Astronomers may have just found the remains of some of the very first stars in the universe. The chemical signatures of these distant objects more than 13 billion years old are remarkably different from those of younger stars, like our sun. By studying them, scientists hope to shed light on the formation of stars, galaxies and even basic elements.
In the early days of the universe, only very simple elements such as hydrogen and helium were available. The first stars were lit from these elements alone. Over time, their white-hot nuclei gradually baked simple atoms into heavier elements, such as carbon, oxygen, magnesium, and eventually metals. Subsequent generations of stars formed from gas clouds containing these heavier atoms, and today most stars observed by scientists are rich in metals like iron. (Our sun is about 98% hydrogen and helium, but contains traces of heavier elements like iron, neon, and carbon.)
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No one has directly observed the original metal-deficient stars; most of them probably died out or exploded a long time ago. But scientists can still observe some of their dusty remains by fixing their sights billions of light-years away.
Using the European Southern Observatory’s Very Large Telescope (VLT), Salvadori and his team peered into three distant clouds of star-forming gas. On their own, these clouds wouldn’t tell scientists much, but incoming light nearby quasars – extremely bright galactic nuclei formed by dust falling into a supermassive black hole – helped reveal the secrets of the cloud. Based on the wavelengths of light absorbed by the gas clouds, the team determined what elements the stellar remnants were made of.
Sure enough, the clouds were extremely low in iron and other metallic elements, but high in carbon, oxygen and magnesium — precisely what would have been left behind after the first stars ran out of fuel and exploded, the researchers said. This joins other research on star origins and may help explain the composition of younger stars, including those found in the Milky Way.
“Our discovery opens up new avenues to indirectly investigate the nature of early stars, fully complementing studies of stars in our galaxy,” Salvadori said in a statement. statement (opens in a new tab).