Introduction to the Solar System and Planetary Characteristics

Vocabulary flashcards covering planetary classifications, the structure of the solar system, hydrostatic equilibrium, and surface impact dynamics.

Asteroid Belt

A region located between Mars and Jupiter that separates the inner planets from the outer planets of the solar system.

Inner Planets

The four planets closest to the Sun—Mercury, Venus, Earth, and Mars—which are characterized by being smaller in size with solid, rocky surfaces.

Outer Planets

Also referred to as giant gas planets or gas giants, these are larger planets mostly composed of gas, with the farthest ones containing ice.

Hydrostatic Equilibrium

A condition in which a celestial body possesses sufficient mass to overcome rigid body forces and form a rounded shape.

Jupiter

The largest and most massive planet in the solar system.

Moon (Satellite Classification)

A celestial body that is not classified as a planet because it orbits around the Earth rather than directly orbiting the Sun.

Lunar Craters

Impact marks covering the surface of the Moon that persist because the Moon lacks an atmosphere and geological activity to burn or erase them.

Atmospheric Shielding

The process where smaller asteroids and space debris burn up in a planet's atmosphere before they can reach the surface.

Sun

The single star at the center of our solar system that contains $99.8\%$ of its total mass.

Planet (2006 Definition)

A celestial body that is in orbit around the Sun, has sufficient mass to assume hydrostatic equilibrium, and has cleared the neighborhood around its orbit.

Planet (2005 Draft Definition)

A proposed definition of a planet as a celestial body in orbit around a star (and neither a star nor a satellite) that has sufficient mass for hydrostatic equilibrium, which would have recognized $12$ planets in our Solar System.

Hydrostatic Equilibrium

A state reached when a celestial body has sufficient mass for its self-gravity to overcome rigid body forces, resulting in a nearly round shape.

Terrestrial Planets

The small inner planets—Mercury, Venus, Earth, and Mars—which possess solid, rocky surfaces.

Jovian Planets

Also known as giant planets or outer planets, this group includes Jupiter, Saturn, Uranus, and Neptune, which are larger and mostly made of gas and ices.

Dwarf Planet Orbits

Tilted and elliptical orbits characteristic of dwarf planets, which differ from the nearly circular orbits in the same plane followed by the eight major planets.

Cosmic Debris

Objects in the solar system other than stars and planets, consisting of asteroids, comets, and meteors.

Crater Counting

A method used by astronomers to estimate the surface age of astronomical objects, based on the principle that a surface with more craters has been around longer.

Radioactive Dating

A scientific technique used to estimate the age of complete objects by measuring elements that spontaneously change over time.

Half-life

The length of time required for half of an original radioactive sample to change or decay.

Meteorite Ages

Ages measured from meteorites on Earth's surface reaching up to $4.56\text{ billion years old}$, which reveal the approximate formation age of the solar system.