The Planet Quiz Show

The sun is about halfway through its life. Since its birth five billion years ago, it has been changing hydrogen gas into helium gas in its center called the core. When the sun runs out of hydrogen gas in its core about five billion years from now, the sun will grow larger in size, becoming a red giant star. It will stay this way for about another billion years, eventually losing its atmosphere to space. What will remain will be the sun’s hot helium core, now called a white dwarf star. It will be just a little bigger than the Earth in size. Our white dwarf sun will cool over billions of years to become a black dwarf.

Since its birth five billion years ago, the sun has been a very stable star. It produces energy by changing hydrogen into helium within its core. Because the helium “ash” is denser than the hydrogen fuel which created it, the helium makes its way towards the core’s center and is compressed. Over time, this results in an increase in the core temperature of the sun which drives the hydrogen fusion at a faster pace. Since its birth, there has been a slight increase in the sun’s energy output. In approximately five billion years, the sun’s luminosity and size will change more abruptly. Hydrogen will be depleted within the core, but the core’s temperature will have increased enough to allow hydrogen to fuse within a thin shell surrounding the core. As more helium falls into the core, the rise in the core’s temperature will cause a rapid increase in the energy production in the hydrogen shell. This will cause the sun to expand into a red giant star with a volume hundreds of thousands of times greater than its present size. Finally, as hydrogen is depleted within the thinning shell, hydrogen fusion will become more erratic, and the red giant sun will begin to pulsate, eventually dissipating its outer regions into space to reveal the hot inner helium core, now called a white dwarf star. The core will only be an object slightly larger than the diameter of Earth, but it will still pack almost as much matter as the sun did when it was actively changing hydrogen into helium. The white dwarf sun will slowly cool over billions of years turning into a black dwarf. The inner planets will be gone. The remaining rocky cores of the Jovian planets stripped of their atmospheres and hydrogen interiors will continue to complete their orbits around the dead sun in the cold darkness of outer space.

In about five billion years the sun will run out of hydrogen fuel in its center. This will cause the sun to expand into a red giant star, perhaps becoming large enough to even swallow the Earth. Our planet will be history, boiled away by the intense heat from the sun. But don’t worry, people will have enough time to develop the rockets and spacecraft that will be allow us to find safety on another Earth-like planet in orbit around another star in our galaxy.