Will the Sun Ever Burn Out? Well, the sad and existential truth is that everything eventually dies — and one day, so will our very own star, our beloved sun.
The sun is a very average star in the Milky Way and only 4.6 billion years young — just a baby if you consider the lifespan of about 75 to 80 percent of stars that can live from anywhere to 150 billion to 100 trillion years. The only unique thing about it is that its solar system contains the only known inhabited planet in the universe.
However, like all stars, it too will die. Our sun will take the last gasps of its hydrogen in 5 billion years and once it does, its cycle of death will unfold. It will take about another 5 billion years for the sun to expand into a red giant and then shrink down into a condensed white dwarf. Sadly, no supernovas for this star, though. Still, it seems our sun will go out in a blaze of glory.
One thing is certain though; humans have only about 1 billion years left to live if they don’t find a way to colonize other planets — somewhere far, far away from our solar system.
How the Sun Burns
Inside the sun, there is a constant fusion process of hydrogen gas that gives life to the star. According to estimates by scientists, there is still about 5 billion years of reserve left before it all burns out.
Stars like the sun are formed when a huge cloud of hydrogen and helium gas become so big, it collapses under its own weight. When that happens, the pressure increases the heat to unfathomable levels in the center of the collapsing cloud. As a result, the hydrogen atoms lose their electron and become fused together with the helium atoms.
This reaction releases a huge amount of energy, which is enough to counter the enormous gravitational force that collapses the cloud.
And so the sun is formed. In fact, the sun burns about 600 million tons of hydrogen every second.
As the sun’s burns away the hydrogen and its core becomes saturated with helium, it shrinks, causing the fusion to accelerate. This means it will give out more energy and become even brighter. In fact, the sun gets 10 percent brighter every one billion years.
That may not seem like a lot, but it will have catastrophic consequences for our planet.
How Life on Earth Ends
About 4 billion years from now, before our planet meets it fiery demise, life on Earth will have ended. Even before the sun finishes burning up hydrogen reserve, its intense brightness will have killed all life on the planet. So, there will probably be no one around to ask, “will the sun ever burn out?”
This 10% increase in brightness will mean that Earth will no longer fall under the habitable zone. Experts theorize that the heat will be enough to boil the oceans in the planet. As the water evaporates, it will form an extremely hot layer on the Earth’s atmosphere, effectively having a greenhouse effect.
As the layer of water vapor traps even more heat, it will cause even more oceans to dry up and parching up the Earth. In time, the water molecules at the highest point of the Earth’s atmosphere will break apart from the increasing heat of the sun, allowing the hydrogen molecule to escape and leaving our Earth cracked and dessicated.
Forming the Red Giant
About 4 to 5 billion years after the demise of humanity, the sun will breathe through the last of its hydrogen. Currently, the sun is in its most stable stage, but once the hydrogen runs out, it will become extremely volatile.
In a star, the immense gravitation force pulls all the gases towards the core. When the sun has hydrogen to burn, it has enough helium left to counter the gravitational force. As the hydrogen is depleted, only helium gas will be left in its core. And so the gravitational forces will take over and the size of the core will shrink.
Ultimately, the force will compress the center of the sun so much that it will start burning a shell of fusion hydrogen around the dead core that is still full of helium. During this turbulent time, the sun will eject huge quantities of stellar matter into space and its body will expand outwards, even if its core continues to shrink.
Eventually, its body will expand to about 100 times its size. Since the star has expanded, it will cool down and will go from white hot to red hot with a temperature of about 3000 K. Since the star looks redder, brighter, and larger than before, it is dubbed as a red giant.
This process in itself can take about a billion years.
Since the core has shrunk, its mass will decrease and its gravitational hold on the planets will loosen. This means that all the planets orbiting the sun will drift a little further away.
Earth’s Fiery Demise
The questions, “will the sun ever burn out?” and “what will happen to the Earth when the sun dies?” usually go hand-in-hand. Most scientists are in agreement that the Earth — even if it contains no life at this point — will not survive the sun’s expansion into a red giant. The sun will have expanded to a degree that it will certainly swallow the inner planets.
It is believed that the full-blown red giant will stretch out to what is the current orbit of Mars. And even though Earth will have moved a bit further away due to the loosened hold of the star’s gravitational force, it probably will not be able to save itself from being dragged into the surface of the sun, where it will be devoured, along with Mercury, and Venus.
Even if Earth doesn’t get completely swallowed, it will be burned down to a crisp.
Mars, though, will have wandered out of the reach of the sun and will escape the fiery demise. The ice of Neptune will also probably melt.
Transitioning Into a White Dwarf
For about one billion years, the sun will continue to burn as a red giant. But when the hydrogen in its outer shell depletes, all that will be left is helium. The element will then fuse with other heavier elements including carbon and oxygen — however; they won’t emit as much heat as hydrogen.
In the end, the sun will be left composed of only carbon and oxygen elements with its outer helium and hydrogen shell blown away.
Once these gases are lost, the gravitational force will condense matter into a highly dense core, which will have about 50 percent the mass of the original sun but will only be about the size of the Earth.
At this stage, the sun will be known as a white dwarf.
The white dwarf will remain hot for a very long time as well. Since the pressure at the center is immense, the “sun” will heat up and will reach a temperature of about 20,000 K. However, a time will come when even this will cool down.
Once the star runs out of all its fuel, it will shrug off all its outer layers, gas, and dust, known as an envelope. This envelope comprises of half the star’s mass and will expose the star’s dying core. At this point, the hot core will make the envelope shine brightly, resulting in a planetary nebula.
Some nebulas are so bright they can be seen as far as tens of millions of light years away, even when the white dwarf itself is not visible.
It will take about 100 trillion to 1 quadrillion years before this stellar corpse fades away and cools down to a little bit above absolute zero or -460 degrees Fahrenheit. This dense ball is now made of carbon and oxygen and is known as the black dwarf.
Most scientists believe that it will simply continue to zip through space along with the other stellar corpses and ultimately get ejected from the galaxy.
And that will be the end of the star which gave life to the liveliest planet known in the universe.
Astronomy is a highly complex system and the model of the sun’s death is not entirely perfect. Possible gas accumulations, mergers with other stellar corpses, or even getting devoured by other celestial bodies (such as black holes) can also happen. However, this seems to be the most probable destiny of our sun. So, will the sun ever burn out? Yes – but not anytime soon.