Planetary Systems: Architecture and Birth

Chapter 5: The Architecture and Birth of Planetary Systems

• A Kuiper Belt Object (KBO) is any object within the Kuiper Belt.
• An exoplanet is a planet that orbits a star outside our solar system.
• A dwarf planet is a celestial body that orbits the Sun, is not a satellite, and has not cleared its orbital path.
• An asteroid belt is a region between Mars and Jupiter where most asteroids are found.
• The Kuiper Belt is a region beyond Neptune containing icy bodies, including dwarf planets like Pluto.
• A scattered disk is a distant region of the solar system with icy bodies on highly eccentric orbits.
• The Oort Cloud is a theoretical sphere surrounding the solar system, source of long-period comets.
• A terrestrial planet is a planet composed mainly of silicate rocks or metals.
• A gas giant is a large planet mostly composed of hydrogen and helium.
• An ice giant is a giant planet composed mainly of elements heavier than hydrogen and helium, like oxygen, carbon, nitrogen, and sulfur.
• Uncompressed density refers to the density a planet would have without gravitational compression.
• Planetesimals are small bodies that could come together under gravity to form a planet
• Trojan asteroids share an orbit with a larger planet but reside in stable Lagrange points.
• Lagrange points are positions in space where a small object remains stationary relative to two larger objects, due to gravitational forces.
• Earth-crossing asteroids are asteroids whose orbits intersect Earth's orbit.
• Differentiation is the process where a planet separates into layers of different densities.
• C-type asteroids are carbonaceous asteroids, the most common type in the asteroid belt.
• S-type asteroids are stony asteroids, primarily made of silicate materials and nickel-iron.
• M-type asteroids are metallic asteroids, thought to be composed mostly of nickel-iron.
• The snow line is the distance from a star where it is cold enough for volatile compounds like water, ammonia, and methane to condense into solid ice grains.
• Albedo is the measure of how much light that hits a surface is reflected without being absorbed.
• A comet nucleus is the solid, central part of a comet, often called a "dirty snowball."
• A comet coma is the nebulous envelope around a comet's nucleus, formed when the comet passes close to the Sun and warms.
• A comet ion tail is a tail of ionized gas pointing directly away from the Sun, pushed by the solar wind.
• A comet dust tail is a tail composed of small dust particles that curves away from the Sun, pushed by solar radiation pressure.
• A short-period comet has an orbital period of less than 200 years.
• A long-period comet has an orbital period of more than 200 years.
• The Rosetta Mission was a space probe launched to study Comet 67P/Churyumov–Gerasimenko.
• Churyumov-Gerasimenko (67P) is a periodic comet studied by the Rosetta mission.
• A meteoroid is a small rock or particle of debris in the solar system.
• A meteor is a meteoroid that burns up as it enters Earth's atmosphere, creating a streak of light.
• A meteorite is a meteoroid that survives its passage through Earth's atmosphere and impacts the surface.
• A bolide is an exceptionally bright meteor that explodes in the atmosphere.
• A meteor shower is an event where numerous meteors are observed to radiate from one point in the night sky.
• Interstellar gas is gas found in the regions between star systems in a galaxy.
• Center of mass is the point around which two or more bodies orbit.
• The radial velocity method detects exoplanets by measuring the wobble of a star caused by the planet's gravity.
• The transit method detects exoplanets by measuring the dimming of a star's light as a planet passes in front of it.
• The Kepler space telescope was designed to discover Earth-sized planets orbiting other stars using the transit method.
• A Super-Earth is an exoplanet with a mass higher than Earth's, but substantially below that of the Solar System's ice giants.
• The Habitable zone (Goldilocks Zone) is the region around a star where liquid water could exist on a planet's surface.
• A Hot Jupiter is a gas giant exoplanet that orbits very close to its star, resulting in high temperatures.
• Conservation of angular momentum is a principle stating that the total angular momentum of a closed system remains constant.
• Condensation theory explains planet formation from a protoplanetary disk in which the temperature determines what materials condense out of the gas to form solid grains.
• A protoplanetary disk is a rotating circumstellar disk of dense gas and dust surrounding a young newly formed star.
• Interstellar dust grain is a small particle of solid matter in interstellar space.
• The Core accretion model is a planet formation theory where planets grow from the repeated sticking and accumulation of solid particles.

Chapter 6: Earth and the Moon

• Radioactive decay is the process by which an unstable atomic nucleus loses energy by emitting radiation.
• Half-life is the time required for half of the atoms in a radioactive substance to decay.
• The core is the innermost layer of a planet.
• The mantle is the layer of a planet between the core and the crust.
• The Lithosphere is the rigid outer layer of Earth, consisting of the crust and upper mantle.
• The crust is the outermost solid layer of a planet or moon.
• Basalts are dark, fine-grained volcanic rocks.
• Seismic waves (P-waves, S-waves) are vibrations that travel through Earth, caused by earthquakes or explosions.
• Heat transfer includes conduction, convection, and radiation
• Conduction: the transfer of heat through a material by direct contact.
• Convection: the transfer of heat by the movement of a fluid.
• Radiation: the transfer of heat by electromagnetic waves.
• A plume is a rising column of hot mantle rock.
• Shield volcanoes are broad, gently sloping volcanoes formed by the eruption of fluid basalt lava.
• Plate tectonics is the theory that Earth's lithosphere is divided into plates that move and interact.
• Continental collision occurs when two continental plates converge, creating mountain ranges.
• Subduction is the process where one tectonic plate slides beneath another.
• A spreading center is where new crust is formed as plates move apart.
• A Hotspot is a volcanic region thought to be fed by underlying mantle that is anomalously hot compared with the surrounding mantle.
• A transform fault is a plate boundary where two plates slide past each other horizontally.
• The troposphere is the lowest layer of Earth's atmosphere.
• The stratosphere is the layer of Earth's atmosphere above the troposphere.
• The mesosphere is the layer of Earth's atmosphere above the stratosphere.
• The ionosphere is the ionized region of Earth's upper atmosphere.
• Ozone is a molecule made of three oxygen atoms (O3) that absorbs UV radiation in the stratosphere.
• The greenhouse effect is the process by which certain gases in the atmosphere trap heat, warming the planet.
• The magnetosphere is the region around a planet dominated by its magnetic field.
• The magnetic dynamo effect is the process by which a rotating, convecting, and electrically conducting fluid can maintain a magnetic field.
• Solar wind is a stream of charged particles released from the upper atmosphere of the Sun.
• Aurora Borealis/Australis are natural light displays in the sky, predominantly seen in the high-latitude regions.
• Tides are the periodic rise and fall of sea levels caused by the gravitational forces of the Moon and Sun.
• Tidal force is the gravitational force exerted by a celestial body on another.
• Spring tides occur when the Sun, Earth, and Moon are aligned, resulting in higher high tides and lower low tides.
• Neap tides occur when the Sun, Earth, and Moon form a right angle, resulting in less extreme tides.
• Tidal locking is when an object's orbital period matches its rotational period.
• Craters are bowl-shaped depressions formed by impacts.
• Lunar maria are large, dark, basaltic plains on the Moon.
• Lunar highlands are the heavily cratered, mountainous regions of the Moon.
• Late heavy bombardment was a period of intense meteorite impacts early in the Solar System's history.
• The Giant Impact hypothesis suggests that the Moon formed from debris ejected after a Mars-sized object collided with Earth.

Chapter 7: Mercury, Venus, and Mars

• Differentiation is the process by which a planet's interior separates into layers of different densities.
• Cooling refers to the loss of heat from a planet over time.
• Cratering is the formation of impact craters on a planet's surface.
• Magma flooding is the eruption of large amounts of lava onto a planet's surface.
• Weathering is the breakdown of rocks and minerals on a planet's surface by physical and chemical processes.
• A wrinkle ridge is a ridge on the surface of a planet, often found in lunar maria.
• Fossil magnetism is the remnant magnetic field preserved in rocks.
• Tidal synchronization (Orbital/Rotational resonance) occurs when an object's rotation period is a simple ratio of its orbital period.
• Retrograde rotation is rotation in the opposite direction to the planet's orbit.
• A caldera is a large volcanic crater formed by the collapse of a volcano.
• A corona is a large, oval-shaped geological feature on Venus.
• Olympus Mons is the largest volcano on Mars and in the solar system.
• Valles Marineris is a large canyon system on Mars.
• Blueberries (hematite) are small, spherical concretions of hematite found on Mars.
• The Noachian period is an early period in Mars' history, characterized by heavy bombardment and liquid water on the surface.
• The Hesperian period is a middle period in Mars' history, characterized by widespread volcanism and drying of the surface.
• The Amazonian period is the most recent period in Mars' history, characterized by a cold, dry climate.

Chapter 8: The Outer Planets

• Stellar occultation is when a planet passes in front of a star.
• Metallic hydrogen is a phase of hydrogen in which it behaves as an electrically conductive metal.
• Belt and Zone circulation is the pattern of alternating bands of rising and sinking air in a planet's atmosphere.
• The Great Red Spot is a giant, persistent anticyclonic storm on Jupiter.
• An oblate sphere is a sphere that is flattened at its poles and bulging at its equator.
• Titan is a moon of Saturn with a thick atmosphere and liquid methane lakes.
• The Cassini Spacecraft was a probe sent to study Saturn and its moons.
• The Huygens probe was a lander that descended to the surface of Titan as part of the Cassini mission.
• Enceladus is a moon of Saturn known for its cryovolcanoes.
• Shepard moons are small moons that orbit near planetary rings and help to confine those rings.
• Orbital resonance occurs when two orbiting bodies exert a regular, periodic gravitational influence on each other.
• The Roche limit is the distance within which a celestial body held together only by its own gravity will disintegrate due to a second celestial body's tidal forces exceeding the object's self-gravitation.
• Saturn's E-ring is a faint ring primarily composed of ice particles sourced from cryovolcanic plumes on Enceladus.
• Miranda is a moon of Uranus with a heavily disrupted surface.
• A retrograde orbit is an orbit that is opposite to the direction of the planet's rotation.
• Triton is a moon of Neptune with a retrograde orbit and cryovolcanic activity.