We can finally get evidence for the existence of the first stars in the universe

(ORDO NEWS) — The very first stars may have appeared when the universe was only 100 million years old, or less than 1% of its current age. Since then, the rapid expansion of the cosmos has blotted out their light, forcing us to look for clues to their existence in cosmic sources closer to home.

While investigating the light emanating from clouds around a distant quasar, researchers from Japan, Australia and the US found that the “distinctive mixture of heavy elements” could come from only one source: a colossal first-generation supernova.

All stars that we can observe are classified as population I or population II, depending on their age. Population I stars are younger and contain more heavy elements, while Population II stars are older and contain fewer heavy elements.

The very first stars, described as Population III, are even older, their existence coinciding with cosmic distances that would put them out of sight even with our best technology. For now, we can only speculate what they might look like.

We can finally get evidence for the existence of the first stars in the universe
An artist’s impression shows that a population III star, which is 300 times more massive than our Sun, is exploding as a pair-instability supernova

Scientists believe that these earliest stars were very hot, bright and massive, perhaps hundreds of times the mass of our Sun.

Without a history of powerful cosmic events with the formation of elements heavier than lithium, Population III stars would consist entirely of the simplest gases.

At that time, the only materials available in the universe were hydrogen, helium, and some lithium found in the primordial gas left over from the Big Bang. Only after the first stars themselves collapsed in a violent collision could heavier elements emerge.

These first stars probably ended their lives in pair-instability supernovae, the theoretical type of supernovae possible only in such massive stars. Unlike other supernovae, this would not leave behind stellar remnants such as a neutron star or a black hole, instead throwing everything outward in an ever-expanding cloud.

This explosion could have seeded ancient interstellar space with the necessary heavy elements. to form rocky worlds like ours thus enabling life as we know it so the overall effect is positive.

For astronomers on Earth who are now hoping to learn about Population III stars, the light from these ancient megabursts has vanished into the distance, leaving only a diffuse cloud containing a complex mixture of elements.

Over time, this mixture of material can itself turn into something new. To find signs of such a concentration of stardust, the authors of the new study used near-infrared spectrograph data from one of the most distant known quasars, such as an active galactic nucleus or the extremely bright center of a young galaxy.

The light from this quasar raced through space for 13.1 billion years before reaching Earth, the researchers note, meaning we see the quasar as it looked when the universe was only 700 million years old.

A spectrograph is an instrument that captures and separates incoming light, in this case from a celestial object, into its component wavelengths. This can show which elements are present in the remote object, although gathering this information is not always easy.

The brightness of lines in astronomical spectra may depend on factors other than the abundance of the element, the authors say. point out what might complicate efforts to identify specific elements.

However, the study’s two authors – astronomers Yuzuru Yoshii and Hiroaki Sameshima, both from the University of Tokyo – have already developed a trick to get around this problem. .

Their method, which involves using wavelength intensities to estimate elemental abundances, allowed the research team to analyze the composition of the clouds around this quasar.

The analysis showed a strangely low ratio of magnesium to iron in the clouds, which had 10 times more iron than magnesium compared to our Sun. The researchers say it was a clue suggesting it was material from the catastrophic explosion of a first-generation star.

“It was obvious to me that the supernova candidate for this would be a pair-instability supernova. stars with population III, in which the entire star explodes without leaving behind any remnants,” says co-author Yuzuru Yoshii, an astronomer at the University of Tokyo.

“I was pleased and somewhat surprised to find that the pairwise instability of a supernova with a mass of about 300 times the mass of the Sun provides a ratio of magnesium to iron that is consistent with the low value we obtained for the quasar.”

At least one other Yoshi and colleagues note that a potential population III star trail was reported in 2014, but they argue that this new discovery is the first to provide such strong evidence.

If they are correct in what they have found, this study could go a long way in revealing how matter has evolved throughout the history of the universe. But to be sure, they add, more observations will be needed to test for similar features in other celestial objects.

Perhaps not all of these observations should come from such distant quasars. Even if there are no more population III stars left in the universe, the longevity of their supernova remnants means evidence could be lurking just about anywhere, including the local universe around us.

“Now we know what to look for. ; we have a path,” says co-author Timothy Beers, an astronomer at the University of Notre Dame.

“If it had happened locally in the very early universe, which it should have, then we would expect to find evidence for it.”

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