Astronomers using the Keck Observatory have measured the spins of distant giant planets and brown dwarfs, finding that the planets rotate faster than more massive brown dwarfs when mass and other factors are accounted for.
Researchers led by Northwestern University's Center for Interdisciplinary Exploration and Research in Astrophysics examined 32 gas giants and brown dwarf companions. They combined these with prior data for a total of 43 stellar companions and 54 free-floating objects.
The observations, made with the Keck Planet Imager and Characterizer, showed that magnetic fields and formation processes influence rotation speeds. In the HR 8799 system, a gas giant seven times Jupiter's mass spins six times faster than a nearby brown dwarf 24 times Jupiter's mass.
Lead author Dino Chih-Chun Hsu said spin records formation history. He noted that the findings help explain how angular momentum is distributed in planetary systems.
The team plans further studies with the HISPEC instrument, set to begin operations in 2027, to measure spins of smaller and closer worlds.