Topic 1b : Solar System

Galaxy

a huge group of single stars, star systems, star clusters, dust, and gas bound together by gravity.

Universe

space and all the energy around it.

Celestial Body

a natural object in space, such as the sun, moon, planet, or a star.

Milky Way

a large spiral galaxy that is home to Earth and the rest of our solar system.

Stars

balls of hot gas, primarily hydrogen and helium, that emit, or give off, light.

Solar System

the sun, the eight planets and their moons in orbit around the sun, together with asteroids, meteoroids, and comets.

Sun

the star at the center of our solar system that supplies heat and light to Earth; it’s enormous gravity keeps the solar system in orbit.

Planets

a celestial body moving in an elliptical orbit around a star.

Inner Planets

small rocky planets, with limited or no moons, that orbit closest to the sun including Mercury, Venus, Earth, and Mars.

Outer Planets

large planets made of gas and ice, with numerous moons, that orbit the sun, farther than the inner planets, including Jupiter, Saturn, Uranus, and Neptune.

Moons

small celestial bodies that orbit planets.

Asteroids

rocky metallic objects that orbit the sun but are too small to be considered planets.

Asteroid Belt

the region of the solar system between the orbits of Mars and Jupiter, where many asteroids are found.

Meteoroids

much smaller bodies than asteroids, moving in the solar system, that would become meteors if they entered the Earth’s atmosphere.

Comets

balls of ice, rock, and dust in space with a tail, that orbit the sun.

Telescope

a device built to observe distant objects by making them appear closer.

Rotation

the spinning motion of a planet on its axis.

Axis

an imaginary line that passes through Earth’s center and the North and South poles, around which Earth rotates.

Orbit

the path of an object as it revolves around another object in space.

Tilt

a sloping position or movement