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NGC 55
MCG-07-01-013
RA 00:14:53
Dec -39° 11.3'
Galaxy |
James Dunlop discovered this galaxy from
Paramatta, New South Wales, and included it as No. 507 in his catalogue of
1827. Using a 9-inch f/12 telescope, he described it as "a beautiful long
nebula, about 25 arcseconds in length; position N.p. and S.f., a little brighter
towards the middle, but extremely faint and diluted to the extremeties. I see
several minute points or stars in it, as it were through the nebula: the
nebulous matter of the south extremity is extremely rare, and of a delicate
bluish hue. This is a beautiful object." Dunlop sketched the galaxy and
observed it on four occasions.
Sir John Herschel studied it at the Cape of
Good Hope with an 18-inch f/13 speculum telescope. His first observation of
it, on 3 May 1834, was recorded as "bright; very large; very much
elongated in a long irregular train, the preceding end being much the brightest.
Whole length = 1.5 diam. of field, or 22' The nucleus is either a double star
or a much more sharply terminated nebulous mass, elongated in a different
position (146.5 ) from that of the nebula (109.8 )." He observed it again
on 23 October 1835, recording it as "very bright; very large; very much
elongated; at least 25' long and 3' broad. The following part is Faint, the
preceding and shorter trinuclear the 2d, nucleus taken. A strange object."
His final observation, on 4 October 1836 reads: "very bright, very large; a
very long irregular crooked ray with 3 nuclei, the second of which appears to
consist of stars." His sketch of the galaxy was executed with his usual
immaculate attention to detail, clearly showing its convoluted form and three
brighter sections. In his discussion, he grouped it together with the galaxy
NGC 300 and the star cluster NGC 1950 as "nebulae of irregular forms having
a tendency to several centres of condensation; in the case of [NGC 1950] but
little conspicuous - in that of [NGC 55] (otherwise remarkable for its
extravagent length and crooked shape) much more so, while in [NGC 300], the
formation of separate nuclei is decided, the intermediate faint nebula barely
sufficing to mark them as forming a connected system."
Burnham notes that a good 10-inch reflector
begins to show noticeable mottling across the body of the galaxy, while large
telescopes reveal great numbers of individual stars, emission nebulosities, and
dark dust clouds; supergiant stars begin to appear in large numbers at about
mag 18.4. Near the centre of the main mass, a little to the east of the nucleur
region, a very prominent and sharp-edged dust cloud may be seen; smaller masses
of this type are scattered across the star clouds of the galaxy. NGC 55 does
not, however, show any definite equitorial dust lane..."
Hartung notes: ".. A 12-inch shows a
bright, remarkably elongated spindle 25' x 2.5' in PA 70 , asymmetric with very
bright preceding region knotted or curdled and a long following region mottled
and less bright. A four-inch telescope shows the brighter lengthened central
part and the spindle shape is clear"
Tom Lorenzin, in the electronic version of "1000+
The Amateur Astronomers' Field Guide to Deep Sky Observing", notes the
magnitude as 7.8 and comments: "25'x 4' extent; very bright and large with
axis oriented WNW-ESE; asymmetrical brightness with W portion brighter;
mottling visible with larger aperture; easily visible in large binoculars; good
supernova prospect."
Houston notes that NGC 55 "is visually
bright, and I estimate its total magnitude to be about 7.6. Most observers see
this nearly edge-on galaxy as a narrow oval that brightens at its western end.
The apparent length of NGC 55 depends on atmospheric conditions, and small
telescopes can reveal 20' to 25', but it is possibly twice this size. Under
good conditions, NGC 55 is visible in binoculars. While travelling in Central
America I turned my 4-inch rich-field reflector to this galaxy and could see
mottling all along its length. At home in Connecticut, however, its a different
story; I feel grateful just to see it with my 4-inch Clark refractor. Even so,
on exceptional nights I've glimpsed some mottling with a 4-inch off-axis
reflector. In some respects, NGC 55 reminds me of the better known, but
smaller, M82 in Ursa Major."
Barbara Wilson, observing it from Columbus,
Texas, under good seeing on a very transparent night, wrote: "Using the
13.1 inch [at 115x with the galaxy 18 degrees above the horizon], NGC 55 appears
very large, extremely elongated, very mottled, slightly tilted, very bright,
however east end fades rapidly." She viewed it again from the same site
with a 17.5-inch scope: "A long streak narrower at one end with mottling in
the central region visible at 97x. It fills the 0.52 degree field of a 21mm
eyepiece. Incredible! Spiral almost edge on, extremely bright, dimmer [east]
end seen easily as it fades into the sky background, it is wider, but of lower
brightness, than west end."
William P. Clarke (San Diego, California, USA)
writes in the The Webb Society Nebulae and Clusters Section Report No. 10, July
1992: "A highly elongated streak with uneven surface brightness. It is
brighter at the N.p. end. Major axis is elongated in about PA 100-110 degrees
(10-inch f/4.5, x48)."
Steve Coe, in "SACNEWS On-line for
November 1996" notes: NGC 55 is bright, very, very large and very, very
elongated at 100X. It is visible in the 50mm finder. At 100X it is longer than
the 40' field of view. There are several H II regions involved, a UHC filter
helps a lot on these gaseous nebulae in another galaxy. The nucleus is stellar
at high power and some mottling is glimpsed. It is at 0hr 15min and -39 11.
Sandage and Tammann (1975, Astrophysical
Journal, 196, 313-328) includes this galaxy in the South Polar Group. Members
include NGC 24, NGC 45, NGC 55, NGC 247, NGC 253, NGC 300 & NGC 7793.
The Southern Galaxy Catalogue (1985, Corwin,
de Vaucouleurs & de Vaucouleurs) notes: "over-exposed bar, well
resolved, many faint knots. IC 1537 is following part of galaxy."
This galaxy is included in a sample of
galaxies with velocity less than 500km/s with respect to the centroid of the
Local Group. [Nearby Galaxies. Schmidt K.-H., Priebe A., Boller T. (Astron.
Nachr. 314, 371 (1993))] Other names: "E293-50". Inclination:
(face-on, in degrees) 84 Total photoelectric blue mag 8.42 Total colour index
.55 Logarithm of the angular diameter D25 (arcminutes) 2.51 Blue photographic
magnitude 8.29 |
