Distant galaxy dies as astronomers look on

James Marshall
January 14, 2021

It has recently come to light that astronomers have observed a rare phenomenon in space - the death of a distant galaxy.

Galaxies begin to "die" when star formation stops inside them or they start losing material that forms stars.

The discovery was a serendipitous accident and occurred when the team was inspecting data from a galaxy survey conducted by ALMA to study the properties of cold gas in far away galaxies.

Future observations of the galaxy could reveal more about the gas being ejected from the galaxy.

However, the galaxy is still quickly forming stars at a rate that is hundreds of times faster than ours - the Milky Way - which will use up the rest of the gas in the galaxy. Until now. A team of astronomers has now been able to witness a galaxy eject about half of its gas which was capable of forming stars. For a galaxy, that's death.

The study published Monday in the journal Nature Astronomy.

They think ID2299 formed after two galaxies crashed together and merged, creating a new galaxy.

Colliding galaxies are identifiable by their "tidal tail" - elongated streams of gas and stars traced out in interstellar space behind the galaxies. They only observed ID2299 for a few minutes, but it was enough to capture the tidal tail. This "tidal tail" is usually too faint to see in distant galaxies.

Hubble Space Telescope captured a galaxy collision known as "The Mice" because of the long tails of stars and gas emanating from each galaxy.

If a merger led to this galaxy's loss of gas, astronomers may need to reconsider theories on the end of star formation in galaxies.

Using the telescope Atacama Large Millimeter/submillimeter Array (ALMA), astronomers observed a galaxy, nine billion light years away from the Earth, ejecting almost half of its star-forming gas and losing fuel.

As stars form, they produce winds.

"Our study suggests that gas ejections can be produced by mergers, and that winds and tidal tails can appear very similar", Emanuele Daddi, a co-author of the study and an astrophysicist at the Saclay Nuclear Research Center in France, said in the release.

"This might lead us to revise our understanding of how galaxies "die", Daddi adds.

The finding could also offer hints about where our own galaxy is headed. The researchers believe that this spectacular event was triggered by a collision with another galaxy.

The galaxy called ID2299 is at a distance of 9 billion light years from the Earth, which means that the galaxy's light takes 9 billion years to reach the Earth, and what the astronomers have witnessed now had actually taken place when the universe was only about 4.5 billion years old.

The researchers stumbled upon this doomed galaxy while studying cold gas in 100 faraway galaxies, using the Atacama Large Millimeter/submillimeter Array (ALMA) in the Chilean desert.

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