The Hubble Space Telescope has been in operation since 1990 and it still can amaze scientists and space fans alike. A team of astronomers has used the Hubble to make a fascinating discovery that links back to the early days of our universe: a collection of over 250 dwarf galaxies.

Researchers date the galaxies to an estimated "only 600-900 million years after the big bang." That sounds like a long time to us, but it's a pittance on the scale of the universe's life span. NASA notes that it took over 12 billion years for the light from the galaxies to reach the Hubble.

The galaxies aren't just interesting for their age, but also for how faint they are. "The faintest galaxies detected in these Hubble observations are fainter than any other yet uncovered in the deepest Hubble observations," says Johan Richard, an astronomer who worked on the project.

Scientists are using the Hubble data to peek into the early stages of the universe. Let's go way, way back in time to when the universe was chock-full of thick hydrogen gas. All that gas once blocked the travel of ultraviolet light in the universe. This fog began to clear, creating what scientists call the epoch of reionization. When it cleared, ultraviolet light was able to cover great distances. NASA refers to this as the universe becoming "transparent to ultraviolet light."

Some of the smallest galaxies detailed in the researchers' findings were likely involved in this process. NASA notes they "could be the major actors in keeping the universe transparent." This discovery helped scientists determine that the epoch of reionization came to a close about 700 million years after the big bang. It's a fascinating point in the timeline of the universe.

A joint project between NASA and the European Space Agency, the Hubble has been in operation for over 25 years with no signs of slowing down. It generates a constant stream of fascinating discoveries and beautiful space images.

Just this year, Hubble delivered some outstanding visuals with fresh looks at the artfully cloudy Lagoon Nebula, the butterfly-like Twin Jet Nebula and a lonely dwarf spiral galaxy. Its ability to peer near and far throughout the universe gives researchers insights into the development of the universe, how stars are formed and where planets come from.

NASA shared the research on the 250 dwarf galaxies on October 22. A study on the findings will be published soon in the Astrophysical Journal.



This article also appears in Spanish. Read: Hubble avista 250 antiguas galaxias enanas