A year-long SETI Institute investigation into a flickering pulsar has revealed how radio waves warp as they travel through deep space, offering a powerful new tool for distinguishing natural cosmic noise from potential alien transmissions.
During the observational period, the SETI Institute closely monitored pulsar PSR J0332+5434 (also known as B0329+54) to study how its radio signal “twinkles” as it passes through interstellar gas. Using the Allen Telescope Array (ATA), researchers observed the pulsar across a range of frequencies (from 900 to 1956 MHz) and documented slow changes in the twinkling pattern, known as scintillation.
“At the end of their lives, massive stars (stars much bigger than our Sun) explode in a supernova,” said Grayce Brown, project lead and a SETI Institute intern, in an email to The Debrief. “During the explosion, the core collapses in on itself, becoming very dense and forming a neutron star.”
“Neutron stars are incredibly dense: think of something as massive as the Sun squeezed into a ball that’s as wide as Manhattan!” Brown said, adding that they spin extremely fast—sometimes up to 700 revolutions per second—on account of their angular momentum.
According to Brown, this quality is “the same physics that causes figure skaters to spin faster when they pull their arms closer to themselves while they’re spinning.”
“The spinning of such a massive, dense object generates a powerful magnetic field, causing charged particles to accelerate to the magnetic poles and be thrown out into space as cones of light,” Brown told The Debrief. “If the magnetic poles are misaligned with the rotation axis, these beams of light sweep around the neutron star as it spins, kind of like a lighthouse.”
“If Earth is in the path of the beams, the star appears to pulse in brightness,” Brown explained. “Hence, we call them pulsars!”
Cosmic Clocks
Brown explains that because of their extreme density and speed of rotation, pulsars tend to rotate with a high degree of consistency.
“We know some pulsar spin periods all the way to 12 digits past zero; that’s a trillionth of a second,” Brown told The Debrief. “Since we know the spin periods should be incredibly consistent over time, we should expect the pulses to be evenly spaced. If they’re not, then we know something else is responsible; that something is affecting the arrival time of the pulse.”
“In this way, we consider them cosmic timekeepers,” Brown says. “If the ticks of a ticking clock weren’t evenly spaced, you’d know something weird was happening!”
Scientists use accurate measurements of these pulses to search for subtle phenomena, such as low-frequency gravitational waves. As the pulsar’s radio waves travel through space, they pass through clouds of charged particles that can bend and slow the signals just a little.
“Just like starlight twinkles as it passes through Earth’s atmosphere, pulsar radio waves twinkle as they move through space,” explained Brown. “Monitoring these patterns helps us not only improve pulsar timing but also advance broader fields of astronomy, including SETI research.”
“Our research isn’t really about the pulsar itself—the pulsar is just a tool to learn more about the space between us and the pulsar,” adds Brown. “By seeing how much the pulsar pulse is scintillated/delayed, we can learn how much ‘stuff’ is in the way, causing the light to be scattered.”
“These same scattering effects will impact any radio waves passing through that area of space, not just those from the pulsar,” Brown said.
As radio waves travel from a pulsar to Earth, they create bright and dim patches across different frequencies. By following these changes in their patterns almost daily over 10 months, the team was able to change the scintillation into detailed timing setbacks.
The Research
Over roughly 300 days, the researchers measured the scintillation bandwidth and found changes on timescales from days to months, including a broader, long-term variation of 200 days. The study also introduced a new method for more accurately estimating how scintillation changes with frequency, leveraging the Allen Telescope Array’s capabilities.
“All radio signals passing through the interstellar medium experience scintillation,” noted Dr. Sofia Sheikh, co-author and Technosignature Research Scientist at the SETI Institute. “Understanding these effects helps distinguish natural signals from potential artificial transmissions, which is vital for SETI and other radio astronomy studies.”
By mapping how signals are delayed and distorted, astronomers can refine techniques for high-precision pulsar timing, which also helps to advance their efforts toward identifying any possible extraterrestrial technosignatures.
“If we receive a transmission from an intelligent civilization in another star system, that signal will have to pass through interstellar space,” says Brown. “Just as we have seen with pulsars, the signal will be scattered and scintillated.”
Still, one of the greatest challenges SETI investigations face involve the potential that a promising signal might turn out to have Earthly origins.
“We need some way to differentiate between signals coming from Earth and signals coming from beyond our Solar System,” Brown told The Debrief. “Because of this research, we know how much scintillation to expect from a radio signal traveling through this pulsar’s region of interstellar space.”
“If we don’t see that scintillation,” Brown concludes, “then the signal is probably just interference from Earth.”
The team’s recent findings were published in The Astrophysical Journal.
Chrissy Newton is a PR professional and the founder of VOCAB Communications. She currently appears on The Discovery Channel and Max and hosts the Rebelliously Curious podcast, which can be found on YouTube and on all audio podcast streaming platforms. Follow her on X: @ChrissyNewton, Instagram: @BeingChrissyNewton, and chrissynewton.com. To contact Chrissy with a story, please email chrissy @ thedebrief.org.