New research from the University of Kansas has solved a decades-old astrophysical puzzle, showing how the competing forces of gravity and magnetospheric plasma split the radio emissions from a club pulsar, the remnant of a supernova observed by ancient astronomers in 1054 AD, into perfectly spaced “stripes.”
This composite image shows the Crab Nebula. The crab pulsar is in the center of the image. Image credit: X-ray – NASA / CXC / ASU / J. Hester others.;Optics – NASA / HST / ASU / J. Hester others.
In 1054 AD, Chinese astronomers were surprised by the appearance of an extremely bright new star. The star was the brightest object in the night sky after the moon and was visible in broad daylight for 23 days. This stellar explosion was also recorded by Japanese, Arabian, and Native American stargazers.
today, crab nebula You can see where that bright star is. Messier 1, M1, NGC 1952, also known as Taurus A, is located approximately 6,500 light years away in the constellation Taurus.
The Crab Nebula was first identified in 1731 by British physician, electrical researcher, and astronomer John Beavis, and rediscovered in 1758 by French astronomer Charles Messier. Its name comes from its appearance in an 1844 painting by Irish astronomer Lord Rose.
of club pulsarAlso known as PSR B0531+21, it is the central star of the Crab Nebula.
Because they are nearby and easily observed, studying the Crab Nebula and Crab pulsars gives astronomers insight into nebulae, supernovae, and neutron stars in general.
‘Gravity changes the shape of spacetime,’ says the University of Kansas. Professor Mikhail Medvedevauthors of the new study.
“Light does not travel straight in a gravitational field because space itself is curved,” he said.
“What would be straight in a flat space-time becomes curved in the presence of strong gravity. In this sense, gravity acts as a lens in a curved space-time.”
Although gravitational lensing has been widely discussed in the context of black holes, this is the only case in which astronomers have observed a “tug of war” between plasma and gravity forming the observed signal.
“In images of black holes, only gravity shapes the structure,” Professor Medvedev says.
“In the club pulsar, both gravity and plasma act together. This is the first practical application of this combined effect.”
“There is a remarkable pattern in the pulsar’s spectrum,” Professor Medvedev said.
“Unlike a normal broad spectrum, such as sunlight, which contains a continuous color range, the crab’s high-frequency interpulses exhibit discrete spectral bands. If it were a rainbow, only certain ‘colors’ would appear, as if there were nothing in between.”
This is one of the largest mosaic images ever taken by Hubble of the Crab Nebula, the six-light-year wide enlarged remnant of a star’s supernova explosion. Japanese and Chinese astronomers, almost certainly as well as Native Americans, recorded this violent event about 1,000 years ago in 1054 AD. Image credit: NASA / ESA / J. Hester / A. Loll, Arizona State University.
Most pulsar radio emissions are spectrally broader, noisier, and not as neatly banded as in club pulsars.
“The stripes are perfectly clear, and between the stripes there is complete darkness,” Professor Medvedev said.
“There are bright bands and no bright bands, and there are no bright bands at all. No other pulsar exhibits this type of banding. That uniqueness made the club pulsar particularly interesting and challenging to understand.”
Although previous models were able to reproduce the striped pattern, they were unable to account for the high contrast of bands actually observed in club pulsars.
In fact, Professor Medvedev recently determined that the club pulsar’s plasma material causes the diffraction of electromagnetic pulses and is the main cause of the neutron star’s unusual zebra pattern.
But now he’s weaved Einstein’s theory of gravity into the mix and finds it plays a pivotal role in Club Pulsar’s zebra pattern.
“Previous theoretical models were able to reproduce the striped pattern, but not the observed contrast. Incorporating gravity provided the missing piece,” Professor Medvedev said.
“Plasma in a pulsar’s magnetosphere can be thought of as a lens, but it’s a defocusing lens. In contrast, gravity acts as a focusing lens. Plasma tends to scatter light rays, and gravity pulls them inward. When these two effects overlap, there are certain paths that compensate for each other.”
The combination of defocused magnetospheric plasma and focusing gravity produces in-phase and out-of-phase interference bands of radio intensity that appear as zebra stripes in club pulsars.
“Symmetry means that there are at least two such paths for light,” Medvedev says.
“When two nearly identical paths bring light to an observer, they form an interferometer. The signals combine. At some frequencies they reinforce each other (in phase), producing a bright band. At other frequencies, they cancel (out of phase), producing darkness. This is the essence of an interference pattern.”
“There appears to be little additional physics required to explain stripes qualitatively.”
“Quantitative improvements could be made; for example, the current processing includes gravity in a static lowest order approximation.”
“Pulsars are rotating, and including rotational effects can lead to quantitative, if not qualitative, changes.”
of new research will be published in Plasma Physics Journal.
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Mikhail V. Medvedev. 2026. Theory of the dynamic spectrum of club pulsar high-frequency interpulse stripes. Plasma Physics Journalin press. arXiv: 2602.16955