The stars are familiar objects. We see them every day and every night. A single star, our sun makes life possible on earth to grow. Stars live so long they seem eternal to us. But they all had a beginning, and they all have a purpose, too.
Stars begin their lives in huge clouds of gas and dust called nebulae. Nebulae contain mostly hydrogen gas, with a little helium. In most places, a nebula Gossamer is often so thin that if you crossed one, you do not notice. However, there are areas in a nebula where gravity causes the gas and dust to gather more and more dense and hot.
As more and more solid materials together in these areas, the temperature inside can become very hot, about fifteen million degrees. The gravitational pressure is so great that electrons in atoms of hydrogen and helium are stripped, leaving only the nuclei. As increases the gravitational force, the fuse atomic nuclei. This event is called nuclear fusion. It creates a huge boost of energy strong enough to offset the crushing gravitational force. The energy flows into space as light, heat and electromagnetic radiation. A new star is born, and he begins to shine.
Throughout his life, a star is caught in a balancing act between the crushing forces of gravity and the explosive force of nuclear fusion in its core. So it is important to the heart of the star can undergo the process of nuclear fusion, the star will fight gravity and continue to shine. But when the star has run out of fuel, it dies.
Most stars are the size of our Sun or smaller. Our sun is a yellow dwarf star, and it is fairly average in the universe. Stars the size of our sun, emit light generally in the spectrum of yellow or orange, and they live for about ten billion years.
The process of nuclear fusion converts hydrogen into helium. A star the size of our sun turns all its hydrogen into helium, then start converting helium into carbon and oxygen as it ages. The oxygen we breathe and the carbon material that provides the most vital for life on earth was created inside a star like our sun.
As middle age stars, the core contracts and the outer envelope expands to many times the original size of the star. This changes the stars from a yellow dwarf to a red giant. What will happen to our sun, one day she will swell until it covers the same orbit of Jupiter. Red giants are several times larger than our sun, but they are also cooler.
Finally, the basic contracts whenever possible. The atoms are packed in so well they can not be contracted. When this happens, a large amount of energy is released, pulling the outer envelope of gas and forming a nebula of gas and dust.
The only thing that remains of the star is well-packed core, called a white dwarf. White dwarfs still emit heat and light, but they no longer undergo nuclear fusion. Finally, when they radiate all their heat, they become cold, lifeless black dwarfs. There are no black dwarf stars of today, the universe has not existed long enough for all white dwarf stars to lose all its heat.
The most important stars have a different fate. A star about three times larger than the sun becomes a red supergiant as it ages, when many stars of the size of a red giant. It will run out of hydrogen and helium. It will start converting helium into carbon and oxygen, as an average star. When he runs out of helium, it will start converting the carbon and oxygen it produces heavier elements such as sodium, magnesium, sulfur and iron.
When such a star dies, contracts based on iron in an instant, sending a massive shockwave. This is a supernova explosion. Supernovae appear in our skies from time to time, many times brighter than the surrounding stars. The outer layers of gas are extracted and form a huge nebula. The explosion ejects also heavier elements like gold, silver and other metals.
The core, however, is another story. In most major stars, the core contracts so strong that even the protons in its remaining atoms are pulled out, leaving only neutrons. This is called a neutron star. Much more than ten miles or more in diameter, but they have an extremely strong magnetic field.
In stars more than three times larger than our sun, the core is so massive that the gravitational forces pulling together are too strong to stop. All remaining mass of the star is crushed into a single point, or singularity, no larger than a single atom. Here’s how a black hole is born.
A gravitational black hole is so great that nothing, not even light, can escape. For this reason, black holes can not be directly observed. However, the question swirling around a black hole may indicate its position. Scientists think that black holes lurk at the centers of most galaxies, including ours.
Without stars, the universe could be an empty place. The stars are the furnaces that forge most of the elements that compose our world, the air we breathe for the metals that we build with the materials that compose our bodies. The next time you see a beautiful gold necklace, handle an iron skillet, or take a breath of fresh air, remember it from the heart of fire of a star.
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Source by kenny jewls