Alcohol in space: Exotic methanol discovered in planet-building zones

An international team of astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA), of which the U.S. National Science Foundation National Radio Astronomy Observatory is a partner (NSF NRAO), has combined expertise from across the globe to open a new window on how the organic molecules that seed planets, and potentially life, form in space.

New results from the ALMA COMPASS Large Program (Complex Organic Molecules in Protostars with ALMA Spectral Surveys) show that young, still-forming stars are surrounded by a surprisingly sophisticated “chemical starter kit,” including organic molecules such as methanol that may one day enrich planets.

“We are getting completely new insights into the complex chemistry occurring around the youngest protostars,” said Jes Jørgensen, professor at the Niels Bohr Institute of the University of Copenhagen and principal investigator of the program. “The interesting question is how these chemical ingredients may influence the conditions on planets and potentially the origin of life there.”

100 hours of ALMA observations

COMPASS is a major international project using ALMA to study 11 nearby, sun-like infant stars in unprecedented detail. It requires more than 100 hours of telescope time to systematically catalog their chemical compositions. By combining signals from up to 66 of its dishes, ALMA detects the extremely faint “fingerprints” of organic molecules and maps how different chemicals are distributed around young stars on scales comparable to our own solar system.

The COMPASS program’s first results appear in seven papers in Astronomy & Astrophysics, offering initial analyses of this data set and the first glimpse of its scientific discoveries.

“With COMPASS we can for the first time systematically compare protostars from different environments and in different evolutionary stages to begin to understand how chemical complexity develops during star formation,” said Dr. Adele Plunkett of the NSF NRAO, one of four co-principal investigators of the program together with Dr. Audrey Coutens of the University of Toulouse in France, Dr. Maria Drozdovskaya of the University of Bern in Switzerland and professor Jeong-Eun Lee of Seoul National University in South Korea.

Alcohol in space

Several of the highlights from this first wave of results focus on methanol, the simplest alcohol, which plays a central role in building larger organic molecules. ALMA’s sensitivity and advanced spectral capabilities allow the detection of faint and obscure variations of methanol, among other molecules.

One key discovery, reported in a paper led by Seoul National University graduate student Jae-Hong Jeong, shows that methanol maser emission—naturally occurring radio beacons produced by methanol molecules—is far more widespread around low-mass protostars than previously thought. The COMPASS data reveal methanol masers in more than half of the young stars studied, suggesting that such emission may be a common feature of early stellar evolution, apparent when observations are sufficiently sensitive.

ALMA observations discover CD₃OD in space

In parallel, the survey enabled the first detection in space of a fully “heavy” version of methanol. In this rare variant, known as fully deuterated methanol (CD₃OD), all of methanol’s hydrogen atoms are replaced by a heavier form of hydrogen called deuterium. Reported in a paper led by Dr. Arnaud Belloche of the Max Planck Institute for Radio Astronomy, CD₃OD was discovered around the young protostar IRAS 4A2 in the Perseus molecular cloud, about 1,000 light-years from Earth.

More analysis to yield more discoveries

These results demonstrate that powerful spectral surveys like COMPASS make ALMA an invaluable tool for uncovering rare and previously unseen chemical phenomena. They also represent only the first step: Analysis of the full COMPASS data set will continue, extending the study to all detected species across all 11 sources. This work aims to determine whether variations in chemical composition among protostars arise from their birth environments or from evolutionary processes during star formation.

“We are just beginning to tap into the richness of this data set,” said Lee. “As we expand the analysis, we expect to uncover entirely new aspects of how chemistry evolves on the path to planet formation.”

This program contributes important pieces to the broader puzzle about how chemistry evolves in different regions of our galaxy and at different stages of star formation. Recent NSF NRAO- and ALMA-supported surveys, including eDisk and the ALMA CMZ Exploration Survey, have taken systematic approaches to investigating the early chemical signatures of planet-forming disks around young stars.

By uniting cutting-edge ALMA observations with laboratory work and advanced modeling, the NSF NRAO and its international partners are charting how molecular complexity flows from interstellar clouds into emerging planetary systems—and, ultimately, into worlds that could resemble our own.

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Lisa Lock

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Robert Egan

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