Evidence of such "first-generation" stars was spotted in the brightest galaxy ever found in the early universe, a galaxy named CR7 (after Portuguese soccer star Cristiano Ronaldo), using the European Southern Observatory's Very Large Telescope, scientists report in a paper that has been accepted for publication in the Astrophysical Journal.
"It really doesn't get more exciting than this," said David Sobral, the astronomer who led the research, in a statement. Sobral is with the Institute of Astrophysics and Space Sciences at the University of Lisbon in Portugal and the Leiden Observatory in the Netherlands.
Scientists have been searching for such first generation or "Population III" stars for a long time. Such stars were thought to be up to a thousand times more massive than the sun and very short-lived, exploding as supernovas after just a couple of million years.
Those first-generation stars were thought to hide in only the earliest, smallest, dimmest galaxies, making them very difficult to find.
But if they were found, the could be easily identified because they would have formed from the only elements that existed in the universe at the time — hydrogen, helium and traces of lithium, the three lightest elements that exist on the periodic table.
That's exactly what CR7 looked like — when Sobral and his team carefully scanned a bright pocket in one part of the galaxy, they found no sign of any heavier elements. Such elements, including carbon, oxygen, iron and calcium formed later in the history of the universe, and have become an important part of our bodies and our world.
The first heavier elements were, in fact, formed by the first generation of stars, noted Jorryt Matthee, a co-author of the paper.
"With this discovery, remarkably, we are starting to actually see such objects for the first time," he said in a statement.
Ray Jayawardhana, an astronomer, astrophysicist and dean of science at Toronto's York University, who was not involved in the research, said the discovery gives us "the first inkling" of the very first generation of stars.
"But we don't know their characteristics yet," he told CBC's Metro Morning. That will have to wait until future observations with powerful telescopes like the James Webb Space Telescope, successor to the Hubble Space Telescope, that is set to launch in 2018.
Look back in time
Sobral and his team say they are now trying to confirm their discovery using the Very Large Telescope, the Hubble Space Telescope and another ground-based telescope called ALMA. They also want to look for other first-generation stars.
The team spotted CR7 while using the Very Large Telescope to hunt for extremely faraway galaxies.
That amounts to looking back in time, since light takes time to travel — the light that arrives on Earth today from those galaxies left on its journey billions of years ago.
Sobral and his colleagues found CR7 while looking for galaxies that existed about 800 million years after the Big Bang — about 13 billion years ago. The galaxy is itself a record-setter — three times brighter than any other galaxy ever found in the early universe. The fact that such a bright galaxy appears to contain first-generation stars means it might not be that hard to find more, the researchers say.