Science for Sleep | How Big Is the M87 Black Hole Really?

In 2019 the Event Horizon Telescope published the first picture of a black hole: a glowing orange ring 55 million light years away at the heart of the giant elliptical galaxy M87. We take that one object and measure it slowly against things the listener already knows: the Sun, Neptune's orbit, the whole planetary Solar System, the jet it throws out for thousands of light years. Before the picture, astronomers had two honest methods that disagreed by nearly a factor of two on its mass, one from the motions of stars (about 6.6 billion Suns) and one from the motions of gas (about 3.5 billion). The ring's measured size settled it near 6.5 billion Suns, and the episode ends on what the ring still does not tell us. Subscribe to The Drowsy Universe for more calm listening.