Plate Nº 62 · recorded October 10, 2026
Space & AstronomyReported finding
JWST Survey of 72 Young Stars Maps How Planet-Forming Gas Escapes
A JWST study of 72 young, Sun-like stars shows that the mechanisms stripping planet-building gas shift as disks age, shrinking the window for gas giants to form.
By Elena Vasquez4 min read745 words
In brief
- JWST survey examined 72 young, Sun-like stars and their protoplanetary disks, published September 28, 2026 in The Astronomical Journal.
- Researchers detected extended emissions from molecular hydrogen or ionized neon in 66 of the 72 disks surveyed.
- Conical molecular hydrogen winds appeared in 46 systems; fast-moving neon jets appeared in 40.
- Every disk containing a neon jet also showed evidence of a wind traced by molecular hydrogen or atomic oxygen.
- The study was led by Naman Bajaj of the University of Arizona, with SETI Institute scientist Uma Gorti as coauthor.
James Webb Space Telescope observations of 72 young, Sun-like stars have revealed that the mechanisms stripping planet-building gas from protoplanetary disks shift in a predictable sequence as systems mature. The findings, published September 28, 2026 in The Astronomical Journal, confirm that giant planets such as Jupiter must build their massive atmospheres before that gas supply disappears.
The study was led by Naman Bajaj of the University of Arizona and coauthored by SETI Institute scientist Uma Gorti. Researchers detected extended emissions from molecular hydrogen and ionized neon in 66 of the 72 disks examined — the broadest observational census yet of disk dispersal mechanisms.
"What is exciting about this study is that we can now see, across a large sample of young systems, how the mechanisms that remove gas from planet-forming disks change with time," Gorti said. "Disk dispersal sets a fundamental clock for planet formation: once the gas is gone, the opportunity to build gas-rich planets is essentially over."
Why does the timing of disk dispersal matter?
Stars form surrounded by dense disks of gas and dust. Our own Sun sat inside such a disk for its first few million years, holding roughly 100 times more gas than dust before nearly all of that gas vanished. Today the solar system is about 4.5 billion years old and mostly empty space.
Gas is essential for building giant planets such as Jupiter and Saturn. If a disk loses its gas too quickly, growing planets cannot accumulate the thick atmospheres needed to become gas giants.
"Planet formation is therefore a race against time," Bajaj said. "Gas giants like Jupiter must assemble their massive atmospheres while the disk is still substantial enough to supply them, before winds and jets carry that raw material away into space."
How did JWST trace the escaping gas?
The team used archival observations from JWST's Mid-Infrared Instrument (MIRI). The 72 targets cover a wide range of evolutionary stages, together forming a sequence of snapshots that show how gas loss evolves with age.
Researchers focused on two indicators of escaping material:
- Molecular hydrogen (H₂), the most abundant molecule in protoplanetary disks
- Ionized neon (Ne), which traces hotter, faster-moving gas
JWST's sensitivity and resolution let the team distinguish broad winds containing molecular hydrogen from narrow jets traced by neon.
What mechanism dominates, and when?
The findings indicate no single process clears a planet-forming disk. Instead, two mechanisms trade dominance as systems mature:
- In the youngest systems, where material still falls onto the central star, the researchers detected powerful jets plus broad winds carrying both molecular and atomic gas. These outflows match winds driven by magnetic fields threading the disk. Gas follows those field lines outward, carrying away both material and angular momentum.
- As material flow onto the star declines, jets weaken. High-energy radiation from the young star then penetrates the thinning material, heating disk gas until it escapes. This radiation-driven process is called photoevaporation.
Gorti has spent decades studying disk dispersal, including the role of ultraviolet and X-ray radiation in driving photoevaporative winds. The new JWST observations provide direct observational support for that theoretical work across dozens of real systems.
How often did each signature appear?
The team tallied the following across the 72 disks:
- 66 showed extended emissions from molecular hydrogen or ionized neon
- 46 displayed conical molecular hydrogen winds
- 40 showed fast-moving neon jets
- Every disk containing a neon jet also showed a wind traced by molecular hydrogen or atomic oxygen
The pattern hints that jets and molecular winds coexist early, with atomic radiation-driven winds taking over later.
What comes next?
Researchers now want to measure how much gas these winds remove over time and identify where within each disk the escaping material originates. Those measurements could reveal not only how quickly the window for planet formation closes, but also which regions of a disk are capable of producing different types of planets.
The new paper builds on earlier work by the same group. In 2020, co-author Ilaria Pascucci of the University of Arizona predicted that molecular winds should exist and be dense enough during the earliest stages to block X-ray photons. A 2024 JWST study led by Bajaj and Gorti confirmed that prediction in the disk around the young star T Cha. The new survey extends the same approach to dozens of stars, tracking how the balance among jets, molecular winds, and atomic winds shifts with age.
via seti.org (Original)
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