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Written
by: Anavi Uppal
|
Oct. 15, 2024
Burst Chasers
ū컨ampa astronomer’s research engages students and a global community of amateur scientists in search of answers to questions of the universe
A gamma-ray burst. Photo courtesy of NASA’s Goddard Space Flight Center
Billions of light years away, a jet of high-energy radiation explodes from a newborn black hole or neutron star, aiming directly for Earth. This is a gamma-ray burst (GRB), and for a brief moment, it is the brightest source of light in the universe, putting out more energy in seconds than our sun will emit in its lifetime.
Within 15 minutes of its light reaching Earth, researchers around the globe have been alerted to point their telescopes at the afterglow of the GRB. One of those scientists is Amy Lien, an assistant professor of physics and astronomy at ū컨ampa. Lien is spearheading a project that engages NASA volunteers to help figure out just what causes GRBs.
MYSTERIOUS ORIGINS
GRBs were discovered by accident during the Cold War. After the U.S. and Soviet Union agreed to ban the use of nuclear weapons in space, the U.S. suspected that the Soviets might try to circumvent the treaty and launched spy satellites to detect gamma rays from possible nuclear tests in space. The satellites did detect gamma rays, but they weren’t man-made.
“Fortunately, they checked their data, so they realized it was not from nuclear bombs,” Lien said.
Researchers currently know about two processes that can trigger a GRB. The longest bursts, lasting anywhere from several seconds to hours, are emitted by massive stars dying violent deaths. Their outer layers explode into a bright supernova, while their inner layers collapse to form a dense neutron star or black hole. Other GRBs last less than two seconds and are caused by the merger of either two neutron stars or one neutron star and one black hole, resulting in the creation of a brand-new black hole.
But researchers also have seen some GRBs that don’t match these descriptions. These GRBs last longer than two seconds, but their pulse shapes — recorded by telescopes and represented visually as peaks and drops over time on a line graph — seem to indicate that they were caused by the merger of two neutron stars, not a supernova.
“It’s just not consistent with our current picture of. how the pulses should look for these sources. Maybe we were completely wrong, and we have to revise some of the theoretical models,” Lien said.
Scientists like Lien want to figure out what causes these unusual bursts. Since GRBs are so bright, telescopes can detect them even from billions of light years away. Signals from that far away take billions of years to reach us, which means that distant GRBs provide a rare way for scientists to study the history of the early universe.
OPENING SCIENCE TO THE PUBLIC
Lien began studying GRBs when she worked at NASA’s Goddard Space Flight Center from 2011 to 2021 as a mission support specialist for the Neil Gehrels Swift Observatory. Swift was launched into space in 2004 to study GRBs in wavelengths across the electromagnetic spectrum, from radio to gamma ray. The observatory watches one-sixth of the sky at a time in an attempt to catch new GRBs. Even after the initial gamma-ray signal of a GRB disappears, Swift can see its afterglow in less energetic wavelengths.
“We don’t know when or where it’s going to happen,” Lien said. “You have to react immediately.” Swift catches multiple GRBs per week, and it has seen over 1,600 GRBs in its 20 years.
While at Goddard, Lien began getting requests from researchers asking if she’d seen GRBs with certain unusual pulse shapes. Though a few NASA interns had worked on classifying bursts over the summers, there had been no largescale effort to classify them. “So that’s why we thought about having a citizen-science project to engage the public and help us do this,” Lien said.
Lien developed a project called Burst Chaser for the popular citizen-science website Zooniverse. The project was launched to the public in January and calls on volunteers of any experience level to identify GRBs in Swift data and classify their shapes. ū컨ampa students Katherine Kurilov ’25, Carter Murawski ’25 and Sebastian Reisch ’24 helped Lien develop the project. Murawski, a physics major minoring in math and computer science, converted the Swift data into a user-friendly interface for Zooniverse. “He’s really our main programmer — this project wouldn’t exist without him,” Lien said.
Burst Chaser volunteers are shown graphs of gamma-ray counts versus time for each GRB and are given a brief tutorial on how to interpret them. There are two separate workflows in the project: One asks volunteers to decide if a graph shows a real GRB or just background noise, and the other asks them to draw boxes around individual peaks in a burst pulse. The different peaks are caused by shocks within a GRB’s jet, and studying them can provide scientists with important information about how the jet was created by the black hole or neutron star.
Carter Murawski ’25 is the project’s main programmer. Photo by Bob Thompson
LOOKING AT GRBS WITH FRESH EYES
But why not use artificial intelligence to classify bursts instead of using volunteers? It turns out that AI doesn’t produce accurate classification results when compared to scientists, but the citizen scientists on Zooniverse do it quite well, even though most of them don’t have any formal training in astronomy.
“Maybe somebody just likes astrophysics, and they have no experience at it. Maybe somebody just goes on the website for fun. Maybe it’s a kid. It’s cool to see that you can get accurate results from stuff like that,” Murawski said.
Sometimes, NASA volunteers pick up on patterns that Lien didn’t notice. Lien’s personal interest is finding bursts that start with a peak and taper off into a low tail, since those are the ones that don’t match scientists’ current theoretical explanations. She asked a group of volunteers to search for that shape in Swift data. When she looked at their classifications, she noticed that some of the bursts had shorter tails than she expected, and she wouldn’t have selected them herself.
“Those will be interesting ones — we should probably take a closer look at them to see whether they also have mysterious physical origins,” Lien said.
After the Burst Chaser project concludes, the classifications from the volunteers could be used as training data to teach AI to accurately classify GRB pulses. But working with citizen scientists is about more than just results. It’s about engaging the community.
“What I learned is that there’s a lot of people genuinely super interested in astronomy, and they just want to learn more and actually help,” Lien said. “This is not their job; they’re not being paid. They participate just because they’re interested.”
Burst Chasers, from left: Sebastian Reisch ’24, Assistant Professor Amy Lien and Carter Murawski ’25. Photo by Bob Thompson
A COMMUNITY OF BURST CHASERS
Danny Roylance is a citizen scientist and U.S. Army veteran from Salt Lake City. For him, working on Burst Chaser is a way to reignite his childhood passion for astronomy while doing real NASA science. Roylance has been working on citizen science astronomy projects for about five years and has become such a prolific contributor that he was selected by NASA to help Lien develop the Burst Chaser project. Roylance was part of the first core group of NASA volunteers who tested the workflows and gave feedback to Lien.
“Amy Lien is probably the neatest citizen-science principal investigator that I’ve had the pleasure of working with,” he said. “She’s got a busy schedule, but you can ask a question that can be extremely advanced or it can be really basic, and she will explain it.” Lien invites top-contributing volunteers like him to weekly research meetings, so Roylance has been on calls with NASA volunteers from all around the globe. He sees this diversity as a huge benefit to the science.
“With all kinds of different religions, races, and all that kind of stuff, you’re gonna get a lot of viewpoints over the subject,” Roylance said.
The dedication of some of the volunteers has completely surprised Lien. “There are two people from India, and our meeting obviously is not at a convenient time for them — it’s like 2 or 3 a.m., but they still call in every two weeks,” she said. “I was like, ’Wait a second, you don’t need to sleep?’”
Her students also have been dedicated to the project. Murawski says he has enjoyed working with Lien. “She gives out tasks that she would have to do herself, so it’s like a collaboration with her rather than feeling like I’m just doing the grunt work,” he said. “We’re all working together to accomplish everything.” He hopes to do software engineering or data science work after he graduates, and programming for Burst Chaser has given him valuable experience in that area.
Last summer, Lien created a catalog of the completed classifications for astronomers to use, and Murawski is working to make this information publicly available on a web page. The catalog shows each burst shape and lists every GRB that matches that profile. Lien hopes to work with gamma-ray theorists to connect each burst shape in the catalog to a model of what the GRB’s source looked like.
A Fū컨URE OF SOLVING MYSTERIES
A citizen-science project isn’t like a typical science project with a clear start and end. “I feel like it’s more organic, which means it grows, and the direction shifts by itself — because it’s all human, right?” Lien said. Once all the GRBs in Burst Chaser are classified, the current Zooniverse project will be retired. However, Lien hopes to do a Burst Chaser 2.0 with spectra of GRBs.
Spectra are images that show the intensity of light at different wavelengths. Each element on the periodic table has a unique fingerprint that shows up as dark and bright regions in a spectrum. When astronomers see these regions in a GRB’s spectrum, they can use them to figure out the chemical makeup of the material that the GRB’s jet is plowing through. The location of these fingerprints also reveals how far away a GRB’s source is.
Lien admitted that she sometimes gets caught up with problem-solving and forgets how exciting the research is, but seeing the enthusiasm of her students and volunteer scientists reminds her.
“I got the gift of working in high energy astrophysics, which is what I wanted all along,” Roylance said. “It’s like we’re Arctic explorers looking for that big mystery.”
“I enjoy that pure curiosity,” Lien said.
Gamma-Ray Grant Will Expand Work
In August, Assistant Professor of Physics and Astronomy Amy Lien was awarded a two-year, $233,768 grant from the National Science Foundation to continue and expand her work. Along with fellow faculty members Denija Crnojevic, assistant professor of physics and astronomy, and Simon Schuler, associate professor of physics and astronomy, Lien will collaborate with scientists at NASA’s Goddard Space Flight Center on studying gamma-ray bursts with machine learning, space telescopes and citizen science. The grant also will allow two students to visit Goddard and perform research there for 10 weeks.
“The goal of this grant is to enable collaboration between primarily undergraduate institutions and NASA,” said Lien. “(It) provides a unique opportunity for students and faculty to work with Goddard scientists and explore the mysterious origins of gamma-ray bursts.”
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TITLE
Billions of light years away, a jet of high-energy radiation explodes from a newborn black hole or neutron star, aiming directly for Earth. This is a gamma-ray burst (GRB), and for a brief moment, it is the brightest source of light in the universe, putting out more energy in seconds than our sun will emit in its lifetime.
Within 15 minutes of its light reaching Earth, researchers around the globe have been alerted to point their telescopes at the afterglow of the GRB. One of those scientists is Amy Lien, an assistant professor of physics and astronomy at ū컨ampa. Lien is spearheading a project that engages NASA volunteers to help figure out just what causes GRBs.
MYSTERIOUS ORIGINS
GRBs were discovered by accident during the Cold War. After the U.S. and Soviet Union agreed to ban the use of nuclear weapons in space, the U.S. suspected that the Soviets might try to circumvent the treaty and launched spy satellites to detect gamma rays from possible nuclear tests in space. The satellites did detect gamma rays, but they weren’t man-made.
“Fortunately, they checked their data, so they realized it was not from nuclear bombs,” Lien said.
Researchers currently know about two processes that can trigger a GRB. The longest bursts, lasting anywhere from several seconds to hours, are emitted by massive stars dying violent deaths. Their outer layers explode into a bright supernova, while their inner layers collapse to form a dense neutron star or black hole. Other GRBs last less than two seconds and are caused by the merger of either two neutron stars or one neutron star and one black hole, resulting in the creation of a brand-new black hole.
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