A nova is a powerful explosion that occurs on the surface of a white dwarf star in a binary star system. When the white dwarf pulls in gas from its companion star, the accumulated material can ignite in a thermonuclear reaction, causing a sudden increase in brightness. This explosion can make the star appear thousands of times brighter than usual for a short period. Unlike a supernova, which results in the complete destruction of a star, a nova allows the white dwarf to survive and potentially undergo further eruptions. Novae are important for understanding stellar evolution and the chemical processes in the universe.