Stars can be born and die in turbulent clouds. How long do stars stay alive? It depends on the star.
A star is in equilibrium for most of its life, in which gravity pulls in on the star and it is balanced by the outward push of the star's nucleus. The star's shape and brightness are maintained by a burst of energy that comes from the fusion of hydrogen and helium. After all the hydrogen is used up, the star is doomed. The biggest stars will continue burning chemical elements up to iron, but it will be fleeting. A star can be as small as 7% of the sun's mass and as large as 250 solar mass. Which ones die in the shortest amount of time?
Ryan French told Live Science that bigger stars have more fuel to burn. They burn harder and brighter. Their large size means that gravity is crushing material down into their core more intensely than in smaller stars, so their nuclear reactions proceed at an elevated rate.
There are pictures of stars.
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French said that bigger stars exhaust the fuel more quickly than smaller stars. The stars that live for a long time are the most massive. They live a long time and die young. Even though they have less fuel to begin with, the stars that are less than 10% of the sun's mass can still live for hundreds of billions of years.
There has not been enough time for a small star to reach old age.
The oldest star discovered is the Methuselah Star. The star is named after a character in the Bible who is said to have lived for almost a millennium. French said that the star's age is around 13 billion years. It would have formed after the big bang.
Astronomers have discovered some stars that are still in the beginning stages of forming. The stars that were observed using the ALMA are less than half a million years old. Stone tools were being used by humans by the time the stars started to burn.
Calculating a star's age is a difficult task. French said it wasn't simple. Astronomers use a combination of measures of the star's mass, brightness and speed in space to compare with other stars and computer simulations to estimate its age.
Our sun is 4.5 billion years old, which is between the stars. It is thought to be almost halfway through its life time. French said that the sun will stop fusion in about 5 billion years.
The sun's core will start to contract once it runs out of fuel. The sun's outer shell will expand as it still has some hydrogen. The sun will swallow up Mercury and Venus as it gets larger. The outer core will have used up its hydrogen after a billion years. The sun's core will shrink into a ball of carbon and oxygen called a white dwarf as it runs out of fuel.
Even the biggest stars don't last forever.
It was originally published on Live Science
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