Science - celestial objects and astronomy

Asteroid

A small, rocky object that orbits the Sun, mostly found in the asteroid belt.

Black Hole

A region in space with gravity so strong that nothing, not even light, can escape.

Comet

An icy, dusty object that develops a glowing tail and coma when close to the Sun.

Exoplanet

A planet that orbits a star outside our own solar system.

Galaxy

A massive system of billions of stars, gas, and dust held together by gravity.

Nebula

A giant cloud of gas and dust where new stars are born or old ones leave remnants.

Neutron Star

The superdense core left behind after a massive star explodes in a supernova.

Star

A massive, luminous ball of gas generating energy through nuclear fusion.

Big Bang

The theory that the universe began as a hot, dense point and has been expanding.

Eclipse

An event where one celestial body blocks or moves into the shadow of another.

Meteor

The bright streak of light produced when a meteoroid burns up in Earth's atmosphere.

Supernova

A powerful, bright explosion that marks the death of a massive star.

Astronomical Unit (AU)

The average distance from Earth to the Sun, about 149.6 million kilometers.

Light-Year

The total distance a beam of light travels through a vacuum in one Earth year.

Gravity

The natural physical force that pulls objects toward one another.

Orbit

A regular, curved path an object takes around another under the influence of gravity.

Natural Satellites

Celestial bodies like planets orbiting stars, or moons orbiting planets.

Artificial Satellites

Man-made devices launched into space for communication, research, or navigation.

Small Solar System Bodies

Asteroids, comets, and outlying bodies traveling around the Sun.

Orbit Balance

Maintained by a balance between forward momentum and gravitational pull.

Orbit Shape

Most orbits are elliptical (oval or egg-shaped) rather than a strict circle.

Orbit Direction

Most objects revolve counterclockwise, but some retrograde objects have >90 degree inclination.

Lunar Cycle

Takes approximately 29.5 days as the Moon orbits Earth and reflects sunlight.

New Moon

The illuminated side faces away from Earth; the Moon is barely visible.

Waxing Crescent

A growing sliver of light appears on the left side in the Southern Hemisphere.

First Quarter

Half of the Moon's visible surface is illuminated.

Waxing Gibbous

More than half of the Moon is lit and continuing to grow toward full.

Full Moon

The entire face of the Moon is illuminated as Earth sits between Sun and Moon.

Waning Gibbous

More than half is lit, but the light begins to decrease.

Third Quarter (Last Quarter)

Half of the visible surface is illuminated again on the opposite side.

Waning Crescent

A shrinking sliver remains before returning to the New Moon.

Tides

The regular rise and fall of ocean water levels caused by gravity and Earth's rotation.

The Moon's Gravity (Tides)

Pulls on ocean water causing it to bulge outward on the facing side.

Earth's Rotation (Tides)

As Earth spins, coastal areas move through water bulges, creating tidal cycles.

High Tide

When water level reaches its highest point along the shore due to a tidal bulge.

Spring Tides

Occur during full and new moons when Sun, Earth, and Moon line up, creating extreme tides.

Neap Tides

Occur when Sun and moon sit at right angles, producing smaller, moderate tides.