Astronomers have discovered the remains of an ancient galaxy “buried” inside the Milky Way. The relic object, which happened to be near the galactic core billions of years ago, was named by Hercules in honor of the mythical ancient Greek hero. The discovery of the object could help scientists explain exactly how the Milky Way formed. This is reported in the preprint of an article published in the arxiv.org repository.
Hercules forms about a third of the galactic halo – the spherical component of the Milky Way, which consists of stars and hot plasma. However, in order to identify it, astronomers needed to study in detail the chemical composition and movement of tens of thousands of stars. Additional complexity was created by dust clouds that hide the center of the galaxy from the eyes of terrestrial observers.
Researchers analyzed data on infrared radiation from stars obtained as part of the APOGEE (Apache Point Observatory Galactic Evolution Experiment) project of the Sloan Digital Sky Survey, designed to map the sky. They managed to isolate alien stars that were so different from the rest in chemical composition and speeds that they could not have arisen in the Milky Way.