Astronomers may have spotted the remains of some of the universe’s earliest stars. These stars would have been very different from those that formed more recently, and studying their ashes could help us understand the beginnings of the cosmos.
Stefania Salvadori at the University of Florence in Italy and his 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 center of distant galaxies, powered by matter falling into supermassive black holes — to infer the existence of these primordial stars.
As light from a quasar travels through the cosmos, it passes through clouds of gas that absorb certain wavelengths depending on the elements they contain. The researchers used this absorption to identify three gas clouds nearly 25 billion light-years apart 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.
Clouds of gas like these are often left behind after a star explodes in a supernova, washing away its contents. But astronomers expect some of the earliest stars didn’t explode completely, leaving their cores and heavier elements intact. These explosions would have left behind clouds rich in carbon, oxygen and magnesium, but with little or no iron, unlike the clouds of the more powerful explosions.
This is exactly what the researchers found. “Our discovery opens up new avenues for indirectly investigating the nature of early stars, fully complementing studies of stars in our galaxy,” Salvadori said in a statement. statement. Some of the oldest stars in our galaxy appear to have formed from gas clouds like this containing the ash of even older stars.
Now that we know these clouds are there, we can point other telescopes at them to better understand their properties. “We will be able to study many of these rare gas clouds in more detail, and we will finally be able to discover the mysterious nature of the first stars,” said Valentina D’Odorico of the National Institute of Astrophysics in Italy, which is part of of the research team, in a press release. It could help us understand how the early universe grew from freezing darkness to light.