Technology explainer
How Can a Star Reveal a Hidden Black Hole?
Some black holes are invisible until a passing star is torn apart, producing a bright flare that reveals the black hole's location and approximate mass.
Black holes emit no light of their own, so astronomers usually find them through their effects on nearby matter. A star that passes too close can provide one of the clearest signals.
What happens when a star approaches a black hole?
The difference in gravity across the star can become strong enough to pull it apart. This is called a tidal disruption event.
Why does the event become bright?
Some of the torn material forms a hot flow around the black hole. As the gas heats and falls inward, it can emit ultraviolet light, X-rays and visible light.
How do astronomers locate the black hole?
Telescopes track the flare and compare its position with the host galaxy. If the light appears far from the galactic center, it may reveal a displaced or previously unknown black hole.
What can the light tell researchers?
The flare's temperature, duration, spectrum and brightness help estimate the black hole's mass and how the stellar debris behaves.
What remains uncertain?
Models of these events are still incomplete. The same observation may allow several explanations, and astronomers often need repeated measurements across different wavelengths.
First appeared in
A Black Hole Far From Its Galaxy’s Center Gave Itself Away by Shredding a Star
