event horizon
n. countablen. the imaginary line around a black hole that prevents anything from getting out. Once something crosses this point, it can never come back because the gravity is too strong.
n. the boundary surrounding a black hole beyond which the escape velocity exceeds the speed of light. Represents a point of no return where gravitational pull prevents all matter and electromagnetic radiation from escaping.
Nothing can escape once it passes the event horizon.
The probe collected valuable data until it reached the event horizon and signals were lost.
In general relativity, the event horizon serves as a threshold where the gravitational field becomes so intense that even light is unable to traverse the path back to the external universe.
Typically used with the definite article 'the' when referring to a specific black hole.