Astronomers may have discovered an extreme pair of light-spewing black holes that are spiraling toward an enormous collision — the effects of which could be felt in the next century.

Using decades of radio telescope observations, the astronomers studied an ultrabright object that was previously thought to be a blazar — a glowing core of a galaxy usually powered by a black hole — some 500 million light-years from our solar system. The observations revealed a hidden jet of energy that suggests the intensely bright object is actually two black holes on the verge of colliding, perhaps less than 100 years from now.