Our Milky Way galaxy grows by eating other galaxies

Istanbul, Nov. 7 (DHA) - We know this for many reasons. For one, we can see other galaxies colliding and merging all over the sky. For another, we can track stars on our galaxy that were once part of another galaxy, but were absorbed into our own. These are usually relatively recent events involving a much smaller galaxy, the SYFY reported.
But a new result changes that. By mapping huge numbers of stars in the galaxy, astronomers have found compelling evidence that the Milky Way ate a galaxy that was, at the time, about a quarter its size. And that time was a staggering ten billion years ago.
The stars in question were mapped by Gaia, a European Space Agency satellite. It is in the process of mapping the positions, motions, colors, and most importantly the distances of well over a billion stars. Yes, a billion.
Gaia has provided nothing short of a revolution in astronomy. How can mapping stars be so important? In some cases it can solve long-standing puzzles that have irritated astronomers for decades. In others it can reveal hidden denizens of the Milky Way. It can resolve uncertainties in distances to critical stars called Cepheids