CHEM 101 – Big Bang Theory & Stellar Nucleosynthesis

Vocabulary flashcards covering cosmological evidence for the Big Bang and the stellar fusion processes responsible for element formation.

Big Bang Theory

A cosmological model describing the early universe as originating from a state of extremely high density and energy and subsequently expanding and cooling.

Georges Édouard Lemaître

Belgian priest-astrophysicist who first proposed the Big Bang model of an expanding universe in 1927.

Hubble's Law

Observation that galaxies recede from the Milky Way at speeds proportional to their distance, indicating universal expansion.

Edwin Hubble

American astronomer who, with Milton Humason, formulated Hubble’s Law using observations of Cepheid variable stars.

Cepheid Variable Star

A pulsating star whose regular brightness variations serve as a “standard candle” for measuring cosmic distances.

Cosmic Microwave Background (CMB)

Faint afterglow radiation at ~2.7 K left over from the hot, dense early universe, detected uniformly in all directions.

Arno Penzias & Robert Wilson

Radio astronomers who confirmed the existence of the CMB in 1964 at Bell Labs.

Primordial/Big Bang Nucleosynthesis

Fusion processes in the first minutes after the Big Bang that produced light nuclei such as H, D, ³He, ⁴He, and ⁷Li.

Light Elements

Hydrogen, deuterium, helium-3, helium-4, and lithium-7 created during primordial nucleosynthesis.

Nuclear Fission

A reaction in which a heavy atomic nucleus splits into lighter nuclei, releasing energy; basis of nuclear reactors and weapons.

Nuclear Fusion

Process where light nuclei combine to form heavier nuclei, releasing large amounts of energy, as in stars.

Proton-Proton Chain

Fusion sequence converting four protons into one helium-4 nucleus with energy and neutrinos; dominant in sun-like stars.

CNO Cycle

Hydrogen-to-helium fusion pathway that uses carbon, nitrogen, and oxygen as catalysts; prevalent in more massive stars.

Deuterium

A hydrogen isotope with one proton and one neutron; first nucleus formed as the universe cooled after the Big Bang.

Neutrino

Nearly massless, weakly interacting particle emitted during nuclear fusion reactions such as the p-p chain.

Helium Burning

Stellar fusion phase where helium nuclei fuse at ~10⁸ K, primarily via the triple-alpha process to form carbon-12.

Triple-Alpha Process

Reaction that fuses three helium-4 nuclei into carbon-12, releasing energy; intermediate ⁸Be is unstable.

Carbon Burning

Fusion of carbon-12 nuclei at ~5 × 10⁸ K, producing magnesium, sodium, neon, and other elements plus energy.

Oxygen Burning

Stellar phase beginning near 10⁹ K in which oxygen nuclei fuse, forming silicon and alpha particles.

Silicon Burning

High-temperature fusion stage that builds elements up to iron and nickel via successive alpha captures.

Alpha Process

Series of nuclear reactions adding helium-4 (alpha) particles to nuclei, leading to heavier elements in massive stars.

Exothermic Reaction

Chemical or nuclear reaction that releases energy as heat or light; describes fusion of light nuclei to helium.

Hydrogen Burning

Generic term for stellar fusion of hydrogen to helium through the p-p chain or CNO cycle.

Heavy-Element Synthesis in Stars

Creation of elements heavier than helium via successive fusion stages (He, C, O, Si burning) in massive stars.

Beryllium-8 (⁸Be)

Unstable intermediate nucleus in the triple-alpha process; quickly decays unless it captures another alpha particle.

Expansion of the Universe

Continual increase in cosmic scale indicated by redshifts of distant galaxies and formulated in Hubble’s Law.