Mysterious radio signals spotted from ‘hungry black hole’ as scientists baffled

04 August 2023 , 22:00

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The black hole spits out a jet stream of particles and is surrounded by its accretion disk - matter it is slowly sucking inwards (stock image) (Image: Getty Images)

Mysterious radio signals have been spotted being fired from deep inside a black hole.

Black holes have long been known to shoot out charged matter, going close to the speed of light. One such object, named GRS 1915+905, is no different. It’s a star and black hole, caught in a mutually beneficial cosmic dance with one another.

The star sheds material which the black hole draws in and some material is shot out into space as a jet stream. However, sometimes, the jet stream can wobble briefly, and a new study has found that when this happens a mysterious radio signal emerges from the black hole too.

The black hole has regularly emitted "persistent" x-ray activity over the last three decades, in line with its jet stream emissions, according to a study in Nature journal. It is believed that this activity comes from deep inside the black hole.

However, more recently, over the past few years, the black hole has emitted a strange new signal on two separate occasions. Instead of being recorded in the normal range of 1-10 Hz, the new oscillations were spotted in January 2021, and June 2022 and were from 1.05-1.45 GHz.

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The study found that these new, little known radio waves were observed during the oscillation phase of the jet stream, firing from the black hole. But raising even more questions, the oscillations took place for just a fraction of a second. The 500m Aperture Spherical Radio Telescope (FAST) in China noticed the changes and researchers theorised that the wobbles were caused by the black hole’s rotation being out of sync with its accretion disk.

Accretion disks are wide, flat circles of particles found surrounding a number of celestial bodies, including black holes. As the black hole in GRS 1915+905 draws in material, it comes in circling in a broad disk structure around it. The particles inside convert kinetic energy into immense amounts of heat as they fall inwards. However, this huge cosmic structure is seemingly misaligned with the black hole’s own rotation, causing the mysterious wobbles and radio signals.

Wei Wang, a professor of astrophysics at Wuhan University in China and the lead author of the study, said in a statement: "The peculiar signal has a rough period of 0.2 seconds or a frequency of about 5 Hertz. Such a signal does not always exist and only shows up under special physical conditions. Our team was lucky enough to catch the signal twice — in January 2021 and June 2022, respectively."

Kieren Williams