“Violent Drag of Dark Matter”– Is Turning Up the Thermostat of the Universe

New Hubble Deep Field Image


“As the universe evolves, gravity pulls dark matter and gas in space together into galaxies and clusters of galaxies,”  said Yi-Kuan Chiang, a research fellow at The Ohio State University Center for Cosmology and AstroParticle Physics. “The drag is violent—so violent that more and more gas is shocked and heated up.”

Thermal History of the Universe

“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,” said  Chiang about a new study that probed the thermal history of the universe over the last 10 billion years, finding that the mean temperature of gas across the universe has increased more than 10 times over that time period and reached about 2 million degrees Kelvin today—approximately 4 million degrees Fahrenheit.

“Missing” — Could Dark Matter Be a Source of Light In the Universe?

Peebles, the Albert Einstein Professor of Science, Emeritus at Princeton University, took on the cosmos, with its billions of galaxies and galaxy clusters. His theoretical framework, developed over two decades, is the foundation of our modern understanding of the universe’s history, from the Big Bang to the present day,” the Nobel Prize academy said.

The large-scale structure of the universe, says Chiang, is the global patterns of galaxies and galaxy clusters on scales beyond individual galaxies– formed by the gravitational collapse of dark matter and gas.

Checking the Cosmic temperature

The findings, Chiang said, showed scientists how to clock the progress of cosmic structure formation by “checking the temperature” of the universe, using a new method that allowed them to estimate the temperature of gas farther away from Earth—which means further back in time—and compare them to gases closer to Earth and near the present time. Now, he said, researchers have confirmed that the universe is getting hotter over time due to the gravitational collapse of cosmic structure, and the heating will likely continue.

“Data on Light & Redshift”

To understand how the temperature of the universe has changed over time, the researchers at the Center for Cosmology and AstroParticle Physics report that they used data on light throughout space collected by two missions, Planck and the Sloan Digital Sky Survey. Planck, the European Space Agency mission that operates with heavy involvement from NASA, makes most the precise measurements to date of tiny variations in the universe’s oldest light, the cosmic microwave background, created more than 13 billion years ago; Sloan collects detailed images and light spectra from the universe as well as creating the most detailed three-dimensional maps of the Universe ever made, with deep multi-color images of one third of the sky, and spectra for more than three million astronomical objects.

“All the Light”– In the History of the Observable Universe

The Ohio State team combined data from the two missions and evaluated the distances of the hot gases near and far via measuring redshift, which works because the light we see from objects farther away from Earth is older than the light we see from objects closer to Earth—the light from distant objects has traveled a longer journey to reach us. That fact, together with a method to estimate temperature from light, allowed the researchers to measure the mean temperature of gases in the early universe—gases that surround objects farther away—and compare that mean with the mean temperature of gases closer to Earth—gases today.

Those gases in the universe today, the researchers found, reach temperatures of about 2 million degrees Kelvin—approximately 4 million degrees Fahrenheit, around objects closer to Earth. That is about 10 times the temperature of the gases around objects farther away and further back in time.

The universe, Chiang said, is warming because of the natural process of galaxy and structure formation. It is unrelated to the current global warming on Earth. “These phenomena are happening on very different scales,” he said. “They are not at all connected.”

Source: Yi-Kuan Chiang et al, The Cosmic Thermal History

The Daily Galaxy, Max Goldberg, via The Ohio State University

Image credit: In the new version of Hubble’s deep-field image– by researchers at the Instituto de Astrofísica de Canarias took almost three years to produce by recovering a large quantity of ‘lost’ light around the largest galaxies in the iconic Hubble Ultra-Deep Field.