Solar System Vocabulary

Galaxies and the Milky Way

A galaxy is defined as a large group composed of stars, dust, and gases. Our home galaxy is known as the Milky Way, which is classified specifically as a spiral galaxy.

The Sun and Earth's Energy

The Earth receives significantly more energy from the sun than from any other star because the sun is the closest star to us. In terms of stellar scale and characteristics, the sun is an averaged size star.

Planetary Rotation, Revolution, and Time Cycles

Day and night are produced by the Earth rotating on its axis. One full rotation of the Earth takes $24\text{ hours}$, which represents $1\text{ day}$. In addition to axial rotation, the Earth undergoes an orbital motion around the sun. One complete revolution around the sun takes $1\text{ year}$, which equals $365\frac{1}{4}\text{ days}$.

Moons and Planetary Satellites

A satellite is a body that revolves around and orbits a planet. The moon is a satellite that orbits the planet, and Earth possesses exactly $1\text{ moon}$.

Inner Planets

The inner planets of the solar system consist of Mercury, Venus, Earth, and Mars. These inner planets are characterized by being rocky in composition.

Outer Planets

The outer planets of the solar system consist of Jupiter, Saturn, Uranus, and Neptune. These outer planets are substantially larger than the inner planets, are known as gas giants, possess a greater number of moons, and ALL have rings.