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Dark Matter Could Be Destroying Distant Galaxies

The mysterious substance may suck gas from the galaxies—and a gasless galaxy is a dead galaxy

smithsonian.com

A group of astronomers in western Australia have stumbled across a murder mystery of cosmic proportions. A recent survey of thousands of far-off galaxies revealed that a process that suddenly strips these massive celestial objects of their gas is far more common than scientists once thought—and it’s unclear what exactly is causing it, Rae Paoletta reports for Gizmodo.

The life cycle of a galaxy is not well defined, but generally goes something like this: Enormous masses of cosmic gas and particles coalesce over long periods of time, creating billions of stars in the process. Once all that free-floating gas is used up, no more new stars can be created and that galaxy is considered “dead,” as astronomer Michael Lam writes for Cornell University’s Ask an Astronomer. Considering the massive timescale that these cosmic processes operate on, this can take billions or trillions of years.

Galaxies, however, don’t always get to live out their natural lifespans.

Astronomers at the International Center for Radio Astronomy Research (ICRAR) in Western Australia recently conducted a survey of about 11,000 galaxies, discovering that a phenomenon whereby galaxies' free gases are suddenly stripped away is far more common than scientists once thought. This process is a swift death for galaxies, rendering them incapable of creating new stars, Paoletta writes. They published the results of their study in the Monthly Notices of the Royal Astronomical Society.

While it’s still unclear exactly what causes this process, this latest study points towards a mysterious culprit with a foreboding name: dark matter.

Halos of this invisible substance that could make up to 25 percent of the universe fit the profile of this galactic killer. As galaxies drift through space, they stand a chance of coming in contact with these nebulous zones, which can suddenly and violently force all of the galaxy’s free gas to dissipate, Brooks Hays reports for United Press International.

“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,” Toby Brown, an ICRAR astronomer and leader of the study, says in a statement. “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.”

While scientists have yet to directly observe dark matter (hence its name), its existence is often inferred by examining odd gravitational effects that occur around galaxies and influence their movement, Paoletta reports. Astronomers have noticed the effect of ram-pressure stripping on galaxies in the past, but this study’s findings suggest that it is much more common than once thought and can happen to galaxies of any size.

“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 says in a statement. “Most galaxies in the universe live in these groups of between two and a hundred galaxies.”

Unfortunately, even the lives of galaxies can be brought to a quick and brutal end.

About Danny Lewis

Danny Lewis is a multimedia journalist working in print, radio, and illustration. He focuses on stories with a health/science bent and has reported some of his favorite pieces from the prow of a canoe. Danny is based in Brooklyn, NY.

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