Chemists know a lot about how atoms and molecules behave—lugging around any chemistry textbook will tell you that. But almost all of that knowledge is about how chemistry happens here on Earth, and the conditions in the vast majority of the universe are very, very different.
Brett McGuire, a newly minted chemistry professor at the Massachusetts Institute of Technology, is trying to figure out the rules of chemistry in outer space, specifically in the dark, cold dust clouds where planets and stars are born.
That would be a lot easier if we could visit these places, but they’re light-years away. Instead, he and his collaborators combine chemistry and astronomy techniques to identify molecules in these regions. First, McGuire makes molecules in the lab he thinks might be found in outer space, then carefully measures the unique signature of light they absorb. Next, using massive telescopes, McGuire and his colleagues search for those spectroscopic fingerprints in the radiation shining out from these clouds. By identifying molecules, McGuire hopes he and others will be able to piece together what kind of chemistry can happen in space.
“Our job, with only photons from the sky, is to figure out what molecules are there, where they came from, and where they go next,” he says.
Research at a glance
McGuire helped identify benzonitrile in space for the first time by matching experimental infrared spectroscopy data of changes in the aromatic molecule’s rotations (red) to data from telescopes (blue). Data shown are updated since the discovery was reported in Science in 2018.
Credit: Brett McGuire/Yang H. Ku/C&EN
So far, McGuire is doing a good job of figuring out what’s there. “He’s one of the most successful new interstellar molecule hunters,” says Ewine van Dishoeck, an astrochemist at Leiden Observatory and one of McGuire’s collaborators. In 2016, McGuire and colleagues identified the first chiral molecule in space, propylene oxide, and in 2018 he helped identify the first aromatic molecule, benzonitrile. Astronomers knew chiral and aromatic molecules existed in interstellar space, but no one had determined which ones, exactly, were out there.
McGuire thinks being both an astronomer and a chemist gives him an edge. “I speak both languages,” he says, and thus he can build teams with experts from both fields. “That’s why we’ve been successful.”
As he prepares to start his own research group at MIT this fall, McGuire is pushing deeper into the unknown. Rather than starting with molecules he thinks are out there, like propylene oxide and benzonitrile, McGuire is letting chemistry guide his search. By performing reactions in the lab that might happen in interstellar dust clouds, his team makes molecules that have never been seen on Earth. Then, they go look for them in telescope data. The first results using this approach will be published later this year.
For McGuire, this is just the beginning of understanding interstellar chemistry, a process he thinks could take decades. Learning the identity and location of new aromatic rings could change scientists’ theories about how stars and planets form. Identifying chiral molecules could help chemists figure out why biological molecules like DNA tend to twist the same direction.
“I wouldn’t say we’re beginning to have answers,” McGuire says. “I’d say we’re beginning to be able to ask the right questions.”
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