Astronomers monitoring an unusual young neutron star report a stellar surprise after years of apparent silence, as the space object has displayed sudden changes in its rotation, including one large event they characterize as a “glitch” that could point to evidence of exotic matter.
The discovery involves a 41,000-year-old pulsar known as PSR J1637−4642, which completes each of its rotations approximately every 154 milliseconds. Glitches like the one recently observed by astronomers are common for young pulsars like this, although this one had shown no similar behavior for close to a decade after its initial discovery.
The new observations have prompted questions over why PSR J1637−4642 has suddenly begun to display such activity.
When a Pulsar’s Spin Speeds Up
Pulsars are a variety of neutron stars characterized by their rapid rotation, which releases beams of electromagnetic radiation that can sweep past Earth at frequent intervals. Because of this, it allows astronomers to track their rotation with extreme precision.
Every so often, the regularity of their activity can become interrupted if a pulsar begins spinning more quickly, and scientists currently don’t fully understand what drives these “glitches.” One possible reason they occur involves interactions between the neutron star’s solid exterior and the exotic superfluid material they are believed to contain.
Based on this interpretation of pulsars, the differences in rotation that occur between the crust and their superfluid centers may give rise to the accumulation of angular momentum, which is suddenly transferred to the crust. This may create the energy required to speed up their observable rotation.
More Than a Decade of Observations
The research, led by Zhaoyi Wang of Xiamen University, looked at more than fifteen years of observations collected using Australia’s Murriyang radio telescope at Parkes. Based on their analysis, three rotational glitches were detected, beginning with a particularly powerful event that occurred in 2018.
At that time, the frequency of the pulsar’s rotation abruptly increased by around 17.54 microhertz—a fractional change of roughly 2.7 parts per million. The two other, much smaller glitches followed at around three years and 2.7 years later.
“PSR J1637−4642 adds to the growing class of young pulsars that exhibit large glitches after extended intervals of apparent quiescence,” the researchers write in a recent study detailing their findings.
During observations of PSR J1637−4642, astronomers found that its most significant glitch didn’t end immediately, and instead underwent a gradual period where it relaxed over more than 100 days of monitoring.
“Our results demonstrate that even ‘quiet’ pulsars can harbor significant glitch activity,” the researchers conclude.
Ultimately, the several years of silence exhibited by this pulsar before its sudden, massive glitch may represent the culmination of a period during which stresses accumulated over time, building up to an unusual detection by astronomers that offers new insights into this peculiar class of stars.
The team’s findings were reported in a recent study, “Discovery of Three Glitches in the previously quiet pulsar PSR J1637−4642,” which was uploaded to the arXiv preprint server and has been accepted for publication in the Astrophysical Journal Letters.
Micah Hanks is the Editor-in-Chief and Co-Founder of The Debrief. A longtime reporter on science, defense, and technology with a focus on space and astronomy, he can be reached at micah@thedebrief.org. Follow him on X @MicahHanks, and at micahhanks.com.