Webb will be able to see the first stars of the Universe, says study – 01/22/2023 – Sidereal Messenger

The brand new and trendy James Webb Space Telescope immediately broke records by detecting some of the oldest galaxies ever seen, dating back to when the Universe was something like 300 million years old. But the ambition is even greater, and now a new study says there’s a good chance that Webb could also see the first stars that formed after the Big Bang.

The models suggest that many of these first stars were huge, with masses hundreds of times greater than that of the Sun, and formed exclusively by hydrogen and helium – since the process of formation of chemical elements after the Big Bang would only have been able to produce these two, plus a tiny dash of lithium, before being cut short by the gradual cooling of the cosmos.

It was these primordial stars that, living lives of a few million years at most, detonated as the first supernovae and seeded other clouds of gas with heavier elements. When new stars formed from them, they already had a wider chemical repertoire and gained the features of the stars that we see today scattered throughout the Milky Way and our immediate surroundings.

Subsequent generations became richer in heavy elements, creating two populations that were easily distinguishable by astronomers for decades. Population I is rich in heavy elements, and Population II is poor. The Sun, born 4.6 billion years ago, is part of the I.

So far, Population III, which would be stars free of heavy elements, has never been observed – it remains hypothetical. But Webb can change that condition. According to Mikaela Larkin and colleagues from the University of California at San Diego (USA), the space telescope will be able to find direct signals from these primordial stars with about ten hours of observation – as long as it has its light amplified by a gravitational lens.

It’s that thing: to see stars that only existed billions of years ago, you have to observe them at enormous distances (so that their light, traveling through space all this time, reaches us now, after crossing several billion years- light).

Very distant objects, on the other hand, are dim. But if there are large masses between them and us (like vast clusters of galaxies, with enormous gravity), they can bend light rays coming from objects behind them, acting like a lens, which would amplify their brightness thousands of times. .

The work, published in the Astronomical Journal, gives indications of how this detection of primordial stars in the cosmos could occur. If you roll a gravitational lens capable of amplifying the signal ten thousand times, it would be possible to capture an individual star with 125 solar masses. With higher magnifications, it would be possible to see even smaller stars, but gravitational lensing events this powerful are considered rare. On the other hand, the researchers point out that these stars must be born in families, and that we will be able to detect the light of many of them together, which will facilitate their detection.

This column is published on Mondays in Folha Corrida.

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