Stars are composed mostly of hydrogen and helium. Within the star’s core, hydrogen fuses into helium, releasing thermal energy that provides light and energy to Earth. Over time, the star’s gravity tries to compact it, but the energy created by nuclear fusion creates an expanding pressure that counteracts gravity. Once the star’s fuel is exhausted, gravity wins, and the star collapses, causing the star to explode spectacularly. But in death comes life. Most of the heavier elements on Earth were formed in stars that distributed these elements across the galaxy when they went supernova and ultimately ended up on Earth. In fact, the elements that make up our DNA were created in the core of stars that went supernova.