Most galaxies live healthy, long lives of billions of years. Eventually, though, they all die as gases slowly escape from them.
However, some galaxies have shorter lifespans, of just a billion years. And now scientists believe they know why: these galaxies lose their gases quickly, at a faster pace.
These results come from a new study that started with understanding the two types of galaxies: "blue" and "red." Blue galaxies are active and still making stars, while red galaxies have stopped star formation and are no longer growing.
Astronomers believe, though, that some galaxies, are, in fact, red before their time, dying faster than they should. But the main question is why?
Astrophysicist Ivy Wong from the University of Western Australia node of the International Center for Radio Astronomy Research (ICRAR), along with her research team, set out to answer that. Using radio telescopes, they studied four galaxies about 275 and 375 million light-years from Earth, those at the end of their star formation cycle. They observed these galaxies at different points in their transitions from blue to red and learned that towards the end of the star formation process, each galaxy had expelled most of its gas.
This suggests that galaxies that die faster than other similar galaxies lose their gas faster. And black holes could even play a role in that process as they tend to absorb a galaxy's gas. Other research even suggests that black holes eject a lot of the gas they ingest, hurling these gases into space at speeds of up to 625,000 miles per hour.
"One possibility is that it could be blown out by the galaxy's supermassive black hole," says Wong. "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."
These new observations, however, were limited, but now the team hopes to expand their research with more powerful telescopes.
It seems that for galaxies, the phrase "live fast, die young" applies.
"We selected four galaxies right at the time where this gas ejection should be occurring," says Swiss Federal Institute of Technology Professor Kevin Schawinski. "It was amazing to see that this is exactly what happens!"
Of course, this still doesn't explain why one middle-aged galaxy, NGC 3226, has stopped star formation. Scientists believe that galaxy, though, collided with another galaxy, causing an influx of warm gas which changed the overall gas temperature, making it too warm for stars to form there.