Star Formation and Hydrogen Burning In Single Star
This book, in its first chapter, gives a glance of the formation of stars, evolution of stars, reactions in the stars, and the alteration of one particle into another due to these reactions.
There are four fundamental forces in the universe, yet found.
- Electromagnetic force → This force acts on electrically charged particles like protons and electrons.
- Strong nuclear force → It is the small scale force and acts on the atomic scale. It is the strongest of all other forces of nature. This binds the proton and neutron together in the nucleus.
- Weak nuclear force → It is also a short-range force but, unlike strong nuclear force, acts on the small mass particles rather than that of heavy mass. For example, photons, neutrinos etc.
- Gravitational force → Gravity is a very large scale force but also weakest of all. It acts on the classical/planetary level.
- Electromagnetic and Weak force are introduced to be the outcome of the Electroweak force. Research is revitalizing intending to show the common origin of all the natural forces. This theory of common origin is known as “Grand Unified Theory(GUT)”.
The succeeding part of the chapter is focused on explaining the conservation laws and their examples. Conservation laws are primarily known for their ability to compress the complex detail of an event into the simple math. Here, the initial units are equal to the final units. These laws are enough- If used skillfully- to understand the function of a black hole, hotness of a star, energy in a nuclear reaction, the binary star system etc.
- One of the most fundamental conservation laws, given, is the conservation of energy. The energy can be converted from the energy of directed motion to that of random motion and from or into a gravitational motion. A famous equation- E=mc2- demonstrates how even a trivial mass at high motion(here, speed of light) can create a considerable amount of energy. A daily-life example of the conversion of motion into energy is falling of chalk on the floor.
- Conservation of momentum energy- in the action of momentum- as the opposite or equal reaction in its opposite direction. For example, imagine that you jumped out of a boat from one point, the boat would move backwards in another direction with the same Momentum until the force of water is not considered. Therefore, P1V1=-(P2V2), thus Pnet=0.
- Conservation of angular momentum measures the tendency of an object of a given mass to continue to spin at a certain rate. For example, a spinning top.
Others are the conservation laws- not found in everyday life. For example, the law of conservation of charge.
Heavy particles are baryons and less massive particles are leptons. The research of GUT says that the Big Bang had not conserved all baryons, but some bare converted to the leptons like photons and neutrinos due to the presence of antimatter.
A star is a hot gas ball of thermal equilibrium. Pressure from the inner core = gravitational inward pull. As the stars radiate the energy in the Stellar atmosphere it gains reduced radii and more heat. This process can be discontinued. Here works the Quantum theory. Here, the chapter explains the Quantum energy generation at the core of stars and why it prevents the stars from collapsing. Quantum theory explains the elementary particles as dual-natured- as discrete particles and as waves. They follow the Uncertainty Principle and Pauli’s Exclusion Principle very strictly. They cannot acquire the same volume at the same energy. However, photons do not follow the exclusion principle. Therefore, if E1 = E2 then V1 = V2, therefore P1 = P2 (p = momentum).
Thus, as a star compresses, V1 = V2 = V3 = V4 =…= Vn. Therefore, P1 P2 P3 P4 … Pn. This roots to the instability of the system and produces more energy. To conserve the radiated energy the quantum pressure exerted on the star, thus it balances the inward pull of gravity. Such stars- supported by a Quantum pressure- are known as the White dwarf stars. Even the sun is estimated to become a white dwarf. Due to the process, which defies the exclusion principle, in the interior of stars the mass increases and gravity too. The quantum pressure can hold up to a certain limit of gravitational pull. The limit is known as the Chandrasekhar limit, which values 22.4 solar masses. The condition of pressure-gravity balance defines the life expectancy of a star. The gain of energy of a star is universally proportional to its temperature. Brief flowchart of star-birth: A star first exists as a protostar → Become hotter and hotter over a period of time → Enough heating causes a nuclear process → The reaction radiates the energy and gains heat for the star → Ignites the nuclear fuel → a star shines with the own nuclear fire.
Most of the stars in the universe are The main sequence stars. The category with the stars in their hydrogen-burning stage is called the main sequence. The rate of fuel consumption of stars is directly proportional to the mass of the stars. Hydrogen burns for a much longer duration as compared to the other elements. First, the conversion of two protons into two neutrons conserves the baryons in this process. Second, for this, nature provides leptons in the form of positrons. Third, these particles provide positive charge, thus again the neutrinos(negative charge) are provided. Fourth, the charge is neutral and the release of Two neutrinos and two leptons take place. In brief, the following reaction takes place in the core. H + H → He +2neutrinos + 25MeV (here, 25 MeV = energy carried by two neutrinos).
Neutrinos are produced at the center of stars and interact only by the weak force. Astronomers study them because they carry information about the core of the star. They are first detected by the underground experiment at South Dakota. Here, the chlorinated water is kept in a huge container. The neutrinos, when interacting with atoms of chlorine, convert the neutron to proton and the Argon is obtained which consists of the neutrino information. But, not all neutrinos get detected. Thus, a corrected experiment built in Japan- kamiokande experiment. Here, the advancement allows us to know the direction of neutrinos through cherenkov radiation. In future, the Super kamiokande experiment is made, which uses the Gallium as the detector. Neutrinos change their type while travelling. The following are its types: electron neutrino, muon neutrino and tau neutrino. One more type of neutrino is estimated as ‘sterile neutrino’.