All good things must come to an end, including the ancient (at least relative to humanity), life-giving star we see each day. Even though the sun is considered a young star, it still has a finite lifetime, and it will eventually “die” in about 5 billion years. The image above shows a rough timeline of what this life cycle looks like, and for the purpose of this blog, we are considering the transition to the red giant phase the death of the sun. This is the point that the sun runs out of hydrogen to fuse in the core. This loss of fusion disrupts the balance between the inward force of gravity and the outward force of pressure that keeps the sun stable. The core will begin to collapse under gravity, and the outer layers of the sun will expand.
These outer layers will envelop Mercury, Venus, and probably Earth too. If our home is not completely vaporized, it will be uninhabitable from the intense heat and radiation. The sun’s outer layers would expand about to about 100 million miles (170 million kilometers or about 1 astronomical unit: the distance from the sun to the Earth). Hopefully by then, if humans are still around, we will be long gone in another planetary system (or at least to the moons of Jupiter and Saturn).