Life Cycle of Stars
What name is given to the initial cloud of gas and dust where stars form?
Stellar Nebula
What is the process called when lighter nuclei combine to form heavier nuclei and release energy?
Nuclear fusion
According to Kepler's First Law, what shape are planetary orbits?
Ellipse (elliptical orbit with Sun at one focus)
What is the rigid outer layer of Earth called that includes the crust and uppermost mantle?
Lithosphere
What process do plants use to remove CO2 from the atmosphere and produce organic carbon?
Photosynthesis
During which long, stable stage does a star fuse hydrogen into helium?
Main Sequence
Which fusion chain dominates energy production in the Sun (two-word answer)?
Proton–proton chain (or proton–proton fusion)
Kepler's Second Law says a line from a planet to the Sun sweeps out equal what?
Equal areas in equal times (areas)
At which type of plate boundary does new oceanic crust form?
Divergent boundary (mid‑ocean ridge / seafloor spreading)
Which reservoir holds the largest amount of carbon accessible on human timescales: atmosphere, soils, or oceans?
Oceans
What is the expanded, cooler phase that an average star enters after exhausting core hydrogen?
Red Giant (average stars) / Red Supergiant for massive stars
What fusion process combines three helium nuclei to form carbon-12?
Triple-alpha (Triple Alpha Fusion)
What is the primary cause for the change in seasons?
The tilt of the Earth's axis
Define subduction in one sentence.
Subduction: one plate sinks beneath another into the mantle, often an oceanic plate beneath a continental plate.
Name two major human activities that increase atmospheric CO2
Burning fossil fuels; deforestation (also some agricultural practices)
What explosive event ends the life of a very massive star and disperses heavy elements into space?
Supernova
Explain, in one sentence, why more massive stars have shorter lifetimes.
More massive stars have higher core temperatures and pressures, burning fuel faster so they exhaust fuel sooner — therefore shorter lifetimes.
Describe how a planet's orbital speed changes as it moves closer to the Sun in its elliptical orbit.
The planet moves faster when closer to the Sun (at perihelion) and slower when farther (at aphelion).
List the three major rock types and write one short phrase for how each forms.
Igneous — formed by cooling and solidification of magma or lava. Sedimentary — formed by deposition, compaction, and cementation of sediments. Metamorphic — formed when existing rock is altered by heat and pressure without melting.
Briefly explain ocean acidification: what causes it and one ecological consequence.
Excess atmospheric CO2 dissolves in seawater forming carbonic acid, lowering pH; this harms calcifying organisms like corals and shellfish.
Name the two possible compact remnants left after a massive star's supernova.
Neutron star or Black hole
Give two ways that energy produced in a star's core leaves the star (name two mechanisms or forms).
Photons (radiation) via radiative transfer, and convection; also particle flows like solar wind carry energy outward.
Name the force responsible for keeping planets in orbit and list two factors that affect orbital motion.
Gravity; factors include the mass of the star and the distance between the two bodies (and the mass of the orbiting object to a much lesser degree for center-of-mass effects).
Explain how mantle convection helps drive plate motion (two–three short sentences).
Mantle material heats, becomes less dense and rises; cooler material becomes denser and sinks, creating convection currents in the mantle that drag plates along.
Contrast the fast carbon cycle and the slow carbon cycle with one sentence each.
Fast carbon cycle: quick exchanges among atmosphere, biosphere, and surface ocean via photosynthesis and respiration (years–decades). Slow carbon cycle: movement of carbon through rocks, fossil fuel formation, subduction, and volcanic outgassing (thousands–millions of years).