Before the Merge: Spiraling Black Holes

Artist's conception shows two merging black holes similar to those detected by LIGO. The black holes—which will ultimately spiral together into one larger black hole—are illustrated to be orbiting one another in a plane. The black holes are spinning in a non-aligned fashion, which means they have different orientations relative to the overall orbital motion of the pair. There is a hint of this phenomenon found by LIGO in at least one black hole of the GW170104 system.