How long stars really live depends on their size and how quickly they use up their nuclear fuel. Big stars die faster and have shorter lives, and younger stars live very long.
Stars range in size from just 7% of the sun's mass to 250 solar masses
How old are stars? What are the factors that cause her death? And why do small stars live longer than massive stars? Many questions may come to the minds of many of us, so how does the science available to us answer them so far?
How long stars really live depends on their size and how quickly they use up their nuclear fuel. Big stars die faster and get younger, and younger stars live very long.
In general, the larger the star, the faster it burns its own fuel reserves, while smaller stars consume their fuel for a longer period, as the largest stars burn and explode after only a few million years, and a star with a mass like the sun can continue to combine hydrogen for about 10 billion years .
If a star is very young, with a mass of less than one-tenth the mass of the Sun, it can continue fusing hydrogen for hundreds of billions of years, longer than the current age of the universe, which is 13.7 billion years.
Star fuel consumption
According to the " Live Science " scientific website, the sizes of stars ranged from only 7% of the mass of the sun up to 250 solar masses, and larger stars have more fuel that burns more strongly and brighter that makes the star shine in the sky.
This happens because the massive size of stars means that gravity crushes material into their nuclei more intensely than smaller stars, so their nuclear reactions continue at a high rate, so they deplete their available fuel much faster than smaller stars and live a brief cosmic period of hundreds of millions of years.
Smaller stars, less than about 10% the mass of the Sun, have much less fuel to start their nuclear reactions with, so they can continue their small fuel supplies for hundreds of billions of years.
The universe only formed 13.8 billion years ago, so there simply hasn't been enough time for a young star to age yet, Ryan French, a solar physicist at University College London UCL, UK, tells Live Science. .
Knowing the age of stars is not easy at all, and to calculate this, astronomers use special measurements of the star’s mass, brightness and speed in space, compared to other stars, and then computer simulations to estimate its age.
Star life
The Scientific American website stated that the star remains throughout its life in a very delicately balanced state called "hydrostatic equilibrium", where the gravity that pulls the star inward is balanced by the external thrust resulting from nuclear reactions in the core of the star itself.
This outward thrust occurs when a star fuses hydrogen nuclei to form helium nuclei, producing an explosion of energy that maintains the star's shape and brightness. This nuclear fusion occurs inside the star's hot, dense core, where temperatures reach 20 million degrees.
The rate of energy generation of a star is very sensitive to both the temperature and the gravitational pressure of its outer layers, and once all the hydrogen in the star is consumed it begins an irreversible path toward its demise.
When we look at the night sky, the stars we see are mostly brighter and more massive stars than the sun, and therefore they are the type that die quickly, but most of the stars that last longer, and that are weaker than the sun are very dark, so that they cannot be seen from Without telescopic aid, its low power output makes it less bright and less visible to the naked eye.
The oldest star in the universe
French says that one of the oldest stars ever discovered is the star "Methosella", 190 light-years away from planet Earth. It was named after a character found in the Bible who lived for nearly a thousand years.
The current estimate of the age of this star is 13.7 billion years, which means that it was formed not long after what is known as the "Big Bang".
In contrast to young stars that lived billions of years, there is another type of star discovered by astronomers, called "protostars", which are still in the process of formation and are less than 500,000 years old.
The Sun is an intermediate type of star in the interstellar region between the protostellar and the young Methusela star, it has been around for nearly 5 billion years, and has enough fuel to last another 5 billion years.
When do stars die?
The Sky & Telescope website stated that the answer to this question also depends on the mass of the star, and that the star dies only when the core runs out of fuel.
The most massive stars quickly deplete their fuel reserves and explode in supernovae, some of the most energetic explosions in the universe, and supernova radiation can easily outpace the rest of their host galaxy, even if only for a short time. The remaining stellar core forms a neutron star or black hole, depending on how much mass is left after the supernova explodes.
As for intermediate stars such as the sun, they face a less strange fate. When they run out of hydrogen, they swell to become giant red stars, before their outer layers fall off, and what remains after that is a white dwarf star.
It is assumed that the white dwarf eventually fades into a black dwarf, but no black dwarfs have been observed so far in the universe, because the white dwarf takes longer than the current age of the universe to fade.
As for small stars that have a very long life, none of them have faced their end yet. Stars with a mass less than one-tenth the mass of the Sun burn so slowly that they may live up to 100 billion years, much longer than the age of the current universe.
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