Posted by New observations from NASA’s James Webb Space Telescope are helping astronomers understand how young planetary systems lose the gas needed to build planets. A study led by University of Arizona researcher Naman Bajaj, with SETI Institute scientist Uma Gorti among the co-authors, analyzed 72 young Sun-like stars and their protoplanetary disks. Published in ‘The Astronomical Journal’, the work is one of the largest JWST studies of disk evolution and shows that different mechanisms dominate gas loss at different stages of planetary formation.
Planets form inside disks of gas and dust surrounding young stars. In the first few million years, these disks contain large amounts of gas, which is especially important for building giant planets such as Jupiter and Saturn. Once the gas disappears, the opportunity to form thick planetary atmospheres largely ends.
Using archival observations from JWST’s Mid-Infrared Instrument, the researchers traced two important signatures of escaping material: molecular hydrogen and ionized neon. JWST’s sensitivity allowed the team to distinguish broad molecular winds from faster jets and atomic outflows.
In younger systems that are still actively feeding material onto their stars, the team found strong jets and winds containing both molecular and atomic gas. These are consistent with magnetically driven outflows that remove mass and angular momentum from the disk. As the systems age and accretion weakens, jets become less important and atomic winds begin to dominate. High-energy radiation from the young star can then heat exposed disk gas until it escapes through a process known as photoevaporation.
Extended molecular hydrogen or neon emission was detected in 66 of the 72 systems. Conical molecular hydrogen winds appeared in 46 disks, while fast neon jets were identified in 40. The findings suggest that disk dispersal is not controlled by a single mechanism. Instead, young systems evolve from magnetically dominated winds and jets toward photoevaporative outflows. This transition determines how long planets have access to the gas needed for growth, making giant-planet formation a race against time.
For more details, read the full article by SETI Institute.
