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 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 extra heat pushes the outer layer of the star out much further than it used to be. This makes the star much larger.
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, its light will shine much further into space than it does right now.
Blue Giant Stars
Blue giant stars are large and compact, this causes them to burn their fuel quickly. This makes their temperatures very hot. These stars often run out of fuel in only 10,000 – 100,000 years.
A blue giant is extremely bright, or luminous. 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.
Red Giant Stars
In a few billion years, our Sun will turn into a red giant star and engulf the inner planets of our galaxy. Red giant stars reach sizes of 100 million to 1 billion kilometers in diameter. This is about 1000 times the size of our sun. Red giants are bigger than blue giants. Their energy is spread over a larger area. This causes red giants to be cooler than blue giants.
Future of Our Sun
When the sun becomes a red giant in approximately 5 billion years, life on Earth will cease to exist. Even if the red giant does not completely engulf Earth, the extreme heat from the sun will boil up the oceans and cause hot rock to form on the surface of our planet. However, when stars become red giants, they may create other solar systems where life can thrive.
Other Great Resources
More on Red Giants: https://www.space.com/22471-red-giant-stars.html
Our Sun Vs. Giant Stars:
BBC on Giant Stars: http://www.bbc.co.uk/science/space/universe/sights/giant_stars