ast101h exam 1

Accretion

The process of material clumping together under gravity during planet formation.

Absorption Lines

Dark lines in a spectrum created when atoms absorb specific wavelengths of light.

Asteroid

A small rocky object orbiting the Sun that is not spherical and has not cleared its orbit.

Asteroid Belt

Region between Mars and Jupiter containing rocky bodies; has gaps due to Jupiter’s resonances.

Atmospheric Stripping

Removal of a planet’s atmosphere by the solar wind when no magnetic field is present.

Atmospheric Escape

When atoms/molecules move faster than escape velocity and leave a planet permanently.

Blackbody Radiation

Light emitted by an object depending only on its temperature.

Carbon Cycle

Recycling of CO₂ between atmosphere, oceans, rocks, and volcanism on Earth.

Centre of Mass

The point around which two orbiting bodies both orbit.

Chemical Differentiation

Heavy materials sink, light materials rise inside a molten planet.

Comet

A small, icy, dusty object that develops tails when near the Sun.

Conduction

Heat transfer through solid material (crust).

Convection

Heat transfer by moving fluid (mantle, gas layers).

Corona

Sun’s outermost atmosphere; extremely hot.

D/H Ratio

Ratio of deuterium to hydrogen; used to infer past water loss (e.g., Mars has high D/H).

Differentiation Heat

Heat released when dense materials sink toward a planet’s center early in its life.

Dirty Snowball

Common phrase describing comet composition.

Doppler Shift

Change in wavelength due to motion of source; used to detect exoplanets by star wobble.

Eccentric Orbit

An orbit shaped like a stretched ellipse.

Edge-on Orientation

Viewing angle required for exoplanet transits.

Electromagnetic Spectrum

Range of light wavelengths; includes gamma, X-ray, UV, visible, IR, radio.

Emission

Object gives off light based on its temperature.

Escape Velocity

Minimum speed required to leave a planet’s gravitational pull.

Flyby Mission

A spacecraft that passes a target once without stopping or landing.

Frost Line

Distance from the Sun where ices can form; divides rocky inner planets from icy outer planets.

Galilean Moons

Jupiter’s four moons discovered by Galileo: Io, Europa, Ganymede, Callisto.

Gas Giant

A large planet composed mostly of H & He (Jupiter, Saturn).

Geological Activity

Surface change from volcanism, tectonics, erosion; requires internal heat.

Greenhouse Effect

Infrared radiation emitted by a planet is trapped by atmospheric gases, warming the surface.

Greenhouse Runaway

Extreme greenhouse warming where oceans evaporate (e.g., Venus).

Habitable Zone

Region around a star where liquid water can exist.

Half-life

Time for half of a radioactive sample to decay.

Heavy Bombardment

Early Solar System period of intense asteroid/comet impacts.

Hydrogen Compounds

Ices like water, ammonia, methane found in outer planets.

Impact Cratering

Holes caused by collisions with space rocks; more craters = older surface.

Infrared Light (IR)

Long-wavelength light useful for seeing through dust/molecular clouds.

Interstellar Object

An object that is not gravitationally bound to the Sun (e.g., ’Oumuamua).

Jovian Planets

The outer gas/ice giants: Jupiter, Saturn, Uranus, Neptune.

Kepler’s First Law

Planets orbit in ellipses with the Sun at one focus.

Kepler’s Second Law

Planets sweep equal areas in equal times (move faster when closer to Sun).

Kepler’s Third Law

Orbital period squared ∝ distance cubed.

Kirkwood Gaps

Empty regions in asteroid belt due to Jupiter’s resonances.

Kuiper Belt

Region beyond Neptune containing icy bodies and dwarf planets.

Light Curve

Graph of star brightness over time; dips show transits.

Magnetic Field

Created by rotating, molten metal core; protects planet from solar wind.

Mantle

Layer where convection transports heat upward.

Meteorite

Rock from space found on Earth; used for radioactive dating.

Microlensing

Exoplanet detection via gravitational focusing of light.

Molecular Cloud

Cold gas/dust region where stars form; blocks visible light.

Nebular Hypothesis

Theory describing Solar System formation from a rotating gas cloud.

Nuclear Fusion

Process powering stars; not active in planets.

Oort Cloud

Spherical cloud of very distant comets around the Solar System.

Orbital Resonance

When two objects influence each other by orbiting at exact integer ratios (e.g., Io–Europa–Ganymede).

Outgassing

Release of gases from a planet’s interior (mostly via volcanoes).

Photosphere

Visible surface of the Sun.

Planet Criteria - 1. Orbits the Sun 2. Spherical 3. Cleared its orbit

P-waves

Seismic waves that pass through solids and liquids.

Radioactive Dating

Measuring isotope ratios to determine ages of rocks/meteorites.

Radial Velocity Method

Exoplanet detection via star’s spectral line wobbling from Doppler shift.

Radiative Zone

Sun’s layer where energy moves via radiation.

Recovery Mission

Mission where a spacecraft lands, returns samples, and comes back to Earth.

Resonance Gap (Rings)

Gaps in planetary rings created by gravitational interactions with moons.

Scattering

Light bouncing in many directions; why we can read a page or see blue sky.

Slingshot Maneuver

A spacecraft accelerates using gravity during a close pass of a planet.

Solar Wind

Charged particles from the Sun that strip atmospheres without magnetic protection.

Spectrum

Range of light broken into wavelengths; reveals temperature, composition, motion.

S-waves

Seismic waves that cannot pass through liquid → prove Earth’s outer core is liquid.

Tectonics

Surface reshaping through plate motion.

Transit Method

Exoplanet detection via dip in starlight when planet crosses star.

Tidal Heating

Frictional heating caused by distortions in a moon’s orbit (e.g., Io, Europa).

Umbra (speaking generally)

Full shadow; not central to AST101, but sometimes appears in lunar eclipse context.

Volcanism

Eruption of molten rock from interior; reshapes surfaces, releases gases.

Visible Light

Light humans see; blocked by dust in molecular clouds.

Wobble (Stellar)

Motion of a star caused by orbiting planets; basis of the Doppler method.

X-ray Astronomy

Must be done from space because Earth’s atmosphere blocks X-rays.

Yellow Dwarf

Category of Sun; not heavily tested but sometimes mentioned.

Zero-Age Main Sequence (ZAMS)

When a star first begins fusion; only indirectly relevant.