I'm given the HR diagram seen below and I need to identify the different regions. I know them all except for the one circled which I have no idea what it is... Can anybody help me out with this? Thank you.
closed as off-topic by Kyle Oman, John Rennie, stafusa, glS, Anders Sandberg Aug 23 '18 at 9:40
This question appears to be off-topic. The users who voted to close gave this specific reason:
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The stars within the circle are "blue stragglers." They inhabit the blue end of the original main sequence, and should have left the main sequence long ago, but for some reason remain. Various theories exist as to their origin/longevity, but none are yet conclusive.