University of Michigan study sheds new UV light on formation of planets

Researchers at the University of Michigan's Department of Astronomy believe a new study has provided insight into the chemistry behind planet formation.

These scientists have found that the chemistry, in the later stages of developing plants, is powered by ultraviolet rays, which create a chemical signature. Researchers use the chemical signature to trace exoplanets back to their cosmic nurseries in planet-forming disks, according to a press release.

“It has been shown that there are bright, complex organic molecules present in the coldest and densest parts of planet-forming disks,” Jenny Calahan, the first author of the study published in Nature Astronomy and a doctoral student, said in the release. “This bright emission has been puzzling because we expect these molecules to be frozen out at these temperatures, not in the gas where we can observe them.”

In the release, Calahan explained that the discovery was made, partly, by chance, plus built on previous work.

Calahan and her team discovered that the molecules, emitting from these regions, are fueled by ultraviolet rays, the release noted. This realization led to Calahan adjusting her model to decrease the mass of the small dust population and allow more UV photons to penetrate deep into these coldest regions of the disk, which reproduced the observed brightness. 

Edwin Bergin, principal investigator, professor, and chair of astronomy, explained that the research shows that the initial steps in making planets, forming larger and larger solids, shifts the chemistry from cosmic rays and X-ray-driven early, to UV-driven during the phase where giant planets are thought to be born. 

The study’s findings have significant implications for understanding the chemistry of planet formation and the potential for life on exoplanets. Calahan’s discovery provides insight into the later stages of planet formation and the evolution of small dust over time. 

The team’s findings will also aid researchers in understanding the composition of material that makes giant planets.