Since its birth 4.6 billion years ago, the Sun’s solar energy provided the initially barren Earth with life. The distance at which the Earth orbits the Sun is ‘just right’ for Earth to hold water at liquid state, hovering at what is called the habitable zone, or the ‘Goldilocks zone’. But what happens if the sun suddenly disappears?
This assumption turns out to be not as improbable as first presumed. Astronomers predict in 5 billion years, the Sun burn through most of its hydrogen fuel, which made up 74% of the Sun’s core, and consequently will no longer be able to sustain its core nuclear fusion reactions. As a result, the Sun’s core’s volume would shrink dramatically, and the Sun will begin to use up helium as its fuel as an alternative to hydrogen. Due to there being insufficient amount of outward pressure generated by the helium fusions to oppose the core’s own gravitational force, the Sun’s core collapses under its own weight, releasing extreme amounts of heat in the process. This explosion of temperature heats up the layers of unreacted hydrogen outside the core, and results in a chain reaction of hydrogen fusions which produces an extraordinary discharge of power output, even greater than the Sun’s original power. Consequently, while the Sun’s core collapses into itself, the Sun’s outer layers will proceed to expand and shine at a greater intensity. This expansion would only be stopped after the Sun reaches a new hydrostatic equilibrium between its own gravitational and expansion force, which happens to be when the Sun has well exceeded 250 times its original size. And in time, the Sun would run out of its store of helium fuel and will eventually shrink in size to become a white, then a black dwarf. So, what does this mean for us humans who live here on Earth? Is it possible for us to survive the Sun’s death on our planet?
A 2021 discovery by the spacecraft ‘Serendipitous’ of a ‘gas giant with a mass 1.4 times of Jupiter’ orbiting around a white dwarf star in the Milky Way hints at what our galaxy would look like after the Sun’s death. Taking on this revelation. astronomers predict that Earth may survive the event, but will, by a high chance, be rendered barren. But for the human race, many state, surviving the Sun’s death with our current technology seems highly improbable. In fact, mankind may come face to face with the first signs of its extinction in only a billion years time, due to the increase in luminosity of the Sun’s brightness by about 10% every billion years as it continues to use up hydrogen in its core. In approximately a billion years, the North and South Pole’s icecaps will begin to melt at a faster rate than the current effects of global warming. Oceans will start to evaporate into gaseous water vapour, which in turn will envelop the Earth’s atmosphere and trap more heat attempting to radiate back into space in a so-called ‘moist greenhouse’ effect. Even before the Sun fully enters into the red giant phase, Earth would be inhabitable for mankind.
The situation only escalates as the Sun becomes a red giant. Once its hydrogen fuel runs out, our Sun will swell to swallow up most of the terrestrial planets, and may come to demolish Earth itself. And by the Sun’s final closing act dimming out of the red giant, the Sun would have lost most of its gravitational influence on its orbiting planets on the account of its diminished mass. The sun’s outer layers would drift off into space, leaving behind a small, dense core known as a white dwarf. If our planet has miraculously survived until this point, it would continue its orbit around the Sun until its orbit gradually degrades, and the Earth ultimately spirals into the Sun.
Although there may be no hope for life on Earth, or Earth itself, the Sun’s dying days may give the universe a hint at new life. Once the Sun has become a red giant, the once frozen celestial objects that had orbited the Sun at a greater distance lies on the new habitable zone. These objects, namely, are Pluto and its neighbours in the Kuiper Belt. These worlds have already showed evidence of holding abundant water ice and other complex organic materials, that lay dormant due to their inhospitably low temperatures. But with the greater heat energy produced by the red giant, these objects may come to hold complex organic compounds seen in Earth’s youth. Life through death: although we may not live to see it, the Sun’s death would start another cosmic cycle, giving birth to new life and possibilities. And that prospect is enough for us to celebrate the coming of a new cosmic era, whenever and wherever it may emerge.
Seowoo (Cathy) Kim