The discovery of the fossil galaxy deep inside the Milky Way is the remnant of a star cluster that collided with our own 10 billion years ago and was absorbed into its hollow, astronomers claim.
- Thousands of experts analyze his composition and speed
- This allows them to detect hidden remnants of galactic collisions
- The ‘fossil’ near the center of the Milky Way has been dubbed Heracles
- Large galaxies are formed through such collisions and fusion processes
Another galaxy has become our own after colliding with the Milky Way about 10 billion years ago,
Liverpool experts found the galactic ‘fossil’ in the depths of the Milky Way by analyzing the motions and composition of thousands of stars.
This cosmic remnant – dubbed ‘Heracles’ as the protagonist of ancient Greek mythology – accounts for one third of the spherical ‘hollow’ of the star and gas Milky Way.
The remnants of several old galaxies have already been spotted in the outer hollows of the galaxy – in fact, galaxies in shape are formed by attachment.
However, the search for the earliest attachments requires an analysis of the most central part of the Milky Way’s hollow – such as the galaxy’s disks and bulges buried deep inside.
Another galaxy has become our own after colliding with the Milky Way about 10 billion years ago. The red rings represent the position of the fossil galaxy
“It’s great to draw attention to that galaxy,” said Ricardo Schiavone, a paper writer and astronomer at Liverpool’s John Moores University.
“In a cosmic context, it’s really small – only 100 million stars – but about half the mass of the entire Milky Way.”
In their study, Dr. Schiavone and colleagues analyzed data collected by the Apache Point Observatory Galactic Evolution Test – or ‘Apogee’ project, which collected data on more than half a million stars across the Milky Way.
“To find a fossil galaxy like this, we need to look at the detailed chemical makeup and motion of thousands of stars,” explained Dr. Schiavone.
‘This is especially difficult for stars in the center of the Milky Way, because they are hidden by interstellar dust clouds.’
“Apogee allows us to pierce that dust and see the heart of the galaxy deeper than ever.”
Liverpool experts found the galactic ‘fossil’ in the depths of the Milky Way by analyzing the motions and composition of thousands of stars. This cosmic relic – dubbed ‘Heracles’ as the protagonist of ancient Greek mythology – depicts accounts of one-third of the circular ‘hollow’ of stars and gas in the Milky Way, the location of the Heracles as seen across the Milky Way plane.
“Of the tens of thousands of stars we’ve seen, hundreds of them had a variety of chemical compositions and velocities,” said Danny Horta, author of the Liverpool John Moores paper.
‘These stars are so different that they could only come from another galaxy.’
‘By studying them in detail we can trace the exact location and history of these fossil galaxies,’ he explained.
Based on their findings, the team concludes that the collision between Heracles and the Milky Way was ‘certainly a major event in the history of our galaxy.’
They added that this made the Milky Way unusual among its peers, because ‘most of the similarly large spiral galaxies were very quiet in early life.’
“As our cosmic home, the Milky Way is already special to us, but this ancient galaxy buried in it has made it even more special,” said Dr. Schiavone.
The full findings of the study were published in The Monthly Notices of the Royal Astronomical Society.