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Scientists selecting data collected by the Apache Point Observatory of the Sloan Digital Sky Survey Galactic Evolution Experiment (APOGEE) have discovered what they call a “fossil galaxy” hidden deep in the Milky Way. Scientists say the proposed fossil galaxy may have collided with the Milky Way 10 billion years ago, when our galaxy was still in its infancy. The fossil galaxy was called Heracles.
The remains of Heracles represent about a third of the spherical halo of the Milky Way. As for why no one noticed that there was a remnant of an ancient galaxy within our galaxy, it is because of the depth within the Milky Way. Researcher Ricardo Schiavon of Liverpool John Moores University says that to find the fossil galaxy, the researchers had to examine the detailed chemical composition and movement of tens of thousands of stars.
Looking at so many stars is incredibly difficult in the center of the Milky Way because they are hidden from view by giant clouds of interstellar dust. APOGEE is perfect for this type of investigation as it allows astronomers to peer through that dust and look deeper into the heart of our galaxy than ever. APOGEE allows scientists to look through interstellar dust using near infrared light, which is not obscured by dust like visible light is.
Finding unusual stars in the heart of the Milky Way is compared to finding needles in a haystack. To separate the stars belonging to Heracles from the stars of the original Milky Way, the team used both the chemical composition and speed of the stars measured by APOGEE.
The researchers say that of the tens of thousands of stars studied, a few hundred had surprisingly different chemical compositions and speeds. The researchers say those stars were so different from the stars in the Milky Way that they could only have come from another galaxy. A detailed study could allow researchers to trace the precise location and history of the fossil galaxy.
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