A new study by a group of MIT professors Brett McGuire has revealed the existence of a previously unknown molecule in space. The team’s open-access paper, “First interstellar detection of 2-methoxyethanol using rotation spectrum and ALMA observations of NGC 6334I,” is published in the April 12 issue of The Astrophysical Journal Letters.

To reach this exciting discovery, Zachary T.P. Fried, a graduate student in McGuire’s group and lead author of the paper, sought to piece together a puzzle made up of pieces collected from around the world, going beyond MIT to France, Florida, Virginia and Copenhagen. . .

“Our group is trying to understand what molecules are present in the regions of space where stars and solar systems will eventually form,” explains Fried. “This allows us to connect how chemistry evolves with the process of star and planet formation. We do this by looking at the spin spectra of molecules, the unique light patterns they emit as they bounce around each other in space.”

“These patterns are fingerprints (barcodes) of molecules. To detect new molecules in space, we first need to have an idea of ​​what molecule we want to look for, then we can record its spectrum in a laboratory on Earth, and finally we look for this spectrum in space with telescopes. “

Searching for molecules in space

The McGuire Group recently began using machine learning to suggest good target molecules to look for. In 2023, one of these machine learning models suggested that researchers were targeting a molecule known as 2-methoxyethanol.

“There are several ‘methoxy’ molecules in space, such as dimethyl ether, methoxymethanol, ethyl methyl ether, and methyl formate, but 2-methoxyethanol would be the largest and most complex yet seen,” says Fried.

To detect this molecule through radio telescope observations, the team first had to measure and analyze its spin spectrum on Earth. The researchers combined experiments from the University of Lille (Lille, France), New College of Florida (Sarasota, Florida), and the McGuire Laboratory at MIT to measure this spectrum in the broadband frequency region, from microwaves to submillimeter frequencies. wave modes (approximately 8 to 500 gigahertz).

Data from these measurements allowed the search for the molecule using Atacama Large Millimeter/submillimeter Array (ALMA) observations in two separate star-forming regions: NGC 6334I and IRAS 16293-2422B. Members of McGuire’s team analyzed these telescope observations with researchers from the National Radio Astronomy Observatory (Charlottesville, Virginia) and the University of Copenhagen, Denmark.

“Ultimately, we observed 25 rotating lines of 2-methoxyethanol that aligned with the observed molecular signal in the direction of NGC 6334I (barcode match), enabling reliable detection of 2-methoxyethanol in this source,” says Fried. “This allowed us to obtain the physical parameters of the molecule before NGC 6334I, such as its distribution and excitation temperature. It also made it possible to investigate possible pathways of chemical formation from known interstellar progenitors.”

Look ahead

Such molecular discoveries help researchers better understand the evolution of molecular complexity in space during the star formation process. Containing 13 atoms, 2-Methoxyethanol is quite large by interstellar standards – as of 2021, only six species larger than 13 atoms have been identified outside the Solar System, most by McGuire’s group, and all exist as ring structures. .

“Continuous observation of large molecules and subsequent determination of their contents allows us to deepen our knowledge of how efficiently large molecules can be created and by what specific reactions they can occur,” says Fried.

“Moreover, because we detected this molecule in NGC 6334I but not in IRAS 16293-2422B, we have a unique opportunity to study how the different physical conditions of these two sources may affect the chemistry that may occur.”