Astronomers have used a way referred to as echo mapping to detect hints that supermassive black holes, such because the cosmic titan on the coronary heart of the Milky Manner, often called Sagittarius A* (Sgr A*), are surrounded by dense clouds and clusters of darkish matter. The analysis might educate us extra about this mysterious substance and the environments round supermassive black holes.
Darkish matter is the universe’s most mysterious stuff, outweighing atypical matter within the cosmos by a ratio of 5 to at least one — however remaining successfully invisible as a result of it does not work together with electromagnetic radiation, together with the sunshine we use to see. The one method scientists may even infer the presence of darkish matter is by way of its interplay with gravity, and the affect that this interplay has on objects manufactured from conventional matter like stars. As an illustration, the gravitational impact of darkish matter permits stars on the edges of galaxies to whip round at a lot better speeds whereas not flying free than the seen matter of these galaxies would enable.
This staff determined to check the gravitational affect of darkish matter on the hearts of galaxies, environments dominated by supermassive black holes which may have lots tens of millions and even billions of instances that of the solar. Strange matter round these supermassive black holes is often very visible, especially when spiraling into the maw of one of these cosmic titans from a flattened cloud called an accretion disk. This is because the gravitational influence of those black holes generates immense amounts of friction, causing them to grow brightly. That wouldn’t work for dark matter; it can’t feel friction because it doesn’t interact with itself or with ordinary matter, and it can’t glow because it doesn’t absorb or emit light.
Clearly, dark matter can’t be spotted around supermassive black holes even using the most advanced telescopes such as the Event Horizon Telescope (EHT), which has captured glowing rings of material around Sgr A* and around a more distant supermassive black hole that rules the heart of the galaxy Messier 87 (M87).
While discussing the problem of detecting dark matter around supermassive black holes, Mayank Sharma, a physics graduate student at Virginia Polytechnic Institute and State University (Virginia Tech), hit on an interesting solution.
“We could actually test this prediction using a technique in astronomy, which allows you to measure the distance to the surrounding gas by looking for echoes of light,” Sharma said in a statement. The method Sharma refers to is “reverberation mapping,” and it has change into a trusted technique of figuring out the mass of black holes.
Echoes of darkish matter
Reverberation mapping relies upon the truth that as matter falls right into a black gap, it releases a burst of vitality that causes the accretion disk it comes from to pulse. This pulse of sunshine travels from the accretion disk to gasoline within the wider setting of the black gap. This gasoline absorbs that gentle and likewise pulses, with this secondary pulse serving as an echo of the primary.
The team applied their method to 14 different galaxies, finding in five cases that mass increases moving away from the central black hole in a way that couldn’t be accounted for by visible matter alone. Despite the early success of this research, it far from proves that supermassive black holes are indeed gathering places for dark matter. The team’s findings do point an interesting way forward for the investigation into the universe’s most mysterious substance and its most mysterious regions.
“These galaxies are definitely showing a hint that there is extra material that cannot be explained by just the supermassive black hole,” Sharma said. “The prospects are exciting.”
The team’s research was published in the journal Physical Review D.
