A nova is a sudden, dramatic explosion on the surface of a star that makes it appear much brighter for days or weeks before fading back to normal.

A nova happens when a dense, collapsed star called a white dwarf pulls gas from a nearby companion star. When enough gas builds up on the white dwarf's surface, it ignites in a thermonuclear explosion, releasing tremendous energy and light. Unlike a supernova, which destroys the entire star, a nova leaves the star intact. The same star can experience multiple novae (or novas) over time as it continues pulling gas from its companion.

Throughout history, sudden bright “new” stars fascinated astronomers and sometimes frightened people who didn't understand what they were seeing. In 1572, the astronomer Tycho Brahe observed what he thought was a nova (it was actually a supernova) and carefully documented it, helping prove that the heavens weren't unchanging, as people once believed. Today, amateur astronomers still discover novae by watching the night sky, contributing valuable observations to science.