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

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

That distance defines the black hole’s spherical event horizon.

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

In the mid-1970s, Hawking and theorist Jacob Bekenstein independently argued that a black hole should possess an entropy proportional to the area of its event horizon.

From Science Magazine ● Mar. 28, 2024

I must admit that in writing this paper I was motivated partly by irritation with Bekenstein, who, I felt, had misused my discovery of the increase of the area of the event horizon.

From "A Brief History of Time: And Other Essays" by Stephen Hawking

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