The searing hot ball of gas at the heart of our planetary neighborhood is home to almost all the mass of the solar system—99.8 percent, in fact. Its surface burns at more than 10,000 degrees Fahrenheit and it constantly spews out a barrage of solar wind.
But the churning furnace won’t burn like this forever. Eventually it will expand into a red giant, frying the inner solar system. Too light to explode as a supernova, it will probably end its life as a hot, dense white dwarf—the relic of a stellar core.
Before its dramatic end several billion years from now, the sun will heat up Earth beyond habitability as it releases more and more energy. One to two billion years from now, as astrophysicist and author Ethan Siegel points out on Forbes, Earth’s seas will boil away as the sun gets hotter and hotter.
Earth sits in the “goldilocks zone” of our sun—not too close and not too far away for liquid water to exist, a fundamental ingredient for life as we know it. But, as Siegel wrote, the sun is slowly getting lighter. It's by far the most massive object in the solar system, but it's shedding mass all the time. The sun’s gravitational pull forged our solar neighborhood, attracting more and more matter to the glowing hulk.
But eventually, he explained, radiation from the sun and from other stars scuppered the growth of our planetary neighborhood. “The matter that would continue to fall in gets blown away, eventually giving rise to our modern Solar System,” Siegel wrote.
Now, the sun is actually losing mass. The fiery ball fuses hydrogen into helium—a lighter element. The energy from this fusion travels to the surface, while the light helium drifts to the heart of the sun. Helium can’t fuse in this blistering furnace, and without this reaction, radiation drops and "the helium-rich inner part starts to contract under its own gravity,” Siegel explained. This contraction forces energy outwards, slowly increasing the energy output of our aging sun.
Meanwhile, the glowing orb is continually releasing a barrage of particles known as solar wind. It spurts out even more particles in the fits and bursts of solar mass ejections. According to Siegel, the sun sheds a mass roughly equivalent to that of one Earth in 150 million years of solar wind.
But fusion is the real kicker. Over its lifetime, he wrote, the sun has shed some 95 Earth masses as a result of fusion. That dwarfs roughly 30 lost to solar wind so far. The swelling store of helium at the sun’s core will heat up our own planet as it grows.
Eventually, temperatures will become so hot that liquid water will disappear. The seas will evaporate and life as we know it will be impossible. But don’t worry. That’s a couple of billion years away.
