In physical cosmology, Big Bang nucleosynthesis or primordial nucleosynthesis refers to the production of nuclei other than H-1, the normal, light hydrogen, during the early phases of the universe, shortly after the Big Bang. It is believed to be responsible for the formation of hydrogen H-1 or simply H , its isotope deuterium H-2 or D , the helium isotopes He-3 and He-4, and the lithium isotope Li Big Bang nucleosynthesis begins about one minute after the Big Bang, when the universe has cooled enough to form stable protons and neutrons, after baryogenesis.
From simple thermodynamical arguments, one can calculate the fraction of protons and neutrons based on the temperature at this point. This fraction is in favour of protons, because the higher mass of the neutron results in a spontaneous decay of neutrons to protons with a half-life of about 15 minutes. Reference Terms.
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July 6, Shot-time image from a June 1 NIF experiment simulating stellar nucleosynthesis fusion reactions. Credit: Lawrence Livermore National Laboratory. Explore further.
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1.1 Nucleosynthesis: the origin of elements in our Solar System - Part 1 – Jim Connelly
While physicists struggled to understand the dizzying variety of ways that new nuclei could be created, astronomers searched the cosmos for a site that could produce the necessary torrent of neutrons. Evidence from existing stars suggested that elements born in the r-process must come from a single type of source. Every star that harbors r-process elements — including the sun — has them in the same relative amounts. For decades, the prime suspects were supernovas, the cataclysmic deaths of stars much more massive than the sun.
Nucleosynthesis - Universe Today
But the more theorists pursued that possibility, the less likely the supernova explanation seemed. In astrophysicists Eugene Symbalisty and David Schramm suggested that collisions between neutron stars might work. Suspected to exist in the s and first detected in the s, neutron stars betrayed their presence by emitting regular pulses of radiation, earning the designation of pulsar.
Observations of the binary pulsar revealed that over the next few hundred million years, the two neutron stars would spiral closer together and eventually merge. Such a collision would probably eject gobs of neutron-rich material, which could then be folded into the next generation of stars and planets. Other data also implicated neutron stars as r-process sources.
Radioactive elements on Earth, for example, can reveal how much of these elements were created long ago based on how much remains around now. The r-process element plutonium, for instance, has a half-life of 81 million years. Its abundance today indicates initial yields much lower than expected from something as relatively common as a supernova. It seems that r-process synthesis must be a relatively rare event. Dwarf galaxies that orbit the Milky Way have also helped trace heavy element origins.
- nucleosynthesis, recombination;
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These wispy collections of stars are considered probable remnants of the early universe, untouched since their formation. Because they are simple and pristine, they preserve a clear record of how their elements were synthesized.
Stellar Nucleosynthesis: How Stars Make All of the Elements
They found that most of its brightest stars were loaded with r-process elements. Nine other dwarf galaxies showed comparatively few of these elements, indicating that at some point Reticulum II hosted a single, rare event that polluted its stars with r-process debris.
Ji and collaborators concluded that a collision between two neutron stars could explain all the observations. But the dwarf galaxy is so tiny that it would never survive that sort of onslaught. While the case for neutron stars was growing, the evidence remained circumstantial. No one had yet witnessed a definitive collision — until last August. LIGO is designed to sense ripples in space-time from a variety of cosmic calamities.
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Virgo, a gravitational wave detector in Italy, helped triangulate where the gravitational wave signal was coming from. Just 1. An automated system alerted the astronomical community. Details of the gravitational wave signal revealed that two neutron stars had spiraled together and merged. Colors of light from the crash scene revealed telltale signatures of newly formed heavy elements. The timescale, energy, colors and amount of ejected material all closely matched theoretical predictions for a neutron star merger.
The numbers are staggering. The neutron stars, whipping around each other hundreds of times per second, merged in just a few milliseconds.
Related which of the following elements are not formed by nucleosynthesis
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