Lesson 2

Celestial Bodies


When you look at the sky at night you can see lots of bright objects.They are celestial bodies. The universe consists of celestial bodies.
We can distinguish two types of celestial bodies:
- Luminous celestial bodies that emit light and illuminate: stars
- Non luminous clestial bodies that do not emit light but do illuminate: planets,satellites,etc...


Stars


Stars are huge balls of gas.They are celestial bodies that emit their own light. For this reason, they can illuminate other celestial bodies.
Stars are very large but they appear very small to us.
Stars are very far away from the Earth.
Stars form groups called galaxy.
Some groups of stars form figures. We call them constellations. We can see some of these constellations at night.     

 Planets

Planets are celestial bodies without their own light. Planets receive light from the stars.They reflect this light.Planets follow a path when they move around stars. 
This path is called an orbit. Planets are round and very large. 






Satellites

Satellites are celestial bodies without their own light.
Satellites receive light from the stars.
They orbit around a planet.
Each planet has a certain number of satellites.
The Moon is the Earth's satellite.





Other celestial bodies

There are other celestial bodies that orbit around the Sun:

- Comets: they are made of ice and rocks. They orbit the Sun and have a tail that reflects light from the Sun.

Link here for more information about comets






- Asteroids: they are giant rocks. When they fall to Earth
they are called meteorites.