ALMA's COMPASS survey detects methanol masers around more than half of 11 infant sun-like stars

More than half of 11 stars means at least six ^[12]. The maser result comes from a paper led by Seoul National University graduate student Jae-Hong Jeong. It reports methanol masers, natural radio beacons produced by methanol molecules, as far more widespread around low-mass protostars than previously thought ^[5]. The release does not give the exact count, or the detection rate in the earlier work it is measured against.

That comparison needs care. The release says the result suggests such emission may be a common feature of early stellar evolution, "apparent when observations are sufficiently sensitive" ^[16]. On that reading, the stars had masers before any survey could pick them up, and the older, lower rate was partly a limit of the instruments. I think that reading holds, and the result still stands. In this sample, a young sun-like star with a methanol maser is the common case.

COMPASS points ALMA at 11 nearby, sun-like infant stars for more than 100 hours ^[2][3]. It combines signals from up to 66 dishes to map where each molecule sits, on scales comparable to our solar system ^[4]. The targets were picked so they could be compared. "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 Adele Plunkett of the NSF NRAO, one of four co-principal investigators ^[9]. The team wants to know whether chemical differences between protostars come from their birth environments or from evolution during star formation ^[10]. Split 11 stars by environment and by stage and each group holds only a few, so that answer will rest on small numbers.

The second highlight is a single detection. A paper led by Arnaud Belloche of the Max Planck Institute for Radio Astronomy reports CD3OD around the protostar IRAS 4A2, in the Perseus molecular cloud about 1,000 light-years from Earth ^[6]. In this form of methanol, every hydrogen atom is replaced by deuterium, a heavier form of hydrogen, and this is its first detection in space ^[6]. As a first detection it shows the molecule exists in at least one place. Whether it turns up around any of the other ten sources ^[13] is a question for the full analysis, which will extend to all detected species across all 11 ^[10].

Methanol is the simplest alcohol and plays a central role in building larger organic molecules ^[7]. The release calls the inventory around these stars a "chemical starter kit" that may one day enrich planets ^[15]. The thing these seven papers ^[1] don't tell you is whether any of it gets there. They map molecules around stars that are still forming ^[4][15]. Following those molecules into a planet is a later step, and the program's principal investigator, Jes Jørgensen of the Niels Bohr Institute, puts it as the open problem. "We are getting completely new insights into the complex chemistry occurring around the youngest protostars," he said ^[8]. "The interesting question is how these chemical ingredients may influence the conditions on planets and potentially the origin of life there." ^[14]

The papers are initial analyses of the data set ^[1]. "We are just beginning to tap into the richness of this data set," said Jeong-Eun Lee of Seoul National University, another co-principal investigator. "As we expand the analysis, we expect to uncover entirely new aspects of how chemistry evolves on the path to planet formation." ^[11]