NGC 253 und 247 in der Sculptor-Gruppe home

 

Two galaxies deep in the South

NGC 253 and 247 in the Sculptor/Cetus region

 

December 2009

Our Local Group comprises besides our Milky Way the Andromeda Galaxy and M33, as well as a number of smaller dwarf galaxies. But what comes next? Which galaxies or galaxy groups are the direct neighbors to our Local Group? The Virgo cluster? The M81 group? None of them, it is the Sculptor group, which is at a distance of about 12 billion light years (for comparison, the distance to M31, the Andromeda Galaxy, is a mere 2.5 billion light years). A nice overview over the positions and distances of the individual galaxy group as seen from our Local Group can be found here.

Sculptor is a constellation that does not ring a bell for most of us observers living far North, me included ( I live at 48 N). It is simply to far in the south and creeps over the horizon only in autumn, when Pegasus is high in the sky. Nevertheless, it can be observed. For our excuse, Sculptor as a constellation is not very impressive at all. However, it is home of a number of fascinating galaxies of the Sculptor group, of which NGC 253 and NGC 247 are the most rewarding from our northern latitudes ... rewarding, given that transparency is exceptional down to the horizon, otherwise they are lost in the haze.

NGC 253 (00h 47, -25 17') as the Sculptor Galaxy even bears the name of the constellation and the galaxy group. As a bright galaxy of 7th magnitude it stretches over almost half a degree and is conspicuous even under mediocre transparency. Under good conditions, however, and a large telescope, it becomes a breathtaking object and even steals the show from M31 with ease. In contrast to the Andromeda Galaxy, NGC 253 is full of inherent structure with dust bands and knots. With a large telescope it becomes a 3-dimensional whirlpool of stars. The view in the eyepiece is then very much comparable to the DSS image to the left. Classified as SABc, NGC 253 is a spiral with open arms and a hint of a central bar.

NGC 247 (00h 47, -20 46') has 21 arc minutes and is sonly slightly smaller than NGC 253. However, it is almost entirely lacking the impressive structural detail of NGC 253. Even with my 22 Inch Dob, NGC 247 appears from our Northern latitude as a large ghostly blob of light, which besides a concentration to the middle hardly reveals any structure. It appears to be hooked and hanging from a mag 9 foreground star. Under less than optimal sky transparency, this galaxy easily disappears in the haze, despite it is 4 and a half degrees further up than the Sculptor Galaxy. The chain of distant galaxies NE of NGC 247 is known as Burbidge's Chain and a challenge for larger scopes.

The little map to the left shows the sky as seen beginning of November around 11pm toward South from latitude 48N. The constellation Sculptor hardly creeps over the horizon.  Starting from beta Ceti (Deneb Kaitos) star hopping leads to a suspicious group of stars and the two galaxies 3 and 7 south, respectively.

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