Astronomers discovered that the star Gaia17bpp gradually brightened over a 2 1/2-year period. But follow-up analyses revealed that the star itself wasn’t changing. Instead, it’s likely part of a rare type of binary system. Its apparent brightening was the end of a years-long eclipse by an unusual, “dusty” stellar companion.
Clues to a black hole’s origins can be found in the way it spins. This is especially true for binaries, in which two black holes circle close together before merging.