Solar System, Planetary Science, and Gravity

Comprehensive vocabulary flashcards covering the basic requirements for life, the structure and celestial bodies of the solar system, and the principles of gravity, inertia, and orbital motion.

Habitable zone (Goldilocks zone)

The region around a star where temperatures may allow liquid water to exist on a planet's surface.

Cellular respiration

The biological process cells use to release energy from food, which requires oxygen in many organisms.

Ultraviolet (UV) radiation

Energy from the Sun that can damage living cells, much of which is absorbed or blocked by Earth's atmosphere.

Thermal energy

Energy related to the movement of particles in matter, which is redistributed around Earth by atmospheric winds and air currents.

Atmosphere

The layer of gases surrounding a planet; on Earth, it is composed mostly of nitrogen and oxygen with small amounts of other gases.

Astronomical unit (AU)

A unit of distance equal to the average distance from Earth to the Sun, approximately $150{,}000{,}000\,\text{km}$.

Sun

An average-sized star at the center of the solar system, composed mostly of hydrogen and helium, whose gravitational pull holds all solar system objects in orbit.

Planet

A celestial body that orbits the Sun, is rounded by its own gravity, and has cleared most other objects from its orbital path.

Dwarf planet

A rounded object that orbits the Sun and has sufficient mass for its own gravity to shape it, but has not cleared its orbital path of other objects.

Moon

A natural object that travels in an orbit around a planet.

Terrestrial planets (Inner planets)

The four small, dense, rocky planets closest to the Sun—Mercury, Venus, Earth, and Mars—composed primarily of rock and metal.

Asteroid

A small rocky or metallic object that orbits the Sun, exhibiting no tails or disc-like features.

Asteroid belt

The region between Mars and Jupiter, located between approximately $2\,\text{AU}$ and $4.5\,\text{AU}$ from the Sun, where many asteroids and the dwarf planet Ceres orbit.

Ceres

A dwarf planet located within the asteroid belt with an average diameter of approximately $950\,\text{km}$.

Meteoroid

A small piece of rock or metal traveling through space, ranging from dust-sized grains up to one meter wide.

Meteor

A visible streak of light produced when a meteoroid enters an atmosphere and burns up due to friction and aerodynamic heating.

Meteorite

A part of a meteoroid or space object that survives passage through the atmosphere and strikes the ground or planetary surface.

Gas giants

The giant outer planets Jupiter and Saturn, composed primarily of gases such as hydrogen and helium.

Ice giants

The giant outer planets Uranus and Neptune, composed primarily of icy materials and gases.

Kuiper belt

A circumstellar disc-shaped region beyond Neptune extending from roughly $30\,\text{AU}$ to $50\,\text{AU}$ from the Sun, containing icy objects, comets, and dwarf planets.

Oort cloud

A theoretical, giant spherical shell of icy debris surrounding the entire solar system, extending from about $2{,}000\,\text{AU}$ out to $100{,}000\,\text{AU}$ from the Sun.

Comet

An object composed of a loose collection of ice, dust, and rock that travels along a narrow elliptical orbit around the Sun and develops a coma and tails when heated.

Coma

The glowing, temporary atmosphere formed around a comet's nucleus when solar radiation evaporates surface ice into gas and dust.

Gravity

A non-contact attractive force between objects with mass that governs the movement of celestial bodies across the solar system.

Universal force

A force, proposed by Isaac Newton, that acts across all distances and affects every pair of objects with mass throughout the universe.

Mass

The quantity of matter present in an object, measured in kilograms ($\text{kg}$), which remains constant regardless of location.

Weight

The downward gravitational force exerted on an object, measured in newtons ($\text{N}$), which varies based on local gravitational acceleration.

Inertia

The tendency of an object to resist changes in its state of motion or rest unless acted upon by an external force.

Orbit

The curved path followed by a celestial object or spacecraft as it revolves around another body under the influence of gravity.

Optics

The scientific study of light and its properties, a field in which Isaac Newton made pioneering contributions alongside mathematics and gravity.