Astronomers find a new “fossil galaxy” deep in the Milky Way

An international team of researchers has found a “fossil galaxy” deep within our Milky Way. This object could not be found due to its inconvenient location.

Scientists working with data from an experiment to study galactic evolution at Sloan Digital Sky Surveys Apache Point Observatory (APOGEE) have discovered a “fossil galaxy” hidden deep in the Milky Way. This data, published in the Journal of the Royal Astronomical Society, could change the understanding of how the Milky Way grew into the galaxy that researchers can observe today.

Scientists believe that this “fossil galaxy” collided with the Milky Way ten billion years ago when our galaxy was still in its infancy. Astronomers named her Hercules after an ancient Greek character who received the gift of immortality.

APOGEE does this by taking spectra of stars in near-infrared light instead of visible light dimmed by dust. Over ten years of observations, APOGEE has measured the spectra of more than half a million stars throughout the Milky Way, including its core, previously obscured by dust.

The researchers also noted that Hercules’ remnants account for about a third of the Milky Way’s spherical halo. However, they found it odd that Hercules’ stars and gas accounted for such a large percentage of the galactic halo, but they had not noticed it before. The answer lies in the fact that it is located deep within the Milky Way.

“To find a fossil galaxy like this, we had to look at the detailed chemistry and motion of tens of thousands of stars,” said Ricardo Schiavone of Liverpool John Moore University (LJMU) in the UK, one of the main members of the research team. “This is especially difficult for stars in the center of the Milky Way since they are hidden from view by clouds of interstellar dust. APOGEE allows us to cut through this dust and look deeper than ever before into the heart of the Milky Way.”

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