(ORDO NEWS) — Scientists at the Apache Point Observatory Galactic Evolution Experiment (APOGEE) of the Sloan Digital Sky Survey have discovered a “fossil galaxy” hidden deep within our own Milky Way galaxy.
These results could significantly change the current understanding of the evolutionary path of the galaxy in which we live.
This hypothetical “fossil galaxy” could have collided with the Milky Way 10 billion years ago, when our Galaxy was still a “baby” by galactic standards. Astronomers named the galaxy they discovered “Hercules”, meaning that the galaxy found in the Milky Way the same immortality as the legendary Greek hero, who received the gift of eternal life from the hands of the gods.
“To find fossil galaxies like this one, we have to determine the detailed chemical composition and motion parameters of tens of thousands of stars,” said Ricardo Schiavon of the University of Liverpool. John Moores University (LJMU), United Kingdom, a key member of the research group. – This is especially difficult for stars located towards the center of the Milky Way, as they are hidden from observation by clouds of dust filling the space between the stars. The APOGEE Sky Survey allows us to peer through this dust and peer into the very center of the Galaxy.”
The APOGEE sky survey allows for such observations, since it operates not in the optical, but in the near infrared (IR) range, and the dust is highly transparent to IR rays. Over the 10 years of the APOGEE sky survey, the spectra of more than half a million luminaries that make up the Milky Way have been recorded, including the stars of the galactic core hidden from optical observations by dust.
Lead author Danny Horta, an undergraduate student at LJMU, said: “Of the tens of thousands of stars we’ve observed, several hundred have radically different chemical compositions and velocities. The differences were so profound that the conclusion suggested itself – these stars could not belong to the Milky Way, but instead belonged to another galaxy, which our Galaxy collided with about 10 billion years ago.”
According to the authors, the stars of the Hercules galaxy account for about one-third of the number of stars in the Milky Way’s halo – and this indicates that the collision was a major event in the history of the evolution of our Galaxy.
The research is published in the Monthly Notices of the Royal Astronomical Society.
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