Brief
JWST shows planet‑forming disks lose gas in stages
Observations of 72 young Sun‑like stars suggest that the mechanisms removing gas from planet‑forming disks change over time, setting a deadline for giant‑planet formation.
By Felo News Desk · Published
NASA’s James Webb Space Telescope (JWST) has provided the most detailed view yet of how gas is lost from the disks that birth planets. A study led by Naman Bajaj of the University of Arizona and co‑authored by SETI Institute scientist Uma Gorti examined 72 young, Sun‑like stars and their protoplanetary disks, the largest JWST planet‑formation survey to date.
Using JWST’s Mid‑Infrared Instrument, the team traced two key indicators of escaping material: molecular hydrogen, the most common molecule in disks, and ionised neon. In the youngest systems, powerful jets and broad winds containing both molecular and atomic gas were detected. These outflows are consistent with magnetic‑field‑driven winds that carry material and angular momentum away from the disk.
As the stars mature and accretion onto the star slows, the jets weaken and the escaping gas becomes increasingly atomic. High‑energy radiation from the young star then heats the remaining gas, a process known as photoevaporation, which ultimately clears the disk of gas. Gorti explained that once the gas disappears, the window for building gas‑rich planets closes.
The findings, published in The Astronomical Journal, confirm earlier predictions that molecular winds would be dense enough in the earliest stages to block X‑ray photons. The study also builds on a 2020 investigation by LPL professor Ilaria Pascucci, Bajaj’s advisor, which examined how jets and winds evolve.
Understanding the timing and mechanisms of gas loss is crucial because giant planets like Jupiter and Saturn require substantial atmospheres that can only form while gas remains in the disk. If the gas is removed too quickly, forming planets may never acquire the massive envelopes needed to become gas giants.
Key facts
- Study examined 72 young, Sun‑like stars and their protoplanetary disks (sciencedaily.com)
- Molecular hydrogen and ionised neon were used to trace escaping gas (sciencedaily.com)
- Young systems show jets and magnetic‑driven winds; older systems show photoevaporation (sciencedaily.com)
- Gas loss sets a deadline for forming gas‑rich planets (sciencedaily.com)
Why it matters
The research defines a critical time window for the formation of giant planets, informing models of planetary system development.
What happens next
The team plans to extend observations to a broader range of stellar ages to refine the timeline of disk dispersal.
Sources
- [1] sciencedaily.com — originally reported as “James Webb reveals why planet formation is a race against time”
