
1. Standard Model (Big Bang Theory)
1.1. Stage 1: Universe is infinitely small/dense, a singularity. All four forces are unified Stage 2: Inflates into a Quark and lepton Soup Stage 3: Quarks form to produce hadrons Stage 4: Primordial helium is formed by fusion Stage 5: Atoms form, nuclei capture electrons allowing the universe to become transparent (photons are free to travel around in the universe) Stage 6: Matter clumps together to form gas clouds, dust, stars and then galaxies. Universe is saturated with E.M radiation with a characteristic temperature of 2.7 K
1.2. Evidence:- 1)The universe is saturated with CMB at a characteristic temperature of 2.7 K, which is what Goerge Gamow predicted the photons released during the transparency to cool down too as space expands. (Also gives evidence for the isotropic nature of the universe) 2)There is an abundance of helium and light nuclei which could only be formed during the high temperatures of the big bang. 3)Red shift shows evidence of galaxies receding, and thus they must have started from a singularity.
2. Life of Stars
2.1. Protostar : 1)Nebula (interstellar gas cloud of hydrogen and dust) has denser regions. 2)There is a gravitational collapse to those dense regions G.P.E turns to K.E and thus temprature rises 3)Hydrogen burning occurs and radiation pressure expands the size of the star
2.2. Main Sequence : 4) Radiation pressure equals gravitational collapse and thus equilibrium is achieved 5)Complex fusion reactions can take place in the core producing carbon,silicon and iron.
2.3. End of the star : 6) The core collapses under gravitational attraction, allowing the helium shell to fuse to produce beryllyium carbon and oxygen , hydrogen starts to fuse aswell 7) This power production from the helium shell causes the surface of the star to swell to a red giant (<3 solar masses) ,super red giant (>3 solar masses). The surface temprature is cooler although the surface area has increased massively causing a collosal output power. 8)Helium nuclei in the outer shell reach a temperature of about 10^8 K and fuses at a phenomenal rate. 9)In a process known as the "helium flash" the material surrounding the core is ejected away as a planetary nebula
2.3.1. Star<3 Solar Masses : Produces a white dwarf which doesn't exceed the Chandrasekhar limit (1.4 Solar masses) prevented from further collapse by Fermi pressure brought about by Pauli's exclusion principle (no more than two electrons can exist in the same quantum state_ 10)A white dwarf is produced -No fusion occurs -Very dense -As the white dwarf becomes more and more compressed the electrons move freely around the star in a state called plasma.
2.3.2. Star>3 Solar masses : Produces a white dwarf which exceeds the Chandrasekhar limit (1.4 solar masses) 10)The high mass of the white dwarf means that gravitational attraction can cause the atoms to exceed Fermi pressure. 11)The neutrons combine with protons to produce nuetrons and nuetrinos , nuetrinoes escape the central core and is now made up of tightly packed nuetrons. 12)Outtershells sorrounding the core collapse and rebound off the solid nuetron core causing shockwaves exploding the surface layers of the star (Supernova) 13)For low mass stars the star remains as a nuetron star 14)For higher mass stars the gravitational attraction causes nuetron star to collapse in on itself.