The conditions of the colossal clusters of galaxies recreated thanks to 196 lasers

The conditions of the colossal clusters of galaxies recreated thanks to 196 lasers

"Clusters of galaxies are one of the most majestic things in the universe," explained Professor Emeritus Don Lamb, a University of Chicago astrophysicist and co-author of a new article published in the journal Science on March 9, 2022, which may show the way towards the resolution of a ten-year mystery. Jena Meinecke is the first author of the article.

Scientists have long known that hydrogen gas in galaxy clusters is extremely hot, about 10 million degrees Kelvin, or about the same temperature as the center of the sun, which is so hot that hydrogen atoms cannot exist. Instead the gas is a plasma made up of protons and electrons.

But an enigma persists: there is no direct explanation of why or how the gas remains so hot. According to the normal rules of physics, he should have cooled down. But is not so. The challenge for anyone trying to solve this puzzle is that you can't exactly create these kinds of powerful, magnetic conditions in your backyard.

However, there is now a place on Earth where it is possible: structure most energetic laser in the world. The National Ignition Facility at Lawrence Livermore National Laboratory is capable of creating such extreme conditions, even if only for a small fraction of a second in a volume the size of a dime. Scientists from UChicago, the University of Oxford and the University of Rochester have worked together to use the National Ignition Facility, located in Livermore, California, to create hot gas-like conditions in giant clusters of galaxies.

“This is truly a surprising result,” added University of Rochester study co-author Prof. Petros Tzeferacos, who oversaw the computer simulations of the complicated experiment. "The simulations were fundamental in unraveling the physics at play in the turbulent and magnetized plasma, but the level of suppression of the heat transport was higher than we expected".

The simulations were done with computer code called FLASH code, which was developed at the University of Chicago and is now housed at the University of Rochester's Flash Center for Computational Science, led by Tzeferacos. The code allows scientists to simulate their laser experiments in exquisite detail before putting them in place, so they can get the results they seek.

This is critical because scientists only get a few precious moments in the facility: if something goes wrong, there is no repetition. And because the experimental conditions last only nanoseconds, scientists need to make sure they are taking the measurements they need at exactly the right time. This means that everything has to be precisely planned well ahead of time. "It's a challenge when you're at the extremes of what can be done, but that's where the frontier lies," said Lamb.

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