Astronomy Vocabulary: Space Objects and Orbits

asteroid belt

Location: region between the orbits of Mars and Jupiter where many asteroids are found.
Composition/Objects: rocky objects larger than a few hundred meters that orbit the Sun. (These are the asteroids that populate the belt.)
Significance: represents a field of rocky remnants from the early solar system that never coalesced into a planet; potential source of meteorites that reach Earth.

Definition: Rocky objects larger than a few hundred meters that orbit the Sun.
Context: They populate regions like the asteroid belt and other parts of the solar system.
Significance: key remnants from solar system formation; studying them provides clues about early materials and processes.

Definition: A small, icy, dusty object with a bright tail in orbit around the Sun.
Tail formation: when it nears the Sun, solar heat sublimes ices and releases dust, creating a glowing tail that points away from the Sun due to solar wind.
Significance: hosts pristine material from the outer solar system; helps study early solar system chemistry and volatile delivery to planets.

Definition: Gravity is a natural force of attraction that exists between all objects with mass or energy in the universe.
Effect: causes objects to pull toward each other; governs orbits, tides, and structural stability of planetary systems.
Mathematical relation (illustrative):
F = G \frac{m1 m2}{r^2}
where $F$ is the gravitational force, $G$ is the gravitational constant, $m1$ and $m2$ are the masses, and $r$ is the separation distance.
Significance: fundamental for understanding planetary motion, satellite dynamics, and why objects stay bound to planets or the Sun.

Definition: Inertia is the tendency of an object to resist changes in its state of motion.
Description: an object at rest tends to stay at rest; an object in motion tends to keep moving at a constant velocity (speed and direction) unless acted upon by an external force.
Everyday intuition: explains why you feel a jolt in a car when it suddenly accelerates, stops, or turns (you keep moving/your body resists the change).
Scientific implication: under Newton's first law of motion, motion changes only when a net external force acts.

Definition: A region or area beyond the orbit of Neptune that contains millions of frozen objects.
Contents: icy bodies and dwarf planet candidates; source region for many long-period comets.
Significance: a key reservoir of primitive material beyond the outer planets and a focus for studies of solar system formation.

Definition: Mass is a measure of how much matter is in an object.
Units: kilograms (kg) in the metric system.
Significance: determines the strength of gravitational interaction (e.g., weight, gravitational pull) and inertia.

Definition: Material from outer space that burns up as it enters Earth's atmosphere.
Process: as a meteoroid enters the atmosphere at high speed, it experiences friction and heat, creating a bright streak called a meteor.
Significance: collection of extraterrestrial material that can be studied to understand outer space composition; some meteors survive as meteorites.

Definition: Fragments of planetary or celestial bodies such as moons, planets, asteroids, and comets that strike Earth’s surface.
Significance: provide direct physical samples of solar system material for analysis on Earth; help reveal formation and alteration histories.

Definition: A small rock in space that has not yet entered Earth's atmosphere.
Significance: may become a meteor (and potentially a meteorite) if it survives atmospheric entry.

Definition: The Oort Cloud is a vast region of space far beyond the planets, where billions of icy objects called comets live.
Significance: source region for long-period comets; acts as a distant reservoir of pristine solar system material.

Definition: To travel in a circular or elliptical path around another object.
Key idea: governed by gravity; orbital shapes can be circular, elliptical, parabolic, or hyperbolic depending on energy and velocity.
Significance: explains how planets, moons, and small bodies maintain stable paths around stars and planets.

Definition: Weight is the force with which an object is pulled towards the Earth (or another celestial body) due to gravity.
Relation to mass: W = m g where $m$ is mass and $g$ is the local acceleration due to gravity.
Significance: varies with location (surface gravity differences) and is separate from mass (mass is constant regardless of location).