event horizon

American  

noun

Astronomy.

1. the boundary around a black hole on and within which no matter or radiation can escape.

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event horizon British  

noun

1. astronomy the surface around a black hole enclosing the space from which electromagnetic radiation cannot escape due to gravitational attraction. For a non-rotating black hole, the radius is proportional to the mass of the black hole

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event horizon Scientific  

/ ĭ-vĕnt′ /

1. A spatial boundary around a black hole inside which gravity is strong enough to prevent all matter and radiation from escaping. The inability of even light to escape this region is what gives black holes their name.

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Etymology

Origin of event horizon

First recorded in 1970–75

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Example Sentences

See Examples For:

event horizon

Unlike black holes, however, they would not contain a singularity or an event horizon.

From Science Daily ● Jun. 14, 2026

In 1971, Stephen Hawking proposed that a black hole's event horizon, its outer boundary where neither light nor matter can escape, cannot shrink.

From Science Daily ● Dec. 8, 2025

They imagine a spherical shell of dust of a given radius and mass lurking behind the event horizon and distorting spacetime there.

From Science Magazine ● Mar. 28, 2024

“We’re seeing for the first time the invisible structure that shepherds the material within the black hole’s disk," said Broderick, and which "drives plasma to the event horizon, helping it to grow.”

From Salon ● Mar. 28, 2024

However, though scientists can detect black holes, they still haven’t spotted the zeros at their centers, since the ugly singularities are shielded by the event horizon.

From "Zero: The Biography of a Dangerous Idea" by Charles Seife

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