After being generated 4.6 billion years ago, the Sun is predicted to exist in its current structure for another 4.5 to 5.5 billion years. And, while we can’t predict what will happen in billions of years, knowing the history of stars has allowed astronomers to draw broad predictions about how the Sun’s life would unfold. Although a supernova, an explosion that terminates the lives of more massive stars, is possible, our own star is unlikely to encounter one.
1. Phase one of hydrogen burning
The Sun converts 600 million tonnes of hydrogen into four million tonnes of energy per second; the remainder is converted into helium “ash.” The Sun has produced more energy during its lifetime, and it is thought to have been 30% brighter in the 4.6 billion years since its birth. Over the next billion years, the Sun is anticipated to become 10% brighter as more hydrogen is converted into helium, increasing the quantity of heat energy. Consider the implications of such an increase when we consider the influence that human-caused climate change is already having on our planet’s weather patterns.
As a result of warming oceans and melting polar ice caps brought on by rising temperatures, water vapour will be released into the atmosphere. More heat will be trapped by that water vapour, leading to a “moist greenhouse” effect that would further increase global temperatures. The Sun will be 40% brighter than it is currently in around 3.5 billion years, which will cause our seas to boil, the ice caps to entirely melt, and our atmosphere to be utterly destroyed. Earth will eventually be becoming as Venus: dry, burned, and dead.
2. Subgiant phase
Even though this scenario is horrifying, it is simply the start of the Sun’s death. The Sun will have exhausted all of the hydrogens in its core and will have reached the end of its main sequence some five billion years from now.
The core will start to compress and get denser over time without a fusion mechanism to counteract gravity. The leftover hydrogen outside the core will ultimately catch fire as a result of its temperature increasing while it does this.
The Sun will grow two to three times its present diameter as a result of this new fuel supply, becoming a subgiant star as the energy it produces pushes the outer layers outward.
3. Red Giant Phase
When the Sun’s surface layers are pushed further outward and continue to gather heat from the dense core buried deep under this ever-expanding shell, it will develop into a big, luminous monster known as a red giant.
These ageing stars can be 100 to 1,000 times the size of the Sun, and due to their expanding surface areas, their outer layers will cool to around 3,000 °C (the surface of the Sun is presently 5,500 °C). Because of their cooler temperatures, these stars shine in the redder part of the colour spectrum, earning them the title “red giant.”
The inner planets Mercury and Venus will be entirely engulfed when the Sun goes through this phase, and it may even approach the path of Earth’s orbit. The Sun will continue to lose mass throughout this expansion; some estimates imply that at its biggest, only 65–70% may be left. This means that our planet may not be fully annihilated.
The remaining planets in the Solar System will start to drift away as a result of the weakening of the gravitational force. Earth could have a lucky escape. The Sun’s core will continue to shrink and heat up until a fresh nuclear reaction takes place 12 billion years after the Sun was formed.
4. A fresh red giant
The core will keep shrinking until temperatures hit roughly 100 million degrees Celsius, which is high enough to ignite the helium created during hydrogen consumption and turn it into carbon and oxygen. Helium will burn with great intensity and fury, resulting in a short explosion known as a “helium flash,” since the dense core won’t be able to expand to accommodate this increased energy output. As a result of the helium being able to burn at a more regulated pace, this will reduce the core’s density and temporarily provide stability.
The new fuel source won’t last very long, just about 100 million years, until it runs out. Similar to how burning hydrogen caused the Sun to grow into a second red giant phase, burning helium will continue to produce furious energy as it burns.
5. Planetary nebula
The Sun’s life cycle is still ongoing despite all of its growth and contraction, loss of mass, and fuel consumption. The red giant will keep converting helium into carbon and oxygen, but the core will never become hot enough to ignite that carbon, causing it to once more contract.
About 12.5 billion years after the Sun’s creation, half of its mass will still be present because when helium is used, the outer layers are pushed further out and lose mass to space. The heated core within will shine light through the expanding outer layers, forming a dazzling cosmic cloud known as a “planetary nebula.”
Astronomers are well aware of these events, which have nothing to do with planets but are characteristic of an ageing star with a mass similar to our Sun. Their name merely derives from their rounded, inflated form.
6. White dwarf
All that will be left of the Sun when its outer layers have completely gone is its hot, dense core, or white dwarf. These objects are often a little larger than our planet while having some of the highest densities in the universe. They may, however, reach temperatures of more than 100,000°C.
This stellar remnant will include a significant amount of the heat produced in the core during the Sun’s ageing process, and it will take tens or possibly hundreds of billions of years for it to cool.
7. Black dwarf
The white dwarf remnant will eventually exhaust all of its remaining heat and light energy and deteriorate into its final state: a lifeless black dwarf (perhaps in hundreds of billions of years). Black dwarfs are currently just postulated because the Universe is not yet old enough to have created any, but it is expected that our Sun will someday become one of these things.
Because of our previously massive star’s low mass, much of its gravitational force will have been dissipated, causing the planets to drift further away, becoming nothing more than frozen, burnt rubble. This contributes to the sadness of the story.
However, when the remains of our Solar System fade into space, particles from our own dead Sun could condense and trigger the star-formation process once more. As a result, planets with stony surfaces, atmospheres, and liquid water that are ready for life may arise. (sciencefocus)