• Scientists spotted a dying galaxy ejecting star-forming material into space
  • It was possible the process was triggered by a previous galactic merger
  • The discovery provides new information regarding the evolution of galaxies

What does it look like when a galaxy is on the verge of death? Astronomers have now spotted the process in a distant galaxy for the first time.

Galaxies "die" when they run out of material to form new stars. Scientists have seen many of these dead galaxies but don't exactly know how they meet their ends.

In a new study, a team of researchers has found a distant galaxy, which is nine billion light-years away from the Earth, that's nearing its death and they also offer an interesting explanation for the phenomenon. The team says the galaxy is dying because of a galactic merger.

The discovery was made using the Atacama Large Millimeter/submillimeter Array (ALMA), which the researchers were using to observe 100 distant galaxies.

Now called ID2299, the galaxy was actually ejecting nearly half of the gasses that were used to form stars. The European Southern Observatory's (ESO) noted that ID2299 was ejecting star-forming material at a rate that's equivalent to 10,000 Suns per year. Since it was also forming stars quickly, the remaining gas will get depleted quickly, leading to the galaxy's eventual death in "a few tens of millions of years."

"This is the first time we have observed a typical massive star-forming galaxy in the distant Universe about to 'die' because of a massive cold gas ejection," lead researcher Annagrazia Puglisi said in the ESO news release.

So what's causing ID2299 to die?

It is believed that galaxies will lose their capability to make stars when black hole activity or intense star-formation ends up expelling gas from galaxies. However, the researchers believe the cause of ID2299's eventual death may actually be a galactic merger.

The clue, in this case, was its "tidal tail." They form when two galaxies merge and are often too faint, ESO explained. However, ID2299's tidal tail was actually bright enough to be identified.

"Observational features of winds and 'tidal tails' caused by the gravitational interaction between galaxies in such mergers can be very similar," a news release from Durham University explained. "But the rate at which the gas is being expelled from ID2299 is too high to have been caused by the energy created by a black hole or starburst as seen in previous studies."

"ALMA has shed new light on the mechanisms that can halt the formation of stars in distant galaxies," study co-author Chiara Circosta said in the ESO news release. "Witnessing such a massive disruption event adds an important piece to the complex puzzle of galaxy evolution."

Galaxies in the cosmos
Pictured: a view of nearly 10,000 galaxies. Called the Hubble Ultra Deep Field, this galaxy-studded view represents a "deep" core sample of the universe, cutting across billions of light-years. NASA, ESA, S. Beckwith (STScI) and the HUDF Team