Incredibly, astronomers have witnessed an ancient and distant galaxy dying out. Galaxies die when their stars stop forming and by using the Atacama Large Millimeter/submillimeter Array of telescopes in Chile, scientists observed the galaxy called ID2299 emit nearly half of the gas that is used to form the stars.
What is so astonishing about this is that the light from ID2299 takes approximately 9 billion years to reach us, so what the astronomers are witnessing is how that galaxy looked when the universe was just 4.5 billion years old (it is currently around 14 billion years old).
The amount of gas that the ID2299 galaxy loses each year is equivalent to about 10,000 suns and so far it has lost approximately 46% of its total amount of cold gas. While it has lost nearly half of its cold gas, stars are still forming within it at an incredibly fast rate (hundreds of times faster than the rate that stars form in our Milky Way Galaxy). At the rate that the ID2299 galaxy is using up its remaining gas, astronomers have estimated that it will completely die out in a few tens of millions of years.
As for what caused it to become that way may have been because of an ancient collision with another galaxy that merged together to form ID2299. This possibility is in reference to its tidal tail which is a long stream of gas and stars that stretch out into space after two galaxies collide and merge together. Tidal tails are normally too faint to be seen, especially in galaxies that are extremely far from us, however, astronomers were still able to view it. As a matter of fact, astronomers made this discovery while focusing on a completely different study on cold gases in distant galaxies and were lucky enough to observe ID2299’s tidal tail. (An artist’s impression of ID2299’s tidal tail can be seen here.)
This provides astronomers with an exceptional opportunity to view how galaxies die out. Emanuele Daddi, who is an astronomer at the Saclay Nuclear Research Centre in France and a co-author of the study, explained this further, “Our study suggests that gas ejections can be produced by mergers and that winds and tidal tails can appear very similar.” “This might lead us to revise our understanding of how galaxies ‘die’.”
Annagrazia Puglisi, who is a postdoctoral research associate from Durham University in the UK and the Saclay Nuclear Research Centre in France as well as the lead study researcher, stated how incredible this news is, “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.”
The study was published in the journal Nature Astronomy where it can be read in full.