Steps in Hydrogen Burning
Step 1 in the p-p chain is fusion of two colliding protons (1H) to form a deutron (2H), which is the nucleus of the hydrogen isotope deuterium, resulting in the emission of a positron (e+) and a neutrino (v). This reaction happens, on an average, once every 14 billion years for each isolated pair of protons. The time for the entire thernomuclear process is determined by this first step, and it is only the enormous quantity of hydrogen in the cores of stars that makes this process a significant source of energy.
The positron is a positively charged particle with the mass and other characteristics of n electron; it is the antiparticle for the electron. The collision of a positron with an electron destroys them as matter and creates two gamma-ray photons. The neutrino, on the other hand, is a massless, chargeless particle traveling at the speed of light and has a low probability of interacting with matter. It immediately escapes from th star, carrying away about 2 percent of the energy released in the p-p chain of reactions.
Step 2 in the p-p chain is the collision within a few seconds of another proton with the deuteron to fuse and form the light isotope of helium, resulting in the emission of a gamma-ray photon.
Finally, in step 3, 3He nuclei collide every few million years and fuse to form the heavy isotope of helium (4He), accompanied by the return of two protons. (We should point out that there are other branches of these reactions leading to the same end.)
All told, six protons have taken part in producing two 'He nuclei, from which one 4He nucleus is produced and two protons returned to the reservoir of fusionable matter.
The other hydrogen-burning reaction, the CNO cycle, has six steps occurring at rates between 80 seconds and 300 million years but leading to the same result as the p-p chain; that is, the conversion of four protons to produce one helium nucleus and to liberate energy. The cycle begins with 12C and closes with the return of '2C so that carbon is only a catalyst that makes the reaction go.
Step 1 in the p-p chain is fusion of two colliding protons (1H) to form a deutron (2H), which is the nucleus of the hydrogen isotope deuterium, resulting in the emission of a positron (e+) and a neutrino (v). This reaction happens, on an average, once every 14 billion years for each isolated pair of protons. The time for the entire thernomuclear process is determined by this first step, and it is only the enormous quantity of hydrogen in the cores of stars that makes this process a significant source of energy.
The positron is a positively charged particle with the mass and other characteristics of n electron; it is the antiparticle for the electron. The collision of a positron with an electron destroys them as matter and creates two gamma-ray photons. The neutrino, on the other hand, is a massless, chargeless particle traveling at the speed of light and has a low probability of interacting with matter. It immediately escapes from th star, carrying away about 2 percent of the energy released in the p-p chain of reactions.
Step 2 in the p-p chain is the collision within a few seconds of another proton with the deuteron to fuse and form the light isotope of helium, resulting in the emission of a gamma-ray photon.
Finally, in step 3, 3He nuclei collide every few million years and fuse to form the heavy isotope of helium (4He), accompanied by the return of two protons. (We should point out that there are other branches of these reactions leading to the same end.)
All told, six protons have taken part in producing two 'He nuclei, from which one 4He nucleus is produced and two protons returned to the reservoir of fusionable matter.
The other hydrogen-burning reaction, the CNO cycle, has six steps occurring at rates between 80 seconds and 300 million years but leading to the same result as the p-p chain; that is, the conversion of four protons to produce one helium nucleus and to liberate energy. The cycle begins with 12C and closes with the return of '2C so that carbon is only a catalyst that makes the reaction go.
