Eric Herbst, a professor of chemistry at the University of Virginia, held a seminar titled “Three Environments for Interstellar Chemistry: Gas, Dust and Ice” on Friday, April 21. He spoke about the species of molecule found in gases, dust and ice and the tools which scientists use to observe them.
Herbst is currently the Commonwealth Professor in the Departments of Chemistry, Astronomy and Physics at the University of Virginia. He completed his Ph.D at Harvard University, and was a postdoctoral fellow there as well as at the Joint Institute for Laboratory Astrophysics at the University of Colorado.
Herbst began by describing the field of astrochemistry, which he defined as “the study of molecules in non-terrestrial environments.”
According to Herbst, scientists first took a strong interest in astrochemistry in the 1970s. Astrochemists use techniques similar to those of other chemists, especially spectroscopy and kinetics.
Herbst described the process of star formation and noted that the structures involved each have their own chemistry. First, interstellar clouds of gas and dust form from the remains of previous stars. Within the cloud, “hot cores” and “cold cores” develop. Under the right conditions, some of the hot cores eventually become stars, while other material might form meteors, comets or planets.
According to Herbst, astrochemists use radio telescopes to study the emission spectra of the molecules within cold cores. Scientists can measure some spectrum lines from the ground using telescopes, such as an array of 60 telescopes in Chile known as the Atacama Large Millimeter Array (ALMA). However, to measure spectrum lines with infrared or far infrared frequencies, they need to use telescopes in space or on airplanes. From these spectra, scientists can study collisions between molecules and the concentrations of molecules.
Herbst finished his talk by discussing current research in astrochemistry, including one of his recent projects. “One of the things we’ve started to worry about in the last year [is] that we’ve missed [that] cosmic rays [make] ions in the gas phase,” he said. “We have not included what happens when cosmic rays hit dust particles. This is a very hard problem, frankly.”
Herbst said that he approached the problem by using a supercomputer to simulate a cosmic ray passing through dust, and then borrowing approximations found by nuclear physicists in the 1950s to analyze his results. He added that there were interesting current projects related to black holes, high-temperature dust chemistry and the spatial distributions of molecules within sources that scientists are still investigating.
The talk was followed by a Q&A session.
After the seminar, Professor of Chemistry Mark Marshall said, “I loved the talk! [Astrochemistry is] the kind of thing that I’ve followed from a distance for many years. I was just glad that we had the chance to bring Professor Herbst to campus and let other people know that these kinds of things that we study here can be applied to the galaxy.”
Senior chemistry major Niyi Odewade said that the subject of the talk was new and different, as it involved “exotic [chemical] species” not seen on Earth. However, he added, “it was easy to relate to, because Amherst also teaches you the basics and makes everything easy to understand, and [Herbst] actually made it very interesting and inspiring, because ... there’s a world out there left to learn about.”
The talk was sponsored by the Department of Chemistry as part of its lecture series.
