Stars are among the most recognizable objects in the sky. They illuminate the darkness and color the galaxy. Stars are born in a cloud of dust and eventually form a mass of gas and chemicals that burns brightly in the sky. But eventually all stars, no matter how big and bright, must also die.
How long do stars live?
The Sun, for example, is a 4.5 billion year old star that will continue its life for another 10 billion years. The sun shines by combining hydrogen and helium in a reaction called fusion. At some point, the sun will use up all the hydrogen in its core and start burning.
(Credit: Lukasz Pavel Szczepanski/Shutterstock)
A star must die
According to NASA, the sun will no longer have enough heat to support it against gravity, and as a result it becomes a fiery red ball burning from above that will eventually engulf the Earth. According to NASA, “the atmosphere [of the sun] will envelop the Earth and our planet will be consumed by a fiery death.”
Read more: How will life on Earth end?
The collapse of the sun has been happening for billions of years, but it is no less dramatic. After gravity causes a star to collapse in on itself, it will take another 100 million years for the star to inflate and form a persistent red cloud. Eventually, about 10 million years later, all that remains is a hot core of carbon and gases that form a “planetary nebula.” As the star continues to burn, it will shrink to a white dwarf planet.
What happens when a star dies?
But while the sun may look huge from our perspective, it is considered a baby in relation to the stars. And the bigger stars go out with a bigger bang. The death of a larger star, for example, about 10 times brighter than the sun, results in a supernova explosion, the largest explosion humans have ever seen. And supernova explosions happen in seconds.
Supernova vs smaller star explosions
According to NASA, a supernova is considered “the last hurrah of a dying star.” Nuclear fuel burning in the core of a massive bright star causes so much heat, pressure and energy that the star cannot collapse like a smaller star because the intense pressure in its core is still fighting against gravity pushing inwards.
Eventually, like the smaller star, a supernova will run out of fuel and gravity will manage to crush the star’s core. This happens so fast that it creates intense shock waves throughout the galaxy. It can even cause the formation of a black hole, the densest part of the solar system, when gravity is so strong that even light cannot escape.
Read more: How many ways can the sun kill us?
Exploding supernovae
In November 2022 Hubble Space Telescope captures a supernova explosion that occurred 11 billion years ago, when the universe was one-fifth the age it is today. The telescope can take images at different stages of the explosion, showing it moving from hot to cold in a series of bright blue to red images that appear before it burns out. This was the first time we were able to witness the death of a massive star.
Supernova explosions are not important just because they are the end of a dying star. They also create the ideal breeding ground for future stars. Without them, the cosmos would have no other carbon or oxygen, the elements that make life on Earth possible. Stars live and then die, but in the time in between they magically illuminate the sky above.
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