Enlarge Image Gupta et al/ASTRO 3D/IllustrisTNG collaboration.

Space can be a ruthless realm. A research team investigated how some ancient, massive galaxies got so big. Turns out they've probably been binge-eating their smaller buddies over billions of years.

We've seen evidence of cannibalistic behavior among galaxies before. Our own Milky Way isn't innocent, either.

Anshu Gupta of the ARC Centre of Excellence in All Sky Astrophysics in 3 Dimensions (ASTRO 3D) in Australia led a study that combined data from observations of galaxies with the brain power of supercomputers running modeling software. The project looked at how gases moved within the giant galaxies.

"We found that in old massive galaxies -- those around 10 billion light years away from us -- things move around in lots of different directions," Gupta said in a release on Wednesday. "That strongly suggests that many of the stars within them have been acquired from outside. In other words, the big galaxies have been eating the smaller ones."

The researchers published their findings in the The Astrophysical Journal this month. They compared the data on the "fat and disorderly" older galaxies with observations of younger galaxies that have more orderly structures. "The modeling showed that younger galaxies have had less time to merge with other ones," said Gupta.

Kim-Vy Tran, a co-author of the paper, summed up the galaxies' behavior as "having a constant case of the cosmic munchies." The research is part of a larger project that is modeling how galaxies form.

If anybody is looking for an idea for a retro sci-fi-horror movie, I would suggest "Monster Cannibal Galaxies from Beyond the Stars" as a winner.