In the beginning there was nothing. Then there was something: the Big Bang, forging gas -- hydrogen, helium, lithium. At some point in the chaos that followed, stars formed from this primordial soup. Pristine gases spun into stellar bodies. A generation of stars (whose existence is theoretical) created light in the darkness.
These Population III stars, as they are known, are theoretically the turning point for the universe: taking the gases and turning them into the heavier elements: carbon, oxygen, iron, nitrogen and metallic elements.
But though there had to have been a first generation of stars, we've never actually seen them. This is because, massive, hundreds of times larger than the sun, they burned huge, hot, bright -- and fast. Scientists believe that these stars from the dawn of time burned out after just two million years.
We haven't seen them -- but we may now have seen the very first evidence of their existence.
A team of researchers led by David Sobral from the Institute of Astrophysics and Space Sciences in Portugal has found what it believes to be good evidence for clusters of Population III stars in a galaxy located some 13.02 billion years away -- 800 million years after the Big Bang.
Using the European Southern Observatory's Very Large Telescope, with help from the Subaru Telescope and the Hubble Space Telescope, the team found a number of very bright, very young galaxies as part of a wide survey of very distant galaxies (as opposed to the more common narrow survey of a smaller patch of sky).
But it was a galaxy they named CR7 that caught their attention -- by far the brightest galaxy ever seen at this stage of the universe, three times brighter than the previous holder of that title, Himiko, which had been thought to be one of a kind.
As well as being exceptionally bright, CR7 contained strong ionised helium emission -- and, crucially, no sign of any heavier elements. Both the ionised helium and the lack of heavier elements are required for Population III stars.
"The discovery challenged our expectations from the start, as we didn't expect to find such a bright galaxy," Sobral said.
"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 realise that it had every single characteristic expected of Population III stars. Those stars were the ones that formed the first heavy atoms that ultimately allowed us to be here. It doesn't really get any more exciting than this."
The survey found blue and red clusters of stars, indicating that Population III stars did not all form at once, but in waves -- and the team directly observed what it believes to be the last wave of Population III stars, alongside regular stars. This means that Population III stars may be easier to find than thought -- not tucked away in the farthest, dimmest galaxies, but close enough to be observable.