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(Nuclear Fusion)
(formation of an atomic nucleus nuclei from multiple smaller nuclei)

Fusion (specifically, Nuclear Fusion) is a type of Nuclear Reaction, specifically, the formation of an atomic nucleus from smaller nuclei. Some fusion reactions release energy in the form of Electromagnetic Radiation and/or Particles such as Neutrinos, while others require energy to take place. Fusion (the former kind, releasing energy) is the primary source of energy in the long life of stars and is a factor in explosions such as supernovae. In both cases, it constitutes Nucleosynthesis as well.

The opposite nuclear reaction, division of a nucleus into multiple nuclei, is Nuclear Fission (or just Fission). In both cases, certain conditions make the event more likely: for fusion, in addition to the particular starting particles for the particular reaction, the particles must have enough Kinetic Energy in the form of heat. The requirements for fission are similar, but the kinetic energy is needed in an extra incoming particle (e.g., neutron) to trigger the fission event.

In both cases, a new nucleus (or nuclei) results, of a different Element (or elements), i.e., with a different Atomic Number (number of protons), and a different Mass Number (number of Nucleons, i.e., protons and neutrons). The actual Atomic Mass is approximately the mass number, but is actually a touch larger or smaller because of the Binding Energy, i.e., the energy that holds this particular nucleus configuration together, which varies with the combination of atomic number and mass number. It is the difference in required binding energy for the initial nuclei and the final nuclei, when it results in an excess of energy, that produces fusion or fission power. A new configuration that requires more binding energy than the initial nuclei draws kinetic energy from the collision (and requires that much kinetic energy and thus a sufficient Temperature).


Referenced by:
Asymptotic Giant Branch (AGB)
Alpha Capture
Binding Energy
Black Hole (BH)
Brown Dwarf (BD)
Carbon Star
CNO Cycle
Compact Object
Compton Scattering
Cross Section
Cataclysmic Variable Star (CV)
Electron Screening
Endothermic Reaction
Gamow Peak
Globular Cluster (GC)
Gravitational Collapse
Horizontal Branch (HB)
Helium (He)
Helium Flash
Helium Runaway Shell
Inflated Radii
Iron (Fe)
Isothermal Core
Kelvin-Helmholtz Mechanism
Lithium (Li)
Main Sequence Star
Mean Free Path
Neutrons from Carbon-13
Nitrogen (N)
Nuclear Energy Generation Rate (ε)
Post Main Sequence Star
Proton-Proton Chain
Quantum Number
Quantum Tunneling
Random Walk
Schönberg-Chandrasekhar Limit
Stellar Core
Stellar Evolution
Stellar Structure
Thermal Pulse
Triple Alpha Process
T-Tauri Star (TTS)
Zero-age Main Sequence (ZAMS)