Contrary to their expectations, astronomers have discovered large young sun-like stars with abundant reservoirs of carbon monoxide gas in their debris disks. They also found sun-like stars with lower mass and non-existent gas in their debris disks.

Scientists expect that the strong radiation from larger stars should take away all of the gas from their debris disks. On the other hand, smaller stars should still contain gas in their disks because their radiation is milder. However, their survey of stars revealed that some stars deviate from this.

The findings, now published in Astrophysical Journal, involved the use of the Atacama Large Millimeter/submillimeter Array (ALMA) in Santiago, Chile. The observations were conducted between December 2013 and December 2014.

Overall, the research team focused on stars with ages between five and ten million years in the Scorpius-Centaurus Association. This is a loose stellar agglomeration with low-mass (like the sun) and intermediate-mass stars, located several hundreds of lightyears away.

They found three stars, two times bigger than the sun, with gas-rich disks. They also found 16 smaller stars without gas in their disks.

“Previous spectroscopic measurements of debris disks revealed that certain ones had an unexpected chemical signature, suggesting they had an overabundance of carbon monoxide gas,” says lead author Jesse Lieman-Sifry from the Wesleyan University in Middletown, Connecticut. “This discovery was puzzling since astronomers believe that this gas should be long gone by the time we see evidence of a debris disk.”

The study’s co-author and a Wesleyan University astronomer, Meredith Hughes, says that they cannot explain this phenomenon.  However, Hughes believes that this could be crucial to planet formation.

Study co-author Antonio Hales, an astronomer with the Joint ALMA Observatory, says that the origin of this gas can be understood using high-resolution instruments, which will hopefully be available in the future.