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Largest organic molecule in a planetary nursery – astronomers discover dimethyl ether in a protoplanetary disk for the first time

Precursors of the building blocks of life: Astronomers have first discovered the organic molecule dimethyl ether in the dust of a protoplanetary disk – thus a precursor to important chemical building blocks. Dimethyl ether is the largest molecule discovered in such a disk to date. It also confirms the presence of more complex organic molecules already in the primordial clouds of planetary systems.

Amino acids, proteins, the building blocks of DNA: According to current theory, the precursors of many of the building blocks of life could have arrived on Earth from space. Because the corresponding organic molecules were already comet iceat Planetary nebulae And discover them in the bras of the stars. In cold molecular clouds, they became polycyclic aromatic hydrocarbons (Polycyclic aromatic hydrocarbons) detected.

Spectral signature of different organic molecules in the dust disk of IRS 48. © ALMA (ESO/NAOJ/NRAO) / A. Pohl, van der Marel et al., Brunken et al.

chasing particles in space

However, the big question is whether and how these organic molecules get into small and on planetary systems. “Studying these molecules in planet-forming disks is critical to understanding how matter is incorporated into planets and what level of complexity exists at different ages of planet formation,” says Nasante Bronken of Leiden University Observatory and colleagues.

The problem, however, is that in protoplanetary disks around young stars, dust and gas usually cool so much that organic molecules are trapped in ice crystals and ice layers around dust grains. Chemical reactions often take place there, which allows the formation of more complex compounds from simple predecessors. However, because these molecules are not released, they are difficult to detect by their spectral fingerprint.

Look at a warm disk of dust

But there are exceptions – one of them is only 444 light-years away from us. It’s the young star IRS 48, surrounded by a highly asymmetric cashew nut-shaped dust disk. But the most important thing: Because this young star shoots out intense ultraviolet radiation, it has heated up its own disk of dust and gas. As a result, bits of the ice sheet sublimate around the dust grains and the particles trapped there are liberated – thus detectable by spectroscopic measurements.

Astronomers previously discovered sulfur dioxide, sulfur monoxide, and ethanol there. In search of other, more complex organic molecules, Brunken and her team have now once again examined this young star and its dust disk spectroscopically using the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile.

Dimethyl ether and methyl formate

In fact, astronomers found what they were looking for: In the dust cloud around IRS 48, they detected the spectral signature of dimethyl ether (CH).3oh3) is then a compound of nine atoms in total. “Dimethyl ether is the largest organic molecule discovered in a protoplanetary disk,” the team says. In addition, their measurement data also indicates the presence of methyl formate (CH3OCHO) is out.

Both molecules were previously detected in stellar cradles but not in protoplanetary disks. They serve as potential precursors to the important building blocks of life. “It’s really cool to finally be able to track down these larger particles in the disks,” says Bronkin’s colleague, Alice Booth. This is also particularly exciting because there may actually be a first protoplanet in the dust disk around IRS 48.

This is how astronomers discovered the organic molecules in the star IRS 48.© ESO

Information about our solar system

The discovery of more complex organic molecules in an emerging planetary system could – astronomers hope – reveal more about the possible origin of life on our planet. “With further observations, we hope to move one step closer to understanding the origin of the prebiotic molecules in our solar system,” says Bronken’s colleague Nienke van der Marel. (Astronomy and Astrophysics, 2022; doi: 10.1051/0004-6361/202142981)

Source: European Southern Observatory (ESO)