DARK MATTER
The largest galaxies we can see have stopped making stars, and astronomers are trying to figure out why.
The largest galaxies we can see have stopped making stars, and astronomers are trying to figure out why. Now, they may have found an explanation.
Six billion years ago, two galaxies collided and their combined forces hurled a powerful stream of gas hundreds of thousands of light-years away. And that unusual feature, an international team of researchers has just explained in The Astrophysical Journal Letters, provides a possible explanation for the mystery of why precisely the largest galaxies seem to be dying, ceasing to form stars.
“One of the most important questions in astronomy – says David Setton, co-author of the study – is why the largest galaxies are dead. And what we saw in our study is that if you take two galaxies and smash them into each other, that can pull gas out of the resulting galaxy itself.”
To make stars, a galaxy needs a good supply of cold gas, without which it becomes inert. Previous studies have suggested that such gas can ‘escape’ from the galaxy by various means, whether entrained by black holes or supernovae. Or it could simply be that the galaxies, once all the necessary raw materials have been exhausted, ‘calm down’ and stop forming new stars.
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