Galaxies, as things go, are incredibly massive entities – some more so than others. When they collide, the smaller of the two is typically absorbed by the larger one. Though our own Milky Way galaxy is sizable in its own right, it’s days are numbered: According to a study published by the Royal Astronomical Society, monster-galaxy Andromeda will consume the Milky Way in about five billion years.

The reason has to do with the way galaxies develop, grow and mature, says Dr. Aaron Robotham, lead author of the study. “All galaxies start off small and grow by collecting gas and quite efficiently turning it into stars,” he said.

The bigger galaxies become, the harder it is for them to collect gas and form new stars on their own. It’s believed that this is because in larger galaxies, the active nucleus effectively “cooks” the gas, preventing it from cooling enough to form into stars. However, they also develop more gravity as they become more massive, and will eventually reach a point where growth occurs via “acquisition” of other galaxies.

The Milky Way is at that tipping point, and remnants of cannibalized galaxies can be seen within it. In about four billion years, it will consume two nearby dwarf galaxies, Robotham says. Unfortunately, about a billion years later the larger Andromeda galaxy will consume our own.

One day, far, far away, the entire universe will coalesce to become one massive galaxy. “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,” Dr Robotham said.