The first stars in the cosmos may have peaked at more than 10,000 times the mass of the sunabout 1,000 times larger than the largest stars alive today, according to a new study.
Nowadays, the biggest stars are 100 solar masses. But the beginning universe was a much more exotic place, filled with mega-giant stars that lived fast and died very, very young, the researchers found.
And once these doomed giants died out, the conditions were no longer right for them to reform.
Related: Our Expanding Universe: Age, History, and Other Facts
The Cosmic Dark Ages
More than 13 billion years ago, shortly after the big Bang, the universe had no stars. There was nothing more than a hot soup of neutral gas, almost entirely composed of hydrogen and helium. Over hundreds of millions of years, however, this neutral gas began to accumulate into denser and denser balls of matter. This period is known as the Cosmic Dark Ages.
In the modern universe, dense balls of matter quickly collapse to form stars. But that’s because the modern universe has something the early universe lacked: lots of elements heavier than hydrogen and helium. These elements are very effective in dissipating energy. This allows dense clumps to shrink very quickly, collapsing at densities high enough to trigger nuclear fusion – the process that powers stars by combining lighter elements into heavier ones.
But the only way to get heavier elements in the first place is to go through that same process of nuclear fusion. Several generations of forming, merging and dying stars have enriched the cosmos to its present state.
Without the ability to rapidly release heat, the first generation of stars must have formed under much different and much more difficult conditions.
To figure out the riddle of those early stars, a team of astrophysicists turned to sophisticated computer simulations of the Dark Ages to figure out what was going on back then. They reported their findings in January in an article published in the arXiv prepublication database (opens in a new tab) and submitted for peer review to the Monthly Notices of the Royal Astronomical Society.
The new work has all the usual cosmological ingredients: Black matter to help grow galaxies, evolution and agglutination of neutral gas, and radiation which can cool and sometimes warm the gas. But their work includes something that others lacked: cold fronts – rapid streams of cooled material – crashing into already formed structures.
The researchers found that a complex web of interactions precedes the first star formation. Neutral gas began to accumulate and clump together. The hydrogen and helium released some heat, which allowed the clusters of neutral gas to slowly reach higher densities.
But the high-density clumps became very hot, producing radiation that separated the neutral gas and prevented it from fragmenting into many smaller clumps. This means stars made from these clusters can grow incredibly large.
These back-and-forth interactions between radiation and neutral gas led to massive pools of neutral gas – the beginnings of the first galaxies. The gas deep within these proto-galaxies has formed rapidly rotating accretion disks – fast-flowing rings of matter that form around massive objects, including black holes in the modern universe.
Meanwhile, on the outer edges of the proto-galaxies, cold fronts of gas were raining down. The coldest and most massive fronts penetrated the proto-galaxies up to the accretion disk.
These cold fronts slammed into the disks, rapidly increasing their mass and density to a critical threshold, allowing the first stars to appear.
Those early stars weren’t just any normal fusion factories. They were gigantic clumps of neutral gases igniting their fusion cores all at once, skipping the stage where they fragment into small pieces. The resulting stellar mass was enormous.
These early stars would have been incredibly bright and lived extremely short lives, less than a million years. (Stars in the modern universe can live for billions of years). After that, they would have died in furious bursts of supernova explosions.
These explosions would have carried the products of internal fusion reactions – elements heavier than hydrogen and helium – which then seeded the next cycle of star formation. But now contaminated with heavier elements, the process could not repeat itself, and these monsters would never again appear on the cosmic scene.
Originally posted on LiveScience.com.
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