While analyzing a 10 billion-year-old radio signal, astronomers discovered a “mini-halo” — a cloud of energetic particles — around a far-off cluster of galaxies. The unexpected findings could further our understanding of the early universe.
This mini-halo is the most distant one ever detected, located twice as far from Earth as the next-farthest mini-halo. It is also massive, spanning more than 15 times the width of the Milky Way, and contains strong magnetic fields. The findings have been accepted for publication in The Astrophysical Journal Letters and are available on the preprint server arXiv.
“It’s astonishing to find such a strong radio signal at this distance,” Roland Timmerman, a radio astronomer at Durham University who co-led the study, said in a statement.
How did the mini-halo form?
Mini-halos are faint groups of charged particles that emit radio and X-ray waves in the vacuum of space between galaxies. They have been detected around galaxy clusters in the local universe, but never as far back in space and time as the one reported in the new study.
There are two theories that could explain the collection of particles, according to the researchers.
One possible cause is the supermassive black holes at the centers of large galaxies within the distant cluster. These black holes can shoot high-energy particles into space, but it’s not clear how the particles would travel away from a powerful black hole and into a mini-halo without losing significant energy.
Another possible means of creation is the collision of charged particles within the plasma in a galaxy cluster. When these high-energy particles smash into each other, often at close to the speed of light, they can break apart into the kinds of particles that can be seen from Earth.
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Implications for astronomy
Observations of the mini-halo come from light so old that it changes the picture of galaxy formation, proving that these charged particles have surrounded galaxies for billions of years longer than was known.
“Our discovery implies that clusters of galaxies have been immersed in such particles since their formation,” Julie Hlavacek-Larrondo, an astrophysicist at the University of Montréal who also co-led the research, told Live Science in an email. It’s “something which we were not expecting at first.”
Scientists can now study the origin of these mini-halos to determine whether black holes or particle collisions are responsible for them.
These particles also have a hand in other astrophysical processes, like star formation. They can affect the energy and pressure of the gas within a galaxy or couple with magnetic fields in unique ways. These processes can keep clouds of gas from collapsing, in turn altering how stars form in the gas.
“We are still learning a lot about these structures, so unfortunately the more quantitative picture is still very much in development,” Timmerman told Live Science in an email.
New radio telescopes, like the SKA Observatory, are in development to help astronomers detect even fainter signals and learn about mini-halos.
“We are just scratching the surface of how energetic the early Universe really was,” Hlavacek-Larrondo said.
