(Science Alert) We humans like to put labels and boundaries on things. For example, the boundary between Earth's atmosphere and space is the Kármán line, the point at 100 kilometres (62 miles) altitude where aeronautics end, and astronautics take over.
But Earth's atmosphere is way more complicated than that (there's even some debate about where the Kármán line should be). Now a team of astronomers has discovered that it's bigger than we even thought - extending all the way out to the Moon, and as far again.
The region is called the geocorona, part of an atmospheric layer called the exosphere. It's a tenuous cloud of neutral hydrogen that glows in far-ultraviolet light.
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