(source: gemini, image by unknown) What are Black Holes     While not obvious, Black Holes are actually the remains of some of the most ancient giants of the cosmos, Red Giant stars.  At the end of the stars life, mass from the star starts to eject and gets more and more unstable, the source of these problems is the slowing nuclear fusion. which is the main force keeping the star from imploding under it's own weight.  As the star runs out of gas the force keeping the star together start to wane, eventually reaching a point where it can't support the immense weight of itself, and the ultimate end of this trend is a supernova and possibly a black hole.        When one thinks of Black Holes, a giant sphere of darkness of the darkest black is what often comes to mind, while this is a good way of thinking about it, it is incorrect.  Black holes are in fact invisible, because the gravity they produce is so strong that not even light can escape it.  Since light can't bounce off of the black hole and then enter your eye nothing can be seen as the image shows, it even distorts what the space around it looks like.