Imagine if Earth were much, much closer to the Sun. So close that an entire year lasts only a few hours. So close that gravity has locked one hemisphere in permanent searing daylight and the other in endless darkness. So close that the oceans boil away, rocks begin to melt, and the clouds rain lava.
While nothing of the sort exists in our own solar system, planets like this—rocky, roughly Earth-sized, extremely hot and close to their stars—are not uncommon in the Milky Way galaxy.
What are the surfaces and atmospheres of these planets really like? NASA’s James Webb Space Telescope is about to provide some answers.