Black hole. Computer artwork of planets approaching a black hole and its accretion disc. A black hole is a super-dense remnant left after the death of a massive star. The gravitational field around it is so strong that not even light can escape. The accretion disc (gold), is made up of matter falling onto the hole which emits light as it is energised by the forces pulling it in. The disc also emits X-rays, and detection of these emissions is the best way to infer the presence of a black hole from Earth.