Our sun is a star that is alive and makes lots of energy. It is yellow and medium in size. The sun is still young enough to last at least 5 billion more years.
The night sky is full of stars of different colors. The blue stars are young and called blue giants. They are so big that they don’t last very long. The stars that last the longest are called red dwarfs. The oldest stars in the universe are red dwarfs. Some of them were born at the very beginning of the universe. Our sun is a yellow dwarf that is still full of energy.
Stars are born in nebulae. The nebula card in this printout has a picture of a nearby nebula and shows baby stars in it. Some of these will become blue giants and others will become yellow dwarfs. When a yellow dwarf gets very old, it becomes a red giant. When a red giant dies, it creates a 'planetary nebula', which will feed new stars that are being created. The center of a planetary nebula is a bright, dense star called a white dwarf. It is tiny and extremely bright because it was the core of the red giant.
Sometimes a star is born that isn't big enough to glow brightly. These are called brown dwarfs. They are similar to Jupiter.