What Types Of Stars End Their Lives With Supernovae

What Types Of Stars End Their Lives With Supernovae – Stars are balls of gas held together by their own gravity. Since the closest star to Earth is our own Sun, there are several closest examples that astronomers can study in detail. The lessons we learn about the Sun can be applied to other stars too.

The life of a star is a constant struggle against gravity. Gravity is always working to bring down stars. But the star’s core is so hot that it creates pressure within the gas. This pressure opposes gravity and puts the star in what’s called hydrostatic equilibrium. Stars are fine as long as they are in a balance between the gravity pulling them in and the pressure pushing them out.

What Types Of Stars End Their Lives With Supernovae

Diagram showing the life cycle of a Sun-like star and a massive star. Click on the image to see a larger version. (Credit: NASA and the Night Sky Network)

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During most of a star’s lifetime, internal heat and radiation are provided by nuclear reactions in the star’s core. This stage of a star’s life is called the main sequence.

Before a star reaches the main sequence, it is contracting and the center is not yet hot or dense enough to start nuclear reactions. Therefore, hydrostatic support is provided by the heat generated by contraction until the main sequence is reached.

One day, the star will run out of material needed for nuclear reactions in its core. When a star runs out of nuclear fuel, its main sequence life ends. If a star is large enough, it can generate internal heat through an inefficient series of nuclear reactions. Ultimately, however, this reaction will not generate enough heat to sustain the star against its own gravity, and the star will collapse.

Like everything else in nature, stars are born, live and die. Astronomers have used their observations of stars at all stages of their lives to construct the life cycles that all stars appear to go through. The fate and age of a star depend mainly on its mass.

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All stars begin their lives with the collapse of matter in a giant molecular cloud. These clouds are clouds that form between stars and consist mostly of gas and dust molecules. Turbulence within a cloud can cause knots to form and then collapse under the cloud’s own gravity. When the knot breaks, the middle material begins to heat up. That hot core is called a protostar, and eventually a star.

The cloud didn’t collapse into one big star, but different nodes of matter each becoming its own protostar. This is why these clouds of matter are often called stellar cores. This is a place where many stars are formed.

As the protostar’s mass increases, its center becomes hotter and denser. At a certain point, it becomes hot and dense enough for hydrogen to start melting into helium. The nucleus must be at 15 million Kelvin to start fusion. When a protostar begins to fuse hydrogen, it enters the “main sequence” stage of its life.

Main sequence stars are stars that fuse hydrogen with helium at the center. The radiation and heat from this reaction prevent the star from collapsing under gravity during this stage of its life. It is also the longest stage of a star’s life. Our sun spends about 10 billion years on the main sequence. But stars that are more massive consume their fuel more quickly and may only exist on the main sequence for millions of years.

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Eventually, the hydrogen at the center of the star will run out. Then the star will not be able to fight gravity. The inner layers begin to collapse, which destroys the core, increasing the pressure and temperature in the star’s core. The outer layers of matter in stars expand outward while the core collapses. The star will swell hundreds of times larger than before. The star at this point is called a red giant.

When a medium-sized star (up to about seven times the mass of the Sun) reaches the red giant stage in its life, its core will have enough heat and pressure to melt helium into carbon, and the core will have a short grace period. period. Given. its collapse.

Without helium in its core, the star loses most of its mass and forms a cloud of material called a planetary nebula. The star’s core cools and contracts, leaving behind a small hot ball called a white dwarf. A white dwarf cannot defy gravity and collapses due to the pressure of the mutually repelling electrons in its core.

With more than seven times the mass of the Sun, the red giant is destined for an even more dramatic end.

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Chandra X-ray image of the supernova remnant Cassiopeia A. Colors show the different wavelengths of X-rays emitted by material ejected from the star’s center. In the center is a neutron star. (Credit: NASA/CSC/SAO)

These high-mass stars go through some of the same steps as medium-mass stars. First, the outermost layer expands to become a giant star, but it grows even larger, forming a red supergiant. The core then begins to shrink, becoming very hot and dense. Next, the fusion of helium into carbon starts in the nucleus. When the supply of helium runs out, the core will contract again, but the increased mass of the core will make it hotter and denser so that carbon can melt into neon. In fact, when the supply of carbon runs out, another fusion reaction takes place until the core is filled with iron atoms.

At this point, the nuclear fusion reactions have released energy, allowing the star to defy gravity. However, smelting iron requires energy input rather than producing excess energy. If the core is filled with iron, the star will lose against gravity.

When iron atoms are squashed together, the core temperature rises to more than 100 billion degrees. The repulsive force between the positively charged nuclei overcomes gravity, causing the core to bounce off the center of the star in an explosive shock wave. In one of the most spectacular events in the universe, the impact forces matter away from the star, causing a spectacular explosion called a supernova. Matter erupts into interstellar space.

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A supernova ejects about 75% of the star’s mass into space. The fate of the remaining cores depends on their mass. If the remaining core’s mass is about 1.4 to 5 times that of the Sun, it will collapse into a neutron star. As the nucleus grows larger, it collapses into a black hole. To turn into a neutron star, the star must depart with a mass of about 7 to 20 times that of the Sun before a supernova can occur. Only stars with a mass more than 20 times that of the Sun are black holes. Star ages, distribution, and composition track the history, dynamics, and evolution of galaxies. Stars are responsible for the production and distribution of heavy elements such as carbon, nitrogen and oxygen.

This artist’s impression represents the early universe. The first stars born after the Big Bang, which astronomers call “population III” stars, are elusive and have yet to be definitively detected. Unlike today’s stars like our Sun (which contain heavier elements such as oxygen, nitrogen, carbon and iron), Population III stars consist only of some of the ancient elements forged in the Big Bang. Much bigger and brighter than our sun, they will shine in the pitch black emptiness of the nascent universe. Credit: ESA/Hubble, M. Kohnmesser, NASA

Different types of stars have different habitable zones. This is the region around a star where conditions are just right, neither too hot nor too cold, for liquid water to exist on the planet’s surface. (For this reason, the habitable zone of stars is often called the “Goldilocks zone”.)

Statistically, there should be over 100 billion planets in our Milky Way galaxy. They come in various sizes and characteristics. Complex organisms appeared on Earth only 500 million years ago, and modern humans have been on Earth for only 200,000 years, just the blink of an eye on cosmological time scales. As the sun heats up and the earth dries up, it will become uninhabitable for higher life in just a billion years. Therefore, stars that are slightly cooler than the Sun (called orange dwarfs) are considered suitable for advanced life. They can burn stably for tens of billions of years. It opens up a wide span of biological evolution, pursuing endless experiments to create powerful life forms. And for every star like our Sun, there are three times as many orange dwarfs in the Milky Way.

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The more abundant class of stars, called red dwarfs (also called M dwarfs), live even longer. A planet in a red dwarf

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