The Sun's Death
Written by Fraser Cain
Artist's impression of a red giant star.
All things must end. That's true for us, that's true for the Earth, and that's true for the Sun. It's not going to happen tomorrow, but one day in the far future, the Sun will run out of fuel and end its life as a main sequence star and die. Let's take a look at the Sun's death.
The Sun was born from the solar nebula 4.6 billion years ago. After a few hundred million years after its birth, the Sun settle down to become a main sequence star. It was happily burning hydrogen at its core, where the intense temperature and pressures allowed the Sun to convert hydrogen into helium. But the Sun actually only has so much of this hydrogen fuel available to it. The Sun's death will come when it runs out of fuel.
The Sun is converting about 5 million tons of hydrogen into helium every second. This sounds like a lot, but it only has enough fuel for another 5 billion years. When the Sun does run out of fuel, it will swell up to become a red giant star, expanding in size beyond the orbits of Mercury and Venus. Astronomers even think it will swallow up the Earth as well. Even if the Earth survives, the intense heat from the red sun will scorch our planet and make it completely impossible for life to survive.
Once it has become a red giant, the Sun's death is just around the corner. It will still have enough heat and pressure at its core to begin a second stage of fusion, burning helium this time to form carbon. But when the helium runs out, the Sun won't have enough gravity to keep the core temperature and pressure up to burn carbon. At this point, the Sun will slough off its outer layers into space in a series of bursts.
The dying core of the Sun, an Earth-sized diamond of carbon and oxygen called a white dwarf, will be all that remains. It will slowly cool off over billions of years, eventually reaching the background temperature of the Universe. It will then be a black dwarf.
The Sun's death will be complete.
We have written many article about red giant stars and the future of our Sun on Universe Today. Here's an article that discusses how the Sun will destroy the Earth, and a glimpse at the future of our Sun.
The BBC has a great article about the future of the Sun, and another article from National Geographic.
We have recorded an episode of Astronomy Cast just about the Sun called The Sun, Spots and All.
Filed under: Astronomy
