The universe was not always full of bright lights. It took about 150 million years for the first stars to shine, and their light was mostly trapped in the large clouds of hydrogen from which they formed. This epoch, known as reionization, is notoriously difficult to study, but instruments like Subaru, Keck, and the Very Large Telescope have allowed us to finally pierce the veil.
Using these, an international team of astronomers was able to discover 133 bright galaxies from the very early universe, which might potentially contain the first generation of stars. These new objects are believed to be akin to CR7, which was discovered last year by the same team.
“Stars and black holes in the earliest, brightest galaxies must have pumped out so much ultraviolet light that they quickly broke up hydrogen atoms in the surrounding universe,” said team leader Dr David Sobral of Lancaster University in a statement.
“The fainter galaxies seem to have stayed shrouded from view for a lot longer. Even when they eventually become visible, they show evidence of plenty of opaque material still in place around them.”
This research is being presented at the National Astronomy Meeting this week. The team’s results highlight how difficult it is to study the early universe. The abundance of neutral hydrogen shrouds the small, faint sources and blocks their light from reaching us.
“This makes the bright galaxies visible much earlier on in the history of the universe, allowing us to not only use them to study reionisation itself, but also to study the properties of the very first galaxies and the black holes they may contain,” explained lead author Jorryt Matthee, a PhD student at Leiden Observatory
The study, published in the Monthly Notices of the Royal Astronomical Society, provides the groundwork for future observation, which will hopefully provide solutions to the many unanswered questions about the early universe.
“What is really surprising is that the galaxies we find are much more numerous than people assumed, and they have a puzzling diversity,” continued Sobral.
“When telescopes like the James Webb Space Telescope are up and running, we will be able to take a closer look at these intriguing objects. We have only scratched the surface, and so the next few years will certainly bring fantastic new discoveries.”