A Review of Nuclear Fusion In Stars

Peter M. Williams, Artem Cheprasov
  • Author
    Peter M. Williams

    Peter holds a Bachelor's degree in Microbiology and Biotechnology, and a Master's degree in Applied Microbiology. In addition, Peter has more than two years of experience in tutoring and writing academic materials for senior and junior schools, mainly in Sciences, Languages, and Humanities.

  • Instructor
    Artem Cheprasov

    Artem has a doctor of veterinary medicine degree.

Understand nuclear fusion in stars. Learn about the sun's nuclear fusion. See an explanation of the process of nuclear fusion and the role played by hydrogen. Updated: 06/29/2022

Table of Contents


Nuclear Fusion in Stars

The sky at night is usually embellished with twinkling stars of all kinds. However, these celestial bodies carry profound mysteries which are beyond imagination. Firstly, the stars are normally categorized based on their sizes and masses; categories of starts include giants, super-giants, white dwarfs, and main-sequence stars. In addition, the stars are similar to the sun since they never reflect light, but they produce their own light. Therefore, the sun is also considered a star. Stars can thus be defined as massive, hot, glowing balls (spheres) comprised of burning gases. These gases are hydrogen and helium, the main constituents of stars.

The Stars

An image of the stars in the sky

The stars are known to generate energy through the process of nuclear fusion. This reaction typically converts hydrogen to helium and other heavier elements in the stars. As the name suggests, nuclear fusion reaction involves the elements of the nucleus of an atom. Inside the nucleus of an atom are subatomic particles, namely protons and neutrons. Therefore, if the bonds of these subatomic particles and broken and then reconnected with another subatomic particle of a higher nucleus, then nuclear fusion is said to have occurred.

For instance, hydrogen has one proton and zero neutrons in its nucleus. On the other hand, helium has two protons and two neutrons in its nucleus. Therefore, a hydrogen nucleus can be combined with a helium nucleus through nuclear fusion because the nucleus of helium is heavier than that of hydrogen. Nuclear fusion can thus be defined as a reaction that combines a lighter nucleus with a heavier nucleus, ultimately releasing energy. The energy release is due to the tighter nuclei bond created when these two nuclei combine. A fraction of this generated energy is then radiated out, thus the light emission. Generally, this is what star nuclear fusion is all about.

The Sun's Nuclear Fusion

The sun is considered a star whose nuclear fusion occurs in its central region known as the core. Generally, the sun's nuclear fusion involves a combination (fusion) of four hydrogen nuclei, which results in one helium nucleus. During this process, energy is also emitted from the conversion of some hydrogen masses (matter quantity) into energy. The fusion of these hydrogen nuclei occurs in a series of reactions known as the proton-proton chain. This reaction aims to build a helium nucleus through the addition of protons.

The core of the sun (Number 1)

Various regions of the sun; number one represent the core of the sun

This begins with the combination of two hydrogen nuclei, forming a heavy hydrogen nucleus called deuterium. This combination leads to the emission of two particles, namely, positrons and neutrinos. A positron is a positively charged electron, while a neutrino is a subatomic particle characterized by low mass and a speed equivalent to that of light.

The heavy hydrogen nucleus formed then absorbs another proton. This results in energy emission in the form of gamma rays and the formation of a light helium nucleus. Two light helium nuclei then combine to form a helium nucleus, releasing energy. The energy in this fusion reaction is in the form of the positrons, neutrinos, gamma rays, and motion energy of other particles. Neutrinos escape from the sun at the speed of light, carrying with them two percent of the energy, which also reaches the earth.

The gamma rays get trapped by the surrounding gases as they try to escape. This entrapment makes the gamma rays heat the surrounding gas. Other gamma rays that keep the gas hot are formed when positrons combine with other electrons, which make them disappear, and their masses get converted to gamma rays. The temperature of the surrounding gases is also kept high by the motion energy of particles that collides at high velocity with the newly formed nuclei. The hot and dense temperatures make it possible for nuclear reactions to occur at the sun's center. Therefore, nuclear energy flows from the sun's core to its outer regions. This energy from the core hits the earth as the sunlight.

The energy from the sun is vital to all living things. For instance, plants require this energy to manufacture food through photosynthesis. This energy is also essential in synthesizing vitamin D in humans and animals. In addition, this energy acts as a source of fuel, especially in solar lighting. Moreover, many human activities, such as sun drying of foodstuff and clothes, depend on the energy from the sun.

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Frequently Asked Questions

Where does nuclear fusion occur in a star?

Nuclear fusion normally occurs at the central part of a star, mostly called the core. High temperatures of up to 10,000,000K characterize this region.

What is fusion in the stars?

Fusion in stars is a nuclear reaction that combines a lighter nucleus with a heavier nucleus, thus releasing energy. For instance, these reactions generally convert hydrogen nuclei into helium nuclei, accompanied by energy emission.

What stars have nuclear fusion?

Nuclear fusion is exhibited in all kinds of stars. This includes the sun, dwarf stars, giant stars, super-giant stars, and main-sequence stars.

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