COSAM News Articles 2024 09 Auburn astrophysicist seeks to view cations never seen before in an astronomical context

Auburn astrophysicist seeks to view cations never seen before in an astronomical context

Published: 09/06/2024

Steven Bromley, a research scientist in Auburn University’s Department of Physics, is the primary investigator of a new National Science Foundation (NSF) Division of Astronomical Sciences award for $604,321. The project, Gas-phase chemical and spectral modeling to unlock the diagnostic potential of cations in small body atmospheres, is a collaborative effort between three leading institutions, Auburn University, Mississippi State University, and the University of Mississippi.

Three researchers are co-principal investigators: Dennis Bodewits, associate professor from Auburn, Donna M. Pierce, associate professor from Mississippi State, and Ryan Fortenberry, associate professor from the University of Mississippi.

Neutral molecules like N₂, O₂, and CO₂ are known to exist in comets but remain undetectable through ground-based astronomy due to their elusive nature. These molecules are highly volatile and provide valuable insights into comet formation and their thermal history. Determining their abundance or whether they are present only in specific comets, however, is extremely challenging. “If you remove one of their electrons, these molecules become cations, which can emit distinct signatures in the ultraviolet and visible wavelengths—wavelengths that ground-based telescopes can detect,” explains Bromley.

“We will be researching three specific ‘cations’ that are either known or are expected to exist around comets: N₂⁺, O₂⁺ and CO₂⁺,” Bromley continued. “All three of these systems may provide an opportunity to remotely diagnose how abundant their parents really are. The most exciting one, for me, is O₂⁺, as we know where it emits in the laboratory, but it has yet to be seen in comets!”

Comet Hale Bopp

The blue comet tail seen above is caused by the CO+ cation emitting ultraviolet light. The dust tail is white and the cation tail is seen in blue. Photo credit: Wikimedia.

Each individual institution will play a critical role in this research over the next three years from 2024 through 2027. The University of Mississippi will perform state-of-the-art quantum calculations to characterize the structure of these molecules. Using the outputs of these calculations, the Auburn team will predict how efficiently these molecules can be excited by sunlight and emit light that we see from comets. The last piece of the puzzle, how these cations might be formed in cometary atmospheres, will be unlocked by new chemical network modeling underway by the Mississippi State University team.

“This research offers the potential of being able to tell ground-based observatories where, and when, these species might be emitting and become detectable in comets. We are very excited, as this doesn’t impact just one observatory, but a whole field,” Bromley said.

The NSF award will bring impacts on the local scale as well. Both Bromley and Bodewits will offer observation opportunities at Auburn’s Telescope Terrace. “Viewing comets from our facilities can be tricky. We need good weather conditions, and also favorable orbits that bring comets close enough to Earth to be bright enough to see. Historically, there has been about one bright comet per year that is visible to us, so the odds are quite good!” said Bromley. The team is planning to undertake several public observing nights to look at bright celestial objects such as the Orion Nebula, planets, and potentially naked-eye visible comets in the coming years.