 In 2023, a team of astronomers detected a possible intermediate-mass black hole of roughly 800 solar masses at the center of the M4 globular star cluster. In our How Fast Is It? video book chapter on black holes, we covered how no intermediate-mass black holes have been confirmed to date. But here's one that might be. They examined 12 years' worth of M4 observations from Hubble and resolved pinpoint stars. The suspected object can't be seen, but its mass is calculated by studying the motion of stars caught in its gravitational field. The black hole has an event horizon that is a little more than half the diameter of our moon. This is a simulation of the motions of stars around the suspected black hole. To the zoom into M4, the center of the cluster where the suspected black hole resides is highlighted by a red X. The red circle has a radius of just under half a light year. It delineates the sphere of influence of the intermediate-mass black hole. It should be noted that, although an intermediate-mass black hole can explain these star movements, other possibilities exist, such as a cluster of stellar-mass black holes or neutron stars. So, by the end of 2023, there has still not been a single confirmed IMBH. In the future, the Webb Space Telescope might help resolve this question by improving the star count and velocities near the center.