Monday, 2 July 2018

Glorious M23

This may sound a little weird, but sometimes a telescope can be too big. Last night, for example, I observed M23, a bright and rich star cluster which lies 2,100 light-years away in the direction of the centre of our galaxy. The largest true field of view my binoscope can offer is less than a degree across, which is a tight fit for this big and relatively close cluster. The view in binoculars or small telescopes, albeit less bright, will certainly be more pleasing but hey... it wasn't all that bad in my binos after all. 

M23 contains about 150 confirmed members and came into existence some 300 million years ago, making it a not a very young cluster. In spite of its many members, it's now starting to break up slowly, after which all of the individual stars will go their own way. For many of them this journey will not be long because bright blue giant stars lead very short lives. The bigger a star, the faster it will burn its fuel and there are quite a few biggies in M23, some of which are already shutting down hydrogen fusion and are evolving towards red giant status. Through my binoscope on the other hand, most of the stars still appeared bright blue as I've tried to reflect in my sketch.

Once more I have to inform you that sometimes appearances can be deceiving because the very bright star near the bottom-right border (HR6679) doesn't belong to the cluster at all. Being only 320 light-years away it's a lot closer to us and with its 2.2 solar masses I wouldn't exactly call it a giant.

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