Here's why 'live fast' galaxies die young

A new study has revealed that some galaxies can die early because the gas they need to make new stars is suddenly ejected.

Most galaxies age slowly as they run out of raw materials needed for growth over billions of years, but a pilot study looking at galaxies that die young has found some might shoot out this gas early on, causing them to redden and kick the bucket prematurely.

Astrophysicist Ivy Wong, from the University of Western Australia, said that there are two main types of galaxies, blue galaxies that are still actively making new stars and 'red' galaxies that have stopped growing.

Most galaxies transition from blue to 'red and dead' slowly after two billion years or more, but some transition suddenly after less than a billion years, young in cosmic terms.

Wong and her colleagues looked for the first time at four galaxies on the cusp of their star formation shutting down, each at a different stage in the transition and found that the galaxies approaching the end of their star formation phase had expelled most of their gas.

The exciting result means the scientists will be able to use powerful telescopes to conduct a larger survey and discover the cause of this sudden shutdown in star formation.

Wong said it is unclear why the gas was being expelled, but one possibility is that it could be blown out by the galaxy's supermassive black hole. Another possibility is that the gas could be ripped out by a neighbouring galaxy, although the galaxies in the pilot project are all isolated and don't appear to have others nearby.

Researcher Kevin Schawinski said that they selected four galaxies right at the time where this gas ejection should be occurring and it was amazing to see that this is exactly what happens.

The study appears in the journal Monthly Notices of the Royal Astronomical Society.