Huge "Structure" of Satellites Found Orbiting Milky Way

A huge "structure" of satellite galaxies and star clusters has been found wheeling around the Milky Way, according to a new study.

The discovery surprised scientists, in part because the structure might spell trouble for theories of dark matter, the mysterious, invisible substance that's thought to make up about 23 percent of the mass in the universe.

The finding is only the latest to question dark matter's existence—last week, for instance, astronomers announced that they'd failed to detect dark matter in the sun's neighborhood, even though the substance should be there, according to accepted theory.