Astronomy Practice Exam 2025 – Complete Preparation Guide

A supernova is defined as the brilliant explosion of a dying supergiant star. This dramatic event occurs during the final stages of a massive star's life cycle. When a supergiant star exhausts its nuclear fuel, it can no longer support the gravitational forces acting on it. As a result, the core collapses under its own gravity, leading to an explosive release of energy that ejects the outer layers of the star into space. This explosion is not only visually spectacular but also plays a vital role in the universe, as it disperses heavy elements into the cosmos, contributing to the formation of new stars and planetary systems.

The other options do not capture the true definition of a supernova. The birth of a new star, while a crucial cosmic event, occurs through a different process and does not relate to the explosive end of a supergiant star. The collision of two black holes is a significant event in astrophysics involving gravitational interactions but is distinct from a supernova. Lastly, a type of planet formation pertains to processes involved in forming planets, which is unrelated to the explosive phenomena of a dying star.