When Does Nuclear Fusion Begin ? 7 Facts You Should Know!

Nuclear fusion is the merging two lighter nuclei to form a bigger nucleus with some energy release. Let’s discuss the beginning of nuclear fusion.

Nuclear fusion begins when two lighter nuclei separated by a certain distance approach each other at high speed to overcome the electrostatic repulsion between them. At a very small distance, two nuclei experience a strong nuclear force that causes them to merge into a single heavy nucleus.

A lighter nucleus consists of protons; thus, there will be only repulsion between them, so combining them is harder. Both nuclei experience a strong nuclear force at a short distance that combines two lighter nuclei into one. In this post, we shall learn some more facts about nuclear fusion.

When does nuclear fusion begin in a star’s life?

Stars are made of hydrogen and helium, which are the lightest elements. Now, let us look at the begging of nuclear fusion in stars.

The nuclear fusion in stars begins when it is hot enough to overcome the coulomb barrier between elements. The hydrogen atoms in the star collide with each other to produce a large amount of heat. This process continues until the temperature reaches 15000000°C.

At very high temperatures, the hydrogen fused to form deuterium. The deuterium molecules further undergo nuclear fusion to form helium. The helium, thus formed by the nuclear reaction, is the star’s main energy source.

Where does fusion begin in a star’s life cycle?

A star’s life begins as a simple hydrogen gas inside a nebula pulled together by its gravity. Let us look into where the fusion reaction occurs in the star.

Nuclear fusion begins at the protostar’s core, the initial stage of a star. The hydrogen gas in a nebula spins very fast and is heated up to become a protostar. When the protostar attains a million degrees of temperature, the fusion of hydrogen gas to give a huge nucleus begins at its core or the center.

nucl fusion
Image: Nuclear fusion reaction by Uwe W., (CC BY-SA 3.0)

Conditions for nuclear fusion

Nuclear fusion is achieved by confining the two lighter elements. Some conditions must be full filled to confine the element. Let us know the condition required for fusion.

  • High temperature –a very high temperature allows the lighter nuclei to overcome the electric repulsion exerted between the protons.
  • High pressure –high pressure squeezes two nuclei together. They must be within the range of 10-15 m to fuse them. The intense magnetic field is generally used to create high pressure in the laboratory.
  • Sufficient density –At high temperatures, the nucleus to be fused exists in the plasma state. The density must be high at the plasma state to ensure the collision between two nuclei.
  • Confinement time –an essential criterion for the occurrence of nuclear fusion is confinement time. The length of time holds the plasma within the defined volume depending on temperature and density to ensure nuclear fusion.

What stage does nuclear fusion begin?

Nuclear fusion does not occur naturally, and the matter is not conserved as some mass of the fused nuclei is released as energy. Let us concentrate on the beginning stage of nuclear fusion.

Nuclear fusion begins when the proton of the two atomic nuclei facing each other is heated at a high temperature and moves with high velocity to collide to form the heavier nucleus. The newly formed nucleus again tends to move towards the third proton to merge with the release of energy.

Temperature required for nuclear fusion

Temperature is the kinetic energy required to fuse the nuclei is associated with temperature. Let us know what temperature is required for fusion.

The temperature required for nuclear fusion is at least 100 million degree Celsius. The minimum temperature of 107K is essential to begin nuclear fusion. The kinetic energy of the nuclei increases with the temperature; thus, they overcome the repulsion and cause fusion.

How does nuclear fusion start?

Hydrogen and helium are the two elements that are preferred for nuclear fusion. Let us concentrate on the fact that it encourages nuclear fusion.

Nuclear fusion starts by heating hydrogen gas. The hydrogen gas turns into plasma with the increase in temperature. The proton acquires maximum kinetic energy at the plasma state and is ready to smash another proton; thus, attractive nuclear force between them will outweigh the electrical repulsion.

When does nuclear fusion end?

Nuclear fusion is an exothermic reaction that releases a massive amount of energy in the form of heat. Now, let us focus on how nuclear fusion can be retarded.

Nuclear fusion is virtually a limitless energy resource; it will last until no proton is available to cause a further reaction. If the temperature decreases, naturally, plasma will terminate, causing the end of nuclear fusion because nuclear fusion is possible only in the plasma state of matter.


Let us wrap up this post by stating that nuclear fusion is why the sun exists. Nuclear fusion occurs in the sun every second, causing them to glow. So we consider nuclear fusion as the main source of renewable energy. It is hard to achieve nuclear fusion in the laboratory as it is highly impossible to generate high temperatures.

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