What is a black hole?

A black hole forms when a massive star reaches the end of its life and its core collapses under its own gravity, contracting to an incredibly small and dense point. Once this happens, the gravitational pull becomes so overwhelmingly powerful that nothing in the universe — not even light, which travels at 300,000 km per second — can escape from it. This is what makes black holes truly unique and terrifying objects in the cosmos. The boundary beyond which nothing can return is called the event horizon, and anything that crosses it is lost forever.

• Formation: When a massive star (at least 20 times the Sun's mass) exhausts its nuclear fuel, the core collapses inward under gravity, creating a black hole
• Intense Gravity: The gravitational field of a black hole is so extreme that it warps space and time itself — a prediction of Einstein's General Theory of Relativity
• Event Horizon: The point of no return around a black hole — once crossed, nothing, not even light, can escape its gravitational grip
• Singularity: At the centre lies a singularity — a point of infinite density where known laws of physics completely break down
• Detection: Black holes cannot be seen directly since they emit no light — scientists detect them by observing their gravitational effects on surrounding stars and gas