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

Example Sentences

See Examples For:

event horizon

The team's solution replaces the traditional event horizon with what physicists call a "dynamical horizon," a concept that is already widely used in computer simulations of black holes.

From Science Daily ● Jul. 13, 2026

It predicts the existence of black holes and the event horizon, a boundary beyond which nothing -- not even light -- can escape.

From Science Daily ● Nov. 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

This difference in the forces would stretch our astronaut out like spaghetti or tear him apart before the star had contracted to the critical radius at which the event horizon formed!

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