snail shell-like pattern tagged posts

Artist’s impression of a perturbation in the velocities of stars in our Galaxy, the Milky Way, that was revealed by ESA’s star mapping mission, Gaia. Credit: ESA, CC BY-SA 3.0 IGO

ESA’s star mapping mission, Gaia, has shown our Milky Way galaxy is still enduring the effects of a near collision that set millions of stars moving like ripples on a pond. The close encounter likely took place sometime in the past 300-900 million years. It was discovered because of the pattern of movement it has given to stars in the Milky Way disc – one of the major components of our Galaxy.

The pattern was revealed because Gaia not only accurately measures the positions of more than a billion stars but also precisely measures their velocities on the plane of the sky...