Don’t freak out but, something mysterious is killing 11,000 nearby galaxies

While researchers are still unsure as to why this is happening –and why at such a large scale— they believe that it has something to do with the halos of DARK MATTER which are believed to surround galaxies, responsible for removing the star-forming gas in a fast-acting process referred to as ram-pressure stripping.

The study which was published in the peer-reviewed Journal Monthly Notices of the Royal Astronomical Society clearly illustrates that this phenomenon is more prevalent than previously thought.

The process basically drives gas from the thousands of galaxies which causes an early death by stealing from them the material they need to create new stars.

According to  Toby Brown, a Ph.D. candidate at ICRAR and Swinburne University of Technology:

“During their lifetimes, galaxies can inhabit [dark matter] 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 superheated 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.”



Simply put, by removing the gas from Galaxies it leaves them unable to form new stars said, Brown:

“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.”

Another process which also causes galaxies to die but a much slower scale is known as strangulation. Brown explained it:

“Strangulation occurs when the gas is consumed to make stars faster than it’s being replenished, so the galaxy starves to death. It’s a slow-acting process. On the contrary, what ram-pressure stripping does is bop the galaxy on the head and remove its gas very quickly — of the order of tens of millions of years — and astronomically speaking that’s very fast.”

Co-Author of the study, ICRAR researcher Barbara Catinella said that astronomers were aware that the process known as ram-pressure stripping was responsible for the death of galaxies in great galaxy clusters around which experts think are the most massive ‘dark matter halos’ in the known universe.

In order to observe 11,000 galaxies, astronomers made use of the largest optical galaxy survey yet completed — the Sloan Digital Sky Survey — with the largest set of radio observations for atomic gas in galaxies — the Arecibo Legacy Fast ALFA survey.


This is the Sloan Digital Sky Survey “Orange Spider.” It illustrates a wealth of information being obtained about galaxies via the most recent surveys.

Brown concluded:

“This paper demonstrates that the same process is operating in much smaller groups of just a few galaxies together with much less dark matter. Most galaxies in the universe live in these groups of between two and a hundred galaxies.”

“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.”


Find out more: [International Centre for Radio Astronomy Research (ICRAR)]

Featured image credit: ICRAR.

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