Meanwhile, all known magnetars rotate at a quick clip of under 10 seconds, not even close to the 18-minute period seen from GLEAM-X J162759.5-523504.3. Hurley-Walker notes that the only other white dwarf known to produce similar pulses is 10 times closer to Earth yet 100 times fainter than the newly discovered object, raising the question of why these two objects would display such drastically different radio brightness. In either case, GLEAM-X J162759.5-523504.3 would be unlike anything seen before. White dwarfs are the corpses of low-to-medium-mass stars, such as the Sun, while magnetars are the highly magnetic corpses of stars that are about 10 to 25 times as massive as the Sun. It seems too bright to be a planet, and its light profile suggests it’s too compact to be a normal star.īy process of elimination, Hurley-Walker and her colleagues think the object is either a white dwarf or a magnetar, both of which are the leftover remains of stars that have burned out. Its radio pulses display strong linear polarization, which hints at the presence of ordered magnetic fields. Though the object was only visible to telescopes for a short time, its bizarre characteristics offer some tantalizing clues about its nature. “But hopefully there are other examples active in the Milky Way, and searches I'm planning this year will find them.” “We did do some follow-up observations in 2021, but we haven't re-detected the object, so it appears to be inactive at the moment,” Hurley-Walker said. The radio source, which is known as GLEAM-X J162759.5-523504.3, was visible between January and March 2018, but the researchers haven't been able to pick it up in observations taken before or after that timespan. The team eventually tracked down 71 pulses in total, each lasting about 30 to 60 seconds and displaying that weird characteristic 18:18-minute period. In a twist that Hurley-Walker likened to the cold open of the Netflix film Don’t Look Up, study co-author Tyrone O'Doherty, who is now a graduate student at ICRAR, noticed the radio source in GLEAM-X observations taken in March 2018 but did not see them in images taken a few months later in May. As part of an undergraduate project, Hurley-Walker had her students comb through a large sky survey called GaLactic and Extragalactic All-sky MWA eXtended (GLEAM-X) captured by the Murchison Widefield Array, one of the most sensitive radio telescopes on Earth. The story of how the team first detected this weird radio source is as interesting as the signal itself. In addition to presenting a fascinating cosmic puzzle about its origin, the unprecedented object could also help scientists understand other mysterious phenomena, such as fast radio bursts, a class of radio emission that has so far defied explanation. “Orbital periods of 18 minutes are possible,” she continued, but “there are no models that produce such bright radio emission from two objects in orbit with each other, with such precision, and any that would produce any kind of radio waves would also produce X-ray emission, which we don't see.” “The fact that it is repeating so regularly (the same rate to within one ten thousandth of a second over the three months it was visible) means it is quite likely to be a rotating object,” said Natasha Hurley-Walker, a radio astronomer at the International Centre for Radio Astronomy Research (ICRAR) who led the study, in an email.
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