A group of Japanese astronomers has described what blanets, planets in orbit around supermassive black holes at the center of galaxies, can look like.
When we imagine a black hole, with the help of cinema. it’s terrifying. An immense abyss devouring everything around it. But in essence, a black hole is a body that exerts gravity, just like a star, and this makes it possible for planets to orbit black holes, thousands of them. Japanese researchers has given name to the planets around black holes ‘Blanets’.
A team of astronomers from the University of Kagoshima in Japan has given a new name to these planets that revolve around black holes. They are called “blanets” (from black planets, black planets). The prepress study published in The Astrophysical Journal looks at the possible mechanisms by which dust can form gigantic eddies around a black hole, and aggregate to form planets in a “safe zone.”
Black holes are the result of the collapse of a star. As fusion reactions inside a star convert hydrogen into increasingly heavy elements, the star’s density increases. After several cycles of explosions and contractions, what remains is an incredibly dense remnant. If the original mass of the star was large enough, the density becomes so high that light cannot escape the gravitational field. That is a black hole.
Black holes are only a few kilometers in radius, but they can have a mass between 10 and 100 times that of the Sun. As they engulf other celestial bodies, they increase in mass and size. They exert such a great gravitational attraction that stellar systems are known in which one or more stars orbit around a black hole.
Planets are formed when the dust clouds around a star are condensed by gravity. Japanese astronomers propose an alternative: there are planets that form directly around active supermassive black holes at the heart of galaxies.
These black holes are surrounded by a disk of dust and gas that swirls as it rushes into the gravitational well. This situation is not very different from the one that occurs around a star during its formation. At a sufficient distance from the black hole, dust can aggregate into thousands of planets orbiting the black hole.
The formation of these planets is determined not only by distance, but by the speed at which the dust whirlwind revolves around the black hole. If it is too fast, the dust aggregates will collide with each other so hard that they will disperse rather than clump together, and will not be able to form larger bodies. But according to the Japanese team’s calculations, bodies between 20 and 3,000 times the mass of Earth could form at a distance of 13 light-years from the black hole.
These are all calculations, because at the moment it is not possible to directly detect these objects. The “blanets” join a growing family of stellar objects with strange names: recently the “lunar moons” (moon moons) have been defined, which are as their name suggests, moons that have other moons revolving around them, and the “ploonets” (from “moon” and “planet”) which are moons of large planets that are ejected from their orbit and begin to rotate around the star, becoming another planet.