Black holes are seemingly invisible spaces where there are strong forces of gravity that prevent light from getting out. Here, matter has been condensed into a tiny space making the gravity pull very strong. Most times, this happens when a star is dying. Because they are invisible, only space telescopes with special tools can be used to see black holes.
When two black holes come into contact with each other, they are moving near the speed of light and they cause ripples in space time which can make things look like a fun house mirror. Nothing can be able to escape the pull of a black hole, not even light. Because of the force, anything that comes in its wake will be ripped apart completely.
A group of scientists from the Laser Interferometer Gravitational-Wave Observatory (LIGO) announced that they had detected gravitational waves. These stemmed from the collision in another galaxy of two supermassive black holes producing ripples in space. More supermassive black holes have been discovered since then.
The most recent pair of black holes has been spotted recently.by scientists from Pune University, India. They are in a galaxy called NGC 7674 and are estimated to be about 400 million light-years away. The black holes are about a million times larger than the sun and are orbiting quite close to one another. Such an orbit is small given their size and the fact that only one single light-year separates them from each other
This means that they are constantly generating gravitational waves which give off some of their energy. Millions of years later, they will continue to spiral close to each other until they finally collide and create a gravitational signal. The answer to what follows after two black holes collide is simply, one massive black hole. The longer version of it is still being worked on by supercomputer-enabled scientists.
When two black holes are approaching each other, the gas and dust orbiting around them merge into one towering force that extends above the accretion disk’s center. When they actually merge, this creates a powerful force stronger than all the light that emanates from galaxies and stars at any time. Models are still being worked on to get an almost similar image of what this would like.