Dimethyl Ether in a Disk!

Today another exciting press release has come from ALMA, detection of emission from the largest molecule yet detected so far in a protoplanetary disk. The molecule in question is dimethyl ether, which has the chemical formula CH3OCH3. On Earth, dimethyl ether exists a colourless gas that has various applications, and is also an isomer (i.e., a molecule with the same atoms but rearranged) of ethanol, the type of alcohol we imbibe in, well, alcohol. Note that dimethyl ether is different from diethyl ether, which is the commonly known anaesthetic also known simply as ‘ether.’ Dimethyl ether is composed of nine atoms, and interesting to see because such large, organic molecules are necessary for the chemistry that produces the molecules that life relies on. Dimethyl ether in particular has been detected before in star-forming clouds, but this detection is the first in the denser, and warmer environment of a planet-forming disk around a young star. The idea here is that these molecules eventually condensed into the ice on the surface of dust grains in the extremely cold and dense parts of clouds that can collapse under their own weight, producing stars. Some of these grains, however, don’t go into young stars, but are instead entrained in disks surrounding them. The grains are warmed up by the young star, melting the ice and releasing previously trapped molecules like dimethyl ether back into the gas phase.

Seeing such complex molecules within disks tells us there exists environments where such complex molecules can remain abundant. Indeed, the team also find hints of another precursor to bio-molecules, methyl formate, in their data. Perhaps even more complicated bio-molecules like sugars or amino acids also are present and brought to the planets forming in those disks. The emission signatures of such molecules are harder to detect in general than simpler molecules though, but future very sensitive observations with ALMA or the Next Generation Very Large Array could see them. This detection, reported in a paper published today in Astronomy & Astrophysics, was work actually led by a graduate student at Leiden University, and involves former NRC PDF Nienke van der Marel who is now an Assistant Professor there. The disk where the dimethyl ether was detected surrounds the young star Oph IRS48, one of Nienke’s favourite targets because its disk has a location within it where dust grains appear to be growing into the seeds of new planets. Notably, all six authors of this paper are women, making it an excellent celebration of today being International Women’s Day. Congratulations to the team for their excellent discovery! Here also is a link to the European Southern Observatory’s press release for those who’d like more information.