When black holes absorb stars, the generated energy heats the dusty sphere.
Imagine yourself heading into the valley to watch the fireworks. The roar from the explosion of gunpowder is likely to be accompanied by an echo produced by one or more sound waves reflected from the sides of the valley. Knowing how fast sound waves travel through the air, you can calculate how far the sides of the valley are from the scene of the fireworks explosion. To do this, you need to detect how much time passes between the intervals from the explosion sound and the return of the echo.
It sounds like a normal physics lesson, but astrophysics has applied a similar principle, but in the most extreme conditions that may exist in our Universe. Namely, in supermassive black holes located in the centers of galaxies. But in this case, the firework is a star absorbed by the black hole, and the sides of the valley are the surrounding rings of dust that are beyond the reach of the gravitational influence of the black hole.
Supermassive black holes “weigh” millions and billions of times the mass of our Sun and are very effective in absorbing stars that are getting too close. When the unfortunate star wanders within the distance, called the “Roche radius (limit),” the tidal shift is directed at this star with such force that it stretches to self-forgetting. This process is known as “tidal stellar destruction”. Star matter stretches and stretches, sucking into the horizon of a black hole event. When this happens, a powerful flash is generated, releasing X-ray and ultraviolet light into space, which can be observed from Earth. If this ionizing radiation falls into a cloud of dust around a black hole, then it will evaporate. But then the energy from this radiation will begin to be absorbed, and later re-emitted in the form of infrared radiation. It is this remission of infrared radiation, acting as an echo, that occurs some time after the initial flash.
Using the data found by the Wide-Angle Infrared Reviewer (WISE), two groups of researchers were able to obtain an amazing amount of information about the amount of space surrounding distant supermassive black holes, and also revealed some nuances of these catastrophic explosions.
Before the WISE mission ended in 2011, the telescope created an infrared map of the universe every 6 months. After finding candidates for tidal star destruction in the centers of galaxies, WISE data can be used to see how the flash affected the black hole's dust ring and how heat evolved. To do this, use a technique known as “photo reflection” or “light echo”. With this information, scientists will be able to determine how far the dust clouds were located from the black hole and how much energy was released during the outbreak. “Our research confirms that there is dust there, and we can use it to determine how much energy was generated when a star was destroyed,” said Varuzhan Gordzhian, an astronomer at NASA's Jet Propulsion Laboratory in Pasadena, California.
In addition, they were able to obtain information about the structure of the surrounding dust. It was blown into a “spotted spherical web of dust, located a few trillion miles (half a light year) from a black hole,” said a NASA press release.
“The black hole has destroyed everything between itself and this dusty shell,” said Siert van Velzen of John Hopkins University in Baltimore. “It’s as if the black hole decided to use a flame to clean out its room.”