A speck of light that scientists once believed to be a distant galaxy may actually be the brightest pulsar ever detected outside the Milky Way.
Named PSR J0523−7125 and located approximately 160,000 light-years from Earth in the Large Magellanic Cloud (a satellite galaxy that orbits the Milky Way), the newly defined pulsar is twice as wide as any other pulsar in the region and 10 times brighter than any known pulsar beyond our galaxy. The object is so large and bright, in fact, that researchers originally interpreted it as a distant galaxy – however, new research published May 2 in the Astrophysical Journal Letters suggests that is not the case.
Using Australia’s Square Kilometer Array Pathfinder (ASKAP) radio telescope in Western Australia, the study authors observed space through a special pair of “sunglasses” that block all wavelengths of light. light, with the exception of a specific type of emission associated with pulsars, highly magnetized pulsars. star shells. When PSR J0523−7125 appeared bright and clear in the results, the team realized they weren’t looking at a galaxy at all, but the pulsating corpse of a dead star.
“It was an incredible surprise,” said the study’s lead author, Yuanming Wang, an astrophysicist at Australia’s Commonwealth Scientific and Industrial Research Organization (CSIRO). said in a press release. “I didn’t expect to find a new pulsar, let alone the brightest one. But with the new telescopes we now have access to, like ASKAP and its sunglasses, it really is possible.”
Pulsars are highly magnetized, rapidly spinning remnants of exploded stars. During their rotation, flows of radio waves erupt from their poles, pulsing like headlight beams as these radio waves flash back to Earth.
The radio waves emitted by pulsars are different from many other sources of cosmic light, in that they can be circularly polarized – that is, the electric field of the light can spin in a circle as it travels. propagates forward. This unique polarization can provide scientists with an important clue in the tricky game of distinguishing pulsars from other distant light sources. In their new study, the researchers used a computer program to filter circularly polarized light sources from an ASKAP survey of candidate pulsars.
The team found that the putative galaxy PSR J0523−7125 emitted circularly polarized light, meaning it is almost certainly a pulsar. And because pulsars are incredibly small – typically occupying the mass of a sun in a ball no larger than a city – that means the object must be much closer and much brighter than scientists previously thought. . Indeed, if this pulsar is hiding in the nearby Large Magellanic Cloud, as the researchers suspect, then it is the brightest pulsar ever found outside the Milky Way.
This exceptional brightness explains why the object was misidentified as a galaxy after its initial detection, the researchers said. And by filtering circularly polarized light from future star surveys, researchers may be able to unmask even more unusual pulsars lurking in plain sight.
“We should expect to find more pulsars using this technique,” Tara Murphy, study co-author and radio astronomer at the University of Sydney in Australia, said in the release. “This is the first time that we have been able to systematically and routinely search for the polarization of a pulsar.”
Originally posted on Live Science.