Galaxy Mass Murder: Scientists Find Entire Galaxies Being Killed By 'Halos,' Quicker Than 'Strangulation'

Scientists have been on the trail of a mysterious galaxy killer for some time, and new research suggests that they just might have pinpointed the culprit -- a process known as ram-pressure stripping. Even worse, it was discovered that this particular method of galaxy killing was far more prevalent than previously believed.

Space Daily reported this week that research done at the International Centre for Radio Astronomy Research (ICRAR) in western Australia has uncovered evidence that dark matter "halos" provide the environment for the violent stripping of gases from galaxies, which effectively deprives the victims of the materials necessary to create new stars. By studying 11,000 galaxies, astronomers were able to determine that ram-pressure stripping was widespread, that far more galaxy murders were occurring within the local Universe than they had thought existed.

For want of a better term, call it mass murder.

Toby Brown, study leader and Ph.D. candidate at ICRAR and Swinburne University of Technology, said astronomers describe galaxies as being embedded in clouds of dark matter that are known as dark matter halos. Now, dark matter is that mysterious material (as yet undetected) that exists in theory and accounts for roughly 27 percent of the Universe, while ordinary matter itself constitutes a mere 5 percent of the same. The remaining 68 percent is filled with the hypothesized dark energy.

That being said, Brown noted that the dark matter halos varied in size.

"During their lifetimes, galaxies can inhabit halos of different sizes, ranging from masses typical of our own Milky Way to halos thousands of times more massive. As galaxies fall through these larger halos, the super-heated intergalactic plasma between them removes their gas in a fast-acting process called ram-pressure stripping. You can think of it like a giant cosmic broom that comes through and physically sweeps the gas from the galaxies."

Without the gases, the galaxies are unable to create new stars, Brown continued.

"It dictates the life of the galaxy because the existing stars will cool off and grow old. If you remove the fuel for star formation then you effectively kill the galaxy and turn it into a dead object."

The process of ram-pressure stripping has been recognized for some time. However, it was thought to exist where dark matter halos were far more massive, like in areas of the universe containing galaxy clusters (where halos are the most massive). This is where Brown's team made the discovery that the stripping was prevalent throughout the universe and that the halos were committing mass murder.

"This paper demonstrates that the same process is operating in much smaller groups of just a few galaxies together with much less dark matter," Brown said. "Most galaxies in the Universe live in these groups of between two and a hundred galaxies. [Note: The Milky Way itself is part of a 54-galaxy cluster known as the Local Group, according to NASA.] We've found this removal of gas by stripping is potentially the dominant way galaxies are quenched by their surrounds, meaning their gas is removed and star formation shuts down."

So not only did the research show that ram-pressure stripping was more widespread, it indicated that the halos were the Universe's primary galaxy killers.

Andromeda galaxy, with some photo elements supplied by NASA
It is difficult to imagine galaxies such as Andromeda could be "murdered," but the Universe has its own set of rules. [Image by Egyptian Studio/Shutterstock]

To be clear, it was found that the stripping method killed off galaxies far quicker than a second known method of galaxy death called "strangulation," which is a process where star-making gases within a galaxy are consumed faster than they are replenished.

Unidentified spiral galaxy
There are two major methods by which galaxies are killed: ram-pressure stripping and strangulation. [Image by NASA Images/Shutterstock]

And it is not as if the universe needs a helping hand in its march toward ultimate entropy; all stars will eventually die. The Earth's star, Sol, will be burning itself down as a white dwarf in a little over 12 billion years, according to But by then, it will be part of another galaxy, the Milky Way having collided with Andromeda about eight billion years earlier to form either a combined galaxy or perhaps two or more distinct new galaxies.

But even with galactic strangulation and ram-pressure stripping, not to mention inexorable entropic run-down, the universe will not see die-offs for billions of years. Even so, as a new study shows, there are 2 trillion galaxies in the universe (per the Inquisitr). That is quite a few stars to extinguish, no matter what method does the job.

[Featured Image by Sander van Sinttruye/Shutterstock]