"When a star like our own reaches the end of its life, it begins to run out of hydrogen fuel in its core. Like a car running out of gas, it will begin to sputter, swelling to a size that could encompass every planet in our solar system out to Mars. When this happens, the sun will swallow the Earth and will spell certain doom for all life on our planet."
First image for psdtuts+ on the series "The Cosmos", a 4 part series of FREE tutorials so get over there hope you enjoy it. [link]