Pulsar Silent for Nearly a Decade Suddenly Displays Three Rotational Glitches
Astronomers detected unexpected spin variations in PSR J1637−4642, including a major glitch in 2018 after years of apparent quiescence.
What happened
Researchers led by Zhaoyi Wang of Xiamen University analyzed over fifteen years of observations from Australia's Murriyang radio telescope and identified three rotational glitches in the 41,000-year-old pulsar PSR J1637−4642, which rotates approximately every 154 milliseconds. The largest glitch occurred in 2018, when the pulsar's rotation frequency abruptly increased by around 17.54 microhertz—a fractional change of roughly 2.7 parts per million. Two smaller glitches followed approximately three years and 2.7 years later. Notably, the 2018 glitch did not resolve immediately but instead underwent a gradual relaxation period lasting more than 100 days. This activity is significant because the pulsar had exhibited no such behavior for close to a decade after its initial discovery.
Context
Pulsars are rapidly rotating neutron stars that emit beams of electromagnetic radiation, allowing astronomers to track their rotation with extreme precision. Glitches—sudden increases in spin rate—are common in young pulsars, though their underlying mechanism is not fully understood. One leading theory involves interactions between a neutron star's solid crust and exotic superfluid material in its interior; differences in rotation between these layers may accumulate angular momentum that is suddenly transferred to the crust, causing observable acceleration. The extended silence of PSR J1637−4642 followed by sudden large glitch activity suggests that stresses may accumulate over time before release. This observation adds to a growing class of young pulsars exhibiting large glitches after periods of apparent quiescence, potentially offering new insights into neutron star behavior and internal composition.