Red and Blue Giant Stars
Remember when we talked about sun-sized stars? We said that at the end of their lives these stars expand, taking up much more space than before. This is exactly what a Giant Star is.
As a sun-sized star gets old, it starts to run out of its hydrogen fuel. When the process of burning hydrogen in the star’s core begins to slow down, the core gets more compact and dense. This means all the stuff in the middle of the star gets really close together. As the center gets smaller and smaller it starts to heat up again. When it gets hot enough it will start to burn a new fuel called helium.
Once ignited, helium burns much hotter than hydrogen. The additional heat pushes the outer layer of the star out much further than it used to be, 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 engulf Mercury, Venus, Earth and Mars.
Did you know?
Many of the stars you see at night are giant stars. This is because like a lighthouse, giant stars glow very brightly. When the Sun becomes a giant star, it’s light will shine much further into space than it does right now.
Blue Giant Stars
Blue stars are large and compact, this causes them to burn their fuel quickly which in turn makes their temperature very hot. These stars often 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. Even though blue giant stars are rare, they make up many of the stars we see at night because they shine so brightly.
Blue giant stars die in a spectacular way. They grow larger just like the sun-sized stars, but then 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.
Did you know?
Because blue giant stars only live a short time, scientists use them to find places in outer space where new stars are forming.