New research led by Dr. James De Buizer at the SETI Institute and Dr. Wanggi Lim at IPAC at Caltech revealed surprising results about the rate at which high-mass stars form in the galactic center of the Milky Way.
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ALMA Reveals Lives of Planet-Forming Disks
Artist’s concept of protoplanetary disk, like the thirty studied for the ALMA AGE-PRO survey. The lifetime of the gas within the disk determines the timescale for planetary growth. Credit: NSF/AUI/NSF NRAO/S.Dagnello
Observations of 30 disks change our understanding of the evolution of gas in the birthplace of exoplanets
An international team of astronomers has unveiled groundbreaking findings about the disks of gas and dust surrounding nearby young stars, using the powerful Atacama Large Millimeter/submillimeter Array (ALMA). These results, published in 12 papers in a forthcoming focus issue of the Astrophysical Journal, are part of an ALMA large program called the ALMA Survey of Gas Evolution of PROtoplanetary Disks, or AGE-PRO. AGE-PRO observed 30 protoplanetary disks around Sun-like stars to measure gas disk mass at different ages. The study revealed that gas and dust components in these disks evolve at different rates.
A protoplanetary disk surrounds its host star for several million years as its gas and dust evolve and dissipate, setting the timescale for giant planets to form. The disk’s initial mass and size, as well as its angular momentum, has a profound influence on the type of planet it could form (gas giants, icy giants, or mini-Neptunes) and migration paths of planets. The lifetime of the gas within the disk determines the timescale for the growth of dust particles to an object the size of an asteroid, the formation of a planet, and finally the planet’s migration from where it was born.
Prior ALMA observations have examined the evolution of dust in disks; AGE-PRO, for the first time, traces the evolution of gas. “AGE-PRO provides the first measurements of gas disk masses and sizes across the lifetime of planet-forming disks,” explained Principal Investigator Ke Zhang of the University of Wisconsin-Madison.
ALMA’s unique sensitivity allowed researchers to use faint molecular lines to study the cold gas in these disks. The survey observed 30 disks at different ages, from less than 1 million years old to over 5 million years old, in three star-forming regions: Ophiuchus, Lupus, and Upper Scorpius. Using ALMA, AGE-PRO obtained observations of key tracers of gas and dust masses in disks spanning crucial stages of their evolution, from their earliest formation to their eventual dispersal. This ALMA data will serve as a comprehensive legacy library of spectral line observations for a large sample of disks at different evolutionary stages.
Carbon monoxide (CO) is the most widely-used chemical tracer in protoplanetary disks, but to thoroughly measure the mass of gas in a disk, additional molecular tracers are needed. AGE-PRO used N2H+ as an additional gas tracer to significantly improve the accuracy of measurements. ALMA’s detections were also set up to receive serendipitous spectral lines, including H2CO, DCN, DCO+, N2D+, CH3CN. “This is the first large-scale chemical survey of its kind, targeting the 30 disks with a broader range of ages to characterize the gas masses,” explained John Carpenter of the Joint ALMA Observatory, and a co-lead on this survey.
AGE-PRO results indicate that as disks age, their gas and dust are consumed at different rates, and undergo a “swing” in gas-to-dust mass ratio as the disks evolve. Zhang explains, “The most surprising finding is that although most disks dissipate after a few million years, the ones that survive have more gas than expected. This fundamentally changes our estimation of the atmospheric accretion of planets formed at a later time.”
ALMA’s ability to detect faint molecular lines provided a window into the detailed processes of gas evolution in disks. By comparing AGE-PRO’s measurements of gas masses and disk sizes with prior studies mapping the same characteristics of dust particles, Zhang and her team are piecing together the interrelationships between mass, size, angular momentum transport, and environmental factors like photoevaporation.
The AGE-PRO team, which released a collective dozen papers today, emphasized the long-term, international, cooperative nature of their shared work. Co-PI Ilaria Pascucci of the University of Arizona adds, “Science is a collaborative effort, driven by people from different countries and different backgrounds, each contributing unique insights to advance knowledge and discovery”.
About NRAO
The National Radio Astronomy Observatory (NRAO) is a facility of the U.S. National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.
About ALMA
The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of the European Southern Observatory (ESO), the U.S. National Science Foundation (NSF) and the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Republic of Chile. ALMA is funded by ESO on behalf of its Member States, by NSF in cooperation with the National Research Council of Canada (NRC) and the National Science and Technology Council (NSTC) in Taiwan and by NINS in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI).
ALMA construction and operations are led by ESO on behalf of its Member States; by the National Radio Astronomy Observatory (NRAO), managed by Associated Universities, Inc. (AUI), on behalf of North America; and by the National Astronomical Observatory of Japan (NAOJ) on behalf of East Asia. The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.
This news article was originally published on the NRAO website on June 13, 2025.
Recent News
Unusual stellar nurseries near our galaxy’s center puzzle scientists
New research led by Dr. James De Buizer at the SETI Institute and Dr. Wanggi Lim at IPAC at Caltech revealed surprising results about the rate at which high-mass stars form in the galactic center of the Milky Way.
From Stardust to Stone: Windswept Grains Hold Clues to Planet’s Beginnings
The Atacama Large Millimeter/submillimeter Array (ALMA) has uncovered a key piece of the puzzle in how rocky planets, such as Earth, form around young stars.
NASA’s Chandra and the Very Large Array See Surprisingly Strong Black Hole Jet at Cosmic “Noon”
A black hole has blasted out a surprisingly powerful jet in the distant universe, according to a new study from NASA’s Chandra X-ray Observatory. This jet exists early enough in the cosmos that it is being illuminated by the leftover glow from the big bang itself.