The brightest galaxy ever observed may contain evidence of the very first stars, formed from hydrogen created in the Big Bang.
Astronomers say that gazing at the galaxy known as C7 is to look far back into time — into the reionization period, to be precise, which occurred just 800 million years after the Big Bang.
Discovered and examined by telescopes in Hawaii and Chile, as well as the Hubble space telescope, C7 displays the best evidence yet of a long-sought class of stars dubbed Population III stars — the very earliest to materialize in the universe, researchers stated in a study published in the Astrophysical Journal.
Long theorized but never before observed, Population III stars would have contained only hydrogen, helium and lithium produced by the Big Bang. They would have had short lives — exploding as supernovae and releasing their heavier elements from within.
Those elements would then have come together to form the later and much more common Population II and Population I stars, the researchers explained. The subsequent heavier chemical elements essential to life – such as carbon, oxygen, nitrogen and iron – would have been forged in those later stars.
The brief lives of Population III stars that burned in a younger universe is probably the reason they've never been detected. C7 is however so distant, we're seeing it – and the galaxy's original stars – as it existed less than a billion years after the Big Bang, noted study team leader David Sobral at the Leiden Observatory in the Netherlands.
Spectroscopic observations showed no sign of any of the heavier elements in a particularly bright pocket of galaxy C7, which is considered strong evidence for the presence of Population III star clusters.
The discovery was surprising from the start — as the team hadn't expected to find such a bright galaxy.
"Then, by unveiling the nature of CR7 piece by piece, we understood that not only had we found by far the most luminous distant galaxy, but also started to realize that it had every single characteristic expected of Population III stars," Sobral says.
The discovery yields insights into the links between the universe's earliest stars and the elements that make up everything in the universe today — including us, according to study co-author Jorryt Matthee of Leiden University.
"Even as a child, I wanted to know where the elements come from: the calcium in my bones, the carbon in my muscles, the iron in my blood," Matthee says. "It all goes back to the first stars ever created, he says, something that has almost certainly been confirmed by the new research.
"With this discovery, remarkably, we are starting to actually see such objects for the first time."