This Strange Star Should Not Exist, And It’s Stumping Astronomers
A cosmic object with the slowest-ever known rotation has been detected by Australian radio astronomers. The discovery may help improve our understanding of what causes these objects to have such a long rotational period.
Over the last three years, the mysterious objects have appeared seemingly out of nowhere. They emit periodic radio pulses at much slower intervals than pulsars, which does not make sense in our current understanding of neutron stars.
Pulsars are neutron stars that produce periodic pulses of radio waves. They spin really fast and can complete a full rotation in just a few seconds or less. Researchers have recently found the slowest “cosmic lighthouse,” which spins once every 6.5 hours.
It is also aligned with Earth in a way that allows the researchers to see radio pulses from both of its magnetic poles, a first for objects that spin so slowly.
The object has been named ASKAP J1839-0756. It was discovered through CSIRO’s ASKAP radio telescope, located in Wajarri Yamaji country in Western Australia.
No other known object has ever been identified at the position that ASKAP J1839-0756 was in. Its radio emission showed up as a fading burst. In just 15 minutes, its brightness plummeted by 95 percent.
At first, the researchers were unaware that the source was producing periodic radio pulses because only a single burst had been detected during the initial observation.
But then, they conducted additional observations with ASKAP and CSIRO’s Australia Telescope Compact Array and the MeerKAT radio telescope in South Africa. Eventually, two pulses that came 6.5 hours apart were revealed, confirming that it had a periodic nature.
Based on the current scientific knowledge of neutron stars, ASKAP J1839-0756 shouldn’t even exist. Neutron stars convert their rotational energy into radiation in order to emit radio pulses. They lose energy and slow down over time.
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Once a neutron star’s spin reaches a rate of about one rotation per minute, it should no longer be able to emit radio pulses. Yet, ASKAP J1839-0756 is still lighting up the night at its leisurely pace.
ASKAP J1839-0756 is also the first slow-moving star of its kind to emit interpulses. About 3.2 hours after its main pulse, it releases a weaker pulse with different properties, suggesting that radio light is coming from the opposite magnetic pole.
“ASKAP J1839-0756 shares several properties with other known long-period radio transients, which suggests a common origin and emission mechanism across this class of objects,” wrote the authors of the study.
“The discovery of ASKAP J1839-0756 can improve our understanding of the population density of long-period radio transients in future studies, and the presence and properties of interpulse emission can test theoretical models of compact objects.”
The study was published in Nature Astronomy.
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