BOULDER, CO.- A team of researchers led by a former undergraduate student at CU Boulder has discovered a dusty mystery in a newly explored region around Earth’s sun.

Anna Pusack got her first glimpse of the enigma when she was studying in the Department of Astrophysical and Planetary Sciences (APS) at CU Boulder. She and her colleagues were peering at data from a NASA space mission called the Parker Solar Probe when they noticed something unusual: A new and unexplained stream of microscopic particles that seemed to be spraying out from around the star.

The researchers published their findings in The Planetary Science Journal. A companion paper led by Jamey Szalay of Princeton University, who earned his PhD in physics from CU Boulder in 2015, also appears today. Pusack said this river of dust could reveal new secrets about the forces that shaped our solar system.

“Dust can come from asteroids and comets or can be left over from the original formation of the planets,” said Pusack, now a research associate at the Laboratory for Atmospheric and Space Physics (LASP) at CU Boulder. “It can show us how our solar system has formed and continues to evolve and even how other solar systems may be evolving.”

The results are the latest coup for the Parker Solar Probe, a daring spacecraft that zips around the sun at incredible speeds.

“Just three years into its seven-year mission, the probe is already shining new light on the intimate connections between Earth and its host star,” said study coauthor David Malaspina, a research scientist at LASP and assistant professor of APS.

Star gazing
Pusack, who graduated from CU Boulder in December 2020, took a non-traditional path to the university and to space science. She previously studied East Asian studies and philosophy at Dickinson College in Carlisle, Pennsylvania. But she discovered a new passion during a summer spent at a yoga retreat in the Rocky Mountains in Rollinsville, Colorado.

“I could see the stars more clearly than I could in ages,” Pusack said. “I would stay up to look at the stars, trying to learn a new constellation every night.”

She enrolled in introductory science classes at Front Range Community College in Boulder, then transferred to CU Boulder in 2018. There, she began working with Malaspina to take a close look at the data Parker was sending back to Earth.




“I really enjoy seeing data that are coming down right now,” Pusack said. “It was real-time science that was happening.”

It’s that same real-time science that led the researcher to an unexpected discovery.

Pusack explained that the Parker Solar Probe doesn’t carry a special instrument for collecting dust. Instead, it detects the brief spikes of electric potential that occur when the spacecraft collides with grains of dust in space (most of which are too small to see with the naked eye).

Solar monitoring
In their new study, Pusack and her colleagues set out to create an inventory of the dust that the spacecraft encountered on its initial eight trips around the sun.

“There are two basic types of dust around the sun,” Pusack said. “You have dust that is in bound orbits around the sun that will eventually spiral into the sun. Then there’s unbound dust that is flung away and out of the solar system.”

During the mission’s fourth orbit, however, the team ran into something else: As the spacecraft was flying away from the sun, it suddenly passed through a concentrated stream of particles zooming out into the solar system at tremendous speeds.

“It’s a very focused, directional spray of these unbelievably small particles,” Pusack said.

No one had seen anything like it before—dust flying away from the sun usually spreads out in every direction, Pusack explained. It doesn’t tend to cluster together. She and her colleagues, in other words, may have spotted a previously unknown third type of dust around the sun.

The researchers are now taking a deeper look at Parker’s data to learn more about the observation. Is that stream of dust, for example, a relatively rare phenomenon or is it a normal occurrence for the sun’s environs? Either way, the group’s discovery could change the picture of how matter blows away from the star and even out of the solar system entirely.

“We have a ready lab in our solar system to understand how so much of the rest of the universe works,” Pusack said. “If we can understand how our sun works, it may help us to understand what we might see in stellar systems much farther out.”

Other coauthors of the new study include Szalay; Stuart Bale and Marc Pulupa of the University of California, Berkeley; Keith Goetz of the University of Minnesota; and Robert MacDowall of the NASA Goddard Space Flight Center.