Fresh research from an MIT professor’s group Brett McGuire revealed the presence of a previously unknown particle in space. The open access team’s article “Rotation spectrum and first interstellar detection of 2-methoxyethanol using NGC 6334I ALMA observations”, appears in the issue of .
Zachary TP FriedAND graduate in the McGuire group and the paper’s lead author worked to put together a puzzle of pieces gathered from around the world, stretching beyond MIT to France, Florida, Virginia and Copenhagen, to make this electrifying discovery.
“Our group is trying to understand what molecules are present in the regions of space where stars and solar systems will eventually take shape,” Fried explains. “This allows us to piece together the evolution of chemistry along with the formation of stars and planets. We do this by looking at the rotational spectra of molecules and the unique patterns of light they give off as they tumble through space. These patterns are the fingerprints (barcodes) of the molecules. To detect new molecules in space, we first have 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 look for that spectrum in space using telescopes.”
Searching for particles in space
More recently, the McGuire Group machine learning began to be used to suggest good target molecules to search for. In 2023, one of these machine learning models suggested that researchers targeted a molecule known as 2-methoxyethanol.
“There are many 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 ever observed,” Fried says. To detect this molecule using radio telescope observations, the group first had to measure and analyze its rotational spectrum on Earth. The researchers combined experiments from the University of Lille (Lille, France), the Fresh College of Florida (Sarasota, Florida), and the McGuire lab at MIT to measure this spectrum in a broadband frequency region from microwaves to submillimeters. wave regimes (around 8 to 500 gigahertz).
The data collected from these measurements enabled the Atacama Enormous Millimeter/submillimeter Array (ALMA) observations to search for the molecule toward two distinct star-forming regions: NGC 6334I and IRAS 16293-2422B. Members of McGuire’s group analyzed these telescopic observations with researchers from the National Radio Astronomy Observatory (Charlottesville, Virginia) and the University of Copenhagen in Denmark.
“We ultimately observed 25 2-methoxyethanol rotation lines that coincided with the molecular signal observed towards NGC 6334I (the barcode matched!), allowing for confident detection of 2-methoxyethanol in this source,” says Fried. “This then allowed us to derive the physical parameters of the molecule toward NGC 6334I, such as its abundance and excitation temperature. It also allowed us to explore possible pathways for the formation of chemicals from known interstellar precursors.”
Waiting for something
Molecular discoveries like this lend a hand scientists better understand how molecular complexity develops in space during the process of star formation. 2-methoxyethanol, which contains 13 atoms, is quite vast by interstellar standards – as of 2021. Only six species larger than 13 atoms have been detected outside the solar systemmany of the McGuire group, and all of them exist as ring structures.
“Continued observations of large molecules and subsequent determination of their abundance allow us to deepen our understanding of how efficiently large molecules can form and through what specific reactions they can be formed,” says Fried. “Additionally, because we detected this molecule in NGC 6334I but not IRAS 16293-2422B, we had a unique opportunity to look at how the different physical conditions of these two sources might influence the chemistry that might occur.”