What’s going to happen to our sun?

We tend to think of the sun as being that old reliable ball of bright light that dispels the aftereffects of the night in the morning and warms us in the day. Without it, we would be toast, well, maybe cold toast.

Actually, if we lived long enough we would eventually become toast. The sun increases its intensity by ten percent every billion years. A ten percent increase in the sun’s intensity would be much worse than any prediction of global warming. We would end up like Venus, a hot dry planet the size of Earth with an atmosphere of sulfuric acid laced carbon dioxide a hundred times denser than Earth’s atmosphere.

Why is the sun increasing its intensity? This has to do with the fact that the main engine that runs the sun is fusion of hydrogen to helium in its core and as it does this the radius of the sun decreases slowly over time and this increases the core’s temperature.

Our sun is a typical G2 class main sequence dwarf star about half way in its life on the main sequence where it fuses hydrogen to helium, or about four and half billion years old. The sun converts 4.28 million metric tons of hydrogen every second, but since the sun is nearly a million miles in diameter and contains 99.86 percent of the solar system’s mass, it has plenty of fuel to last for another four billion years.

However, it will eventually run out of hydrogen, and when it does, it will begin to fuse helium to carbon. This fusion reaction requires a much higher temperature, and it will make the sun expand to a red giant by heating the outer layers, expanding them. This expansion will take a billion years and engulf the inner planets, including the Earth. The red giant that results will be thousands of times the intensity of the present sun and make Earth hotter than hell. Yikes!

However, we won’t be around by then, at least not living like we do now. As I said, a ten percent increase of intensity or brightness will happen in a billion years. This will cause the oceans to evaporate and bad things to happen to all life. Actually, I give humanity a half billion years at best before the Earth becomes inhabitable, and this assumes that nothing else apocalyptic happens in the meantime.

The strange thing about the sun dying is that its death will be mild compared to the large blue stars that go out with a bang that’s called a supernova. Our sun is too small to do that. It will go out with a whimper and eventually blow away its outer layers in what’s known as a ‘helium flash’ into what is called a planetary nebula, a circular cloud of illuminated gas that will slowly dissipate. The core will remain as a white dwarf and be a dismal artifact of its former self. The white dwarf will remain for trillions of years with a temperature of 100,000 K before it slowly cools and goes dark. The outer planets will still be around and they will orbit this tiny dense hot white dwarf star forever, whatever that means.

So there you have it. We don’t have to worry about the sun because these changes take place over a long period of time. The future generations will have a problem, but by them maybe mankind will go to another solar system to live. Who knows?

Thanks for reading.