Researchers say they have detected remnants of a universe that existed before our own.
Astronomers previously thought these events only occurred around 3 billion years after the Big Bang, but they were happening when the universe was only half that age.
The strange events were identified by a project set up to investigate dark energy, an unexplained force that scientists think is accelerating the universe's expansion.
When massive stars come to the end of their life cycles, they self-destruct in a cataclysmic final explosion.
The discovery could help scientists work out how fast the universe is expanding.
Physicist Brian Greene explains why the world is actually kind of like a garden hose.