Astronomers detect Freon-40 around infant stars, comet

Freon-40, also known as chloromethane, belongs to a class of molecules called organohalogens. The radio telescopes at the ALMA observatory in Chile are the first to detect an organohalogen in interstellar space. The compound was found within several young star clusters located 400 light-years away.

Analysis of new data collected by the ROSINA instrument on ESA's Rosetta probe also revealed the presence of methyl chloride on comet 67P, the comet upon which ESA's Philae lander crashed.

"ROSINA was able to capture some of the molecules around the comet, separate them by mass, and count them with an exquisite precision," Kathrin Altwegg, an astronomer at the University of Bern, Switzerland, said in a news release. "This highly sensitive instrument enabled us to detect a host of chemicals around the comet, including the one also discovered by ALMA far from our solar system."

Most organohalogens consist of halogens, like chlorine and fluorine, that have formed covalent bonds with carbon. The compounds can be created synthetically to make plastics, drugs, dyes and other products. They're also formed naturally by a variety of biological processes.

Until recently, scientists held out hope that the discovery of methyl chloride and other organohalogens on exoplanets might signal the presence of life. But the latest discovery -- detailed this week in the journal Nature Astronomy -- suggests the compound forms naturally in interstellar clouds.

Scientists still believe organohalogens are important precursors to the organic compounds essential to the formation of life, but were surprised to find the compounds in such great abundance inside faraway stellar nurseries.

"We simply didn't predict its formation and were surprised to find it in such significant concentrations," said Edith Fayolle, a researcher with the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. "It's clear now that these molecules form readily in stellar nurseries, providing insights into the chemical evolution of planetary systems, including our own."

Researchers were also surprised to find similar isotopic ratios among the methyl chloride concentrations detected near the stellar clusters and on comet 67P. The discovery suggests comets can inherit the chemical signatures of stellar clouds in young star systems and deliver those compounds to young planets.