For the first time, astronomers have captured the perception of collision waves through the resonant strings of the cosmic web, the vast array of galaxies, gas, and dark matter that makes up the observable universe.
By combining hundreds of thousands of radio telescope images, he revealed that the faint glow of the pulses had sent out shock waves of charged particles traveling through magnetic fields through the cosmic web. Spotting these shock waves would allow astronomers to get a better look at these large magnetic fields, whose properties and origins are largely mysterious, researchers report on Dec. 17. Journal of Sciences.
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Finally, astronomers “can confirm what has so far only been predicted through simulations – that these shock waves exist,” said astrophysicist Marcus Brüggen of the University of Hamburg in Germany, who was not involved in the new studies.
In its size, our universe looks like a Swiss cheese. Galaxies are not evenly distributed through space, but are clustered together in enormous clusters of filaments of dilute gas, galaxies, dilute matter, galaxies and not quite separate vacuums (a.SN: 10/3/19).
Pulled back by gravity, galaxy clusters sink, filaments collide, and gas falls from the voids into filaments and clusters. In simulations of the cosmic web, all that activity constantly sets the pulses in waves and between the filaments.
Filaments make up most of the cosmic web but are much more difficult to spot than galaxies (SN: 1/20/14). While scientists have observed shock waves around galaxy clusters, shocks in filaments “have never really been seen,” says astronomer Reinout van Weeren of Leiden University in the Netherlands, who was not involved in the study. “But it must be mostly around the cosmic web.”
Shock waves around filaments accelerate particles through the magnetic fields that permeate the cosmic web.SN: 6/6/19). When that happens, the particles emit light at wavelengths that radio telescopes can detect, although the signals are very weak.
A single shock wave in the filament “looked like nothing, it looked like noise,” says radio astronomer Tessa Vernstrom of the International Center for Radio Astronomy Research in Crawley, Australia.
Instead of looking for individual shock waves, Wernstrom and his colleagues took radio images of more than 600,000 pairs of galaxy clusters close enough to be connected by filaments to create a single “smooth” image. These weak signals were amplified and revealed to be, on average, radio emission from the filaments between the coils.
“When you can dig beneath the noise and still get results — to me, that’s very exciting,” Wernstrom says.
The weak signal is highly polarized, meaning the radio waves are highly aligned with each other. Highly polarized light is unusual in the cosmos, but expected from light pulses thrown in waves, says van Weeren. “So, I think it’s very good evidence that the crops are really going to be present.”
The finding goes beyond confirming the predictions of cosmic simulations. Polarized radio emissions also offer a rare peek into the magnetic fields that permeate the cosmic web, if only indirectly.
“These crops,” says Brüggen, “can really show that there are large magnetic fields that form. [something] like a wrap around these threads. “
He, van Weeren and Wernstrom all note that it is still an open question how cosmic magnetic fields arose in the first place. The role these fields play in shaping the cosmic web is equally mysterious.
“It’s one of the four main forces of nature, right? Magnetism, says Wernstrom. “But at least on these large scales, we don’t really know how important it is.”
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