This is the largest molecule found in such a disc yet, with nine atoms. It’s also a precursor to larger organic compounds, which could lead to the birth of life.

Researchers at the Leiden Observatory in the Netherlands have found dimethyl ether in a planet-forming disc for the first time using the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile.

This is the largest molecule found in such a disc yet, with nine atoms. It’s also a precursor to larger organic compounds, which could lead to the birth of life.

Dimethyl ether is a common chemical compound in star-forming clouds, but it has never been discovered in a planet-forming disc before. The researchers also detected methyl formate, a complex chemical that is a building component for even larger organic compounds and is similar to dimethyl ether.

“It is really exciting to finally detect these larger molecules in discs. For a while we thought it might not be possible to observe them,” adds co-author Alice Booth, also a researcher at Leiden Observatory.

With the help of ALMA, an observatory co-owned by the European Southern Observatory, the molecules were discovered in the planet-forming disc surrounding the young star IRS 48 (also known as Oph-IRS 48). Since its disc contains an asymmetric, cashew-nut-shaped “dust trap,” IRS 48, situated 444 light-years away in the constellation Ophiuchus, has been the subject of multiple research. This region, which is thought to have formed as a result of a newly born planet or small companion star passing between the star and the dust trap, holds a large number of millimetre-sized dust grains that can collide and grow into kilometer-sized objects like comets, asteroids, and possibly even planets.

Many complex chemical compounds, such as dimethyl ether, are expected to develop in star-forming clouds prior to the birth of the stars. Atoms and basic molecules like carbon monoxide adhere to dust grains in these freezing conditions, generating an ice coating and performing chemical reactions that result in more complex molecules.

Researchers have revealed that the IRS 48 disc’s dust trap is actually an ice reservoir, including dust grains wrapped in complex molecule-rich ice. ALMA has now detected indications of the dimethyl ether molecule in this part of the disc, as warmth from IRS 48 sublimates the ice into gas, freeing the trapped molecules inherited from the cold clouds.

“What makes this even more exciting is that we now know these larger complex molecules are available to feed forming planets in the disc,” explains Booth. “This was not known before as in most systems these molecules are hidden in the ice.”

Dimethyl ether’s finding hints that many additional complex compounds found in star-forming regions could potentially be hiding on frozen structures in planet-forming discs. These chemicals are precursors to prebiotic molecules like amino acids and carbohydrates, which are some of life’s most fundamental building blocks.

By studying how prebiotic molecules are made and how they change over time, researchers can learn more about how they get to planets like our own.

Source: 10.1051/0004-6361/202142981

Image Credit: ESO/L. Calçada, ALMA (ESO/NAOJ/NRAO)/A. Pohl, van der Marel et al., Brunken et al.

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