seeing:Atmosphere stable with little interference.
Limiting Magnitude:Magnitude 6.
First Impression:This object looks like a cloud of gas and dust.
Chart Number:No.20(Extract taken out of "Atlas of the Night Sky").
Size:26mm Eyepiece:Field Of View:57'/10=5.7'.
20mm Eyepiece:Field Of View:50'/9=5.5'.
Size in Arc Minutes:5.6'.
Nebula is 5.6'*1.1'.
Brightness Profile:From the far outskirts to the central outskirts this nebula grows slightly brighter.
Challenge Rating:Fairly easy.
All over this nebula I have detected areas of uneven brightness while towards the far outskirts of this nebula there is dark lanes and some dark patches.
The Messier objects
The Bennett objects
The Caldwell list
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