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Astronomers Observe Galactic Collisions From Young Universe

Astronomers have been able to peer back in time — 7 billion years back — to see gigantic collisions of galaxy clusters, in the form of radio waves picked up by a low-frequency radio telescope here on Earth.

(CN) — Billions of years ago, a cluster of galaxies collided in our young universe to create a swirling soup of magnetic particles that sped up to nearly the speed of light and emitted radio waves. All we had to do is listen.

For the first time, data from these collisions in the distant reaches of a young universe were observed as the radio waves were picked up by a network of antennae and other instruments investigated by an international team of scientists at Leiden University in the Netherlands.

Researchers are aware of this cosmic ballet of crashing galaxy clusters and countless stars because the excited particles emit radio waves as they encounter magnetic fields, according to a study published Monday in the journal Nature Astronomy.

Galaxy clusters are a congregation of thousands of galaxies with billions of stars that could be considered the largest structures in the known universe, but there’s a lingering question on what happens when magnetic fields are generated and speed up particles during these celestial crashes that took place when the universe was just 7 billion years old — about half the age it is now.

Researchers documented and mapped nine collisions in their study, which covers how they measured the magnetic fields using the low-frequency radio telescope LOFAR in the Netherlands and took eight-hour exposures on the distant galaxies.

The astronomers ascribe to the theory that the turbulence and shock of these collisions re-accelerate cosmic rays, which in turn produce radio relics or signals.

Now, distant radio waves from some of the furthest parts of the universe produce radio halos that are faint and dim due to the distant trip they need to travel to be picked up by instruments on Earth.

But the LOFAR study shows diffuse radio emissions. From 19 observed clusters, nine are producing these radio emissions which are “mostly centrally located in the clusters, with an overall roundish shape, and extending over scales spanning from a few hundred of kiloparsecs to about one megaparsec,” according to the study.

In other words, the signal of red light or radio waves are much stronger for such a young part of the universe and are brighter than previous theories would suggest.

Lead researcher and doctoral candidate Gabriella Di Gennaro from Leiden University said in a statement, “We therefore think that the turbulence and vortices caused by the collisions are strong enough to accelerate particles also in a young universe.”

In an email, Di Gennaro said this is supposed to be a slow process — think several billion years slow — that could amplify to the levels documented in the report.

“We are observing galaxy clusters that are close to the moment they form, therefore there should not be enough time for the magnetic fields in these systems to reach those strengths,” said Di Gennaro. “We concluded that the magnetic amplification is a much faster process than previously thought.”

This is all unexplored territory for humans as this would be the first time distant cluster waves were picked up. Previous studies investigated other clusters closer to home.

Assistant professor Dr. Reinout van Weeren from Leiden University said that a few years ago these types of measurements would not have been possible, because telescopes lacked the sensitivity to reach out to the furthest reaches of our universe.

Van Weeran said understanding how magnetic fields are amplified and created is an open question in astrophysics.

“Measurements of magnetic fields in these distant objects (and thus far back in time) are therefore very important to help us in this quest,” van Weeran said in an email.

He noted the magnetic fields are about a million times weaker than what would be measured on Earth.

According to the study, the observed clusters are 7 billion light-years away, but a previous study found the oldest observed galaxy cluster is about 13 billion years old, one of the oldest star systems to date.

The Leiden University research team took their data from the LOFAR Two-meter Sky Survey, an ongoing, high-resolution survey of the northern sky.

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