From Cold Cloud to Hot Protostar

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Paradoxically, stars begin in the galaxy’s coolest places: the dense giant molecular clouds (or GMCs).

This is not quite the paradox it seems, as in the beginning, stars require little else but gravity to form. And that’s really quite lucky, because one thing they do need is regions of high density, and high density is unlikely to occur where temperatures are high.

And so stars begin in perhaps the most surprising of ways: as a high-density bundle of very cool gases within an equally cool interstellar cloud.

But they do heat up eventually. How? Continue reading