Through AGE-PRO, astronomers studied 30 disks around Sun-like stars to measure gas content at varying evolutionary phases. Their analysis confirmed that gas and dust within these disks do not dissipate at the same rate. "AGE-PRO provides the first systematic measurements of gas disk masses and sizes across the lifetime of planet-forming disks," stated Ke Zhang, Principal Investigator from the University of Wisconsin-Madison.
Protoplanetary disks endure for several million years around young stars, and their changing gas and dust content determines what kinds of planets form and how they evolve. The disk's initial properties-mass, size, and angular momentum-shape the architecture of planetary systems.
ALMA's precision enabled detection of faint molecular signatures within these disks. AGE-PRO focused on systems between one and five million years old in the Ophiuchus, Lupus, and Upper Scorpius regions. This extensive survey captured key gas and dust tracers, assembling a foundational dataset for future planet formation research.
While carbon monoxide (CO) remained a primary tracer, the team also utilized the molecular ion N2H+ to refine gas mass estimates. ALMA's capabilities further revealed molecules like H2CO, DCN, DCO+, N2D+, and CH3CN. "This is the first large-scale chemical survey of its kind, targeting 30 disks spanning a broad age range to characterize gas masses," said John Carpenter, ALMA Observatory Scientist and program co-lead.
The study revealed that gas often outlasts dust in aging disks, resulting in a shifting gas-to-dust mass ratio. Zhang noted, "The most surprising finding is that although most disks dissipate after a few million years, those that survive retain more gas than we expected. This fundamentally alters our understanding of how and when planets acquire their final atmospheres."
Chilean researchers from the University of Chile and the Center for Astrophysics and Associated Technologies (CATA) played key roles. Laura Perez emphasized the study's unique contribution: "Until now, most of what we knew about disk evolution was based on solids. With AGE-PRO, we finally have direct, consistent measurements of how the gas evolves throughout the disk's lifetime-crucial for understanding how giant planets form."
Postdoctoral researcher Carolina Agurto led the Upper Scorpius analysis, revealing that longer-lived disks retain more gas than models predicted. Anibal Sierra focused on an old, bright disk-2MASS J16120668-3010270-where he detected two candidate forming planets, including one inferred through gravitational signatures. Future JWST observations aim to confirm these worlds.
Contributions also came from Chilean students: Benjamin Cabrera calculated stellar masses, Jose Mondaca explored the youngest disks, and Camila Pulgares investigated dust evolution across the entire sample.
"The advancement of science is a truly collaborative endeavor, driven by people from different countries and backgrounds, each contributing their unique perspective to push the boundaries of discovery," said co-Principal Investigator Ilaria Pascucci of the University of Arizona.
Research Report:ALMA Survey of Gas Evolution of PROtoplanetary Disks
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