When we look up at our sky on a clear night, we see a canvas of incredible blackness that is dotted with the distant fires of countless dazzling stars. How did these fiery stars come to be and where did they come from? The first stars to shatter the primordial darkness of the ancient Universe were mysterious objects that were responsible for our very existence; we wouldn’t be here if the first stars hadn’t forged literally every atomic element heavier than helium in their searing heat. , burning hearts. The iron in our blood, the calcium in our bones, the oxygen we breathe, the water we drink, the sand beneath our feat, and the carbon that is the basis of life on Earth, were all created by the stars, which fired their batches of newly forged, heavy-duty life-sustaining elements screaming into space as they “died”, having burned their requisite hydrogen fuel. In May 2019, astronomers at the Massachusetts Institute of Technology (MIT) in Cambridge, Massachusetts, announced their new findings that instead of inflating into spheres, as scientists once thought, ancient asymmetric supernova explosions may be responsible. to seed bright new baby stars that made life possible on Earth, and anywhere else life might exist in the Cosmos.
Several hundred million years after the birth of the Universe by the Big Bang, which is believed to have occurred around 13.8 billion years ago, the first generation of stars ignited, illuminating the Universe in the form of gigantic, dazzling globes of hydrogen and helium gas. . . Within the hot cores of these early primordial stars, extreme thermonuclear reactions forged the first batch of heavier elements, including carbon, iron, and zinc.
It has been proposed that the first stars were probably giant fireballs that lived fast and died young. The bigger the star; his shortest life. Massive stars burn through their fuel faster than their smaller stellar siblings because they are so much hotter. Therefore, they live only for millions of years, while their less strong relatives shine brightly for billions, or even trillions–of years, in burning hydrogen main sequence of the Hertzsprung-Russell diagram of stellar evolution. Astrophysicists have assumed for many years that these ancient massive stars exploded as similar spherical supernovae.
However, the team of astronomers from MIT and other institutions have now discovered that these early stars may have been shattered in a much more powerful and asymmetrical explosion, launching jets into space that were violent enough to eject heavy atomic elements into the space. space. nearby galaxies. These newly forged elements, the first of their kind in the ancient Cosmos, served as precious seeds for the second generation of stars, some of which can still be seen dancing brilliantly in our Universe today.
In a research article published in the May 8, 2019 issue of the astrophysics journalscientists report a large amount of zinc in HE 1327-2326, which is an ancient stellar survivor that is among the second generation of stars in the Universe. They believe that the star could only have managed to obtain such an abundant amount of zinc as a result of an asymmetric supernova explosion that heralded the “death” of one of the first stars to inhabit the primordial Cosmos. The now-defunct and short-lived first-generation star thus enriched the natal gas cloud of the younger second-generation star with its newly forged batch of heavier atomic elements.
“When a star explodes, a part of that star is sucked into a black hole like a vacuum cleaner. Only when you have some sort of mechanism, like a jet that can pull material out, can you later observe that material in a next-generation star. And we think that’s exactly what could have happened here,” Dr. Anna Frebel explained in a May 8, 2019 statement. MIT press release. Dr. Frebel is an Associate Professor of Physics at MIT and an MIT Fellow Kavli Institute for Astrophysics and Space Research.
“This is the first observational evidence that such an asymmetric supernova occurred in the early Universe. This changes our understanding of how the first stars exploded,” said Dr. Rana Ezzeddine, who is a postdoc at MIT and lead author of the study. .
star generations
The first generation of stars was not like the stars we see today. This is because the first stellar generation was born directly from pristine hydrogen and helium, the two lightest atomic elements in the familiar Periodic table. Both hydrogen and helium were born in the Big Bang. (Big Bang Nucleosynthesis). The first stars are believed to have been gigantic and extremely bright, and their existence changed our Universe from what it is. was to what now is.
There are three generations of stars. Our Sun is a member of Population I, which means that it is a member of the youngest stellar generation. Population III stars are the oldest and formed from pristine gas that remained after the Big Bang. In astronomers’ jargon, all atomic elements heavier than helium are called rails. Therefore, the term metal, as used by astronomers, it is different from the same term when used by chemists. Population II stars are stars that lie between Populations I and III. These stars are older than our Population I Sun, but younger than the earliest Population III stars. The first stars were depleted of metals, but Population II stars show small amounts of the rails forged in the hot hearts of Population III stars. Population I stars, like our Sun, have the largest metal delighted. However, this neat ranking is somewhat misleading. This is because all stars, regardless of their generation, are moving balls made mostly of hydrogen gas.
Because rails can only be produced through the process of stellar Nucleosynthesis, the existence of even traces of rails indicates that a previous Population of stars had to exist before the Population II stars were born. There had tp there has been a population of stars that existed before them to create these rails. Population III stars, which no longer exist in the visible Universe, left their chemical “footprints” in the generation of stars that followed them, and these stellar “footprints” speak of that now-vanished primordial population of the older generation. of stars
Astronomers roughly classify stars as Population I (high metal content) or Population II (low metal delighted). But, because even the most metal-Poor Population II stars sport a small amount of rails, reveal that its composition is composed of more than just the pristine primordial gas that formed in the Big Bang at the birth of the Universe. The Population III stellar giants were composed of only the lightest pristine gases: hydrogen, helium, and scant amounts of lithium. Therefore, the gas that makes up the Population III stars was not “contaminated” by the heavy rails forged in the warm hearts of former stars. The Population III stars triggered the gradual rise of the stellar. metallicity into younger and younger generations of stars.
Population III stars are generally believed to have been born in pure cradles of uncontaminated gas. Computer numerical simulations have shed light on the very old and mysterious process of star formation and the extremely short life of the first stars. The gigantic Population III stars did not go quietly into that good night, and they shattered noisily in brilliant supernova explosions, spewing out their supply of newly formed stars. rails howling loudly in the space between the stars. This made the newborn heavier atomic elements available to be incorporated into the cold dark giant. molecular clouds of gas and dust that served as strange nurseries for later generations of more metal-rich stars.
Because the first stars were so massive, they quickly used up their necessary supply of pristine hydrogen gas, then blew apart in what were likely extraordinarily powerful, bright, and violent supernovae. Population III stars burned out at a relatively young age by stellar standards. These ancient supernovae were largely responsible for triggering a remarkable sea change in the Universe. These dazzling stars completely changed the dynamics of the Universe by heating it up. This new heat ionized the ambient gas.
The lingering legacy of the early stars
Dr. Frebel discovered the gossipy star, nicknamed HE 1327-2326in 2005. At that time, the star held the title of the most metal-known deficient star. This means that it had extremely low concentrations of elements heavier than hydrogen and helium, indicating that it was a people II star. HE 1327-2326 was born at a time when most of the heavyweights in the Universe rails it had not yet been forged.
“The first stars were so massive that they had to explode almost immediately. The smaller stars that formed as the second generation are still available today and retain the initial material left behind by these early stars. Our star has only a speck of elements. than hydrogen and helium, so we know it must have formed heavier as part of the second generation of stars,” explained Dr. Frebel on May 8, 2019. MIT press release.
“People thought, from the first observations, that the first stars weren’t that bright or energetic, and that when they exploded, they wouldn’t do much to reionize the Universe. In a sense, we’re rectifying this picture and showing that maybe the first stars had enough oomph when they exploded, and may now be strong contenders for contributing to reionization and for wreaking havoc on their own small dwarf galaxies,” added Dr Frebel.
The first supernovae that heralded the explosive death of the first stars may also have been powerful enough to fire off their newly formed batch of heavy stars. rails in nearby “virgin galaxies” that had not yet given birth to their own stars.
Dr Frebel went on to explain that “once you have some heavy elements in a hydrogen and helium gas, you have a much easier time forming stars, especially small ones. The working hypothesis is that maybe second generation stars of this type were formed in these contaminated places”. virgin systems, and not in the same system as the supernova explosion itself, which is what we had always assumed, without thinking otherwise. So this is opening up a new channel for early star formation.”