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This image shows the Milky Way as seen from Earth. The reddish rings highlight where the stars of Heracles linger in our galaxy.
Danny Horta-Darrington (Liverpool John Moores University), ESA / Gaia and SDSS
Our Milky Way galaxy had a dramatic childhood. Astronomers have unveiled a new chapter in his memoir with the discovery of a probable “fossil galaxy” hidden close to his heart.
The proposed fossil galaxy is called Heracles for the Greek hero. It probably got tangled with the Milky Way about 10 billion years ago when our galaxy was small.
“Stars originally belonging to Heracles account for about a third of the mass of the entire Milky Way halo today, which means this recently discovered ancient collision must have been a major event in the history of our galaxy,” says Sloan Digital Sky Survey. (SDSS) said in a statement Thursday. The SDSS was involved in the research.
This illustration shows how Heracles fits into the heart of the Milky Way if viewed from above. The yellow dot indicates our sun.
Danny Horta-Darrington (Liverpool John Moores University), NASA / JPL-Caltech and SDSS
A research team led by Liverpool John Moores University (LJMU) graduate student Danny Horta published an article on Heracles in the Royal Astronomical Society’s Monthly Notices this week.
To find Heracles, the team spotted stars that didn’t match those in the Milky Way. “These stars are so different that they could only come from another galaxy. By studying them in detail, we could trace the exact location and history of this fossil galaxy,” Horta said.
We have seen evidence of dramatic galactic mergers in the Milky Way’s deep past. Recent studies have looked at a time when our galaxy engulfed a dwarf galaxy called Gaia-Enceladus.
Heracles was particularly elusive, as the signs of his existence are obscured by clouds of interstellar dust. The research team used the SDSS Apache Point Observatory Galactic Evolution Experiment (APOGEE) to peer through this mess using near-infrared light. “To find a fossil galaxy like this, we had to examine the detailed chemical composition and movements of tens of thousands of stars,” said study co-author and LJMU astrophysicist Ricardo Schiavon.
The Milky Way may not be finished with its collision paths between galaxies. A Milky Way-Andromeda galaxy crash lurks billions of years into the future. It’s hard to be a galaxy. Sometimes you are the Milky Way, eating them. Sometimes you are Heracles, the one who is swallowed.
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