THE Milky Way galaxy violently devoured a neighbouring cluster of stars and planets approximately 10 billion years ago, astronomers have shockingly announced.
Galaxies like our Milky Way frequently collide with one another when attracted by their powerful gravitation pull. The galactic mergers are mostly harmless – there is too much empty space between planets and stars for them to connect – but it shows how dynamic the cosmos is. In March 2019, for instance, NASA’s Hubble Space Telescope witnessed the merger of two galaxies collectively dubbed NGC 6052. And now, for the first time, astronomers at the Institute of Astrophysics of the Canary Islands (IAC) have demonstrated how the Milky Way took part in a galactic feast of its own 10 billion years ago.
In a study published on Monday in the journal Nature Astronomy, scientists identified a “violent collision” in the Milky Way’s earliest days.
The IAC said: “Thirteen thousand million years ago stars began to form in two different stellar systems which then merged: one was a dwarf galaxy which we call Gaia-Enceladus, and the other was the main progenitor of our galaxy, some four times more massive and with a larger proportion of metals.
“Some ten thousand millions years ago there was a violent collision between the more massive system and Gaia-Enceladus.
“As a result, some of its stars and this of Gaia-Enceladus were set into chaotic motion, and eventually formed the halo of the present Milky Way.”
After that, the IAC said there were more “violent bursts of star formation” until about six billion years ago.
As soon as the stellar gas settled into the galactic disc, they formed the Milky Way’s so-called thin disc.
The thin disc is a feature of spiral galaxies like the Milky Way and contains star clusters, stellar dust and gas.
Because of our solar system’s position in the galactic plane, astronomers have been able to study the disc in great detail.
And because thin discs are home to vast quantities of dust and gas, they are often considered a breeding ground for new stars to form.
So, how exactly did the astronomers come to these conclusions about the Milky Way?
Using the incredible Gaia space telescope, the IAC study charted the position, brightness and distance of nearly a million stars in the Milky Way.
This allowed the astronomers to compare and contrast stars within the galaxy’s thick disc – an area around the thin disc – and the galaxy’s glowing halo.
Stars within the halo were found to be bluer and had a smaller quantity of metals in their composition.
The opposite was true for “redder” stars in the thick disc.
This difference lead the researchers to believe the bluer stars were the remnants of a dwarf galaxy – Gaia-Enceladus.
The IAC said: “These findings, with the addition of the predictions of simulations which are also analysed in the article, have allowed the researchers to complete the history of the formation of the Milky Way.”