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"Dancing Ghosts" Formed By Intergalactic Winds From Black Holes Seen For First Time


Katy Evans

Managing Editor

clockAug 6 2021, 12:28 UTC
dancing ghosts

These cosmic dance partners are shaped by the intergalactic winds from two supermassive black holes about a billion light-years apart. Image credit: Jayanne English/EMU/Dark Energy Survey

Astronomers have observed what they have dubbed “dancing ghosts” deep in space for the first time. These cosmic dance partners are actually clouds of electrons shaped into being by the intergalactic winds of two supermassive black holes about a billion light-years apart.

“When we first saw the ‘dancing ghosts’ we had no idea what they were,” said Professor Ray Norris from Western Sydney University and CSIRO. “After weeks of work, we figured out we were seeing two ‘host’ galaxies, about a billion light-years away. In their centres are two supermassive black holes, squirting out jets of electrons that are then bent into grotesque shapes by an intergalactic wind.”


The extraordinary observation is one of many detailed in a paper accepted for publication in Publications of the Astronomical Society of Australia – available as a preprint on arXiv – describing the first data from the Evolutionary Map of the Universe (EMU) project.

These giant spectral clouds, named PKS 2130-538, reveal information about black hole behavior and what happens in the space between galaxies – and, the astronomers readily admit, they also throw up more questions than ever.

"New discoveries however always raise new questions and this one is no different. We still don’t know where the wind is coming from? Why it is so tangled? And what is causing the streams of radio emission?" said Professor Norris, lead author on the study and project lead for EMU's pilot survey.  

dancing ghosts
The galaxies forming the "ghosts" can be seen at the top and bottom. Image credit: Norris et al., arXiv, 2021 

The EMU project is no stranger to new and unusual observations. Using CSIRO’s new Australian Square Kilometre Array Pathfinder (ASKAP), an extremely sensitive radio telescope probing deeper into the cosmos than any other, the team's first big "huh?" discovery last year was ORCS, known slightly more formally as "Odd Radio Circles".


These appear to be giant rings of radio emissions nearly 1 million light-years across, surrounding distant galaxies – puzzlingly without any obvious source. They still don't know what they are.

"We are even finding surprises in places we thought we understood," said Professor Norris. "Next door to the well-studied galaxy IC5063, we found a giant radio galaxy, one of the largest known, whose existence had never even been suspected. Its supermassive black hole is generating jets of electrons nearly 5 million light-years long."

"ASKAP is the only telescope in the world that can see the total extent of this faint emission."

ASKAP can explore large expanses of sky very quickly, probing to depths previously only reached with very small patches of sky. It's unsurprising, then, that they are spotting objects never seen before. Norris and colleagues have even dubbed these as-yet unexplained phenomena WTFs.


"When asked, I say it stands for "Widefield ouTlier Finder," Norris shared on Twitter

As the team of 400 researchers sort through more data from EMU's pilot survey, we can expect many more WTFs on the horizon.



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