The star of the universe
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The Star of the Universe: Formation and Evolution
Formation of the First Stars in the Universe
Primordial Star Formation and Dark Matter
The formation of the first stars in the universe, often referred to as Population III stars, is a critical event in cosmic history. These stars formed in the early universe, within pregalactic halos dominated by dark matter. The process began with gravitational instabilities in small initial density perturbations, leading to the assembly of primordial gas through hierarchical merging. This gas cooled via molecular hydrogen lines and sank to the center of dark matter potential wells, forming dense molecular clouds1 2.
Protostar Development
As the gas cloud's central regions became self-gravitating, a dense core of approximately 100 solar masses underwent rapid contraction. At particle number densities exceeding 10^9 per cubic centimeter, a 1 solar mass protostellar core formed, becoming fully molecular due to three-body hydrogen molecule formation. Contrary to previous expectations, this process did not lead to fragmentation, resulting in the formation of a single massive star1.
Radiative Feedback and Star Growth
The newly formed protostar began accreting material rapidly, at a rate of about 0.01 solar masses per year. Radiative feedback from the star eventually halted its growth and inhibited the formation of other stars in the same pregalactic object until the first star ended its life, likely as a supernova1 7.
Evolution and Impact of the First Stars
Cosmic Reionization
The first stars played a pivotal role in transforming the early universe by emitting the first light and producing the first heavy elements. Their radiation ionized the surrounding hydrogen atoms, leading to the reionization of the universe. This process is crucial for understanding the transition from the cosmic dark ages to a universe filled with light9.
Star Formation History
The star formation history of the universe reveals that star formation peaked around 3 billion years after the Big Bang, corresponding to a redshift of approximately 2. This peak is consistent with observations from gamma-ray attenuation and other methods, confirming the timeline of star formation5 6.
Protostellar Feedback
Simulations suggest that the first stars might have been less massive than previously thought. Protostellar radiation from these stars evaporated the circumstellar accretion disk when the star's mass reached about 43 solar masses, halting further growth. This finding helps explain the absence of pair-instability supernovae signatures in metal-poor stars in our galaxy7.
Observational Evidence and Future Prospects
Early Star-Forming Galaxies
Observations of distant galaxies, such as MACS1149-JD16, indicate that star formation began around 250 million years after the Big Bang, at a redshift of about 15. This early star formation period is crucial for understanding the initial stages of galaxy formation and the subsequent evolution of the universe8.
Upcoming Telescopes
Future telescopes, such as the James Webb Space Telescope (JWST), are expected to provide more detailed observations of the earliest galaxies and the first stars. These observations will help refine our understanding of the formation and evolution of the first stars and their impact on the universe2.
Conclusion
The formation and evolution of the first stars in the universe marked a significant transformation from darkness to light. These stars, formed within dark matter halos, played a crucial role in cosmic reionization and the enrichment of the universe with heavy elements. Observations and simulations continue to enhance our understanding of these primordial stars, with future telescopes poised to uncover even more about this fascinating period in cosmic history.
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Most relevant research papers on this topic
The Formation of the First Star in the Universe
At most one massive metal-free star forms per pregalactic halo, with radiation feedback inhibiting star growth and preventing further star formation in the same pregalactic object.
Highly CitedFormation of the first stars
The first stars were predominantly massive, and understanding their formation is crucial for understanding the early universe and its transformation.
Highly CitedThe star-formation history of the Universe from the stellar populations of nearby galaxies
The peak of star formation was more recent, around five billion years ago, and high-mass galaxies have different histories from low-mass galaxies.
Highly CitedProtostar Formation in the Early Universe
Primeval density fluctuations from the Big Bang can drive the formation of a tiny protostar with a mass 1% that of the Sun, which serves as a seed for the subsequent formation of a massive primordial star.
Highly CitedA gamma-ray determination of the Universe’s star formation history
Star formation peaked about 3 billion years after the Big Bang, with gamma rays from distant blazars revealing the history of the Universe over 90% of cosmic time.
Highly CitedThe history of star formation in a lcdm universe
Our model predicts that about 50% of stars formed in halos less massive than 10 11:5 h i1 Mfl, with the UV background being dominated by stars for redshifts z > 4.
Highly CitedProtostellar Feedback Halts the Growth of the First Stars in the Universe
The first stars in the universe may have been less massive than previously thought, potentially explaining the lack of pair-instability supernovae in abundance patterns of metal-poor stars in our galaxy.
Highly CitedThe onset of star formation 250 million years after the Big Bang
Star formation began at a redshift of about 15, around 250 million years after the Big Bang, and may be detectable in similar galaxies with future telescopes.
Rigorous JournalHighly CitedAn analytical model for the history of cosmic star formation
The cosmic star formation rate peaks at an intermediate redshift, z = z p e a k, and can be used to compute global cosmological quantities related to star formation.
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