What is a black hole?
It is not really a hole, but a region in space with extremely strong gravity, so strong that not even light can escape. It is called black, because it gives off no light. It is impossible to observe or detect a black hole directly. Nobody has ever done this. But most astronomers believe they exist and continue to look for signs of indirect evidence that they exist. They do this by looking for the influence of black holes on other objects in space.
What is a comet?
It is an icy object found in our solar system, sometimes called a ‘dirty snowball’. As the comet passes near the Sun, the outer ice turns into gas and leaves a trail – the comet’s tail. The comet’s tail always points away from the Sun, even when it is moving away from the Sun. At those times the comet is flying tail first.
When is Halley’s comet due?
Halley’s comet is visible every 76 years. It was last seen in 1986. It will next be visible in 2061.