Galaxies don’t like to be alone. These huge swirls of stars, dust, and dark matter gravitate together in their thousands to form clusters, offering wonder and puzzlement to us humans watching them.
The mystery of the super-hot hydrogen
As with many aspects of our awe-inspiring universe, there is a multitude of unanswered questions about how these clusters form and maintain themselves. One of these mysteries concerns the hydrogen that a large portion of the galaxy clusters are composed of.
This element reaches temperatures around 18 million degrees Fahrenheit, similar to the temperature of the Sun. This aspect of the Sun is perplexing because it is thought that hydrogen atoms cannot exist in this kind of heat. Whereas in the galaxy clusters, hydrogen has a problem with cooling down instead. Even after billions of years it’s still scorching.
Finding the answer
A group from the University of Chicago looked into this puzzle, seeking to answer why hydrogen reaches such extreme temperatures and how it stays hot. The first challenge they had to overcome was getting the correct conditions to conduct their tests. As you can imagine, creating such powerfully hot and magnetic conditions here on the Earth is no easy task.
The team took a trip to The National Ignition Facility (NIF) at Lawrence Livermore National Laboratory, the most powerful laser facility in the world where the extreme conditions could be reproduced. “The experiments conducted at the NIF are literally out of this world,” said Jena Meinecke, the first author on the paper.
Focusing 196 lasers on a single target created extremely hot plasma – the kind galaxy clusters are composed of – with intense magnetic fields. These conditions were only stable enough to hang around for a few billionths of a second, just enough time for the team to get what they needed.
How does hydrogen stay so hot in galaxy clusters?
The magnetized plasma was not a uniform temperature under these conditions, as it turned out. It consisted of hot and cold spots, aligning with an existing theory of how these intense temperatures are achieved in galaxy clusters. It is thought that magnetic fields impact electron activity in the structures, changing the course of their movement and how they distribute energy.
“This is an incredibly exciting result because we’ve been able to show that what astrophysicists have proposed is on the right track,” said Prof. Emeritus Don Lamb, co-author of the paper published in Science.
While there are still many aspects of galaxy clusters we don’t understand, this study opens the door for many more to come. Gaining a deeper understanding of the universe and the natural laws it follows uncover truths about our own lives and can have applications in energy production, biology, AI, and more.