This video was constructed using data derived from observations by ESA’s Gaia satellite. It starts with the stars shown in their positions as of a bit more than a million years ago, tracks the changes in their positions up to the present day, and ends with a view of the sky as seen by Gaia between 2014 and 2015. The trajectories highlighted in yellow show six unusual stars that are moving through the Milky Way at hypervelocities of several hundred km/s. Most likely, these stars’ high speeds are the results of past interactions with the supermassive black hole that sits at the center of the galaxy. Analysis of their paths provides information about the gravitational field of the Milky Way from the center to its outskirts.
One of the six stars (numbered 1) is moving at over 500 km/s, which is above escape velocity for the galaxy. It will eventual fly off into intergalactic space. The other five stars are somewhat slower and are still bound to the galaxy.
Video Credit: ESA