Scientists Estimate Black Hole Size By Observing Matter Consumed

Researchers around the world are endeavoring to learn more about one of the most mysterious phenomenons in the universe – black holes. Scientists at the University of Illinois are attempting to determine the size of the black hole by observing how it consumes matter in the accretion disk around it. Researchers conducted a new study that has shown changes in brightness that are observed during the active feeding of supermassive black holes is directly related to their mass.

Supermassive black holes are some of the most massive objects in the universe, with masses of millions or billions of times that of the sun. Typically, supermassive black holes are found in the center of galaxies, and since they emit very little light, scientists have to find them based on their gravitational influence on stars and gas near them. Researchers believe that in the early universe, supermassive black holes were rapidly growing and were consuming material at high rates resulting in the emission of enormous amounts of radiation.

In some instances, they emitted such massive amounts of radiation that they glowed brighter than the entire galaxy around them. For the new study, researchers observed light from a supermassive black hole actively accreting and noted that the observed light was not constant. Why the brightness of the light isn't a constant is currently unknown.

While the exact cause is unknown, scientists know that accreting supermassive black holes display flickering over wide-ranging timescales varying from hours to decades. By compiling a large data set on actively feeding supermassive black holes, the team was able to study the variability of flickering and identify a timescale for pattern changes that closely correlate with the mass of the supermassive black holes.

The data was compared to results gathered from accreting white dwarfs, which are remains of stars similar to the sun. They found the same time scale and mass relation is true for white dwarfs. Study researchers found light flickers are caused by random fluctuations in the feeding process of the black hole, and the flickering pattern can be quantified by measuring the power of light variability as a function of timescale. The study's main takeaway is that the variability of brightness happens at longer intervals the more massive a black hole is.