Black holes are the Universe’s ultimate garbage disposals: Stuff falls in, and never gets back out. It can’t. To get out, you’d have to travel faster than the speed of light, which (as far as we know) is impossible.
Black holes grow by consuming matter, and in the centers of galaxies they can grow to huge size. In the gorgeous barred spiral galaxy NGC 1365 (shown below), there’s one lurking in the core that has about two million times as much mass as our Sun. Not only that, it is actively gobbling down matter, and that allows us to measure some interesting properties of this cosmic monster, including its spin. Astronomers observed NGC 1365’s black hole using the NuSTAR and XMM-Newton observatories, and were surprised to find out it’s spinning so fast that the outer edge is moving at very nearly the speed of light!
This takes some explaining. Hang on tightly, and for your own safety please keep your arms inside the blog post at all times.