The Intergalactic Wanderer

NGC 2419 photo courtesy of Mike RichmannAs I discussed in an earlier story, globular clusters hold up well when viewed from washed-out skies. In that story I highlighted the biggest and brightest globulars. Today I want to discuss a globular cluster that is neither big nor bright, but is nevertheless very interesting: NGC 2419, the so-called Intergalactic Wanderer. It got its name because it is so far from the galactic center (300,000 light years, farther than the Magellanic Clouds and well beyond the “halo” containing most globular clusters) that it was long believed to wandering through space independently. We now know that NGC 2419 is indeed gravitationally bound to our galaxy, taking about 3 billion years to complete an orbit. (Photo courtesy of Mike Richmann)

NGC 2419 is a large, intrinsically bright globular cluster, comparable to Omega Centauri. But its great distance makes NGC 2419 rather faint and small, at magnitude 10.4 and less than 4 arc min across. It is somewhat challenging to see in urban skies, harder than its official magnitude suggests. In my experience you’ll need at least a 6 inch (150 mm) aperture and great transparency to see NGC 2419 under light polluted skies. If the transparency isn’t very good or if NGC 2419 isn’t close to zenith, it can be hard to see even in my 10 inch Dob. But seeing this unusual globular cluster is worth the effort and here is some information for you if want to take up the challenge.


Winter Cluster Challenge

M38 and NGC 1907M35 and M38 are two beautiful open clusters that are well positioned for observing during the winter months. M35 is located in western Gemini, just a few degrees north and west of η Geminorum. It is a big cluster spread across an area nearly the size of the full moon. At magnitude 5.3 overall, and with nearly a hundred stars of 7th through 11th magnitude, M35 is an easy target even in heavily light polluted skies. Smaller and fainter at magnitude 7.5 overall, M38 is also a beautiful object. It consists of about a hundred stars, with the brightest ones forming a very distinctive letter “π” that is clearly visible even with small telescopes (you can see the “π” upside down in the photo to the right).


M35 and NGC 2158While these clusters are quite beautiful and easily observed from washed-out skies, there is something that sets them apart from the other many bright open clusters visible in the winter skies: both of these have fainter clusters within the same field of view. The combination of two clusters in one field of view makes them a particularly interesting sight. Because these fainter clusters are at the edge of visibility for urban observers, they make great challenge objects when observing in washed-out skies. I have more information for those of you wanting to take up this challenge....


Photos of M38  (upper, with NGC 1907 at the bottom edge) and M35 (lower, with NGC 2158 at the bottom-right edge) courtesy of Land of Oz Observatory.


Great Globulars

Globular clusters generally look great even in washed-out skies. Many globulars—especially the Messier globulars—are bright enough to be relatively easy to find even in heavy light pollution. And when you use high magnification to try to resolve the globular, you also improve the contrast by darkening the background. In washed-out skies it will certainly be harder to resolve some of the globulars, and you won’t see the fainter stars so you will loose a bit of star density. But any of the major globular clusters still look spectacular. When I have guests at the telescope, I first turn the telescope to any visible planets. But the very next thing I turn the telescope to is a globular cluster: I can count on it to generate plenty of “wows” from my audience.

Now there are a lot of globular clusters, so you might wonder which ones look best in an urban environment. Everyone has their favorites, but here are mine, all proven performers observing from washed-out skies…


Star Clusters

 NGC 884 and NGC 869Star clusters, both open and globular, generally show up well in washed-out skies. There are lots of relatively bright clusters, and their stellar nature allows you to use magnification to darken the background and enhance the contrast. YGlobular cluster M3ou won’t catch quite as many stars as you would in dark skies, but there is still plenty to see: clusters that look spectacular in dark skies still look quite stunning even with light pollution. The brighter globular clusters do particularly well in washed-out skies.



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