Understanding the fate of our Sun offers a profound perspective on the eventual end of Earth. The Sun, like billions of other main sequence stars in the Milky Way, follows a predictable life cycle. Its destiny, tied to its mass, entails a vibrant youth, a stable middle age of about 10 billion years, and a peaceful demise.
At approximately 4.567 billion years old, as determined by radioactive meteorite dating and solar wind analyses, our Sun is about halfway through its life. As it ages, the Sun’s hydrogen fuel depletes, gradually increasing its temperature. In about a billion years, this heat will be sufficient to evaporate Earth’s oceans. After 5 billion years, the Sun will exhaust its hydrogen, causing the core to contract and heat up, expanding the outer layers and transforming the Sun into a red giant.
This red giant phase will be dramatic, with the Sun expanding to about 250 times its current size, engulfing the inner planets, including Earth. As the Sun depletes helium and other elements, it will shed its outer layers into space as a planetary nebula, recycling the atoms of the now-obliterated Earth into new star formations. The remaining core will shrink into a white dwarf, gradually cooling and fading into the cold expanse of space.
While Earth’s fate is sealed, the prospect of life enduring beyond our planet remains. Our survival and expansion as a multi-planet and eventually a multi-solar system species could allow our descendants to find new homes around younger stars, continuing the legacy of life in the universe.
