All galaxies grow by pulling in cosmic debris, gas and dust, and are rather efficient at converting it into new stars. But as galaxies age and grow more massive over time, their ability to create their own stars wanes, and they are forced to add on mass by swallowing up other smaller galaxies.

A new study claims our own galaxy, the Milky Way, has already reached that tipping point -- no longer able to produce our own fresh stars, we must resort cosmic cannibalism. It's a strategy that will eventually come back to haunt us.

"The Milky Way hasn't merged with another large galaxy for a long time but you can still see remnants of all the old galaxies we've cannibalised," explained Dr. Aaron Robotham, an astronomer with International Center for Radio Astronomy Research currently working at the University of Western Australia.

Robotham led the research into the growth patterns of the universe's more than 22,000 galaxies. The results were detailed in the journal Monthly Notices of the Royal Astronomical Society.

"We're also going to eat two nearby dwarf galaxies, the Large and Small Magellanic Clouds, in about four billion years," added Robotham. But eventually we're going to be on the other side of the fork. In five billion years, the Milky Way will collide with the Adromeda Galaxy, which is roughly twice our size.

Eventually, the universe's 22,000 galaxies will merge into just a few super-giant galaxies. But eventually is a long way off.

"If you waited a really, really, really long time that would eventually happen but by really long I mean many times the age of the universe so far," Robotham said.