The Crab Pulsar, which sits at the center of the Crab Nebula, has puzzled scientists over the last several decades due to its display of bright, evenly spaced stripes in the radio wave frequencies, which alternate with completely dark areas, which were termed ‘zebra stripes’. No other pulsar demonstrates this feature; they generally broadcast in many frequencies and radio emissions are spectrally broader.
Now, a professor at the University of Kansas, Mikhail Medvedev, has refined a theory he first developed in 2024, which can account for these anomalies by hypothesizing that there’s an interaction between the plasma in the pulsar and gravitational waves surrounding it, such that the gravity behaves as a lens, which focuses the plasma (increased light), and the force of the plasma itself, which pushes the waves apart (darkness). The paper had been pre-published before his presentation at the American Physical Society’s 2026 Global Physics Summit, which took place March 15-20 at the Colorado Convention Center in Denver, reported Science Daily.
“There’s a remarkable pattern in Pulsar’s spectrum,” Medvedev said. “Unlike ordinary broad spectra—such as sunlight, which contains a continuous range of colors—the Crab’s high-frequency inter-pulse shows discrete spectral bands. If it were a rainbow, it’s as if only specific ‘colors’ appear, with nothing in between.”
“Gravity changes the shape of spacetime...Light doesn’t travel in a straight line in a gravitational field because space itself is curved. What would be straight in flat spacetime becomes curved in the presence of strong gravity. In that sense, gravity acts as a lens in curved spacetime,” Medvedev explained.
In related news, new images of the Crab Nebula have been generated by the Hubble Telescope, and the comparison to the images from 25 years ago show a rapid expansion of the gases of the nebula.
The Crab Nebula’s age corresponds to a supernova first observed in 1054 AD by Arab, Chinese, Japanese and Mayan astronomers. It isn’t visible to the naked eye, but may be observed with a pair of good binoculars. The Crab Pulsar lies at the center of the Crab Nebula in the Perseus Arm of the Milky Way, about 6,500 light-years from Earth. Its visibility and relative proximity has made it a fascinating object for studying nebulae and neutron stars.
