Astronomers detect unusual methanol signals around young stars forming planets
Using the ALMA radio telescope, an international team led by Maria Drozdovskaya found a rare deuterated methanol molecule and methanol maser emission around young stars, offering new clues about how planetary systems and the chemistry linked to life may form.
Astronomers have identified unexpected chemical anomalies in the gas and dust discs surrounding young stars where planets are forming. The observations, made with the ALMA radio telescope, could help scientists understand how the distribution of methanol influences the birth of new planets and the emergence of conditions that might one day support life.
Methanol is the most common complex organic molecule found in protoplanetary discs, which makes it a key target for research into the origins of life. An international team of more than 30 researchers, led by Maria Drozdovskaya of the University of Bern, studied the gas discs around 11 of the nearest low-mass protostars. Their findings were published in the journal Astronomy & Astrophysics.
Among the targets, the researchers detected a rare form of methanol in which ordinary hydrogen atoms are replaced by deuterium, a heavy isotope of hydrogen. The anomaly appeared in only one of the 11 objects studied, the young star IRAS 4A2, located roughly 1,000 light years from Earth in the Perseus molecular cloud.
The COMPASS project, which stands for Complex Organic Molecules in Protostars with ALMA Spectral Surveys, also recorded methanol maser emission in more than half of the protostars examined, mostly in the youngest systems. A maser is the microwave counterpart of a laser, in which radiation is naturally amplified when methanol molecules are excited and collide within shock waves.
Methanol masers had previously been seen only near massive stars. Their detection around smaller, calmer stars suggests that such regions of unusually high energy also exist in systems with lower-mass central stars. The researchers suggest this may mean that these radio signals arise during planet formation around stars of many different masses, not only the most massive ones.
The team also proposed a mechanism: as a young star accretes gas from its surrounding disc, it periodically heats up and generates shock waves. These can activate methanol in the gas and cause it to emit intense radio signals. The scientists additionally found differences in oxygen and nitrogen content between stellar systems, indicating that the chemical makeup of the material from which planets form may vary considerably from one system to another.
The first detailed results of the COMPASS project were published in seven papers in Astronomy & Astrophysics. Astronomers are continuing the systematic analysis of the ALMA data and preparing a series of follow-up observations with the James Webb Space Telescope.
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