NANOGrav on PBS

Hunting Monster Black Holes

by Kate Becker

It’s a basic scary-movie rule: Never show the big, bad monster. Show his shadow, his tooth marks, his trail of slime. But as soon as you show his face, the fright bubble pops.

The universe seems to understand this rule. Its biggest, baddest monsters—supermassive black holes that haunt the center of nearly every galaxy, containing as much mass as millions or billions of stars—are totally invisible. Sure, by looking at the way stars whip around the center of the Milky Way and observing the electromagnetic fireworks going off in faraway galaxies, astrophysicists infer that supermassive black holes are lurking there. But they can never see the black holes themselves. And that’s not just storytelling—it’s physics.

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