a galaxy in space

This is the Veil nebula. It's distinct appearance is the result of a massive star exploding in our night sky 2600 light years away from us and as there is no gravity in space, it's still rapidly expanding to this day. Its simply too far away for us to observe it. A supernova is what happens when a star of sufficient mass has reached the end of its life and explodes in a brilliant burst of light. Supernovae can briefly outshine entire galaxies and radiate more energy than our sun will in its entire lifetime. According to NASA, supernovae are "the largest explosions that takes place in space."