When you buy through links on our articles, Future and its syndication partners may earn a commission.Credit: Robert Lea (created with Canva)Astronomers have used a technique called echo mapping to detect hints that supermassive black holes, such as the cosmic titan at the heart of the Milky Way, known as Sagittarius A* (Sgr A*), are surrounded by dense clouds and clusters of dark matter. The research could teach us more about this mysterious substance and the environments around supermassive black holes.Dark matter is the universe’s most mysterious stuff, outweighing ordinary matter in the cosmos by a ratio of five to one — but remaining effectively invisible because it doesn’t interact with electromagnetic radiation, including the light we use to see. The only way scientists can even infer the presence of dark matter is via its interaction with gravity, and the impact that this interaction has on objects made of traditional matter like stars. For instance, the gravitational effect of dark matter allows stars at the edges of galaxies to whip around at much greater speeds while not flying loose than the visible matter of those galaxies would allow.AdvertisementAdvertisementThis team decided to test the gravitational influence of dark matter at the hearts of galaxies, environments dominated by supermassive black holes which can have masses millions or even billions of times that of the sun. Ordinary matter around 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 …
