On these slides you will find lots of interesting facts about stars. Miss Leveridge Year 2r

LO: To learn that stars belong to groups. Success Criteria: I can write some facts about a star. I can use capital letters and full stops I can use newly learnt words There are more stars in the universe than grains of sand on all the beaches on Earth. That’s at least a billion trillion. When you look at the night sky you can see many beautiful stars. If you are out in the country or camping in the mountains or the desert away from the city lights, you may see thousands of them. In a town or city, you can't see nearly as many stars because the city lights create a glow in the sky hiding many of them.  There are several different kinds of stars in the sky. Some are very big. A couple of stars have been found that are 100 to 200 times larger than the sun.  Some very old stars are smaller than the Earth.  Scientists study stars and place them in groups based on how they are alike and how they are different.

Red Stars

Red Dwarf stars are smaller than our sun and live a very long time Red Dwarf stars are smaller than our sun and live a very long time. These stars do not shine as brightly as others.  Some red dwarf stars will live trillions of years before they die.   Why are red dwarf stars red? Because red dwarf stars only burn a little bit of fuel at a time, they are not very hot compared to other stars.  Think of a fire.  The coolest part of the fire is at the top of the flame where it glows red, the hotter part in the middle glows yellow, and the hottest part near the fuel glows blue.  Stars work the same way.  Their temperature tells us what colour they are.  We can tell how hot a star is just by its colour. Red dwarf stars are the most common type of star in outer space. However, very few stars that you see in the sky are red dwarfs. This is because they are so small and make very little light.

Giant Stars

As a sun-sized star gets old, it starts to run out of fuel and all the stuff in the middle of the star gets really close together.  As the centre gets smaller and smaller it starts to heat up again. When it gets hot enough it will start to expand making the star much larger. Imagine a hot air balloon. As the air inside the balloon gets hotter, it stretches the balloon out further and further. As the giant star gets hotter, its outside stretches out further and further. When our own sun begins to stretch into a giant star, it will cover Mercury, Venus, Earth and Mars. Many of the stars you see at night are giant stars. This is because like a lighthouse, giant stars glow very brightly.

yellow stars

Like the Sun, these yellow medium-sized stars are yellow because they have a medium temperature. They burn faster so they will not live as long, only about 10 billion years or so.  Near the end of their lives these medium-sized stars swell up, becoming very large. When this happens to the Sun, it will grow large enough to cover Earth. Eventually they shrink again, leaving behind most of their gas. This gas forms a beautiful cloud around the star called a Planetary Nebula.  When will the Sun expand into a giant, and then shrink leaving behind a planetary nebula? Don't worry, the sun is only about 5 billion years old. It still has another 5 billion years or so before it will expand and turn into a planetary nebula!

blue stars

Blue stars are very hot.  These stars run out of fuel in only 10,000 - 100,000 years.  A blue giant is extremely bright.  Like a lighthouse, they shine across a great distance. Blue giant stars make up many of the stars we see at night because they shine so brightly. Blue giant stars die in an amazing way.  They grow large but instead of shrinking and forming a planetary nebula, they explode in what is called a supernova. Supernova explosions can be brighter than an entire galaxy, and can be seen from very far away. The next picture shows a supernova…