Imagine a cosmic lighthouse blinking rhythmically in the dark for tens of thousands of years—then suddenly, it skips a beat. That’s the strange and fascinating behavior recently observed in one of the most enigmatic objects in the universe: a gamma-ray pulsar known as PSR J0007+7303.
This distant, spinning neutron star—born from the explosive death of a massive star—is located about 4,500 light-years away in the supernova remnant CTA1. It’s invisible to our eyes and even to ordinary radio telescopes, but in the high-energy world of gamma rays, it shines like a celestial beacon. And it just got even more intriguing.
A team of Chinese astronomers, led by Zhi-Xiang Yu from Guizhou Normal University, has conducted a 15-year-long study of this star using data from NASA’s Fermi Gamma-ray Space Telescope. Their work, published on July 24 on the arXiv preprint server, reveals that PSR J0007+7303 is glitching—its rotation skipping and stalling like a clock with an unpredictable heartbeat.
What Are Pulsars, and Why Do They Glitch?
Pulsars are neutron stars, the ultra-dense remnants of supernova explosions. A single teaspoon of a neutron star’s matter would weigh as much as a mountain. These compact objects spin rapidly—sometimes hundreds of times per second—and emit beams of electromagnetic radiation from their magnetic poles. As they rotate, these beams sweep across Earth like the light from a lighthouse, creating a regular blinking pattern detectable from thousands of light-years away.
But sometimes, that regularity breaks.
These disruptions are called “glitches,” sudden and mysterious increases in a pulsar’s rotation rate. Scientists believe glitches originate from the superfluid interior of the neutron star—a bizarre state of matter with zero viscosity and quantum properties unlike anything we experience on Earth. When this internal superfluid suddenly transfers angular momentum to the crust of the star, the whole pulsar jolts forward—like a dancer unexpectedly leaping in mid-twirl.
Understanding these glitches is key to probing the internal structure of neutron stars, objects so extreme they challenge the limits of physics.
Tracking a Celestial Mystery Over 15 Years
PSR J0007+7303 has already carved out a unique identity in the annals of astronomy. Discovered by Fermi’s Large Area Telescope (LAT) in 2008, it was the first pulsar ever detected by the gamma-ray observatory and is unusual in that it emits no radio waves. That makes it harder to study, requiring high-energy detectors like those aboard Fermi to follow its pulse.
Earlier observations had recorded four glitches in this pulsar, but Yu’s team went deeper—mining 15 years of archival data from Fermi. Their findings revealed a total of nine glitches, with five previously undetected events coming to light thanks to their long-term, careful analysis.
The detected glitches varied in strength—from relatively large changes in rotation frequency to subtle shifts as small as one part in a billion. Two of these new glitches were particularly interesting for their timing, occurring between known events and showing just how unpredictable this star’s behavior can be.
The team calculated that glitches in PSR J0007+7303 occur approximately every 1–2 years, though not on a fixed schedule. The shortest time between glitches was a mere 44 days, while the longest stretched over three years. That randomness adds to the intrigue—and the challenge—of modeling the inner life of pulsars.
A Stable Light, Even in Chaos
Despite the violent-sounding nature of these glitches, the pulsar’s outward behavior remains remarkably steady. Yu and his colleagues examined whether these sudden rotational jumps had any effect on the gamma-ray flux, pulse profiles, or spectral characteristics—the fingerprints of how energy is emitted from the pulsar.
To their surprise, they found no significant changes. The pulsar continues to shine consistently, its light unaffected by the internal tremors that occasionally rattle its spin.
This stability is both puzzling and illuminating. It suggests that while the star’s interior is undergoing powerful shifts, its surface emission remains insulated from those internal changes—at least in a way that current instruments can detect.
That resilience makes PSR J0007+7303 even more fascinating: a cosmic machine that skips gears but never falters in its glow.
Peering Into the Star’s Hidden Heart
One of the key outcomes of the study was the team’s parametric analysis of the glitches. By measuring the magnitude and frequency of the rotational shifts, they calculated that the glitches likely involve about 1.06% of the neutron star’s crustal moment of inertia.
In simpler terms, this means that a small fraction of the star’s outer layers are receiving energy from the deep, superfluid interior during each glitch. This confirms the theory that the glitches have an internal origin, rooted in the exotic, quantum world beneath the star’s rigid crust.
This kind of analysis offers one of the only windows into the interior dynamics of a neutron star, which cannot be observed directly. Every glitch tells a story of quantum fluid motion, nuclear interactions, and gravitational extremes occurring inside an object smaller than a city but more massive than the Sun.
Why This Matters: The Bigger Picture
While the behavior of a single pulsar might seem like a niche subject, the implications are vast. Pulsars are natural laboratories for physics under conditions that cannot be recreated on Earth. They allow scientists to test theories of relativity, quantum mechanics, and even superconductivity in environments millions of times more extreme than any found in a lab.
Moreover, understanding pulsar glitches can help refine models of neutron star evolution, crust-core interactions, and energy dissipation. It can even play a role in detecting gravitational waves, the ripples in space-time predicted by Einstein and confirmed in recent years through observatories like LIGO.
As the universe’s most precise natural clocks, pulsars are also being explored as tools for interstellar navigation and space-time mapping. But those tools need calibration—and that means accounting for glitches.
By studying PSR J0007+7303 in such detail, Yu’s team is contributing vital data to a broader understanding of how pulsars work, evolve, and sometimes surprise us.
The Road Ahead: More Glitches, More Clues
The researchers are not done yet. In their paper, they expressed plans to continue monitoring PSR J0007+7303, hoping to detect more glitch events. The longer the pulsar is observed, the better scientists can understand its behavior—and refine models that explain why and how these disruptions occur.
Each new glitch is like a knock on the door of nature’s most tightly guarded secrets. What causes the superfluid to suddenly shift? How is the crust affected? Can we predict the next glitch?
These questions remain open, but with tools like Fermi-LAT and the dedication of researchers across the globe, the answers may not remain hidden forever.
In a universe filled with mysteries, PSR J0007+7303 is just one spinning enigma. But as its light pulses across time and space, breaking rhythm only now and then, it reminds us that even the most constant things can surprise us—and that science, like the cosmos, never stands still.
More information: Zhi-xiang Yu et al, Results of 15-Year Pulsar Timing of PSR J0007+7303 with Fermi-LAT, arXiv (2025). DOI: 10.48550/arxiv.2507.18187