Astronomers Discover Andromeda Is A Cosmic Cannibal Feasting On Smaller Galaxies
A team of scientists led by a University of Sydney astrophysicist has discovered a structure of stars, known as globular clusters, which originated outside the galaxy. The new structure has been named the Dulais Structure, Welsh for a black stream, by Professor Geraint Lewis. The new findings point to the Dulais Structure being representative of a "colossal feeding event in the 'recent' past."
"A few years ago, we discovered that in the far outskirts of Andromeda, there was a sign in the objects orbiting it that the galaxy hadn't been grazing, but it had eaten large quantities in two distinct epochs," remarked lead author Professor Geraint Lewis from the University of Sydney. "What this new result does is provide a clearer picture of how our local universe has come together—it is telling us that at least in one of the large galaxies, that there has been this sporadic feeding of small galaxies."

Credit: Geraint Lewis
"That then leads to the next question of, well, what was actually consumed? Because it doesn't look like it was just one thing, it looks like it's been a collection of things which are all being slowly torn apart," explained Professor Lewis. "We've come to realize over the last few decades that galaxies grow by eating smaller systems—so little galaxies fall in, they get eaten—it's galactic cannibalism."

Credit: Geraint Lewis
The initial findings of the Dulais Structure came from two honor students exploring data: Tim Adams and Yuan Li.
"It's opened a new door in terms of our understanding. But exactly what it's telling us I think we still have to work that one out," stated Professor Lewis.