An Emission
Nebula, Containing a Rare Feature, Resides in a Nebulae Complex Tens of Thousands of Light Years Away From Us
Well, do not be afraid of the strange name of this object. It is, after
all, an NGC nebula that any observer can detect when observing from the
Southern Hemisphere even with telescopes as small as 8-inch of aperture.
Figure 1. The position of N214 in the Large Magellanic Cloud. North is up. |
N214C1 (also NGC 2103, DEM L2 293, and MCELS L367) is an
emission nebula included in the catalog of LMC emission nebulae published in 1956 by
Karl Henize. This object was originally discovered by John Frederick William Herschel in 1834. With an estimated visual magnitude of 10.8, it is the
brightest portion of a bigger nebula complex-N214-situated about 2° 15ʹ south
of 30 Doradus, the most conspicuous nebular
structure in our neighboring galaxy, the Large Magellanic Cloud. N214 is one of
the southernmost complexes in our satellite galaxy, lying south of the stellar
bar of that galaxy. It is a remarkable ongoing star-forming region
containing at least 8 components, most of them very faint (see Figure
2) according to F. Meynadier,
M. Heydari-Malayeri, and N R. Walborn in their paper “The
LMC HII region N214C and its peculiar nebular blob”. This
nebula holds the OB association3 LH 110 (Lucke & Hodge).
Most of the components are out of the reach of an
8-inch telescope, with N214C being the biggest and brightest portion by far,
thus being visible through that kind of optical instrument.
At 42x, this
object is clearly visible even without any nebular filter, looking like a
slightly north-south elongated nebulosity of smooth brightness. A more detailed
observation makes possible to detect, for moments, some brighter dots within
it. Through a UHC filter, N214C is, undoubtedly, a conspicuous nebula. The
filter improves the contrast of this HII region. Its overall shape is slightly elongated and its western edge looks a little less bright than the rest of this nebula (see lower panel on Figure 2).
Figure 2. The N214 complex (upper panel)
and the N214C nebula (lower panel) with
its two features. DSS image. North is up,
East to the left. |
78x – At this magnification, N214C appears somewhat elongated ( overall oval shape of N214C) and some stars members of the OB association LH110 start to
be discerned. These faint stars, embedded in the smooth nebulosity, have a longitudinal distribution coincident with the elongated direction of the HII region. In the central area of the nebula the brightest star of the whole object can be glimpsed, Sk -71°514, which is the main exciting source of the HII region and, in fact, is not a single
star but a compact cluster (Garmany & Walborn 1987). It has at least 6
members (massive stars) in an area 4" wide.
Using a UHC filter the view of N214C is interesting, being noticeable against the background sky with its shape being slightly elongated.
An inner brighter zone containing at least one star or bright
dot is visible at this power for moments using averted vision. This zone seems
to have a slight elongation and its edges look somewhat
fainter, with one of them appearing wider than the other. Orion Ultrablock filter helps to
see the entire nebula more detached but it is not as useful as the UHC.
At 106x, N214C is an evident nebula at this higher power, appearing slightly
oval in shape and showing a star-type feature in its central part matching with the
position of the aforementioned stellar cluster SK-71°51. On the north-northwest corner of the nebula (see Figure
2) what seems to be a very small nebulosity, fainter than the central cluster, can be glimpsed with averted vision, with a relative
position with the Sk cluster almost parallel to the three stars took as reference (linked to each other with white lines on Figure 2). The opposite region, the southern zone of the nebula, looks narrower.
Through a UHC filter, this part of the nebulae complex
looks pretty detached from the background sky. Some dark areas seem to be present within N214C, jumping to the view when is observed at this power. For moments, SK -71°51 also clearly jumps to the view.
Figure 3. HEB in N214C. Photo by ESO |
The view with UHC filter shows N214C more round than the view without this filter. The sight through the Orion Ultrablock filter seems to be better than that through UHC at this high magnification.
Bigger telescopes will surely show more features of the N214C nebula and more subtle details on the features visible with smaller telescopes.
Figure 4. DSS image |
This complex lies in constellation Mensa, an inconspicuous group of stars between constellations Hydrus, Volans, and Dorado that are easier to identify in the summer nights from the Southern Hemisphere.
Figure 4 shows a 1-degree field of view centered on N214 (R.A. 05 40 54 Dec. -71 14 42), about 2° 15ʹ south of 30 Doradus as I said before. As you can see, N214 is, by far, the most prominent feature there. The other components of the complex, situated upper right of N214C in the DSS image here (i.e. N214A, B, D, E, F, G, H), and see in more detail on Figure 5, where the 7 faint components of the N214 HII complex are labeled, are targets for owners of big mirrors and/or astrophotographers. The positions of the components in Figure 5 were taken using data from the SIMBAD Astronomical Database.
If you have the opportunity of observing this small nebula immersed in our satellite galaxy in a clear and dark summer night from any place in the Southern Hemisphere, remember that some peculiar features reside in the depths of this deep sky object.
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1_ LHa-120 N is the full name of an entry in the Henize catalog of LMC emission nebulae. "L" refers to the Lamont-Hussey Observatory of the University of Michigan; "Ha" means the Hydrogen-alpha emission line, the key signature line used in the survey; "120" refers to the plate number (objective prism plate) for the LMC; "N" labels the object as a nebula, as distinct from a star (label "S").
2_
3_ The concept of a stellar association was originally introduced in 1949 by V. A. Ambartsumian, who later separated them into OB and T associations (Ambartsumian 1968). Morgan, Sharpless, & Osterbrock (1952) considered as a stellar association any loose group of stars within an area where bright OB stars exist and with evidence of a common origin.
A recent definition of a
stellar association (Kontizas et. al. 1999) refers to it as a single, unbound
concentration of early-type luminous stars, embedded in a very young star-forming region.
4_ Sk-71◦51 is the abbreviation of Sanduleak -71◦51. The American astronomer Nicholas Sanduleak published an important list of objects (stars and nebulae showing emission lines in their spectra) in the Magellanic Clouds in 1970. The “-71” in the name is the declination of the object, while the “51” is the entry number in the catalog.
5_ HEB
(High-excitation blobs) are very dense, small regions (∼4 00, to 1000, in diameter corresponding to ∼1–3 pc)that are often observed
lying adjacent or projected onto giant HII regions and are younger than the
associated giant HII regions.