'Out-Of-Ordinary' Zebra Signals From a Dead Star Were Not Beamed by Aliens, Researchers Have Finally Found the Answer

It's always been the dream of every SciFi aficionado to get a message from aliens. Therefore when news about flashes of 'out-of-ordinary' radio lights coming from a dead star broke, the whole world was watching like a hawk, Science Alert reported.

The lights were first observed around two decades ago, sending researchers into a frenzy regarding its origins. After a long wait, Mikhail Medvedev of the University of Kansas has finally managed to provide all curious souls with an answer, and it is not any extraterrestrial being.

The dead star from which the high-frequency radio pulses were coming was Crab Pulsar, SciTech Daily reported. The pulsar is a 12-mile-wide neutron star, inside a nebula that emits beams of electromagnetic radiation while spinning. The beams caught the notice of astronomers because of the unique zebra pattern in which they arrive towards the Earth.

The Nebula is the fragment of a supernova which is located some 6,200 light-years away from the Earth, Science Alert reported. The fragment was formed due to an explosion in space that destroyed a massive star. The fragment's core because of the violent incidents that took place during the star's destruction, no longer had the support of the outward pressure created by processes like fusion. Hence the pulsar inside the nebula became a neutron star, which essentially means a 'dead' star.

Crab Pulsar's signals towards Earth were eye-catching because of its different features, Science Alert reported. "It’s very bright, across practically all wave bands," Medvedev explained. "This is the only object we know of that produces the zebra pattern, and it only appears in a single emission component from the Crab Pulsar. The main pulse is a broadband pulse, typical of most pulsars, with other broadband components common to neutron stars. However, the high-frequency interpulse is unique, ranging between 5 and 30 gigahertz — frequencies similar to those in a microwave oven."

The signals generated by Crab Pulsar were distinct from similar signals from outer space, Science Alert reported. To understand the reason behind the patterns in the signal Medvedev took all the data available regarding the Crab Pulsar and analyzed it in detail. He started his examination assuming that the zebra pattern represents a diffraction fringe. The astrophysicist developed a model to calculate the plasma density inside the pulsar. The outcomes and behavior displayed by the model helped him in theorizing his explanation.

Medvedev understood the unique pattern was a result of events happening inside the pulsar's magnetosphere, Science Alert reported. He explained that different plasma densities diffracted the light present inside the star, which in turn created an interference pattern, that reaches the Earth in the form of signals arranged like a zebra stripe. 

Medvedev explained his theory in a study published in Physical Review Letters. "If you have a screen and an electromagnetic wave passes by, the wave doesn't propagate straight through," Medvedev said. "In geometrical optics, shadows cast by obstacles would extend indefinitely – if you're in the shadow, there's no light; outside of it, you see light. But wave optics introduces a different behavior – waves bend around obstacles and interfere with each other, creating a sequence of bright and dim fringes due to constructive and destructive interference."

Medvedev further added that such signals were not released by any other neutron star because of the pulsar's magnetic field, Science Alert reported. "A typical diffraction pattern would produce evenly spaced fringes if we just had a neutron star as a shield," Medvedev said."But here, the neutron star's magnetic field generates charged particles constituting a dense plasma, which varies with distance from the star. As a radio wave propagates through the plasma, it passes through dilute areas but is reflected by dense plasma. This reflection varies by frequency: Low frequencies reflect at large radii, casting a bigger shadow, while high frequencies create smaller shadows, resulting in different fringe spacing."

Medvedev hopes that the study on Crab Pulsar helps other astrophysicists understand the behavior displayed by the countless neutron stars in space, Science Alert reported. "The Crab Pulsar is somewhat unique – it's relatively young by astronomical standards, only about a thousand years old, and highly energetic," he said. "But it's not alone; we know of hundreds of pulsars, with over a dozen that are also young. Known binary pulsars, which were used to test Einstein's general relativity theory, can also be explored with the proposed method. This research can indeed broaden our understanding and observation techniques for pulsars, particularly young, energetic ones."