The most amount of matter you can possibly think of. Condense it in to the smallest space, and you have a black hole.
The destroyer of suns, the gravitational pull of the galaxies, the one place in the universe where no light can ever be.
Scientists theorize that the smallest black holes are the size of atoms, while they have the mass of a large mountain. But one of the most fascinating things about them, and what most people do not know, is that black holes are invisible. Only space telescopes with special tools can help to find them. However, the fact that they are invisible is not the topic of this blog post. Rather, I will be going into how awesomely destructive they are, and why you should care.
Scientists believe that the smallest black holes appeared when the universe began. However, the largest black holes are the result of dying stars.
When a star reaches the end of its life cycle, it has a few options depending on its size. Stellar black holes are created when the center of a very big star collapses on itself, causing a supernova (a massive explosion) that shoots part of the star into space. However, supermassive black holes (black holes that have masses equivalent to approximately 1 million suns together), the topic of this post, are at the centers of galaxies and are thought to be made at the same time as the galaxies they are in.
For many years, astronomers had no evidence for the existence of supermassive black holes, and even now there are only a few that are confirmed (with most being too far away to be observed). While they were trying to find evidence of their existence, the most compelling evidence were in the form of quasars (a massive and extremely remote celestial object, emitting exceptionally large amounts of energy, and typically having a starlike image in a telescope). The only mechanism capable of producing such enormous amounts of energy is the conversion of gravitational energy into light by a massive black hole. More recently, direct evidence has come from observations of materials orbiting the centers of galaxies. Their highly accelerated orbital velocities can only be easily explained by their acceleration through a massive object with huge gravitational energy within a small region of space. This most directly explains the composition of galaxies, as there have been evidence of large positive correlations of size of supermassive black hole to size of galaxy, indicating that some of the largest galaxies in the universe (the Milky Way and Andromeda galaxies) are only able to be held together by supermassive black holes at their centers.
That being said, why should you care?
Not only are they super cool, but you should care for the same reason that you should care about the event discussed in my last post. The eventual collision of the Andromeda and Milky Way galaxies is going to directly affect our descendants, the human race, and Earth as a whole. Because of the future of our planet, the presence of supermassive black holes in the universe is important, and further study of them is necessary to ensure complete predictions.
https://www.nasa.gov/audience/forstudents/k-4/stories/nasa-knows/what-is-a-black-hole-k4.html
http://astronomy.swin.edu.au/cosmos/S/Supermassive+Black+Hole
https://www.cosmotography.com/images/supermassive_blackholes_drive_galaxy_evolution_2.html