One of the most intriguing involves a star that happened to pass near the Sun long before modern humans walked the Earth and that quiet flyby might have shaken loose a wave of comets from the Oort Cloud and sent them toward our young planet. A recent study suggests this stellar brush altered Earth’s environment at a crucial moment in early human evolution.

What Is the Oort Cloud?

The Oort Cloud is a huge shell of icy remnants orbiting far beyond the planets. Dutch astronomer Jan Oort first proposed its existence, in 1950, to explain the source of long-period comets. Though no telescope has yet imaged it directly, evidence for this far-away reservoir of comets strengthens with each comet studied.

Oort Cloud Scale & Distance

This cloud begins thousands of astronomical units from the Sun

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