Dark matter

The surprising discovery of a massive, Milky Way–size galaxy that is made of 99.99 percent dark matter has astronomers dreaming up new ideas about how galaxies form.

The astrophysicist Tracy Slatyer is searching for faint wisps of dark matter annihilating in the early universe — and perhaps in hiding places closer to home.

The physicist Asimina Arvanitaki is thinking up ways to search gravitational wave data for evidence of dark matter particles orbiting black holes.

The search for exotic new physical phenomena is being led by huge experiments like the Large Hadron Collider. But at the other end of the spectrum lie tabletop experiments — small-scale probes of hidden dimensions, dark matter and dark energy.

In the new, free-for-all era of dark matter research, the controversial idea that dark matter is concentrated in thin disks is being rescued from scientific oblivion.

The irreversibility of time may be a clue as to what makes up the universe’s dark matter.

The physicist James Bullock explains how a complicated “dark sector” of interacting particles may illuminate some puzzling observations of the centers of galaxies.

For five years physicists have been tantalized by possible evidence of dark matter in the Milky Way’s center. But new results from small satellite galaxies have complicated the story.

Katherine Freese, a physicist who will soon lead the Nordic Institute for Theoretical Physics, reflects on the hunt for dark matter and how dark matter heating may have produced the first stars.