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3 mins read 25 Mar 2021

It’s A Bird! It’s A Plane! It’s A… Space Jellyfish?

Researchers have observed a cosmic phenomenon that bears striking resemblance to a jellyfish using the Murchison Widefield Array.

The MWA radio telescope has revealed a ghostly jellyfish while observing the Abell 2877 galaxy cluster. Credit: Torrance Hodgson, ICRAR/Curtin University.

When PhD candidate Torrance Hodgson from the Curtin University node of the International Centre for Radio Astronomy Research (ICRAR) observed a cluster of galaxies known as Abell 2877, he wasn’t expecting to see a jellyfish. 

Part of an Australian-Italian team using the Murchison Widefield Array (MWA) radio telescope to observe the galaxy cluster, Hodgson said, “We looked at the data, and as we turned down the frequency, we saw a ghostly jellyfish-like structure begin to emerge.”

The team observed the cluster for 12 hours at five radio frequencies between 87.5 MHz and 215.5 MHz. While looking at the data, they found that a jellyfish-shaped structure emerged at regular FM frequencies, but disappeared unusually quickly at 200 MHz. 

“No other extragalactic emission like this has been observed to disappear anywhere near so rapidly,” said Hodgson. 

To understand this steep spectrum, the team had to undertake some cosmic archaeology - the building of a history of a cosmic phenomena from the physical evidence that remains today (very separate from space archaeology which is a humanities-based exploration of space). 

“Our working theory is that around 2 billion years ago, a handful of supermassive black holes from multiple galaxies spewed out powerful jets of plasma. This plasma faded, went quiet, and lay dormant.

“Then quite recently, two things happened—the plasma started mixing at the same time as very gentle shock waves passed through the system.

“This has briefly reignited the plasma, lighting up the jellyfish and its tentacles for us to see,” said Hodgson. 

The Murchison Widefield Array

An aerial photograph of the Murchison Widefield Array in outback Western Australia. Credit: ICRAR/Curtin.

The MWA, located in outback Western Australia at the Murchison Radio-astronomy observatory, is a precursor to the Square Kilometre Array (SKA), Australia’s first mega-science project

Hodgson’s supervisor and co-author, Professor Johnston-Hollitt, said, “The SKA will be thousands of times more sensitive and have much better resolution than the MWA, so there may be many other mysterious radio jellyfish waiting to be discovered once it’s operational.

“Discoveries like the jellyfish only hint at what’s to come, it’s an exciting time for anyone seeking answers to fundamental questions about the cosmos,” she continued. 

Located on the land of the Wajarri Yamatji peoples, the traditional owners, the MWA received a million-dollar grant last year to fund upgrades to continue its use in research, such as the GLEAM survey

We acknowledge the Wajarri Yamatji peoples as the traditional owners of the Murchison Radio-astronomy Observatory site. 

Read the paper, now available from The Astrophysical Journal