A patch of light that scientists once dismissed as a distant galaxy may actually be the brightest pulsar ever spotted outside the Milky Way.
Named after PSR J0523−7125 and located about 160,000 light years away Earth in the Large Magellanic Cloud (a satellite galaxy containing the Milky Way) the redefined pulsar is twice as wide as any other pulsar in the region and ten times brighter than any known pulsar beyond our galaxy. In fact, the object is so big and bright that researchers originally interpreted it as a distant galaxy, but new research was released on March 2 Astrophysical Journal Letters indicates that this is not the case.
Using the Australian Square Kilometer Array Pathfinder (ASKAP) radio telescope in Western Australia, the study’s authors viewed space through special “sunglasses” that block all wavelengths of light except for a specific type of emissions associated with pulsars, the highly magnetized ones shells of stars. When PSR J0523−7125 showed up bright and clear in the results, the team realized they weren’t looking at a galaxy at all, but at the pulsing corpse of a dead star.
“It was an amazing surprise,” said the study’s lead author Yuanming Wang, an astrophysicist at Australia’s Commonwealth Scientific and Industrial Research Organization (CSIRO). said in a statement. “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 his sunglasses, it really is possible.”
Pulsars are highly magnetized, rapidly spinning remnants of exploded stars. As they spin, streams pour from radio waves erupt from their poles and pulse like beacon beams as these radio waves flash toward Earth.
The radio waves emitted by pulsars differ from many other cosmic light sources in that they can be circularly polarized—that is, the light’s electric field can rotate in a circle as it propagates. This unique polarization can give scientists 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 out circularly polarized light sources from an ASKAP survey of pulsar candidates.
The team found that the suspected galaxy PSR J0523−7125 emits circularly polarized light, meaning it is almost certainly a pulsar. And because pulsars are incredibly small — typically packing the mass of a sun into a ball no wider than a city — this means the object must be much closer and much brighter than scientists previously thought. If this pulsar is indeed lurking in the nearby Large Magellanic Cloud, as the researchers suspect, then it’s the brightest single pulsar ever found outside the Milky Way.
This extraordinary brightness explains why the object was misidentified as a galaxy after its initial detection, the researchers said. And by filtering out circularly polarized light from future star surveys, researchers may be able to unmask even more unusual pulsars hiding in plain sight.
“We should expect to find more pulsars with this technique,” study co-author Tara Murphy, a radio astronomer at the University of Sydney in Australia, said in the statement. “This is the first time we have been able to systematically and routinely search for the polarization of a pulsar.”
Originally published on Live Science.