A group of scientists has recorded a more than 10-fold increase in the average temperature of gas accumulations in the universe over the last 10 billion years, including galaxies. This confirms the theory that explains the emergence of large-scale structures in the universe.
According to the prevailing cosmological theory among the scientific community, the universe was created about 13,000 million years ago in a process known as the Big Bang. Since then, the space has been expanding and cooling. However, recent research by Ohio State University, in conjunction with Johns Hopkins University and the Max Planck Institute for Astrophysics, delved into the thermal history of the universe and showed that this is not entirely true.
Large concentrations of matter have been heating up for the past 10 billion years. So much so that the average temperature of the galaxies in the universe has reached about 2 million degrees Celsius. This is almost 350 times hotter than the surface of the Sun.
This increase is due to the fact that gravity binds dark matter and visible matter in galaxies and galaxy clusters. As a result of the formation of gigantic space structures, huge volumes of gas become denser and warmer, especially in stars.
“As the universe evolves, gravity pulls dark matter and gas in space together into galaxies and clusters of galaxies. The drag is violent—so violent that more and more gas is shocked and heated up”explains Yi-Kuan Chiang, lead author of the study and researcher at the Center for Cosmology and Astronomical Physics of Particles at The Ohio State University (USA).
To reach this conclusion, astronomers estimated the temperature of the gas far from Earth and compared it to the gas near the Milky Way and the solar system. Since the farther an object is from the observer, the further away it is in the past, scientists were able to determine what the temperature of the matter was in the universe billions of years ago.
The authors of the study, published in The Astrophysical Journal, used space light data about collected by two missions, Planck and Sloan Digital Sky Survey. They then combined these data and evaluated the distances of the hot gases near and far by measuring the redshift, a notion that astrophysicists use to estimate the cosmic age at which distant objects are observed.
This is how scientists measured the degree of shift of the spectral lines to the red wave region of the spectrum, which is observed when the object moves away from the observer.
This fact, along with a method for estimating temperature from light, allowed the researchers to calculate the average degrees of gases in the early Universe and compare them with those of gases closest to Earth.
It took astronomers more than 15 years to collect the necessary data using one telescope on the ground and another in space. On the analysis side, our team spent four years developing the algorithms necessary to extract the signal from this data.
In this way, astronomers have confirmed that the galaxies of the universe are warming over time due to the gravitational collapse of the cosmic structure and the warming is likely to continue.
“Our new measurement provides a direct confirmation of the seminal work by Jim Peebles—the 2019 Nobel Laureate in Physics—who laid out the theory of how the large-scale structure forms in the universe”summarizes Yi-Kuan Chiang.
However, scientists point out that this increase is due to the natural process of formation of galaxies and structures and is not related to global warming on Earth.
“These phenomena are happening on very different scales. They are not at all connected”Chiang said.