Researchers in the Department of Physics & Astronomy at Texas Tech University recently used audio to represent the spectacular explosion of a star in deep space while also delving into the data to better understand how the phenomenon unfolded.
The explosion of NovaV612 Scuti, also known as ASSASSN-17hx, was discovered in 2017 and observed by astronomers around the world. Those observations produced a rich set of data that allowed researchers to study how the eruption changed over time. At Texas Tech the work has been led by undergraduate student Pragati Acharya under the guidance of Assistant Professor Elias Aydi.
By transforming the nova’s changing light into audio, the team has added a new dimension to understanding how the explosion unfolded.
“This sonification allows people not only to see the changing brightness of the explosion, but also to hear its evolution,” Aydi said. “In other words, we can now offer audiences a way to experience what a stellar explosion might ‘sound’ like when astronomical data are translated into audio.”
The findings have been accepted for publication in the journal Monthly Notices of the Royal Astronomical Society (Oxford Press).
The project is another example of the high-quality research taking place in Physics & Astronomy, said Sung-Won Lee, department chair.
“This study is an outstanding achievement that showcases the international stature and research excellence of the Texas Tech astrophysics program,” he said. “By combining observations from around the world and transforming the nova’s data into sound, the team has opened an innovative pathway for exploring and communicating astronomical discoveries.”
For Acharya, the opportunity to work on a real stellar explosion was especially meaningful.
“The chance to study a star was deeply meaningful to me,” said Acharya. “Growing up in Nepal, there wasn’t much awareness or conversation about astronomy, but the night sky was so clear and beautiful that it was impossible not to ignore. The stars themselves were the reason I became interested in this field. There was a moment when they stopped being twinkling dots and revealed themselves as entire worlds, the universe itself.
“That shift changed everything for me. My curiosity grew from wondering why stars twinkle to exploring why they brighten, erupt and evolve. Texas Tech, and especially Dr. Aydi’s patient guidance, helped me build the foundation to turn that curiosity into real research.”
A nova occurs when a dense stellar remnant, known as a white dwarf, pulls material from a companion star. As that material builds up on the white dwarf’s surface, it can trigger a sudden thermonuclear explosion, causing the system to brighten dramatically.
Novae occur fairly regularly in the Milky Way with about 10 to 15 discovered each year. Because they take place within our own galaxy, astronomers can study them in far greater detail than many stellar explosions in distant galaxies.
Aydi explained that although scientists have long studied these explosions, recent discoveries have changed how researchers understand these events.
“About 15 years ago, NASA’s Fermi gamma-ray satellite detected strong high-energy gamma rays from novae,” Aydi said. “This was not expected at all, so we had to rethink how these explosions happen. It turned out there is a lot we don’t know, and what we thought we understood very well, apparently, we don’t understand at all.”
These discoveries led astronomers to explore how novae could produce such energetic radiation. One explanation centers on shock waves. During a nova eruption, gas can be ejected at different speeds. Later faster-moving material may collide with gas ejected earlier, creating powerful shocks.
“These later ejections slam into the earlier ones, creating shock waves that lead to high-energy emission,” Aydi said.
The shocks also heat the surrounding gas, causing it to radiate at visible wavelengths. Recent studies have shown that much of the visible light typically observed from novae, long thought to come primarily from nuclear reactions on the surface of the white dwarf, may instead originate, at least in part, from the shock-heated gas.
“This has further changed our understanding of how these explosions unfold, Aydi said. “We now know that novae are far more complex than once thought, and that they can serve as important laboratories for understanding other stellar explosions across the cosmos, especially because they occur relatively nearby in astronomical terms.”
Nova V612 Scuti was particularly interesting because it showed major flares, or jumps in brightness, for several months after the initial explosion was discovered.
“The jumps within the explosion were extreme,” Aydi said. “We had a huge amount of energy somehow released after the explosion happened, and we didn’t know what was causing it. One of our hypotheses was that, after the initial explosion, there were subsequent substantial ejections of gas colliding with previously ejected material, creating powerful shock waves. The challenge was to confirm this using observations and detailed analysis.”
To investigate the eruption, the researchers used spectroscopy, a technique that separates light into different wavelengths, much like spreading light into the colors of a rainbow. This allows astronomers to measure how strongly the object emits at different wavelengths and to track the motion of gas during the explosion.
Astronomers around the world observed V612 Scuti using spectroscopy and shared their data with the broader scientific community. The Texas Tech team used those observations to examine when the brightness jumps occurred, what caused them and how the gas moved during the eruption.
Aydi said the team found evidence that new ejections occurred with each jump in the light curve. By studying shifts in the spectra, they were also able to calculate the velocity of the material. Over several months of observations, they found that the gas increased significantly in velocity with each major jump.
The team decided to take the analysis a step farther.
“We had high-resolution spectra, which measure intensity versus frequency, and we said, ‘We can actually convert this extensive set of data into an equivalent of sound.’” Aydi said. “So, we converted the intensity of light into sound pitch and the frequency of light into frequency of sound.”
The process allowed the researchers to hear how the explosion changed over time. When the nova’s brightness jumped, the sound changed as well. The team could not only see the evolution of the explosion in the data, but also could hear it.
The sound also makes the discovery more accessible, including for people who are visually impaired.
“It is very difficult to transform astronomy data into audio data,” Aydi said. “You need really good data, and when we were working on this, I thought it was a perfect example. We had enough data because of the almost daily observations astronomers were taking, which allowed us to turn this set of spectra into a continuous sound that visually impaired people could listen to and use to imagine what was happening.”
Acharya carried out much of the data analysis, including creating the figures for the paper and producing the sonification.
“She created the graphs we are publishing in the paper, and she also did the sonification of the data,” Aydi said. “We experimented with multiple types of codes and decided on one that would make the sound as clear as possible for someone who could not see the data.
“This is significant scientifically because we are confirming something with the data for the first time in a very strong way. It is also significant because the work was done and led by Texas Tech students.”
Along the way, Acharya gained valuable experience in coding, spectroscopy and astronomical data analysis.
“I realized how it works bit by bit, code by code, and what the sonification script actually does,” she said. “When I did it all by myself and changed the wavelengths into frequencies and produced a sound, it felt like the best thing I had ever done, and it’s something I will never forget.”
Aydi said involving undergraduates in significant research is a point of pride for the Department of Physics & Astronomy.
“We are living in a very competitive academic world,” he said. “Our aim is that when our undergraduate students graduate and want to apply for graduate school, they already have the experience, the skills and the achievements that allow them to be competitive. This project is a clear example of the pioneering work we do with our students.”
Lee said the project reflects the department’s emphasis on challenging students to stretch themselves academically.
“It is especially noteworthy that this project was led by our very own undergraduate student, Pragati Acharya, whose leadership reflects both her remarkable potential and the strong research environment cultivated by Dr. Aydi and our astrophysics group,” Lee said. “I extend my sincere congratulations to Dr. Aydi’s team, particularly Pragati, for conducting this study with exceptional excellence.”
For Acharya, the project has been unforgettable.
“I cannot imagine this whole thing, but it actually feels like, ‘OK, I did something I always wanted to do.’ It’s why I chose physics,” she said. “You want people to hear you and understand your perspective on how you see the world and understand it. Overall, it feels like you are doing something meaningful for humanity and for science.”