Do Stars Burn Out? (A Simple Explanation)

We all know stars give off an unbelievable amount of heat and light.

But that might make you wonder: do stars ever burn out? And if so, what happens next?

A quick answer to whether stars burn out

Yes, stars do burn out, but maybe not in the sense you’d expect. Their cores mostly contain elements like hydrogen and helium, which produce huge amounts of light and heat. They release all of this fuel over time, but it may last billions of years, followed by perhaps another million years to “burn out.” When nothing much is left, they finally go out in a blaze of glory known as a supernova. The remains are scattered around the universe, but may leave a neutron star or black hole behind.

How exactly do stars “burn” anyway? 

Stars are huge astronomical bodies in the sky made mostly of elements such as hydrogen and helium. From the churning forges inside their cores, they produce huge amounts of light and heat. 

The “burn-out” happens through a phenomenon called nuclear fusion. Nuclear fusion happens when the atoms inside the star collide together (often the element hydrogen). Fusion usually turns hydrogen into helium–going “up” the periodic table, so to speak.

This process generates heat, light energy and other forms of energy including high-energy particles. 

The light produced during this phase of atomic burning is what we see as a bright star in the sky. 

In fact, the light during this phase is so intense that most of the stars we see in the heavens are in the “burn out” phase!

As their main hydrogen supply dwindles over billions of years, they expand into something called a red supergiant. They’re much cooler by star standards–a few thousand degrees–which is still unbelievably hot by human standards.

This can go on for another million (or even a few million) years as they fuse hydrogen from farther and farther outside their cores. 

After they exhaust the remaining fuel, they explode into a supernova. That’s one of the brightest objects in the sky for perhaps just one week, then it dissipates into space dust. 

The elements that once made the core of the star are now scattered throughout the sky and the stardust eventually makes other stars and planets.

What happens when stars burn out? 

It is during the burn out phenomenon that we see the tiny sparkling dot in the sky as a star. When it runs out of hydrogen fuel, the core starts to contract and gets heated up inflating it into a giant.  

For example, our sun would expand clear past the orbit of Venus, perhaps all the way to Earth! (And more on this a bit below.) 

Meanwhile, the core gets hotter and dense enough to fuse helium which is an equally inflammable fuel.  

The star starts to pulse menacingly. Over the next thousand years, the star smokes out its entire atmosphere into the space leaving behind a naked core of carbon and oxygen. 

The oxygen and carbon later collapses to form a white dwarf star which is approximately the size of earth but much denser. 

Can you see stars after they die? 

Yes! There is a good possibility that the stars you are looking at in the night are “dead” already. But most of them are perfectly active and will remain in the sky for quite some time.  

With the help of a telescope or even powerful binoculars, you can see these stars which are billions of light years away. Considering the fact that a star like our Sun has a lifetime of about 10 billion years, most of the stars even in the distant galaxies could have died long ago. 

The good news is that we are not running out of stars. The time passage we are talking about in astrophysics is huge, and far beyond our imaginations. There have been many new stars born but which we just can’t see yet.

The average lifespan of a star 

The lifespan of stars greatly varies according to their characteristics such as size. For example, a star like our sun will live for 10 billion years whereas a star which weighs ten times that of the Sun will live much more briefly than the Sun.

The majority of stars live for millions of years, but their exact lifespans depend on their mass. 

Larger stars tend to burn at a greater pace and hence live for less time than the smaller ones. 

Massive stars undergo faster burnout due to quick fusion of the elements like helium. They may explode as a supernova after only a few million years of fusion. That sounds like a long time already, but smaller stars (like the Sun) will continue fusing hydrogen for several billion years. 

Theoretically, the tiniest of stars can keep fusing hydrogen for up to a trillion years–yes, really! That may be hundreds of thousands of times longer than very large stars.

What will happen to our sun when it dies? 

Just like any other star, our sun will exhaust its fuel some day and eventually die. 

Seeing as life on earth depends on sunlight, the death of the Sun will mark the end of life on Earth. 

Scientists say that the death of a star like the Sun will be a gentle and orderly process (well, relatively speaking!). 

The time scale is long: think 7 billion or 8 billion years from now, at least.

The thermonuclear reactions happening within the Sun will cease and it will become a red supergiant. The temperature increases drastically and the heat will vaporize the earth. 

And that’s just as well, since the outer layers of the Sun will swallow Mercury and Venus, and may reach as far as Earth (or where Earth was, anyhow). 

The Sun will stop releasing any forms of energy, including light energy, of course.

According to researchers in the journal Nature Astronomy,  “the Sun is almost exactly the lowest mass star that still [after dying] produces a visible, though faint, planetary nebula.” 

And all the space dust in the nebula of our former sun will one day give birth to new stars, beginning the cycle once again.

It’s often hard to see details of distant stars with the naked eye. Even enormous galaxies, which contain countless stars, all tend to blend together. 

However, a basic telescope or good stargazing binoculars will reveal all sorts of incredible nuances. Read our guide here to learn whether a telescope or binoculars are right for you.