Quasars are some of the brightest objects in the Universe—powerful jets emanating from supermassive black holes as they gorge on gas. However, their light is irregular, both varying in brightness between different quasars and fluctuating in time. A new analysis may have found regularities within those fluctuations, which might allow them to be used as standard candles: objects whose intrinsic properties are known, and therefore can be used to measure large distances in space.

The researchers then fitted straight lines to periods of flux increase and decrease longer than 90 days. They found the slopes of these lines to be nearly the same. While the amount and duration of the change in flux differed, the rate of change in flux was similar. (This is analogous to comparing several cars with different top speeds, but the same acceleration capabilities). The data points were scattered, but still showed a clear trend: the quasars all seemed to vary in their light output at a certain rate, independent of their distance from Earth. [Read more….]

Could quasars be standard candles?