A tidal disruption event happens when a star wanders too close to a black hole. The black hole’s gravity tears the star apart.

The side of the star nearer the black hole feels a stronger pull. This stretches the star into a long, thin stream of gas. Some gas falls into the black hole. The rest is thrown out into space.

The falling gas heats up and glows brightly. Telescopes can see this flash across millions of light-years.

Sometimes the star survives. In a partial or repeating disruption, the black hole only nibbles at the star on each orbit. The star loses a little gas every time it passes.

One example is Swift J0230, found by NASA’s Swift Observatory. A Sun-like star there orbits a black hole more than 200,000 times the Sun’s mass. It loses about three Earth masses of gas per pass.

These events help astronomers weigh black holes. The brightness and timing of the flare reveal the size of the black hole and the star it is consuming.