Let's just say it suggests an imminent galactic collision.
Astronomers knew that the edges of the Milky Way warped, wobbled, and swayed like a bowl of jelly – but no one knew why.
But according to a new study using data collected by the European Space Agency's stellar mapping satellite Gaia, the Milky Way's disk of hundreds of billions of stars is warping as it slowly collides with a smaller neighboring galaxy.
To come to this conclusion, a team of physicists from the Italian National Institute of Astrophysicists in Turin analyzed how 12 million giant stars move along our Milky Way, as observed by the ESA space telescope.
Their study, as detailed in an article published in the journal Nature Astronomy, suggests that the unique curvature of the edges of our galaxy is caused by a 'recent or ongoing collision with a companion galaxy'.
“We measured the strain rate by comparing the data with our models,” said Eloise Poggio, lead author of the Turin Astrophysical Observatory study. “Based on the speed obtained, the distortion will complete one revolution around the center of the Milky Way in 600-700 million years.”
It is significantly slower than stars, including the Sun, travel all the way around the center of the Milky Way. Previous theories have tried to explain the deformation by suggesting that the inner disk of the galaxy spins like an oblique top, leaving ripples. This slow rotation rate belies them, the researchers say.
So which galaxy is slowly colliding with ours? Astronomers speculate it could be Sagittarius, a dwarf galaxy that orbits the Milky Way.
