This is M13 (AKA NGC 6205), the Great Globular Cluster in Hercules (145 light years in diameter and 22500 light years away). This is a region of densely packed stars (the cluster contains over a hundred thousand of them) orbiting around our own galaxy. The majority of the stars in it are rather old (hence their yellowish color) but they are so densely packed that sometime they collide against each other. This forms new young stars, which are hotter and glow bluish. Can you see them?
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