A Star Is Born

Where do stars come from, how are they formed, and what are they made of?

Fusion is the process of two atoms combining together to become one new, larger atom. This process is also typically exothermic and releases energy to its surroundings. Fusion is the main process that powers stars. Gravity is what first forms stars and fusion is what keeps the stars from falling into themselves completely due to gravity. Nuclear fusion is a process in which two atomic nuclei are combined to form a heavier nucleus, releasing an enormous amount of energy in the process. This process is the fundamental source of energy in stars, including our Sun.

In the early 20th century, scientists such as Albert Einstein and Arthur Eddington laid the theoretical groundwork for nuclear fusion. They proposed that the Sun's energy was generated by the fusion of hydrogen nuclei. In the 1930s, the first experimental steps towards nuclear fusion were taken. Mark Oliphant and Ernest Rutherford in England conducted experiments that led to the discovery of deuteron, often called heavy hydrogen due to its neutron. The post-World War II era saw increased research in nuclear fusion. In 1951, the first successful demonstration of a controlled fusion reaction occurred with the development of the stellarator device by Lyman Spitzer. International Thermonuclear Experimental Reactor (ITER), a collaborative project involving 35 nations, began construction in 2007. It aims to demonstrate sustained fusion reactions and produce net energy from fusion.

Stars, including the Sun, generate energy through nuclear fusion. The primary fusion reaction in the Sun involves the combination of hydrogen nuclei (protons) to form helium nuclei. This process releases a tremendous amount of energy in the form of light and heat. Gravity is the force that allows particles needed for star formation to get close in the first place. Once there is a critical mass of particles nuclear fusion becomes possible. The activity shows here models this. Nuclear fusion requires extremely high temperatures and pressures to overcome the electrostatic repulsion between atomic nuclei. At such conditions, the atomic nuclei come close enough for the strong nuclear force to bind them together.

Nuclear fusion has the potential to provide a safe, clean, and virtually limitless source of energy here on Earth. Unlike nuclear fission, which is currently used in nuclear power plants, fusion does not produce long-lived radioactive waste and does not carry the risk of runaway chain reactions or meltdowns. Achieving controlled nuclear fusion on Earth is challenging due to the extreme conditions required. The fuel must be heated to millions of degrees Celsius to form a plasma state, where atomic nuclei can collide and fuse. Additionally, the plasma must be confined and stabilized for a sufficient period to extract useful energy. You can explore this topic more in Activity 4: The Three-Legged Challenge of Thermonuclear Fusion.

• Real world connections:
  • Have students read about the different types of stars. Have students choose one type of star and explain the role that nuclear fusion plays in its creation/categorization.
• Suggestions for drawing, illustrating, presenting content in creative ways:
  • Have students research the life cycle of a star (Life Cycle of Stars).
  • Have students draw the evolution of a star from birth to death OR write a short story from the star’s perspective that follows it from birth to death. Students can choose what kind of star it will evolve into (i.e., neutron star, white dwarf, etc.).
• Engineering and design challenges connected to the content:
  • Fusion energy is the engineering and design process of trying to “bottle” stars. Learn more about this in lesson 4!

Real world situations/connections can be used as is, or changed to better fit a student’s own community and cultural context.

• MS-PS1-1
  Develop models to describe the atomic composition of simple molecules and extended structures.
• MS-PS1-4
  Develop a model that predicts and describes changes in particle motion, temperature, and state of a pure substance when thermal energy is added or removed.
• Science and Engineering Practices (SEPs)
  Developing and Using Models ▪ Analyzing and Interpreting Data ▪ Constructing Explanations and Designing Solutions ▪ Obtaining, Evaluating, and Communicating Information
• Cross Cutting Concepts (CCCs)
  Cause and Effect Energy and Matter Scale, Proportionality, and Quantity Systems and System Models Stability and Change

Credits