Astronomers may have spotted the remains of some of the universe’s first stars. These stars would have been very different from ones that formed more recently, and studying their ashes could help us understand the early days of the cosmos.
Stefania Salvadori at the University of Florence in Italy and her colleagues spotted these traces using the Very Large Telescope in Chile. They didn’t observe them directly, but used light from quasars – extraordinarily bright objects at the centers of distant galaxies, powered by matter falling into supermassive black holes – to infer the existence of these primordial stars.
As light from a quasar propagates through the cosmos, it passes through clouds of gas that absorb certain wavelengths depending on what elements they contain. The researchers used this absorption to identify three distant gas clouds nearly 25 billion light years away with strange chemical signatures. Because light takes time to travel through space, the researchers observed these clouds as they appeared more than 11 billion years ago.
Gas clouds like these ones are often left behind after a star explodes in a supernova, blasting away its contents. But astronomers expect that some of the first stars wouldn’t have exploded completely, leaving their cores and the heavier elements therein intact. These explosions would have left behind clouds rich in carbon, oxygen and magnesium, but with little to no iron, unlike the clouds from more powerful blasts.
That is exactly what the researchers found. “Our discovery opens new avenues to indirectly study the nature of the first stars, fully complementing studies of stars in our galaxy,” said Salvadori in a statement. Some of the oldest stars in our galaxy seem to have formed from gas clouds like this containing the ashes of even older stars.
Now that we know these clouds are out there, we can point other telescopes at them to get a better grip on their properties. “We will be able to study many of these rare gas clouds in greater detail, and we will be able to finally uncover the mysterious nature of the first stars,” said Valentina D’Odorico at the National Institute for Astrophysics in Italy, part of the research team, in a statement. That could help us figure out how the early universe transitioned from frigid darkness to light.