The main branch of the PP chain consists of the following reactions: Two mass-1 isotopes of hydrogen undergo a simultaneous fusion and beta decay to produce a positron, a neutrino, and a mass-2 isotope of hydrogen (deuterium).
What are the 3 steps of the proton-proton chain?
- 1 helium nucleus.
- 1 positron (this positron will bump into a electron and annihilate, creating a gamma ray – energy!).
- 1 gamma ray (energy!)
- 1 neutrino.
What happens in the proton-proton chain?
The Sun gets its energy when hydrogen nuclei are fused together to form helium nuclei within the solar core. This hydrogen burning is described by a sequence of nuclear fusion reactions called the proton-proton chain. Overall, this chain successively fuses four protons together to make one helium nucleus.
How long does the PP chain take?
Since the conversion of hydrogen to helium is slow, the complete conversion of the hydrogen initially in the core of the Sun is calculated to take more than ten billion years.
What is the first step in the PP chain?
The first step in this process is the collision of two protons where proximity permits the strong nuclear force to bind them together. The resulting combination is not stable, and one of the protons will decay to become a neutron, and this forms a stable nucleus of deuterium.
What stars use the CNO cycle?
The CNO cycle is hypothesized to be dominant in stars that are more than 1.3 times as massive as the Sun.
What is the second step in the PP chain?
The second step involves the collision of a deuterium nuclei (produced in Step 1) with a proton to form a nucleus of Helium-3. The increased stability results in the release of some energy in the form of a gamma ray.
What do the CNO cycle and the PP chain have in common?
The proton-proton chain and the CNO cycle both convert four hydrogen nuclei into one helium nucleus, releasing energy.
Why are neutrinos so difficult to detect?
Why are neutrinos so hard to detect? Neutrinos are very hard to detect because they have no electric charge. But when a neutrino passes through matter, if it hits something dead-on, it will create electrically charged particles. And those can be detected.
What is the meaning of CNO cycle?
carbon-nitrogen-oxygen cycle
CNO cycle, in full carbon-nitrogen-oxygen cycle, sequence of thermonuclear reactions that provides most of the energy radiated by the hotter stars.
What is the role of C 12 in the CNO cycle?
The ‘CNO cycle’ refers to the Carbon-Nitrogen-Oxygen cycle, a process of stellar nucleosynthesis in which stars on the Main Sequence fuse hydrogen into helium via a six-stage sequence of reactions. A carbon-12 nucleus captures a proton and emits a gamma ray, producing nitrogen-13.
What is the end product of CNO cycle?
In the CNO cycle, four protons fuse, using carbon, nitrogen, and oxygen isotopes as catalysts, each of which is consumed at one step of the CNO cycle, but re-generated in a later step. The end product is one alpha particle (a stable helium nucleus), two positrons, and two electron neutrinos.
What is the significance of the PP3 chain?
The pp III chain is not a major source of energy in the Sun (only 0.11%), but was very important in the solar neutrino problem because it generates very high energy neutrinos (up to 14.06 MeV). This reaction is predicted but has never been observed due to its great rarity (about 0.3 parts per million in the Sun).
Why is the PPI chain the only possible reaction chain?
With only hydrogen available (for example, a first generation star) the ppI chain (see previous slide) is the only possible sequence of reactions. (other reaction chains require catalyst nuclei). The ppI chain proceeds as follows: This does not work because the d abundance is too low. d + p leads to rapid destruction of d.
How much energy is released in a PP1 chain reaction?
In the Sun, branch pp1 takes place with a frequency of 86%, pp2 with 14% and pp3 with 0.11%. There is also an extremely rare pp4 branch. The complete pp I chain reaction releases a net energy of 26.7 MeV.
What is the difference between PP1 and PP2 and PP4?
There is also an extremely rare pp4 branch. The complete pp I chain reaction releases a net energy of 26.7 MeV. The pp I branch is dominant at temperatures of 10 to 14 megakelvins (MK). Below 10 MK, the PP chain does not produce much 4 He. The pp II branch is dominant at temperatures of 14 to 23 MK.
