Lecture Notes: Formation of the Universe, Solar System, and Planet Formation (Week 2)

A set of vocabulary flashcards covering key terms and concepts from the notes on the formation of the universe, solar system, and planet formation.

Big Bang

The beginning of the universe about 13.8 billion years ago; the universe is expanding, matter and energy were created at the start, and no new matter is made.

Ga

Abbreviation for giga annum; a unit equal to one billion years.

Nebula

A large cloud of gas and dust in space where gravity can cause collapse to form stars.

Hydrogen (H) and Helium (He)

Light elements produced in the early universe; primary constituents of the first stars and fuel for fusion.

Nuclear fusion

Process by which light nuclei fuse to form heavier elements, releasing energy; powers stars and builds elements up to carbon.

First Stars

Early generation of stars (about 13 Ga) formed from H and He; sites of fusion and heavy-element production.

92 elements

All naturally occurring elements heavier than hydrogen and helium produced in stars and supernovae.

Supernova

Explosive death of a massive star; disperses heavy elements into space and can create all 92 elements.

Dust & Gas

Solid grains and volatile molecules in space that make up nebulae and participate in star formation.

2nd Generation Stars

Stars formed from gas enriched with heavy elements (all 92 elements) after prior supernovae.

Red Giant

A late evolutionary stage of medium-sized stars where the star expands and cools, appearing red.

Planetary Nebula

Shell of gas expelled by a dying low- to intermediate-mass star; core becomes a white dwarf.

White Dwarf

Dense, hot stellar remnant left after a planetary nebula; small but very massive.

Protoplanetary Disk

Disk of gas and dust surrounding a newborn star from which planets form.

Planetesimals

Small asteroid-sized bodies formed from dust in the protoplanetary disk.

Protoplanets

Larger bodies formed by accretion of planetesimals; begin to clear their orbits.

Clearing an Orbit

Gravitational process by which a planet removes or accretes nearby bodies to establish a clear orbit.

Terrestrial Planets

Rocky planets made primarily of refractory materials (e.g., Mercury, Venus, Earth, Mars).

Gas Giants

Large planets composed mainly of volatile materials (hydrogen, helium) with thick atmospheres.

Solar Wind

Stream of charged particles emitted by the Sun that can move volatiles outward in the solar system.

Sol

The Sun; our star.

Nebular Theory

Model of solar system formation from a collapsing nebula; 4.6 Ga formation with planets forming from the same material.

4.6 Ga

Approximately 4.6 billion years ago when Earth and the Solar System formed.

13.8 Ga

Approximately 13.8 billion years ago when the Universe formed.

3.7 Ga

First evidence of life on Earth.

250 Ma

About 250 million years ago; first dinosaurs appeared.

65 Ma

About 65 million years ago; dinosaur extinction event at the end of the Cretaceous.

~200,000 yrs – Homo sapiens

Approximately 200,000 years ago; appearance of anatomically modern humans.

Differentiation

Process by which dense materials sink to the center of a forming planet, creating a layered interior.

Refractory materials

Materials that resist melting or evaporation easily and form rocky interiors (e.g., iron, silicon).

Volatile materials

Materials that evaporate easily (e.g., water, CO2, H, methane) and are often found in ices and atmospheres.

Iron, Silicon, Oxygen = Rock

Rocky planetary material formed from these elements through differentiation and accretion.

Generation of the Sun

The Sun is a 3rd–to–5th generation star, formed from material enriched by previous generations of stars.