When a black hole erupts, part of the light may have to orbit the black hole once, twice or even thousands of times until it can be released from the massive gravitational force of the black hole. Because of this a number of small “ghost” eruptions can be seen after the eruption. According to scientists, observations of these ghost eruptions could provide a new way to measure the masses and rotation speeds of black holes.

This method could only work with fast spinning black holes because the speed increases the possibility that a single foton stays orbiting the black hole for a while. As an example, a fast spinning black hole with a mass ten times bigger than the mass of the Sun, could provide even 1400 ghost eruptions in a second.

Anyhow, ghost eruptions are very difficult or even impossible to see because their intensity is just a fraction of the main eruption. Additionally the eruptions are born in the disc of matter, which probably would suck all the atoms circulating.

Read also my previous news post on Galaxy Black Hole Fires at Neighboring Galaxy.

Read more about this news in New Scientist.

Illustration: NASA/Dana Berry/SkyWorks Digital