New research from MIT Professor Brett McGuire’s group has revealed the presence of a previously unknown molecule in space. The team’s open access paper, “Rotational spectrum and first interstellar detection of 2-methoxyethanol using ALMA observations of NGC 6334I,” appears in the April 12 issue The Astrophysical Journal Letters.
Zachary TP Fried, a graduate student in the McGuire group and lead author of the paper, worked to assemble a puzzle made up of pieces collected from around the world, stretching beyond MIT to France, Florida, Virginia and Copenhagen, to achieve this exciting discovery.
“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 piece together how chemistry evolves along with the process of star and planet formation. We do this by looking at the rotational spectra of molecules, the unique patterns of light they emit as they roll end-to-end in space. These patterns are fingerprints (barcodes) for molecules. To find 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 the lab here on Earth, and finally search for that spectrum in space using telescopes.
Searching for molecules in space
The McGuire Group recently started using machine learning to suggest good target molecules to search for. In 2023, one of these machine learning models suggested that researchers target a molecule known as 2-methoxyethanol.
“There are a number of ‘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 seen,” says Fried. To detect this molecule using radio telescope observations, the group first had to measure and analyze its rotation spectrum on Earth. The researchers combined experiments from the University of Lille (Lille, France), the New College of Florida (Sarasota, Florida), and the McGuire Laboratory at MIT to measure this spectrum in a broadband region of frequencies ranging from microwave to submillimeter wave modes (approximately 8 to 500 gigahertz).
The data gathered from these measurements enabled a search for the molecule using Atacama Large Millimeter/submillimeter Array (ALMA) observations of two separate star-forming regions: NGC 6334I and IRAS 16293-2422B. Members of the McGuire group analyzed these telescope observations along with researchers from the National Radio Astronomy Observatory (Charlottesville, Virginia) and the University of Copenhagen, Denmark.
“Ultimately, we observed 25 rotational lines of 2-methoxyethanol that lined up with the molecular signal observed for NGC 6334I (the barcode matched!), leading to a confident detection of 2-methoxyethanol in this source,” says Fried. “This allowed us to then derive physical parameters of the molecule to NGC 6334I, such as its abundance and excitation temperature. It also enabled the investigation of possible pathways of chemical formation from known interstellar progenitors.
I expect
Molecular discoveries like this help researchers better understand the evolution of molecular complexity in space during the star formation process. 2-Methoxyethanol, which contains 13 atoms, is quite large by interstellar standards—as of 2021, only six species larger than 13 atoms have been found outside the solar system, many of the McGuire group, and they all exist as ring-like structures .
“Continued observations of large molecules and subsequent inferences of their abundance allow us to expand our knowledge of how efficiently large molecules can be formed and by what specific reactions they can be produced,” says Fried. “Furthermore, because we detected this molecule in NGC 6334I but not in IRAS 16293-2422B, we were given a unique opportunity to look at how the different physical conditions of these two sources might affect the chemistry that might occur.”
Republished with permission from MIT News. Read the original article.
