BY:SpaceEyeNews.
Pulsar glitches have revealed a surprising side of a neutron star that once appeared unusually steady. Astronomers found three sudden increases in the rotation of PSR J1637−4642 across 15.5 years of observations. One event dwarfed the other two, while its gradual aftermath offered clues about the star’s interior.
The discovery raises an intriguing question: what happens beneath a pulsar’s surface during years without a detected glitch? For researchers, the answer may involve superfluid matter exchanging angular momentum with the star’s solid crust.
Why This Quiet Pulsar Deserved Attention
PSR J1637−4642 completes one rotation every 154 milliseconds, or roughly 6.5 turns per second. Its characteristic age is approximately 41,000 years. That figure comes from its rotation and slowdown, rather than a directly measured birth date.
Despite its youth, earlier monitoring revealed no glitches for roughly a decade. This made its later behavior particularly interesting. A young pulsar could appear steady for years, then produce several clearly different changes.
However, “quiet” needs careful interpretation. The label refers to the absence of previously detected glitches. It does not mean the star stopped emitting signals or lacked other timing variations.
That distinction matters because a long stretch without a detected event tells only part of the story. Researchers needed an extended observational record to investigate what followed.
How Astronomers Detected the Pulsar Glitches
A team led by Zhaoyi Wang of Xiamen University examined observations from Australia’s Murriyang radio telescope at Parkes Observatory. Their dataset covered February 19, 2009, through October 6, 2024.
The researchers studied when radio pulses arrived and compared those measurements with a model of the star’s rotation. Differences between expected and observed arrival times helped reveal sudden rotational changes.
Finding Reliable Timing Clues
The team extracted 166 reliable pulse arrival times from the observations. Weak signals made some observations unsuitable for precise timing.
This process required more than spotting an unusual pulse. Researchers had to trace the rotation across different periods and determine where abrupt changes occurred.
The long record gave each event context. It showed how the pulsar behaved before a jump and how its rotation evolved afterward.
Crucially, these observations ended in 2024. The findings describe events recovered from historical data, rather than three changes occurring together when the research appeared.
Three Rotational Jumps With Very Different Sizes
The first glitch occurred around 2018 and produced the largest change. The pulsar’s rotation frequency increased by approximately 17.54 microhertz, equivalent to about 2.7 parts per million.
That fraction sounds tiny. Yet precise pulsar timing allows astronomers to identify changes far smaller than anything a person could notice directly.
A Large Jump Followed by Smaller Events
About three years later, the second glitch increased the rotation frequency by roughly 14 nanohertz. A third appeared approximately 2.7 years afterward, adding around 179 nanohertz.
For comparison, the first increase corresponds to about 17,540 nanohertz. It was therefore more than a thousand times larger than the second. The third occupied the middle ground.
This range makes the sequence informative. The same object produced substantially different rotational adjustments within the observational window.
However, three events cannot establish a dependable schedule. The intervals describe this particular sequence; they do not tell astronomers when another glitch will occur.
Each jump adds a separate piece of evidence. Comparing their sizes helps describe the star’s behavior, while following their aftermath lets scientists investigate how its internal components respond to a sudden change.
The next clue came from how the largest event faded.
What the Largest Glitch Revealed Inside
After the first jump, part of the frequency increase gradually relaxed. Researchers identified a recovery timescale of roughly 100 days.
This timescale describes how the recovering component declined. It does not mean the entire star returned to its previous rotation rate after 100 days.
A Partial Recovery, Not a Complete Reset
Only about 1.5% of the initial frequency jump belonged to the relaxing component. Most of the change remained as a lasting offset in the timing model.
That distinction helps explain why the aftermath matters. Scientists can study both the sudden acceleration and the slower adjustment that follows.
The first glitch was the only event with detectable exponential recovery. That does not establish that the smaller events had no recovery whatsoever.
The Superfluid Connection
The leading explanation involves superfluid neutrons inside the star transferring angular momentum to its crust. This exchange makes the crust rotate faster, creating the observed glitch.
Researchers modeled the aftermath within a framework called vortex creep. Their results indicated a superfluid moment-of-inertia fraction of approximately 1.9%, consistent with an inner-crust contribution.
Moment of inertia describes how mass distribution affects rotation. Consequently, this percentage is not a direct measurement of how much of the star’s mass is superfluid.
It also differs from the 1.5% recovery fraction. One describes an inferred interior contribution; the other describes the portion of the frequency jump that relaxed.
The model supports the superfluid explanation, while leaving the exact trigger uncertain.
Why Continued Monitoring Matters
These pulsar glitches show why scientists should keep observing objects with apparently uneventful histories. Years without a detected jump do not rule out significant changes later.
Further observations could reveal whether future events resemble the largest glitch or the smaller ones. Additional recovery measurements would also help researchers assess their interior models.
For now, the findings support an established physical explanation without resolving every detail. Possible internal buildup remains an interpretation, rather than something the telescope observed directly.
Pulsar Glitches Turn Quiet Years Into New Questions
PSR J1637−4642 has transformed a seemingly quiet record into evidence of complex internal behavior. Its three rotational jumps reveal different event sizes, while the largest offers a measurable recovery.
Pulsar glitches give astronomers an indirect way to investigate matter hidden beneath a neutron star’s surface. Continued timing can sharpen that picture, connecting subtle changes in radio pulses with the physics governing an inaccessible interior.
Main sources:
Original research — Wang and colleagues, “Discovery of Three Glitches in the previously quiet pulsar PSR J1637−4642”:
https://arxiv.org/abs/2608.19555
Full research paper:
https://arxiv.org/pdf/2608.19555
Universe Magazine — original supplied article:
https://universemagazine.com/en/a-quiet-pulsar-suddenly-exhibited-three-anomalies-over-15-years-of-observation/