Monster mash-up: Milky Way was shaped by galactic collision 10 billion years ago, scientists say
- The collision created the cloud of stellar rubble that makes up the Milky Way’s halo, equivalent to 600 million Suns
The Milky Way’s signature halo is mostly stellar rubble from a cosmic collision 10 billion years ago with another galaxy a quarter of its size, scientists reported Wednesday.
The slow-motion crash with Gaia-Enceladus – named after the giant of Greek mythology born of Earth and Sky – not only provided the halo’s raw material, equivalent to 600 million Suns, it also filled out our galaxy’s distinctive disk, they reported in the journal Nature.
“We have basically unravelled the formation of the Milky Way,” said lead author Amina Helmi, an astronomer at the University of Groningen’s Kapteyn Astronomical Institute.
“The merger led to what we now call the halo of our galaxy, and – because it was so massive – to the puffing up of the disk that was already present at the time.”
“We didn’t expect to find that most halo stars have a shared origin,” she added.