Using black holes to measure the Universe's rate of expansion

Using black holes to measure the Universe's rate of expansion: By adding together measurements of the amount of energy being emitted from the vicinity of the black hole to the amount of radiation which reaches Earth, it's possible to infer the distance to the black hole itself and the time in the history of the universe when the energy was emitted.
Getting an accurate estimate of the radiation being emitted depends on the properties of the black hole. For the specific type of black holes targeted in this work, the amount of radiation emitted as the object draws matter into itself is actually proportional to its mass, say the researchers. Therefore, long-established methods to measure this mass can be used to estimate the amount of radiation involved.