Wednesday, October 3, 2012

Globular Cluster Photo Series (Part 26): NGC 5466

Today I have a picture of the surprisingly sparse globular cluster NGC 5466 for your perusal. NGC 5466 is located very far away in the constellation Boötes at 51,800 light-years from Earth, making it the third-farthest I've shown so far after M53 and M72. At this great distance its larger-than-average size of 166 light-years in diameter gives it a visual angle of 11.0 arc-minutes, about a third the width of the full Moon. Interestingly, NGC 5466 makes nearly an isosceles triangle with Earth and the galactic center, being about 52,800 light-years away from the core.

NGC 5466 in Boötes.
As you can see from the picture NGC 5466 lacks any sort of concentration in its core, in sharp contrast to most globular clusters. It's almost difficult to tell that it's a globular cluster at all. In fact, under the globular cluster classification scheme devised by Harlow Shapley in 1927, NGC 5466 is a class XII, the most loosely concentrated class there is (class I being the most highly concentrated towards the center). You may have noticed that there is general lack of stars both in the globular and in the foreground of this image; this is because Boötes is located away from the galactic plane, and thus there are relatively fewer stars between us and the cluster.

Finally, in an interesting historical aside, it turns out that NGC 5466 was discovered by William Herschel exactly two hundred and five years to the day before I was born, back in 1784.

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