Earth Science & Astronomy Review

Vocabulary flashcards covering major terms and definitions from the provided Earth science and astronomy lecture notes.

Galaxy

A gravitationally bound system of stars, stellar remnants, and interstellar gas and dust.

Elliptical Galaxy

Galaxy whose lines of equal brightness form concentric ellipses; lacks spiral arms.

Spiral Galaxy

Galaxy with spiral-shaped arms extending from a central nucleus, e.g., the Milky Way.

Irregular Galaxy

Grainy, highly irregular galaxy with no symmetry or defined nucleus.

Barred Spiral Galaxy

Spiral galaxy featuring a central bar-shaped structure of stars.

Planet

Large body that orbits a star and shines by reflected light.

Natural Satellite

Body that revolves around a planet and reflects starlight; e.g., the Moon.

Galilean Moons

The four largest moons of Jupiter discovered by Galileo: Io, Europa, Ganymede, Callisto.

Nebula

Interstellar cloud of dust and gas from which new stars form.

Quasar

Extremely luminous, distant active galactic nucleus.

Pulsar

Highly magnetized, rotating neutron star emitting periodic radio pulses.

Star

Self-luminous sphere of gas held by gravity; energy from nuclear fusion.

Protostar

Early stage star formed from collapsing nebular gas and dust.

Sirius

Brightest star system in Earth’s night sky.

Black Hole

Stellar remnant whose gravity is so strong that not even light escapes.

White Dwarf

Dense, Earth-sized, cooling remnant of a low-mass star.

Nova

Star that suddenly increases in brightness before fading.

Giant Star

Low-mass star swollen near the end of its life.

Supergiant Star

Very massive, luminous star nearing end of life; largest and brightest type.

Comet

Icy body that develops a glowing coma and tail when near the Sun.

Meteor

Visible streak of light from debris burning in a planet’s atmosphere.

Meteoroid

Rocky or metallic debris in outer space before it enters an atmosphere.

Meteorite

Fragment of meteoroid that survives passage through atmosphere and hits the ground.

Dark Matter

Unseen mass that exerts gravitational effects yet emits no detectable light.

Dark Energy

Mysterious form of energy thought to accelerate cosmic expansion.

Open Universe

Cosmic model where gravity is too weak to halt expansion, so it continues forever.

Closed Universe

Model in which gravity eventually reverses expansion, causing a Big Crunch.

Flat Universe

Universe whose expansion slows but never stops; overall spatial flatness.

Accelerating Universe

Currently accepted model where expansion speeds up due to dark energy.

Big Bang Theory

Idea that the universe began from an extremely hot, dense state and has been expanding.

Hubble’s Law

Relationship v = H₀d showing galaxy recessional velocity is proportional to distance.

Cosmic Microwave Background

Leftover thermal radiation from the Big Bang filling all space.

Singularity

Infinitely dense point that marks the universe’s beginning in Big Bang theory.

Inflation

Brief epoch of exponential cosmic expansion immediately after the Big Bang.

Planck Time

Earliest meaningful moment after the Big Bang (~10⁻⁴³ s).

Solar System

Sun and the bodies gravitationally bound to it, including planets, moons, and debris.

Terrestrial Planets

Rocky, high-density planets: Mercury, Venus, Earth, Mars.

Jovian Planets

Gas/ice giants with many moons: Jupiter, Saturn, Uranus, Neptune.

Mercury

Sun-skimming planet with no atmosphere; 88-day revolution.

Venus

Thick-atmosphere planet with retrograde rotation; brightest after Sun and Moon.

Earth

Only known habitable planet; possesses 1-atm atmosphere and one moon.

Mars

Thin-atmosphere ‘Red Planet’ featuring Olympus Mons and 687-day year.

Jupiter

Largest planet, 67 moons, hydrogen-helium atmosphere, Great Red Spot storm.

Saturn

Gas giant with prominent ring system and about 61 known satellites.

Uranus

Methane-blue ‘sideways planet’ whose axis is nearly parallel to its orbit.

Neptune

Distant ‘windy planet’ with Great Dark Spot and dynamic atmosphere.

Astronomical Unit (AU)

Average Earth-Sun distance, about 150 million km or 8.3 light-minutes.

Asteroid

Rocky or metallic minor body, mostly in belt between Mars and Jupiter.

Coma (Comet)

Bright, fuzzy sheath of gas and dust around a comet’s nucleus.

Halley’s Comet

Famous periodic comet visible from Earth roughly every 75–76 years.

Dwarf Planet

Solar-orbiting body too small to clear its orbit; e.g., Pluto, Eris.

Kuiper Belt

Region beyond Neptune containing icy bodies and dwarf planets.

Sun

Middle-aged G-type star; central energy source of the Solar System.

Core (Sun)

Innermost solar layer where nuclear fusion occurs.

Solar Envelope

Radiative and convective zones surrounding the Sun’s core.

Chromosphere

Reddish solar layer above photosphere visible during eclipses.

Photosphere

Visible ‘surface’ layer of the Sun where sunlight is emitted.

Corona

Outer, tenuous solar atmosphere seen as halo during total eclipse.

Sunspot

Dark, cooler patch on photosphere linked to magnetic activity.

Solar Flare

Sudden brightness flash ejecting energetic particles from the Sun.

Solar Wind

Stream of charged particles flowing outward from the Sun.

Aurora Borealis

Light display produced when solar wind particles interact with Earth’s magnetosphere.

Phases of the Moon

Regular changing illuminated shape: new, first quarter, full, third quarter, etc.

Solar Eclipse

Event where Moon passes between Sun and Earth, casting a shadow on Earth.

Lunar Eclipse

Event where Earth’s shadow falls on the Moon.

Spring Tide

Enhanced high-low tide range when Sun, Moon, Earth are aligned.

Neap Tide

Reduced tide range when Sun and Moon are at right angles to Earth.

Geocentric Model

Ancient view placing Earth at the center of the universe (Ptolemy).

Heliocentric Model

Model placing the Sun at the center of the Solar System (Copernicus, Galileo).

Nebular Hypothesis

Theory that planets formed from a collapsing rotating nebular cloud.

Vortex Theory

Descartes’ idea of whirlpool motions shaping planetary orbits.

Collision Theory (Buffon)

Hypothesis that a comet’s collision with the Sun produced planets.

Tidal Hypothesis

Jeans-Jeffreys idea that a passing star pulled material from the Sun to form planets.

Solar Nebular Theory

Modern refined nebular hypothesis involving a rotating disk and protostar.

Planetisimal Theory

Chamberlin & Moulton model where small solid bodies accreted into planets.

Lithosphere

Rigid outer layer consisting of crust and uppermost mantle.

Asthenosphere

Ductile upper mantle layer enabling plate movement.

Mesosphere (Earth)

Solid lower mantle beneath the asthenosphere.

Outer Core

Liquid iron-nickel layer generating Earth’s magnetic field.

Inner Core

Solid iron-nickel center formed by pressure freezing.

Mohorovičić Discontinuity

Boundary between Earth’s crust and mantle.

Continental Drift Theory

Wegener’s idea that continents moved from a supercontinent called Pangaea.

Plate Tectonics

Theory that Earth’s lithosphere is divided into moving plates.

Transform Boundary

Plate boundary where plates slide horizontally past each other.

Convergent Boundary

Boundary where plates collide, causing subduction or mountain building.

Divergent Boundary

Boundary where plates move apart, creating new crust at ridges.

Sea-Floor Spreading

Process of new oceanic crust forming at mid-ocean ridges and moving outward.

Earthquake

Sudden ground shaking caused by energy release along faults.

Focus (Hypocenter)

Point inside Earth where earthquake rupture starts.

Epicenter

Point on Earth’s surface directly above the focus.

P Wave

Fast compressional body wave traveling through solids, liquids, gases.

S Wave

Slower shear body wave traveling only through solids.

Love Wave

Surface wave causing horizontal ground motion; very destructive.

Rayleigh Wave

Surface wave producing rolling motion; causes strong shaking.

Richter Scale

Logarithmic scale measuring earthquake magnitude.

Modified Mercalli Scale

Scale ranking earthquake intensity based on observed effects.

Volcano

Mountain formed by accumulation of eruptive products around a vent.

Magma

Molten rock beneath Earth’s surface.

Lava

Magma that reaches the surface.

Composite Volcano

Steep-sided cone made of alternating lava and pyroclastic layers.