Finding patterns through the noise

Today’s top hit songs, the 5 o’clock news, and coverage of the local hockey game all travel several dozen miles from a radio station’s transmitters to your car’s radio receiver, but radio waves don’t just come from man-made sources. Some objects and events in space produce radio waves that travel across the universe, carrying clues about their cosmic origin. A group of students from Penn State has been sifting through man-made signals and noise picked up by radio telescopes on Earth to try to spot signals of pulsars, a type of astronomical object that emits radio waves.

These students make up the Penn State branch of the Pulsar Search Collaboratory (PSC), a nationwide citizen-science project that uses both undergraduates and high school students in the search, providing information about not only pulsars but also the broader universe.

Pulsars are a type of neutron star—the particularly dense remnant of a collapsed star—that shoots out jets of light and other particles. As the star rotates, the jets periodically align with the line of sight from Earth, allowing ground-based telescopes to detect emitted radio waves. Members of the Penn State PSC analyze data from two radio telescopes on Earth, the Green Bank Telescope in West Virginia, and the now-decommissioned Arecibo Observatory in Puerto Rico, in hopes of finding signals of previously unknown pulsars.

“Radio telescopes pick up a lot more than just signals from space, because we use radios on Earth and, well, we're not very good about containing their signals,” said Joshua Hicks, a fourth-year undergraduate double-majoring in astronomy and astrophysics and physics and president of the Penn State PSC. “We look for patterns that we would expect to see from pulsars. The data has some amount of noise filtered out before it gets to us, but a lot of our work is finding the junk and filtering out the noise.”

The students specifically look at data collected when the telescopes were undergoing repairs and, although they were not pointed at anything in particular, they were still collecting data as objects in the night sky drifted by—called drift scan data.

“By identifying ‘space noise,’ or radio-frequency interference, we can ultimately help improve models that identify it and filter it out,” said Erin Gavin, a fourth-year undergraduate double-majoring in astronomy and astrophysics and physics and vice president of the Penn State PSC. “Eventually they’d like to automate the process, and our work helps make that a possibility.”

The broader PSC was founded in 2007 by a team that includes Penn State alumna Maura McLaughlin, who received a bachelor’s degree in astronomy and astrophysics from the Eberly College of Science in 1994 and is now Eberly Distinguished Professor of Physics and Astronomy at West Virginia University. In addition to getting help analyzing more than 300 observation hours of data, the PSC was created to help build students’ interest in STEM careers.

“I had wanted to get a branch of the PSC started at my high school, but it didn’t really work out during the pandemic,” Gavin said. “So, when I came to college, I was excited to join. I participated over Zoom during my first year, when I was at Penn State Berks. When I came to University Park, it was really helpful to show that I had some research experience when applying for later research experiences.”

At Penn State, members of the PSC earn research credit for their efforts, which is uncommon for student organizations. Hicks says the unique opportunity to get involved in research as early as a student’s first semester is a big draw to the organization.

“It can be difficult for first-semester students to find research opportunities, so the PSC is a great way for students to get involved in research right away,” he said. “There are no prerequisites, and we teach members everything they need to know, so it’s very accessible.”

The organization attracts students from across campus. They currently have about 30 active members with a wide range of majors and minors, from astronomy to linguistics to engineering.

“I didn’t know much about the astronomy major or different fields of astronomy during my first semester, and I thought the PSC was a great way to get more involved,” said Abigail Raytsis, a second-year astronomy and astrophysics major with a Russian studies minor and secretary of the PSC. “I ended up really liking it, so I stuck with it.”

New members go through some initial trainings over Zoom through WVU but otherwise rely on more-senior members of the Penn State branch for training.

“Our training is a lot more hands on,” Gavin said. “We demonstrate how to read plots and have Wheel of Fortune- and Jeopardy-like games designed to get members to learn, practice, and remember all the information they need to know. These activities help add an extra layer of confidence, so members know how the research works before we set them loose on the database.”

Meetings early in the year focus on training, while later meetings include research focus time as well as professional development opportunities and community building. They cover topics including scientific writing and giving effective presentations, and members also hear presentations about radio astronomy from faculty members.

“Last year we ordered components and built radio telescopes,” added Luke Royer, a third-year undergraduate majoring in astronomy and astrophysics and treasurer of the PSC. “Now that they are built, it would be really cool to have people design experiments and point them at known objects in space and see what we can pick up.”

Although the research process is mostly done individually, members often confer with one another when they have questions or interesting data, and some meetings also are quite social, Hicks said. “It’s not just research all the time.”

It was the community aspect that led to the formation of the Penn State branch in 2014 by then-undergraduate Cecilia McGough, making it one of the first branches at a university. McGough had participated in a PSC club in high school and became one of the few participants to have actually discovered a pulsar in 2012. At McLaughlin’s suggestion, she came to Penn State and formed the student organization, in part to help replicate the community that was so important to her in high school.

Although most PSC members may never actually discover a pulsar like McGough, their dedication provides important contributions to radio astronomy. For example, alumna Sofia Sheik, who helped mentor students with the PSC as a graduate student, led research using PSC data that was recently published in the Astrophysical Journal. When radio waves travel over long distances, their signals can be distorted, and the research team helped explain the nuances of this phenomenon, called scintillation. Several alumni of the Penn State PSC are co-authors on the paper.

Monitoring and detecting pulsars also contributes to the study of the early universe through the detection of gravitational waves—ripples in space time originally predicted by Einstein’s theory of relativity. While detectors like LIGO and VIRGO can detect gravitational waves more directly, the international collaboration NANOGrav uses pulsars to detect them indirectly. Gravitational waves can cause millisecond distortions in the typically consistent signals of pulsars, and large numbers of pulsars form what is called a galactic timing array. Tracking the minuscule variations allows the array to function as a galactic-sized detector, which NANOGrav uses to study the universe.

“Even if it’s not a super tangible, immediate benefit, knowing that our work is used in science and contributes to projects like NANOGrav is motivating,” Hicks said.

“The PSC provides a unique opportunity to both connect with other students interested in science and get involved with scientific research,” he added. “I know how intimidating it can be for students when you're just starting out, and I have really enjoyed helping students navigate the world of astronomy research and building our small community.”

Editor's notes:

• Hicks is a recipient of the Bert Elsbach Honors Scholarship in Physics and the M. Dean and Jean L. Underwood Scholarship in Physics.
• Gavin is a recipient of the John and Elizabeth Holmes Teas Scholarship.
• Raytsis is a recipient of the Bonnie S. and Gregory A. Szymik Trustee Scholarship.
• Royer is a recipient of the Mercedes T. Richards Memorial Scholarship in Astronomy and Astrophysics.
• Sheik was a recipient of the Cecilia Payne- Gaposchkin Graduate Scholarship in Astronomy. She graduated with a master's degree in 2019 and a doctoral degree in 2021.