Astronomy Practice Exam

What is a black hole?

1. A type of supernova

2. A celestial object that emits light

3. A remnant of a very high mass star from which nothing can escape

4. An area in space devoid of all matter

The correct answer is: A remnant of a very high mass star from which nothing can escape

A black hole is defined as a remnant of a very high mass star from which nothing can escape, due to its incredibly strong gravitational pull. This phenomenon occurs when a massive star exhausts its nuclear fuel and can no longer support itself against gravitational collapse. As the star's core collapses under its own weight, it can form a singularity, a point of infinite density, surrounded by the event horizon, which is the boundary beyond which nothing, not even light, can escape the gravitational grip of the black hole. The other options present concepts that are not accurate descriptions of a black hole. While supernovae are explosive events that can lead to the formation of black holes, it is not correct to define a black hole as a type of supernova itself. A black hole does not emit light; rather, it doesn't emit any radiation in the conventional sense, making it effectively invisible against the backdrop of space. Lastly, describing a black hole simply as an area devoid of all matter overlooks the crucial aspect of its gravitational influence and the fact that it can contain an immense amount of mass, concentrated at its singularity, thereby affecting surrounding space and objects.