NUCLEOSYNTHESIS - SCI
& TECH
News: What is nucleosynthesis?
What's in the news?
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Stellar nucleosynthesis is the process by which
stars forge elements inside their cores.
Key takeaways:
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The only element not formed in this way is
hydrogen, the most abundant and lightest element in the universe: it was formed
in the initial aftermath of the Big Bang.
Nucleosynthesis:
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Nucleosynthesis is the process by which stars create elements within their cores.
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The sole exception is hydrogen, the most abundant and lightest element in the universe,
which originated in the immediate aftermath of the Big Bang.
Extreme Conditions in
Stellar Cores:
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The cores of stars experience immense pressures and
temperatures.
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For instance, the temperature in the Sun’s core
reaches approximately 15 million degrees Celsius. Under these extreme
conditions, atomic nuclei undergo nuclear fusion.
Fusion Process in
Hydrogen:
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The hydrogen
nucleus consists of a single proton. In the stellar core, these nuclei fuse
to create helium nuclei, which
contain two protons and two neutrons. This fusion process is known as the
proton-proton (p-p) chain.
Nucleosynthesis in
Massive Stars:
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However, in more massive stars, stellar
nucleosynthesis follows a different route due to the higher energy available.
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These stars have hotter cores where the carbon-nitrogen-oxygen (CNO) cycle
operates.
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In this cycle, the nuclei of carbon, nitrogen, and
oxygen interact in various ways to form elements starting from helium.
Iron Production:
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When a star runs out of nuclei to fuse, its core
contracts, leading to an increase in temperature that reignites nuclear fusion.
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This cycle of contraction and fusion continues
until the star begins producing iron in its core. Iron is the lightest element
for which fusion requires more energy than it releases.
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Elements heavier than iron can only be synthesized outside a star when it
goes supernova.