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Nucleosynthesis: The Formation of Elements in the Universe, Lecture notes of Astrophysics

University of the Philippines Visayas (UPV)Astrophysics

A comprehensive overview of nucleosynthesis, the process by which new atomic nuclei are formed from existing smaller nuclei. It explores various types of nucleosynthesis, including big bang nucleosynthesis, stellar nucleosynthesis, and supernova nucleosynthesis. The document delves into the role of stars and supernovae in element formation, explaining how heavier elements are created through nuclear fusion and fission processes. It also discusses the structure of atoms, isotopes, and radioactive decay, providing a detailed explanation of the different types of radioactive decay and their impact on nuclear stability. The document concludes with a discussion of the role of nucleosynthesis in the formation of galaxies and the classification of stars based on their metallicity.

Typology: Lecture notes

2023/2024

Available from 01/01/2025

mistymarie
mistymarie 🇵🇭

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NUCLEOSYNTHESIS
- It is the process of forming a new
atomic nuclei from existing
smaller nuclei.
- An atomic nuclei may be formed
through the combination of light
elements or from the breakdown of
heavier elements.
Nuclear Fusion
- a combination of two or more
atomic nuclei to form one or more
new atomic nuclei
Nuclear Fission
- breakdown of a nuclei into two or
more separate nuclei
TYPES OF NUCLEOSYNTHESIS
a. Big-bang Nucleosynthesis
-Formation of lighter
elements from the first
moments of the universe
(H and He, traces of Li, Be,
B) formed
- 3 minutes – 300,000 years
after Bigbang
- Hydrogen (75%), He (25%),
Lithium (small amount)
b. Stellar nucleosynthesis
- Formation of post-iron
heavy nuclei/elements
from supernovae and
nebular dusts
- He to Fe
- Extreme temperature is
required at the core
- '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.
STARS
- Very hot ball of gas or a “nuclear
fire”
c. Supernova nucleosynthesis
- Heavier elements formed during
supernova explosions of stars
- conditions: extremely high temp (100
billions degree C) and abundant
neutrons
SUPERNOVAE
- Stars that explode upon
death
● Elements are classified
based on their atomic
number
ATOMIC NUMBER
- Number of protons in their
respective nuclei
Isotopes
- Are atoms with the same number
of protons but with a different
number of neutrons
Nucleons
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NUCLEOSYNTHESIS

  • It is the process of forming a new atomic nuclei from existing smaller nuclei.
  • An atomic nuclei may be formed through the combination of light elements or from the breakdown of heavier elements. Nuclear Fusion
  • a **combination of two or more atomic nuclei to form one or more new atomic nuclei Nuclear Fission
  • breakdown of a nuclei into two or more separate nuclei TYPES OF NUCLEOSYNTHESIS a. Big-bang Nucleosynthesis**
  • Formation of lighter elements from the first moments of the universe (H and He, traces of Li, Be, B) formed
  • 3 minutes – 300,000 years after Bigbang
  • Hydrogen (75%), He (25%), Lithium (small amount) **b. Stellar nucleosynthesis
  • Formation of post-iron heavy nuclei/elements from supernovae and nebular dusts**
  • He to Fe
  • Extreme temperature is required at the core
  • '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. STARS
  • Very hot ball of gas or a “nuclear fire” **c. Supernova nucleosynthesis
  • Heavier elements formed during supernova explosions of stars**
  • conditions: extremely high temp ( billions degree C) and abundant neutrons SUPERNOVAE - Stars that explode upon death ● Elements are classified based on their atomic number ATOMIC NUMBER - Number of protons in their respective nuclei Isotopes
  • Are a toms with the same number of protons but with a different number of neutrons Nucleons
  • The number of nucleons affects the properties of elements, most especially their abundance Atom
  • Basic unit of an element that can undergo chemical reactions Structure of Atom
  • Contains a nucleus that is composed of a proton and a neutron that is surrounded by electrons Proton
  • Positively charged particle Electron
  • Negatively charged particle
  • Contribute to the element’s chemical properties Atomic Number and Mass Number Radioactivity
  • A phenomenon when unstable nuclei emit particles and/or electromagnetic radiation spontaneously
  • Elements with atomic number greater than or equal to 83 (< or =) are radioactive Belt of stability (solid line)
  • A stable nuclei is found on the area of the graph known as the belt of stability (solid line)
  • Radioactive isotopes are found outside this belt. To obtain stability, these isotopes must undergo radioactive decay Nucleus
  • Has the mass of an atom

Too low -in order to reach the belt of stability, they need to move upward by increasing this ratio either through positron emission or electron capture Too many protons ADDITIONAL NOTES: electron ● atomic number (-/+) charge ● pag (+) magsusubtract ● pag (-) maga-add ● does not contribute mass to the atom neutrons ● mass number (-) atomic number ● neutral (no charged particle) protons ● below the mass number ● provided the positive charge for an atom ● Atoms of the same element must always have the same number of protons. mass number ● the sum of the protons and neutrons in the nucleus of that atom isotopes ● Two atoms of the same element but with different mass numbers

● are elements with a different amount of neutrons ● are atoms with the same number or protons but with a different number of neutrons PROTONS and NEUTRONS contributes to the element's nuclear stability ELECTRON contribute to the element's chemical properties

Stars explode as supernovae, and formed galaxy Astronomers classifies stars according to the elements that they possessed METALS

  • Any elements (in the periodic table) heavier than helium Classification of Stars Population 1
  • Sun 2-3% of its mass is metals Population 2
  • Metal core -.1% of metals or lower, oldest stars, galactic bulge Population 3
  • No heavy elements, stars formed after Big Bang
  • They were gigantic No red dwarf has ever burned out The more mass, the greater the pressure Small increase in mass, small increase in temperature Stars ten times the mass of the sun is ten thousand times brighter Metalicity
  • Is the study of the nuclear processes responsible for the formation of the elements which constitute the baryonic of matter Contemporary nucleosynthesis theory
  • Associates the production of certain elements/isotopes or groups of elements with a number of specific astrophysical settings, the most significant of which are: (i) cosmological Big Bang, (ii) stars, (iii) supernovae Cosmological nucleosynthesis studies
  • Predict that the conditions characterizing the Big Bang are consistent with the synthesis only of the lightest elements: 1H, 2H, 3He, 4He, and 7Li