Alien planet spins revealed a hidden clue to how worlds form

Astronomers used the Keck Observatory to measure spins of dozens of giant planets and brown dwarfs, discovering that giant planets can spin faster than more massive brown dwarfs. This finding advances understanding of planetary formation by revealing that magnetic fields and formation processes—not just mass—determine rotational speed.

This does not prove complete understanding of planetary formation mechanisms, nor does it explain all variations in exoplanet properties.