Evolution

• Cosmology - the scientific study of the large-scale properties of the universe as a whole.
• Big Bang Theory - the prevailing cosmological model for the universe's birth.
• Big Bang Theory - states that 13.77 billion years ago came from "singularity" from which the universe has been expanding in all directions ever since.
• Stellar Evolution - the process which a star changes over the course of time.
• Stellar Evolution - depending on the mass of the star from "most massive" to "least massive".
• Three Cosmic Stages

  1. Big Bang Nucleosynthesis
  2. Stellar Nucleosynthesis
  3. Supernova Nucleosynthesis
• Big Bang Nucleosynthesis - "primordial nucleosynthesis"
• Big Bang Nucleosynthesis - the formation of the nuclei of light elements a few minutes after the Big Bang. Formed light elements (H, He, Li)
• Stellar Nucleosynthesis - combining the protons and neutrons together from the nuclei of lighter elements.
• Stellar Nucleosynthesis - formed elements heavier than Be to Fe .
• Life Cycle of a Star

  1. Birth ( Stellar Nebula )
  2. Main Sequence ( Average Star, Massive Star )
  3. Old Age ( Red giant, Red supergiant )
  4. Death ( Planetary Nebula, Supernova )
• Supernova Nucleosynthesis - by Fred Hoyle (1954)
• Supernova Nucleosynthesis - production of many different chemical elements in supernova explosions. Formed elements heavier than Fe.
• Atom - Smallest unit of matter that has all the properties of an element.
• Atom - Composed of smaller subatomic particles.

  1. Protons
  2. Neutrons
  3. Electrons
• Electron - negatively charged particles.
• Neutrons - particles with no charge or neutral.
• Proton - positively charged particles.
• Isotope - refer to atoms with the same number of protons but different number in neutrons.
• Nuclear Reaction - formation of new elements through acquired changes within the nucleus of an atom.
• Fusion - combination of two small atomic nuclei to form a heavier nucleus.
• Fission - the splitting of large nuclei into smaller ones.
• Radioactive Decay - the process of an unstable nucleus attempts to become stable.
• Proton-Proton Chain reaction — occurs the main sequence for low and medium mass stars.
• Carbon, Nitrogen, Oxygen Cycle (CNO Cycle) — occurs the main sequence for high mass massive stars.
• Tri Alpha Process - occurs the red giant star once they leave the stage of the main sequence star.
• Alpha Ladder - "Alpha Process"
• Alpha Ladder - occurs in the red supergiant once they leave the stage of the main sequence star.
• Neutron Capture - a neutron is added to a seed, a nucleus.
• Neutron - can be slow or rapid.
• S-Process - "slow process"
• S-Process - happens when there is a slow rate of capturing neutrons while there are faster rate of radioactive decay.
• R-Process - "Rapid Process"
• R-Process - faster rate of capturing neutrons before it undergoes radioactive decay thus, more neutron can be combined.