The Hubble Space Telescope has made use of its gravitational lensing to produce an image containing the highest number of faint, early galaxies in the universe. According to a report from Phys.org, many of these galaxies were born just 600 million years after the Big Bang, and are fainter than any other galaxy previously photographed by NASA or the European Space Agency.

The study was conducted by an international team of astronomers, headed by Hakim Atek from the École Polytechnique Fédérale de Lausanne in Switzerland. The team found over 250 small galaxies that existed between 600 and 900 million years following the Big Bang. It is one of the largest samples of dwarf galaxies taken from this time. It took the light from these tiny galaxies over 12 billion years to reach the Hubble’s lenses. Even though they are visible today, they ceased to exist long ago.

The team was fascinated by how faint the light from these galaxies was. According to Johan Richard from the Observatoire de Lyon in France, “The faintest galaxies detected in these Hubble observations are fainter than any other yet uncovered in the deepest Hubble observations.”

The photos of the early galaxies could help astronomers solve one of the most pressing mysteries of the time – the period of reionization in the early universe. This process began when a thick cloud of hydrogen gas that shrouded the universe began to lift, and ultraviolet radiation was allowed to travel across space for the first time. In other words, this is the first time the universe became transparent.

The ultraviolet light from the galaxies in the study allowed astronomers to calculate whether or not they were involved in the reionization process. The team found that the smallest and most common galaxies could have had a major influence in repelling the hydrogen cloud and keeping the universe transparent to ultraviolet radiation. The time of reionization, the researchers believe, ended roughly 700 million years after the Big Bang.

According to the study’s lead author, Atek, only accounting for the contributions from large and bright galaxies paints an incomplete picture of the entire reionization process. Dwarf galaxies had a significant role to play in the process, and this new study confirms their contributions.

The team the farthest images of gravitational lensing created in three galaxy clusters, which were captured by the Hubble Frontier Fields program. The clusters in the photos generate massive gravitational fields that have a serious magnifying effect on the light that passes by from other, fainter galaxies. Knowing the curvature of the gravitational field, researchers can adjust the Hubble’s lens to peer behind these three clusters and look back even further in time.

According to co-author Jean-Paul Kneib from the École Polytechnique Fédérale de Lausanne in Switzerland, the clusters in the so-called “frontier fields” allow researchers to see galaxies that would otherwise be invisible. Mathilde Jauzak, from Durham University in the U.K. and the University of KwaZulu-Natal in South Africa believes that the discovery is extremely significant. “Hubble remains unrivaled in its ability to observe the most distant galaxies. The sheer depth of the Hubble Frontier Field data guarantees a very precise understanding of the cluster magnification effect, allowing us to make discoveries like these.”

The research is slated to be published in the Astrophysical Journal, and offers amazing new insight into the earliest years of our universe’s existence.