Largest molecule ever seen in planet-forming disc detected

Researchers at the Leiden Observatory in the Netherlands using the Atacama Large Millimeter/submillimeter Array (ALMA) at the Chiledetected dimethyl ether around the young star Oph-IRS 48. With nine atomsit is the largest molecule ever identified in a planet-forming disc to date.

This image from the Atacama Large Millimeter/submillimeter Array (ALMA) shows dust trapped in the disk around the Oph-IRS 48 system. Credit: ALMA (ESO/NAOJ/NRAO)/Nienke van der Marel

According to the scientific article published this Tuesday (8) in the journal Astronomy and astrophysics describing the discovery, dimethyl is a precursor to organic molecules such as methane, which in some cases can be indicative of life.

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Also according to the study, dimethyl ether (CH3OCH3) is an organic molecule commonly seen in cloud-forming clouds. stars, but had never been found in a planet-forming disk. The researchers also performed an intermediate detection of methyl formate (CH3OCHO), a complex molecule similar to dimethyl ether that is also considered a “building block” for even larger organic molecules.

Artist’s rendering shows the planetary formation disk around the star Oph-IRS 48. Credit: European Southern Observatory (ESO)

Located 444 light years from Earth, in the constellation of Ophiuchus, the star Oph-IRS 48 has been the subject of many studies because its disc contains an asymmetrical cashew-shaped “dust trap”. Such a region contains a large number of millimeter-sized dust grains that can coalesce and grow into kilometer-sized objects such as comets, asteroids, and even potential planets.

Chemical reactions between simple molecules and dust grains give rise to more complex molecules

“From these results, we can learn more about the origin of life on our planet and thus have a better idea of ​​the potential for life in other planetary systems,” said lead author Nashanty Brunken, a student to the master’s degree at the Leiden Observatory, in a press release published by the European Southern Observatory (ESO). “It’s very exciting to see how these findings fit into the bigger picture.”

“It’s really exciting to finally be able to detect these large molecules in discs. For a while we thought it wouldn’t be possible to observe them,” says co-author Alice Booth, also a researcher at Leiden Observatory.

Many complex organic molecules, such as dimethyl ether, are thought to appear in star-forming clouds, even before the stars themselves were born. In these cold environments, atoms and simple molecules like carbon monoxide stick to dust grains, forming a layer of ice and undergoing chemical reactions that result in more complex molecules.

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Researchers have discovered that the dust trap of the disc of Oph-IRS 48 is also an ice reservoir, sheltering grains of dust covered with this ice rich in complex molecules. As the heating of the young star sublimes the ice into gas, the dimethyl ether molecules inherited from the cold clouds are released and become detectable.

“What makes this even more exciting is that we now know that these larger, complex molecules are available to power the planet-formers in the disk,” Booth says. “This was not known before, because in most systems these molecules are hidden in ice.”

Discovery could give clues to the formation of prebiotic molecules on Earth

The discovery of dimethyl ether suggests that many other complex molecules commonly detected in star-forming regions may also be lurking in the icy structures of planet-forming discs. These molecules are the precursors of prebiotic molecules like amino acids and sugars, which are part of the building blocks of life.

By studying their formation and evolution, researchers can better understand how prebiotic molecules are deposited on planets, including ours. “We are extremely excited to now be able to begin tracking the entire journey of these complex molecules, from the clouds that form stars to the disks that form planets and comets. I hope that with more observations we can get closer to understanding the origin of prebiotic molecules in our own solar system,” says Nienke van der Marel, a researcher at Leiden Observatory who also participated in the study.

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