Astronomers have identified some strange stars in the Milky Way that may have once belonged to a different galaxy. By studying the chemistry of these stars and their motion close to the galactic disk, the researchers found that the stars' home galaxy, nicknamed "Loki," might have merged with our galaxy about 10 billion years ago. Massive galaxies are not born whole. They are assembled over billions of years through mergers with smaller galaxies, which are sometimes absorbed. In the early universe, shortly after the Big Bang , matter clumped into clouds of gas that collapsed into the first primitive galaxies. These small systems then fell into one another, merged and gradually built up into the large structures we see today.…