Astronomers around the globe have long seen big galaxies like the Milkyway swallow up some of their little brothers and sisters. In fact, the sky is full of cannibals. They swallow up stars that are in their cosmic neighbors, and over time eat up whole galaxies. It seems only natural, that even in space, the rules of survival of the fittest still apply.
Yet one thing that may come as a surprise, is little galaxies actually have pretty big appetites. In a recent publication in Monthly Notices of the Royal Astronomical Society, a group of astronomers was able to witness and details first hand this phenomenon. Where a little dwarf galaxy decided to go on the offensive. And it actually happened not very far from home at all, a tiny galaxy that is just outside of the Milky Way known as the Sextans dwarf spheroidal.
It is an extremely old galaxy, around 12 billion years old and just very small. But it was at one point even smaller, this dwarf galaxy decided to go on the offensive and eat up one its neighbors. When studying this galaxy, the makeup of its stars is just too different. Its just was not possible for the researchers that they had all started in the same place. Upon digging deeper, they discovered the uncanny truth: this little dwarf galaxy had an extreme appetite.
They figured this out by looking at the pattern of the stars inside, all the blue stars appeared natural and organized following an orbit that made sense. But then there were red stars that had irregular movements and just seemed out of place, undoubtedly these red stars are actually from a galaxy that was eaten.
These discoveries seem to prove the hierarchical theory of galaxy formation, that galaxies can grow by eating up smaller ones. And that this applies even for the smallest of cases.