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Astronomy

Weighing the Invisible: How Astronomers Measure Supermassive Black Hole Masses

Quick fact

The supermassive black hole at the center of our Milky Way, Sagittarius A, has a mass of about 4 million Suns, yet it would fit within the orbit of Mercury.

Why this is interesting

You can't see a black hole, but you can still weigh it. How do astronomers put a number on something that swallows light itself?