Why pulsar stars are defying our understanding of physics
What's the story
Pulsars, the ultra-dense remnants of massive stars, are known for their rapid rotation and radio wave emissions. However, some pulsars have been defying our understanding of physics by continuing to emit signals even when they should have "died." A new study from Peking University suggests that these persistent pulsars may be hiding something on their surfaces—tiny mountains. These are responsible for the phenomenon.
Unsolved puzzle
The mystery of 'dead' pulsars
The study highlights two puzzling cases, PSR J0250+5854 and PSR J2144-3933, which continue to emit signals despite being well below the theoretical limit for pulsar activity. This phenomenon has long baffled scientists who could not explain how these "dead" pulsars were still pulsing. Now, researchers led by Zi-Hao Xu have proposed that tiny mountains on the surface of these stars could be the answer.
Surface features
What are these tiny mountains?
These aren't mountains in the traditional sense, but rather small bumps that could be as high as your fingernail. On a neutron star, where gravity is 100 billion times stronger than our Earth, even such small features can have dramatic effects. The researchers used advanced computer models to study how these tiny peaks would influence the powerful electric fields around pulsars.
Enhanced activity
Like a magnifying glass focusing sunlight
The study found that the steep slopes of these tiny peaks greatly amplify the local electric field. This makes it easier for the pulsar to accelerate particles and generate cascades of electrons and positrons, which in turn create radio waves. The researchers likened this effect to focusing sunlight with a magnifying glass, where the mountain's curved surface concentrates the electric field into a powerful beam.
Exotic material
Strangeon matter and the research implications
The study also suggests that these mountains could be made of "strangeon matter," an exotic form of matter that is bound by the strong nuclear force instead of electromagnetic forces. This material would be tough enough to withstand the intense bombardment of high-energy particles on a neutron star's surface, preventing ordinary matter from eroding away. The research opens up new areas for understanding neutron stars and testing fundamental physics theories.
Observational prospects
Next steps for researchers
The study's findings suggest that if the surface mountains are common on pulsars, astronomers should be able to detect their effects through careful observations of pulse timing as well as intensity patterns. The upcoming Chinese FAST telescope might be able to spot the tell-tale signatures of these tiny peaks. The research also hints at a possible connection between neutron star "glitches"—sudden changes in spinning speed—and the formation/destruction of surface mountains during starquakes.