For about 150 million years after the Big Bang, the Universe was a dark place, made of just hydrogen and helium atoms, as the first stars had yet to be formed.
This all changed with the first generation of stars, so bright and powerful that their light started to break apart hydrogen atoms around them, whilst their cores produced the elements essential for life itself.
By peering back through time, Dr David Sobral and his team at Lancaster University have now confirmed a sample of galaxies that are giving us a unique glimpse into that era.
The fifth galaxy to be discovered and confirmed (at a Redshift of 7) has been named VR7, in tribute to the astrophysicist Vera Rubin, who in 1996 became the first woman to win the Gold Medal of the Royal Astronomical Society for 150 years.
The Lancaster team used the Subaru and Keck telescopes on Hawaii, and the Very Large Telescope in Chile to discover several galaxies which seem to have large bubbles of ionised gas around them, allowing light to pass through.
Dr Sobral said: “Stars and black holes in the earliest, brightest galaxies must have pumped out so much high energy/ultraviolet light that they quickly broke up hydrogen atoms. These galaxies are visible because large enough bubbles have been carved around them, but what is really surprising is how numerous these spectacular galaxies are.”
Sergio Santos is another co-author of the study and will soon be a PhD student at Lancaster University. He adds: “Our results highlight how hard it is to study the small faint sources in the early universe. The neutral hydrogen gas blocks out most of their light, and because they are not capable of building their own local bubbles as quickly as the bright ones, they are much harder to detect.”
The full team consists of David Sobral (Lancaster), Sergio Santos (Lancaster), Jorryt Matthee (Leiden), and Behnam Darvish (Caltech).
In 2015, Sobral led a team that found the first example of a spectacularly bright galaxy that may harbour first generation stars.
The galaxy was named Cosmos Redshift 7 or CR7 (the name also pays homage to footballer Cristiano Ronaldo). The team also discovered a similar galaxy, MASOSA, which, together with Himiko, discovered by a Japanese team, hinted at a larger population of similar objects, perhaps made up of the earliest stars and/or black holes.
With five bright sources now confirmed, and more to follow, CR7 is now part of a unique team of bright early galaxies, suggesting there are tens to hundreds of thousands of similar sources in the entire visible Universe.
Astronomers are now using the largest existing telescopes on the ground and in space to better assess the composition, size and shape of the newly discovered ancient galaxies. Results from this work are presented at the National Astronomical Meeting and will appear in papers in the journal Monthly Notices of the Royal Astronomical Society.