The life cycle of stars

The life cycle of stars

Solar system

The life cycle of stars

The life cycle of stars – The first stage for all stars, including our Sun, is when a dense region in a nebula begins to shrink and warm. This is usually the result of one of several events that occur to determine the collapse of a molecular cloud. What happens is that it involves galactic collisions or the destructive explosion of a supernova at close range that sends the discrete matter to the clouds at very high speeds. Each event can form tens of thousands of stars. To form a star like the Sun, which is 1391,000 kilometers in diameter, requires a set of gas and dust hundreds of times larger than our entire solar system, and this is just the beginning. When a large amount of gas and dust stick together, a “protostar” is formed. For the sun and stars of similar mass, the pre-star phase ends after an estimated time of one hundred thousand years. After that, the growth of the protostar stops, and the disk of the material that surrounds it is destroyed by radiation. If the “protostar” does not succeed in absorbing enough mass, a brown dwarf will appear. These tiny bodies are sub-stars that are unable to maintain hydrogen fusion reactions in their nuclei due to their insufficient mass. The mainstream of the stars has no problem with this, while it makes the brown dwarfs jealous. Simply put, a brown dwarf is too big to be a planet and too small to be a star. These objects were only a theoretical concept until 1995, but it is now believed that there is one brown dwarf for every six stars.

If a star is large enough to convert hydrogen atoms into helium, it enters a phase similar to the sun, called mainstream stars. (In astronomy, a curve in a Herzsprung-Russell diagram is called the star in which most stars are located. One star spends most of its life in the mainstream phase. At this stage, fusion converts the hydrogen nucleus to helium. The star is stable only because the pressure from this energy prevents the star from gravitational collapse. (The collapse of an object due to its own gravity is called) Hertzprung Russell diagram showing the relationship between the absolute magnitude, luminosity, classification, and effective temperature of stars. On average, 9 out of 10 stars are in the star group. Are in the main field. These stars can be one-tenth the mass of our Sun, or 200 times its mass. The length of time a star stays in the main sequence depends on its size. A high-mass star may have more fuel to burn, but it burns faster due to higher temperatures due to higher gravitational forces. A star with the mass of the Sun also spends about 10 billion years of its normal life. But stars 10 times larger than our Sun only spend 200 million years at this point and can burn.

The life cycle of stars

The life cycle of stars

After completing the mainstream phase, “Our Sun” becomes a “red giant”. A red giant is a dying star that is in its final stages of evolution. Eventually, over billions of years, the sun goes to death and swells. It then devours the inner planets, including Venus, Mercury, Mars, and even Earth. but do not worry. We died billions of years ago. If we could survive for billions of years, Earth’s surface temperature would be too hot for us humans and not a good place to live. After the stars stop converting hydrogen to helium through nuclear fusion, gravity controls Take over. In fact, the size of the red giant stars reaches 100 million to 1 billion kilometers, which is 100 to 1000 times the current size of the Sun. In the next stage, the star’s energy expands to a larger region and cools when it reaches half the heat of the sun. Changing the temperature causes the stars to get closer to the red part of the spectrum; That is why they are known as the “Red Giants”.

rotation of planets

From here, the path of the star depends on its size. Let’s start with the less violent version. Small stars in the main orbit of the sun, up to eight times the mass of the sun, slowly run away from their fuel and after the red giant stage, scatter their gas and dust around, and this gas and dust is a “planetary nebula.” They form, and over time the core of the star eventually cools and a “white dwarf” star remains. White dwarf stars are remnants of old, extremely dense stars. A teaspoon of them weighs the equivalent of an elephant on the ground, which is equal to 5.5 tons in a very strong teaspoon! The radius of a white dwarf is only 0.01 of our Sun, but its mass is almost the same. Estimating how long a white dwarf is cooling down will help astronomers figure out how old the universe is. After an unimaginable time, tens or even hundreds of billions of years, a white dwarf cools enough to turn into a black dwarf. Black dwarfs are invisible because they have the same temperature as the cosmic background radiation. There is no black dwarf because of the age of the universe and what we know about the oldest stars.

The life cycle of stars

The life cycle of stars

Another type of star that is smaller than the Sun is called the Red Dwarf Star. These stars are the most common type of star in the universe, belonging to the group of main-sequence stars, but they have so little mass that they are colder than stars like our Sun and have lower surface temperatures than 3500 degrees Kelvin. Red dwarfs also called M dwarf stars, are more than 50 times darker than the Sun and only have a mass of 2 to 6 percent. These cosmic bodies make up 3% of the world’s stars. Astronomers estimate that some red dwarf stars will continue to burn for up to 10 trillion years. These very small stars have only one-twelfth the mass of the Sun and can have a mass up to half the mass of the Sun. Fortunately, red dwarfs produce powerful flames only during the first few billion years of their lives. After that, for the rest of their trillion years of life, they relax and create a stress-free environment around them. On the other hand, a star with a mass of at least 8 times that of the Sun will have a more violent and at the same time more beautiful death. When they run out of fuel for massive stars, they can become a supernova. For them, destruction with an explosion is better than gradual destruction. When a star ends its life as a supernova, it launches its particles into space at speeds of 14,000 to 40,000 kilometers per second.

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