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

At the microscopic level, the bridge allows information to pass across what appears to us as an event horizon – a point of no return.

From Science Daily • May 22, 2026

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

“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

On the other hand, gravastars do not have an event horizon, that is, a boundary from within which no information can be sent out, and their core does not contain a singularity.

From Science Daily • Feb. 15, 2024

If there were no event horizon, no cosmic censor that shields the singularity from the rest of the universe, very strange things might happen.

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