Once you have the urge to look for specific peculiarities, the real challenge begins. Is the sky dark and clear enough? Do you have sufficient aperture? Looking for these features might be considered the “ultimate quest” for the serious galaxy observer, but for many these challenges are worth the time and effort.
Challenging the peculiars
NGC 4038/9 is the famous “Ring-tail Galaxy.” A very peculiar galaxy indeed, some astronomers consider it an interacting pair of spiraIs, while others theorize that we are actually seeing a galaxy in the process of splitting in two! The Ring-tail is very bright, and its strange “U” shape is visible in even a 6-inch telescope. This impressive object lies very near NGC 4027, a slightly fainter peculiar galaxy shaped like a hook.
NGC 1961 has recently been identified as the largest known spiral galaxy in the universe, containing some 2 trillion stars in a galaxy 600,000 light-years across. It is also unusual in having a highly asymmetric spiral structure, as if it had interacted with another galaxy, but there are none around. Since the arms are too low in surface brightness to be seen in a 21-inch telescope, their structure seems to be beyond the capability of amateur instruments. But just seeing this cosmic giant is sufficiently appealing.
NGC 3718/29 are a pair of peculiar galaxies found in the same field, both bright enough to be seen with an 8 inch aperture. Whether their peculiarities are caused by a mutual interaction is uncertain, but they don’t appear to be. NGC 3718 has a strangely placed dark lane, which may be visible in moderate-size telescopes. It seems to be arching over the nucleus. NGC 3729’s two peculiarities — an outer ring and a jet — are beyond the reach of amateur telescopes. Still, it’s interesting to find more than one peculiar galaxy in the same field of view.
NGC 5195 is the peculiar companion to the most famous interacting galaxy, M51. It is a small, dusty, and very dense star-city. Visually, this galaxy is bright enough to be seen through small aperture instruments as a roundish patch with a brighter center. With moderately large telescopes, NGC 5195 reveals a bright stellar nucleus. For a challenge, try to see all of the bridge connecting M51 and NGC 5195.
NGC 4861 is an irregular galaxy that contains a semi-nuclear region and a very large emission nebula off to one side. This nebula is rather small and very concentrated. When I first observed this galaxy, I carefully sketched it, unaware of the type of galaxy or peculiarity I was seeing. As it turned out, the sketch made with an 8-inch under excellent skies revealed the nebula as a faint star. Such large HII regions seen at great distances appear nearly stellar.
NGC 5128, also known as Centaurus A, is a bright galaxy which appears as an elliptical. with a large dark lane cutting across it. At −43°, this galaxy is not favorably-placed for observation from the northern United States. With a magnitude of 7.5, it would be one of the most spectacular sights in a small telescope from a Southern Hemisphere location. If you do observe this galaxy, remember that you are looking at the nearest of all double-lobed radio sources, and if your eyes could see radio waves, Centaurus A would appear truly immense, with giant lobes spreading out of the eyepiece field on both sides.
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