The Universe includes all of space and all the matter and energy in space. For example, the universe contains stars, planets, satellites and billions of galaxies.
The universe is continually expanding, which means that it’s getting bigger over time. Let’s look at some examples of what we can find in the universe.
A galaxy is a massive collection of gas, dust and stars, which are all held together by gravity. Our galaxy is called the Milky Way. However, there are billions of galaxies in the universe.
A constellation is a group of stars that form particular patterns in the sky.
A light year is a unit of astronomical distance used to describe distances in space. So, the distance that light travels in one year is a light year.
There are many objects, other than planets, that we can find in space.
In the solar system, objects called asteroids orbit the Sun in elliptical paths. Asteroids are mostly made of rock and metal and they are typically found in the asteroid belt. Although they vary in size, they are much smaller than planets.
When asteroids collide in space, small pieces can break off. We call these pieces meteoroids and they can vary in size. If a meteoroid breaches the Earth’s atmosphere, it becomes a meteor.
Meteors, often seen as shooting stars, can be observed in the sky. They rarely ever hit the Earth’s surface. However, if they do, they are called meteorites.
A comet is a ball of dust and ice that orbits the Sun.
The orbits of comets are different from the orbits of planets. Comets have a highly elliptical orbit. When a comet approaches the Sun, it vaporises (turns to gas), giving the comet its distinctive tail.
Satellites are objects that surround and orbit planets. They can either be natural or artificial. The Earth has a natural satellite, which is the Moon.
The Moon is a natural satellite, which we can see in the night sky. It makes a complete orbit of the Earth every 27 days.
Earth is not the only planet with a moon; other planets have moons too. For example, Uranus has over 25 moons.
Satellites that humans launch into space are called artificial satellites. There are thousands of artificial satellites. For example, the international space station and communication satellites.