Representative image of Galaxy cluster MACS J0717

(X-ray: NASA/CXC/SAO/van Weeren et al.; Optical: NASA/STScI; Radio: NSF/NRAO/VLA)

The apple falls from the tree because gravity follows precise rules on our planet. We feel sleepy after eating rice because it helps release calming hormones in our bodies. In nature, everything is organised and in place. But once in a while, it loves to throw a spanner in the works, seemingly just to toy with the perplexed scientists brave enough to study natural law.

This is exactly what is happening with a particularly cheeky galactic cluster called the Abell 3266, whose latest bizarre tantrums have made astronomers and physicists tear out their hair and scrummage hastily through their books in order to find some explanation for its odd behaviour.

But before we get into the complicated (and gorgeous) cosmic mess that are these galactic clusters, let’s try to understand it in terms everyone is extremely familiar with: fossils!

The fossils of ancient cosmic cities

We know dinosaurs and other flora existed much before us because they left tangible evidence behind that we could study. In the way that we could date these ancient fossils to determine exactly how old they were, scientists also use similar techniques to study radio emissions of dying black supermassive holes in space, which are essentially the “fossils” of these magnificent cosmic behemoths.

Radio emissions are a sort of “invisible” light given out by celestial bodies that radio astronomers study to understand their composition and age, among other things. Its study reveals some of the most amazing and well-kept secrets of the universe, such as the origin of the Big Bang via the study of the infamous Cosmic Microwave Background radiation.

A lot of what makes a cluster is plasma — a chaotic state of matter that is formed when gas is heated to piping 10 million degrees celsius. When radio waves are generated through this plasma, some known patterns emerge, which scientists categorise to gain an insight into the galactic environment.

So what’s happening with Abell 3266?

While the nitty-gritty of many of these radio relics from colliding clusters and supermassive black holes still remain elusive to us, their mere existence gives us fundamental answers to some plain questions. If there is a shadow, we know something opaque exists to cast it. But Abell, the cluster from 800 million light-years away, was already an enigma because despite fulfilling all the conditions, it cast no proverbial shadow!

The cluster had no detectable radio relics until recently. And when Australian scientists tried to study it using the combined might of more than three separate powerful satellite arrays, they noticed that some of the extremely elusive emissions challenged everything they thought they knew about them.

The radio emissions emanating from one part of the cluster formed a sonic boom-like arc, likely powered by shockwaves travelling through the plasma from some massive cosmic scruffle. However, its highly unusual concave shape baffled radio scientists, as they had never seen anything of the sort before. Plus, its weird orientation facing away from the centre of the cluster earned it the “wrong-way relic” nickname.

“If it’s a shock wave, you might think it would bend down like an arc around the edge, but this one is flipped around,” one of the astrophysicists behind the study, Dr Tessa Vernstrom, explained. “So we don’t really understand what that’s telling us”.

A new type of science?

Dr Vernstrom adds that her team thinks this is real, and likely not a mistake from the image processing. Further, the unexpected brightness of the relic also meant that there were massive gaps in understanding how these radio fossils behave, and that scientists had to go back to the drawing board to form explanations.

“Maybe there’s some kind of new physics going on there that we haven’t fully understood when our models can’t match the observations,” she added.

Colliding galactic clusters, such as some in Abell 3266, are scary places in space that leave scientists tingling with excitement, but also bring rattle to their bones. These environments have so much plasma and dark matter activity that they produce a whole variety of data that would be otherwise impossible to gather in a lab.

Abell 3266, in particular, is a special cluster because there are tons of anomalies and rare phenomena that are absent from most other observed clusters, or just haven’t been detected yet. However, this also serves as a testament to the growing might of radio telescopes, and the exciting opportunity to study the remaining parts of the universe.

“By looking in the radio, you see a kind of different physics than when you look in the other wavelengths,” explains Dr Vernstrom. “We’re going to see a lot more of this kind of stuff.”

The research was published in the Monthly Notices of the Royal Astronomy Society, and can be accessed here.

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