There's a "dark impactor" blasting holes in our galaxy. We can't see it. It might not be made of normal matter. Our telescopes haven't directly detected it. But it sure seems like it's out there.
"It's a dense bullet of something," said Ana Bonaca, a researcher at the Harvard-Smithsonian Center for Astrophysics, who discovered evidence for the impactor.
Bonaca's evidence for the dark impactor, which she
presented April 15 at the conference of the American Physical Society in Denver, is a series of holes in our galaxy's longest
stellar stream, GD-1. Stellar streams are lines of stars moving together across galaxies, often originating in smaller blobs of stars that collided with the galaxy in question. The stars in GD-1, remnants of a "
globular cluster" that plunged into the Milky Way a long time ago, are stretched out in a long line across our sky.
