January 4, 2019
A New Study Has Provided The First Evidence Of 'Dark Matter Heating' And The Movement Of Dark Matter

Scientists have finally found proof that once dark matter has been heated up, it can move around -- and that this occurs because of stars that are being forged within galaxies. In a new study, scientists successfully demonstrated how they have observed something known as "dark matter heating," while also providing further details about the nature and makeup of dark matter.

As Phys.org reports, a team of international scientists from ETH Zurich, the University of Surrey, and Carnegie Mellon University looked specifically for dark matter inside the center of dwarf galaxies. Dwarf galaxies, of course, are much smaller galaxies that can be found orbiting larger ones around them. The dwarf galaxies that scientists looked into for their research, in this case at least, were ones that were all very close to the Milky Way.

Despite the fact that most of the mass in the universe is believed to be dark matter, none of it is directly observable -- and can only be inferred from the gravitational effects it produces on objects around it. However, it is thought that the nature of dark matter may be better understood by looking at the formation of stars within galaxies.

During the creation of stars, large amounts of solar wind oftentimes blow dust and gas far away from the center of the galaxies where these stars are forming, which means that the centers have considerably less mass than they would otherwise. This, in turn, changes how gravity responds to the dark matter that has been left behind -- and with less gravity present, this dark matter has been known to increase its energy markedly. It is posited that dark matter will then actively move away from galaxy centers, a process which is called dark matter heating.

In the new study, scientists studied 16 different dwarf galaxies to learn more about the dark matter within them. They discovered that the galaxies that had the oldest stars within them also had a much higher density of dark matter within their centers, particularly when compared with dwarf galaxies that had much newer stars that were still in the process of being formed. What this demonstrated to scientists was that there is much less dark matter heating within older dwarf galaxies.

Lead author Professor Justin Read -- who is Head of the Department of Physics at the University of Surrey -- explained that researchers found the distribution of dark matter quite different in dwarf galaxies that had older star formations, especially when compared with galaxies that still had newly forming stars within them.

"We found a truly remarkable relationship between the amount of dark matter at the centers of these tiny dwarfs, and the amount of star formation they have experienced over their lives. The dark matter at the centers of the star-forming dwarfs appears to have been 'heated up' and pushed out."
Professor Matthew Walker -- a co-author of the new study from Carnegie Mellon University -- noted, "This study may be the 'smoking gun' evidence that takes us a step closer to understanding what dark matter is. Our finding that it can be heated up and moved around helps to motivate searches for a dark matter particle."

The new study which has provided evidence of dark matter heating, and the movement of dark matter within dwarf galaxies, has been published in Monthly Notices of the Royal Astronomical Society.