Researchers claim to have found the first stars in the universe

 By JONATHAN O'CALLAGHAN

January 

Astronomers studying data from the James Webb Space Telescope (JWST) have caught a glimpse of light from a rare helium isotope in a far-off galaxy, which may be a sign of the existence of the universe's earliest generation of stars.

These elusive stars, dubbed "Population III," would have been enormous balls of hydrogen and helium formed from the first gas in the cosmos. In the 1970s, theorists initially imagined these earliest fireballs, speculating that they had brief lives before exploding as supernovas, creating heavier elements and releasing them into space. Later, this star material gave rise to Population II stars richer in heavy metals, Population I stars much richer than our sun, planets, asteroids, comets, and ultimately life itself.

We know there must have been a first generation of stars because we are here, according to Rebecca Bowler, an astronomer at the University of Manchester in the UK.

Now, astronomer Xin Wang and his colleagues at the Chinese Academy of Sciences in Beijing believe they have located them. It's extremely bizarre, Wang said. The team's research, which was published on the preprint platform arxiv.org on December 8, is still pending peer review by Nature, so confirmation is still required.

Even if the researchers are mistaken, it could not be long until a more reliable discovery of the earliest stars is made. It is believed that JWST can look far enough into the future to observe them, changing broad areas of astronomy. The enormous floating telescope has already identified far-off galaxies whose peculiar brightness implies they may contain Population III stars. Additionally, other research teams competing to use JWST to find new stars are now evaluating their own data. Mike Norman, a physicist at the University of California, San Diego who analyses the stars in computer simulations, said, "This is without a doubt one of the hottest problems going."

If a conclusive find is made, astronomers will be able to investigate the stars' dimensions and characteristics as well as their existence and how they suddenly became visible in the blackness of the universe.

It's actually one of the most fundamental transformations in the universe's history, according to Bowler.

Electrons, protons, and neutrons all slowed down sufficiently to unite into hydrogen and helium atoms some 400,000 years after the Big Bang. Dark matter began to gather as the temperature continued to plummet, dragging the atoms along with it. Gravity compressed the hydrogen and helium inside the clusters, forming massive gas balls that, once sufficiently dense, unexpectedly erupted in nuclear fusion at their centres. The initial stars were created.

In 1944, the German astronomer Walter Baade divided the kinds of stars in our galaxy into I and II. Our sun and other stars high in metals are found in the former, whereas older stars with lighter components are found in the later. A few decades later, the concept of Population III stars had its literary debut. The British scientist Bernard Carr discussed the crucial part that this unique species of star may have played in the creation of the universe in a study published in 1984 that helped enhance their visibility. According to Carr and his colleagues, "their heat or explosions might have reionized the cosmos, and their heavy-element production could have caused a burst of pregalactic enrichment," spawning subsequent stars that were richer in heavier elements.

Because there was a lot of hydrogen and helium gas accessible in the early cosmos, Carr and his co-authors calculated that the stars may have grown to enormous sizes, ranging anything between a few hundred and 100,000 times more massive than our sun.

The so-called supermassive stars at the heavier end of the spectrum would have been relatively chilly, red, and bloated, with sizes that could almost completely enclose our solar system. Population III stars that were denser and smaller in size would have been blue hot, with surface temperatures of about 50,000 degrees Celsius, as opposed to our sun's 5,500 degrees.

Norman's computer simulations from 2001 provided an explanation for how such massive stars may arise. Gaseous clouds in the cosmos today break up into a number of little stars. However, the simulations demonstrated that because the early universe's gas clouds were far hotter than those in the present, they couldn't condense as readily and were consequently less effective at star formation. Instead, a single, enormous star would form from the collapse of vast clouds.

The stars were fleeting, with lives of little more than a few million years due to their enormous size. (Stars that are more massive burn up their fuel more quickly.) With the remaining pockets of primordial gas dissipating, Population III stars may not have survived for very long in the history of the universe; possibly a few hundred million years.

There are a lot of unknowns. How big did these stars actually get? How far back in the cosmos did they come from? And how numerous were they in the beginning of the universe? They are entirely different from the stars in our own galaxy, according to Bowler. They're simply such fascinating things, I think.

Finding evidence for them has been difficult since they are so far away and only existed for a small period of time. However, in 1999, astronomers from the University of Colorado, Boulder projected that the stars would emit a distinctive frequency of light from helium-2, which would serve as a detectable signal. While conventional helium also includes two neutrons in its nucleus, this unstable type of helium only has two protons. James Trussler, an astronomer at the University of Manchester, revealed that the helium emission was really formed when intense photons from the stars' scorching surfaces smashed into gas surrounding the star rather than from within the stars themselves.

It's a rather straightforward forecast, according to Daniel Schaerer of the University of Geneva, who developed the concept in 2002. The search began.

The First Stars' Location

Schaerer and his associates believed they may have discovered something in 2015. They discovered a potential helium-2 signal that could have been connected to a collection of Population III stars in a far-off, ancient galaxy. The galaxy seemed to contain the earliest signs of stars in the cosmos when it was first observed 800 million years after the Big Bang.

Later research directed by Bowler refuted the results. "We uncovered proof that the source was emitting oxygen. That disqualified a scenario involving just Population III, she added. Later, a different team was unable to find the helium-2 line that the previous team had discovered. It wasn't there, according to Bowler.

Might others perform better?

Astronomers hoped that the JWST, which launched in December 2021, would be successful. The telescope can see into the early cosmos more readily than any telescope before it thanks to its huge mirror and unmatched sensitivity to infrared light. The telescope views distant, dim things as they were long ago because light travels slowly here. The telescope also has spectroscopic capabilities, which allow it to separate light into its constituent wavelengths and search for the helium-2 signature of Population III stars.

More than 2,000 JWST objects' spectroscopic data were examined by Wang's team. A faraway galaxy that was visible 620 million years after the Big Bang is the first example. The astronomers claim that the galaxy is divided into two halves. According to their investigation, one-half of the galaxy appears to contain the crucial helium-2 signal combined with light from other elements, perhaps indicating a mixed population of thousands of Population III stars and other stars. Although the second half of the galaxy has not yet undergone spectroscopy, its brightness suggests that it may have a more Population III-rich environment.

To "have a shot of verifying such things," Wang added, "we are seeking to apply for observing time for JWST in the next cycle to cover the entire galaxy."

For Norman, the cosmos is "head-scratching." He stated that "a cluster of Population III stars is one option" if the helium-2 results hold up under inspection. He is doubtful, though, whether Population III stars and subsequent stars could mingle that easily.

University of Portsmouth astronomer Daniel Whalen used comparable caution. It may show that a galaxy has both Population III and Population II stars, he added. Whalen noted that even though this would be "the first direct proof" of the origins of stars, "it's not clean evidence." Helium-2 can also be produced by other extremely hot cosmic phenomena, such as the searing discs of matter that revolve around black holes.

Because they did not find certain indications of oxygen, nitrogen, or ionised carbon that would be anticipated in that situation, Wang and his team believe they can rule out a black hole as the source. Peer review is still pending, and even then, further observations will be required to verify any potential conclusions.

Ahead of the Game

The first stars are being sought after by other JWST-using groups as well.

In addition to searching for helium-2, astronomer Rogier Windhorst of Arizona State University and colleagues suggested using the gravity of massive galaxy clusters to seek for individual stars in the early cosmos. Astronomers frequently use a method called gravitational lensing to magnify and bend light from distant objects using a huge object, such as a cluster. Even individual Population III stars, according to Windhorst, "may in principle experience virtually infinite amplification" and suddenly appear in view when they get close to the edge of a dense cluster.

Windhorst is the director of a JWST initiative that is testing the method. In the next year or two, he said, "we will have seen some." "There are several candidates already," Similar to this, Eros Vanzella, an astronomer at the National Institute for Astrophysics in Italy, is in charge of a programme that uses gravitational lensing to examine a group of 10 to 20 potential Population III stars. We're simply messing about with the data for now, he said.

The intriguing prospect that some of the unusually brilliant galaxies already observed by JWST in the early cosmos may have been caused by huge Population III stars is also still present. According to Vanzella, "these are precisely the epochs when we expect the earliest stars to be developing." "I hope that the first stars will be identified in the next weeks or months."

Under the terms of a Creative Commons licence, this article has been taken from Quantamagazine. Go here to read the original article.