Astronomers have witnessed a distant galaxy die for the first time

When stars in a galaxy stop forming, that galaxy will die. Astronomers, for the first time ever, have observed this phenomenon in a distant galaxy.

According to a report by CNN, scientists using the Atacama Large Millimeter/submillimeter Array of telescopes in Chile, were able to capture a “rare observation” of a galaxy “as it ejected almost half of the gas it uses to form stars.”

It has taken nearly nine billion years for the light from this galaxy, known as ID2299, to reach Earth, CNN reported - which means essentially astronomers are “observing how it appeared when the universe was only 4.5 billion years old (it’s now estimated to be 14 billion years old).”

The ID2299 galaxy is losing the fuel it needs to form stars - 10,000 suns-worth of gas per year - and so far has removed 46% of the galaxy’s total cold gas, the report explained.

However, at a “rate that is hundreds of times faster than our own Milky Way,” ID2299 is still quickly forming stars, the report noted.

The formation of these stars will deplete the remainder of the gas in the galaxy, and will effectively “cause ID2299 to die in a few tens of million years,” the report explained.

The study, which CNN has cited, was published Monday in the journal Nature Astronomy.

CNN cited Annagrazia Puglisi, lead study researcher and postdoctoral research associate from Durham University in the UK and the Saclay Nuclear Research Centre in France, who said in a statement: “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.”

What may have caused the galaxy’s demise?

According to the report, the cause of this galaxy’s death, may have been a collision with another galaxy, “which eventually merged to create ID2299.”

Is there compelling evidence that the loss of gas may have been the result of a collision? According to the CNN report, the study says there is - and it’s called a tidal tail - “a long stream of gas and stars that extend out into space after two galaxies come together in a collision.”

Although these tidal tails are typically “too faint” to be seen in galaxies of this distance, the study noted that in this case the bright tail was visible to astronomers as it was extending out into space, CNN reported.

Astronomers may need to reconsider previous theories.

Previously, scientists have believed that the “ending of star formation” happened when the “winds created by the formation of stars, combined with active black holes at the centers of giant galaxies, sent the material needed to form stars hurtling out into space,” CNN cited.

However, the study noted that if this galaxy’s loss of gas was caused by a merger, “astronomers may need to reconsider theories on the end of star formation in galaxies.”

CNN cited Emanuele Daddi, study coauthor and astronomer at the Saclay Nuclear Research Centre in France, who said: “Our study suggests that gas ejections can be produced by mergers and that winds and tidal tails can appear very similar.” He added, “This might lead us to revise our understanding of how galaxies ‘die.’”

This observation was an unexpected discovery.

An interesting aspect about this discovery is that “it was made while the astronomers were working on a different survey of cold gas in distant galaxies,” and although their observation of ID2299 only lasted a few minutes, “it was enough to capture the tidal tail,” CNN reported. And, the possibility remains that more could be revealed about the galaxy’s gas ejection, through future observations.

CNN cited Chiara Circosta, study coauthor and researcher at the University College London, who said in a statement: “ALMA has shed new light on the mechanisms that can halt the formation of stars in distant galaxies. Witnessing such a massive disruption event adds an important piece to the complex puzzle of galaxy evolution.”

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