The sun warms our planet every day, provides the light by which we see and is necessary for life on Earth. But what is it exactly, and what will happen when it burns itself out?
" " The sun warms our planet, provides us with light and is crucial to all life on Earth. DrPixel / Getty Images When's the last time you gazed upward and marveled at the mysterious, life-giving force that is the sun? If you believe the whole staring-at-the-sun-makes-you-go-blind thing (which is actually true), you're probably not doing a whole lot of sun-gazing. But it's a real marvel: The sun warms our planet every day, provides the light by which we see and is necessary for life on Earth. It can also cause cell death and make us blind. It could fit 1.3 million Earths inside its sphere [source: SpaceDaily]. It produces poem-worthy sunsets and as much energy as 1 trillion megaton…