We have learned about many things that we will find in space, but besides from the Sun and Moon, everybody knows when they look up at night, they see the stars. Maybe you do not know the names of the stars, but you know that they are beautiful to watch.
Lets gather some more information on stars.
A star is a ball of burning gas - it is held together by gravity. The hydrogen in the star burns and it makes helium. This is called 'hydrogen fusion'.
When a star is close to being burned out, the helium will change into gases like oxygen and carbon dioxide and it will also change in colour and size.
We rarely think of the Sun as a star, but the Sun is the closest star to Earth.
After the Sun in our Solar system, the nearest star to Earth is Proxima Centauri. It is about 39.9 trillion km away or 4.2 light years. This means it takes light from this star 4.2 years to reach Earth. Using the newest, fastest space probe propulsion systems would still take a craft about 75,000 years to get there.
The stars in our solar system are very old and they can be anywhere between 1 and 10 billion years old and there are between 200-400 billion stars in our Milky Way.
It happens that some stars are pulled to one another through gravity and they orbit around each other. These stars are called 'binary or multi star systems'.
Different stars have different names and colours .
- red dwarfs are the most common stars and the are half the size of the Sun, the burn slowly and life a long time (over 100 billion years)
- a brown dwarf is a star that cannot burn hot enough for hydrogen fusion to happen so they burn very dimly
As yellow dwarf stars like our Sun start to run out of hydrogen fuel, the core shrinks, heats and pushes out the rest of the star turning it into a red giant.
- white dwarfs are stars that have used up all their fuel and are starting to die and they will eventually turn into a black dwarf.
- There are very big stars that are called 'supergiants' burn their fuel up very quickly and the will explode as massive supernovas.
- If the supernova is very heavy, it can actually turn into a black hole.
Stars range in color depending on how hot they are, in order from lowest to highest temperature they are can be brown, red, orange, yellow, white, or blue in color.
You know the song 'Twinkle twinkle little star'? If you look up at the sky you see them twinkle, but they actually do not twinkle, we just see it that way because there is a lot of moving air in the atmosphere and it bends the light that reaches our eyes.
The stars have played a very important role throughout human history. They have formed part of religious practices, been grouped into constellations, used in astrology star signs, helped to design calendars and were very important navigational tools for early explorations across land and seas.
Read more about constellation here.