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The average gas temperature in the universe has risen more than 10 times over the past 10 billion years and has reached about 2 million Kelvin today, according to new research published in Astrophysical Journal.
As the Universe evolves, concentrations of matter are surrounded by gas halos that get hotter and hotter. Image credit: D. Nelson / Illustris Collaboration.
“Our new measurement provides direct confirmation of the fundamental work of Jim Peebles, who exposed the theory of how large-scale structure is formed in the Universe,” said lead author Dr. Yi-Kuan Chiang, a researcher at the Center for Cosmology and AstroParticle Physics at Ohio State University.
The large-scale structure of the Universe refers to the global models of galaxies and clusters of galaxies on scales beyond individual galaxies. It is formed by the gravitational collapse of dark matter and gas.
“As the Universe evolves, gravity pulls dark matter and gas into space together into galaxies and clusters of galaxies. The resistance is violent, so violent that more and more gas is shocked and heated, “said Dr. Chiang.
“The results showed scientists how to monitor the progress of the formation of the cosmic structure by ‘controlling the temperature’ of the Universe.”
Dr Chiang and colleagues used a new method that allowed them to estimate the temperature of the gas further from Earth – which means further back in time – and compare them to gases closest to Earth and closer to present time.
Using data collected by ESA’s Planck satellite and the Sloan Digital Sky Survey, they estimated the redshift of gas concentrations seen in microwave light images going back in time to 10 billion years ago.
They found that gases in today’s Universe reach temperatures of around 2 million Kelvin around objects closest to Earth. This is about 10 times the temperature of the gases around the farthest and furthest objects back in time.
This trend is also predicted by numerical simulations that show how dark matter and atoms in the gas evolve over time.
“The universe is warming due to the natural process of galaxy formation and structure,” said Dr. Chiang.
“It is not related to warming on Earth. These phenomena are happening on very different scales. They are not connected at all. “
“We’ve measured temperatures throughout the history of the Universe,” said co-author Professor Brice Ménard, a researcher at the Kavli Institute for the Physics and Mathematics of the Universe and the Johns Hopkins University Department of Physics and Astronomy.
“As time goes by, all of those galaxy clusters are getting hotter and hotter because their gravity is pulling more and more gas towards them.”
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Yi-Kuan Chiang et al. 2020. Cosmic thermal history probed by Sunyaev-Zeldovich effect tomography. ApJ 902, 56; doi: 10.3847 / 1538-4357 / abb403
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