New researchers indicates that giant planets can spin faster than more massive brown dwarfs, revealing important clues about how planetary systems form and evolve.
Astronomers have long suspected that a planet’s mass may be linked to how quickly it spins. In our solar system, Jupiter and Saturn rotate especially fast, each completing a full turn in about 10 hours, and together they hold much of the solar system’s rotational energy.
To test this idea, researchers used the W. M. Keck Observatory on Maunakea in Hawaii to study 32 distant gas giants and brown dwarfs. The group included six giant planets larger than Jupiter and 25 brown dwarf companions.
Using high-resolution spectroscopy from the Keck Planet Imager and Characterizer (KPIC), the team found that gas giant planets rotate faster than more massive objects after accounting for mass, size, and age. The researchers also combined their results with earlier spin measurements, building a curated sample of 43 stellar and substellar companions and giant planets, along with 54 free-floating brown dwarfs and planetary-mass objects.
The research was led by scientists at Northwestern University’s Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA). The team also included researchers from the Center for Astrophysics and Space Sciences (CASS) at UC San Diego, the Division of Geological & Planetary Sciences (GPS) at Caltech, W. M. Keck Observatory, Steward Observatory, the James C. Wyant College of Optical Sciences, NASA’s Jet Propulsion Laboratory, and several universities. Their study was published in The Astronomical Journal.
