Newfound 'Kraken merger' may have been the biggest collision in Milky Way's history
By Brandon Specktor - Senior Writer 7 hours ago
Our galaxy was built on collisions — and this one may be the largest ever.
A globular cluster (yellow) glows in the Large Magellanic Cloud, one of the Milky Way's smaller satellite galaxies. Astronomers studied clusters like these to recreate the ancient mergers that made the Milky Way what it is.
(Image: © NASA, ESA, and Martino Romaniello European Southern Observatory, Germany)
The Milky Way contains more than 100 billion stars, but it didn't come by them all honestly. At least a dozen times over the last 12 billion years, the Milky Way collided with a neighboring galaxy and devoured it, swallowing up that neighbor's stars and mixing them into an ever-growing stew of pilfered suns.
With each galactic merger, the shape, size and motion of our galaxy changed forever, ultimately becoming the iconic spiral we recognize today. Now, in a recent study published in the October 2020 issue of the journal Monthly Notices of the Royal Astronomical Society, researchers have attempted to unwind that spiral. Using artificial intelligence (AI) to match distinct clusters of stars by their ages, motions and chemical compositions, the team found evidence of five large-scale galactic mergers (each involving 100 million stars or more) dating back more than 10 billion years — including one ancient collision that has never been described before.
This newfound crash with the so-called Kraken galaxy not only helps fill in the Milky Way's mysterious family tree, but could also help astronomers piece together what our galaxy looked like in its earliest days, the study authors said.
"The collision with Kraken must have been the most significant merger the Milky Way ever experienced," lead study author Diederik Kruijssen, an astronomer at the University of Heidelberg in Germany, said in a statement. "The merger with Kraken took place 11 billion years ago, when the Milky Way was four times less massive [than today]. As a result, the collision must have truly transformed what the Milky Way looked like at the time."
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https://www.livescience.com/milky-way-ancient-kraken-merger.html
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