The sun is not the only star in this universe. There are still stars out there that continue to be born, appear, and live for any length of time.
But how long can these stars actually live?
Quoted from Live scienceMonday (2/1/2023) Most of a star’s life exists in a state of equilibrium called hydrostatic equilibrium, in which the gravitational pull on the star is balanced by the outward push created by nuclear reactions in the star’s core .
The outward thrust occurs when a star fuses hydrogen nuclei to form helium nuclei, which produce a burst of energy that maintains the star’s shape and brightness.
But once all the hydrogen is used up, the star will start heading towards its demise.
Stars will temporarily burn helium, and larger stars will continue to burn chemicals until they turn into iron for a short while.
Since stars vary in size, from 7% of the mass of the Sun to 250% of the mass of the Sun, which star will die first?
The short answer depends on the size of the star itself.
“Larger stars have more fuel to burn. Their large size means that gravity squeezes the matter in the star’s core harder than in smaller stars, so their nuclear reactions occur at a high rate,” said Ryan French. physicist at University College London, England. .
So it’s safe to say that a star with a higher mass actually consumes available fuel much more quickly than a smaller star.
So much so that even the French called the most massive stars living for hundreds of millions of cosmically short years. They live fast and die young.
Meanwhile, the smallest stars, which are less than 10 percent the mass of the Sun and have far less fuel, can actually live for hundreds of billions of years.
However, since the universe formed just 13.8 billion years ago, there isn’t enough time for a small star to reach old age.
Digitized Sky Survey, STScI/AURA, Palomar/Caltech and UKSTU/AAO HD 140283, the oldest known star in the Milky Way galaxy. Lisa Kaltenegger said old stars could save a second Earth. “One of the oldest stars ever discovered is the star Methuselah. This star, which is 190 light-years away from Earth, is named after a Biblical character who is said to have lived for nearly a millennium,” French said.
While the star Methuselah is estimated to be 13.7 billion years old. This means it was formed shortly after the Big Bang.
Instead, astronomers have discovered several stars called protostars that are still in the process of forming.
Observed using the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, these stars are less than 500,000 years old.
But the question is: how do astronomers know the age of a star?
“It’s not simple. Astronomers use a combination of measurements of a star’s mass, luminosity and velocity through space to compare it to other stars. As well as computer simulations to estimate its age,” French explained.
The sun itself is about 4.6 billion years old, which is said to be between the age of the protostar and that of the star Methuselah. French believes that in about 5 billion years, the Sun will stop fusing hydrogen into helium in its core.
Once the Sun’s core runs out of fuel to fight gravity, the Sun will begin to contract. The Sun’s outer shell will expand because it still has hydrogen to melt.
“The Sun will become so large that it will engulf the orbits of Mercury and Venus,” French said.
After about 1 billion years, that outer core will consume its hydrogen and switch to helium fusion.
Eventually, the Sun will run out of fuel, its core shrinking into a ball of carbon and oxygen called a white dwarf. Meanwhile, the outer layer will disappear and become a nebula, i.e. the envelope of hot residual plasma.
It’s a reminder that while the biggest stars survive humans, nothing lasts forever.
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