A snapshot of the early Universe from the James Webb Space Telescope shows galaxies formed faster and earlier than astronomers previously thought, after they discovered some of the oldest and earliest galaxies formed.

Astronomers said the two galaxies, smaller than our own, existed approximately 450 and 350 million years after the big bang. The previous record holder for the earliest formed galaxy is GN-z11, which existed 400 million years after the big bang. That galaxy was discovered by the Hubble Space Telescope and Keck Observatory in 2016.

The discoveries were published in two research papers found in the Astrophysical Journal Letters. 

Garth Illingworth of the University of California at Santa Cruz said the two galaxies may have started forming roughly 100 million years after the big bang.“The primal universe would have been just one hundredth its current age. It’s a sliver of time in the 13.8 billion-year-old evolving cosmos.”

Illingworth also said the two stars are exceptionally bright, which means they could have been massive with plenty of low-mass stars (like galaxies that formed later on). They could also have been less massive, with a few extraordinarily bright stars — known as Population III stars. 

Population III stars are believed to be the first ones formed after the big bang. Astronomers theorize they are blisteringly hot, and made of only primordial hydrogen and helium — existing before stars included heavier elements in their nuclear fusion. So far, these primordial stars have not been seen and remain a theory.

“These observations just make your head explode. This is a whole new chapter in astronomy. It’s like an archaeological dig, and suddenly you find a lost city or something you didn’t know about. It’s just staggering,” said Paola Santini, fourth author of one of the papers, in a NASA statement.