Between 2 and 3 billion years ago, a dramatic event unfolded in our galaxy. A burst of star formation may have taken place and it could be responsible for up to half of the stars currently present in the galactic disk, the thin region of the galaxy that's home to the Solar System.
As reported in Astronomy & Astrophysics, researchers found evidence that between 6 and 10 billion years ago, the overall star formation rate declined, as has been seen throughout the universe. But roughly 5 billion years ago, it picked up the pace once again, reaching its peak in the star-forming burst.
The team suspects that a satellite galaxy might have been cannibalized by the Milky Way. This event would have brought new material to our galaxy that could be used to make stars. It wouldn’t be the first time scientists have found evidence of the Milky Way gobbling up a neighboring dwarf galaxy.
“The time scale of this star formation burst together with the great amount of stellar mass involved in the process, thousands of millions of solar masses, suggests the disc of our galaxy did not have a steady and paused evolution, it may have suffered an external perturbation that began about 5 billion years ago,” lead author Roger Mor, from the Institute of Cosmos Sciences of the University of Barcelona, said in a statement.
The discovery was only possible thanks to vast and high-quality data provided by the Gaia observatory. The European Space Agency's mission has been collecting detailed information about billions of stars in the Milky Way (and slightly out of it), which has allowed researchers to construct accurate maps of stellar distributions across our galaxy.
“We have been able to find this out due to having – for the first time – precise distances for more than 3 million stars in the solar environment,” explained Mor. “Thanks to these data we could discover the mechanisms that controlled the evolution more than 8-10 billion years ago in the disc of our Galaxy, which is not more than the bright band we see in the sky on a dark night and with no light pollution.”
Understanding the evolution of the Milky Way has an impact on both the smaller and wider scales. It can certainly help us explain how the Solar System came to be. But it can also help us understand the wider universe. Our galaxy is an ideal testing ground for cosmological models and can provide new insights into how these models work on bigger scales.