triple-alpha presentashon

Triple-alpha pr cess

The triple-alpha process is a set of nuclear fusion reactions by which three helium-4 nuclei are transformed into carbon.

(The primary goal is to produce a carbon 12)

Why is it called triple-alpha?

It is called the triple-alpha process because three helium atoms, also known as alpha particles, are involved. This is where the term 'triple-alpha' comes from.

What is the importance of the triple-alpha process?

The triple alpha process is responsible for the conversion in stars of the alpha particles (or 4He nuclei) made in the Big Bang to the carbon we find around us and in us. This process underlies Carl Sagan's famous statement that “we are made of star-stuff.”

What is produced during the fusion of the triple-alpha process?

After stars become red giants, their cores eventually become hot enough to produce energy by fusing helium to form carbon (and sometimes a bit of oxygen.) The fusion of three helium nuclei produces carbon through the triple-alpha process.

The triple-alpha process will occur in red giant stars that have left the main sequence (and have consumed their core hydrogen) and have core temperatures of 108K and higher. Once 12C has been formed it is possible with temperatures around 6 × 108 K to continue forming heavier nuclei by the combination of two 12C nuclei to make 16O, 20Ne, and 24Mg, and with temperatures around 109K, the combination of two 16O nuclei can make 28Si, 31P, 31S, and 32S.

The triple-alpha process

The triple-alpha process begins when two 4He nuclei fuse to form an unstable 8Be nucleus. If this nucleus collides with another 4He nucleus before it breaks apart, the two will fuse to form a nucleus of carbon-12. The energy released is carried off both by the motion of the 12C nucleus and a gamma ray.

The ALpha ladder

The alpha process (or alpha ladder or helium capture) is a sequence of nucleosynthesis steps, by which elements are synthesized within extreme heat (e.g., inside stars). Each step is the combination of an alpha particle (basically, a helium nucleus) with another nucleus (e.g., of carbon or oxygen, etc.) In this, an alpha particle is added to an atomic nucleus (such as carbon) to form oxygen. The addition of an alpha particle to an atom adds 2 protons (and therefore the atomic number of the product is 2 larger than the original) Odd elements are not formed through the alpha ladder in stars.

The triple-alpha process

The Oddo-Harkins rule states that even-numbered elements are inherently more stable (and therefore more common) than odd elements . Odd elements can be formed during the Big Bang, radioactive decay, or supernova nucleosynthesis.

The triple-alpha process

During a star’s lifetime, it burns heavier and heavier elements. Heavier elements burn faster. When it accumulates Fe (iron) in the core and can no longer maintain a balance of temperature and pressure, the star will undergo core collapse.

Summary

Following the initial hydrogen fusion phase, more massive stars progress to fuse heavier elements in their cores. Red Giants utilize helium fusion to produce carbon through the triple-alpha process. Super Giant Stars go beyond, synthesizing elements through subsequent stages of alpha fusion. The alpha ladder facilitates the formation of even elements lighter than iron. Odd elements can arise from supernovae or nuclear decay processes. Even elements exhibit greater prevalence compared to their odd counterparts. As a star depletes its energy reserves, its core predominantly comprises iron, surrounded by outer shells of lighter elements.