Stars are born, grow old, and die, at rates that are related to their mass and any external pressures acting on them, similar to the life-cycle of all living things in the universe. The process in which stars change dramatically throughout their existence is called stellar evolution and can take millions to billions of years. Stellar evolution describes how stars transform over time, from birth, through life, which includes growth, and ending in death. Fusion, the force that generates energy, is balanced by the pull of gravity, resulting in the progression and development of the star.
Stars begin their life cycle as molecular clouds, or nebula. Some event, such as a shock wave or collision of a galaxy, causes the cloud to collapse and form smaller pieces, which contract inward and form a protostar. As the star
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Once the helium in the core is exhausted, the star emits its outer layers into space, contracts down, and emerges as a White Dwarf. Ultimately, the White Dwarf will lose all of its energy, collapse due to gravity, and enter a Black Dwarf stage. No Black Dwarfs have been observed in our universe because the time it takes for a White Dwarf to cool completely is likely to be trillions of years. A Black Dwarf is simply an explanation for what would result following the death of a White Dwarf.
In larger stars, the core’s temperature increases enough to burn carbon into neon. Burning and contraction are repeated until iron is established in the core. The pressure of neutrons will interrupt the collapse of the core, creating a neutron star. The sudden cease in the contraction of the core allows some of the mass to flow inward. The core becomes heavier and can’t tolerate it’s own gravitational force. This creates a shock wave blowing the outer layer of the star apart in a core-collapse supernova eruption. This explosion results in the distribution of elements throughout the
After a time, the hydrogen runs out almost completely, and it collapses. New reactions begin to take place in the core and these reactions cause the star to expand rapidly. As the stars begin to deplete their new fuel, they switch to others. New elements are formed in the cores of stars but they become too heavy. The star has reached its end growth. When it reaches the end, a tremendous amount of energy is released and it begins to shed its outer layers, the gravity is too weak hold onto them anymore. Once the layers are removed, in the stars place is a fiery core called a planetary nebula. Eventually, the core runs out of fuel and it collapses. This star is now in a very dense state, and is called a white dwarf. Eventually, the white dwarf cools until it no longer shines. This dead star is called a brown dwarf.More massive stars, however, have more violent ways of dying. Some stars turn it into a supergiant. Supergiant stars are extremely bright, and are extremely large. Supergiant stars cores, can collapse violently and suddenly. This collapse causes a tremendous explosion, called a
The changes that occur during a star 's life are called stellar evolution. The mass of a star determines the ultimate fate of a star. Stars that are more massive burn their fuel quicker and lead shorter lives. Because stars shine, they must change. The energy they lose by emitting light must come from the matter of which the star is made. This will lead to a change in its composition. Stars are formed from the material between stars, shine until they exhaust their fuel, and then die a predictable death based upon their initial mass.
Stellar evolution stars exist because of gravity. The two opposing forces in a star are gravity (contracts) and thermal nuclear energy (expands). Stage 1 Birth is where gravity contracts the cloud and the temperature rises, becoming a protostar. Protostars are a hypothetical cloud of dust and atoms in space which are believed to develop into a star. Astronomers are fairly certain of their existence. Protostars are formed about a million years after a gas clump from an interstellar gas cloud has started
The life cycle of the Sun starts like all stars with a cloud of dust and gas made up of mostly hydrogen. If the cloud cools, it will shrink because of the gravitational pull between the particles
The life cycle of a star is dependent on its mass. The larger the mass, the quicker it will die out, whereas stars which are no more than half the size of our Sun can live up to hundreds of billion years. However no matter how large the star is, they all begin their lives in a nursery known as a molecular cloud.
Just like humans, everything in the universe has a purpose. From the beginning of the moment anything is created into existence it grows and fulfills its purpose. Stars are no different. Every day, stars are created by gravity which pulls the star together, the star builds up heat and pressure, and then fusion begins. The process in which a star goes through is known as a star's life cycle. All stars start at the basic nebula phase, change to a protostar, and go on to the main sequence star phase. After the main sequence star phase, there are two different divisions that are determined by the mass of the star. If a star is known as a low-mass star it will have different life changes than a high-mass star. A low-mass star will become a
The larger a star, the shorter their lifespan is, and they explode as supernovae, blasting out powerful shockwaves that create a chain-reaction that spews throughout the galaxy. Within just a few million years, the galaxy is forming stars up to hundreds of times more than a normal galaxy would. When all of the gas available is used up in about ten million years, the galaxy calms down and the period
The life cycle of star is on an eternal cycle of birth, death and regeneration where the gases that form stars are ejected by the very stars when they die. This all starts with the helium gas and fusion of hydrogen. The life cycle of a star is formed from stellar nebula to high mass stars and low mass stars. Hertzsprung and Russell classified stars on the main sequence of the H-R diagram about 1910 that shows the relationship between luminosities and spectral types.
What is left after the huge explosion is another dwarf star, a neutron star, or the fierce black hole. A neutron star is about the size of a city like Los Angeles, but has the mass of about two suns. This means it is incredibly dense and has an unbelievable gravitational pull, almost 2 billion times that on earth. In fact, this pull is so strong that it bends radiation and allows astronomers to see the back of the star. They also spin up to 48 thousand times per minute due to the energy from the supernova.
A Solar Mass Main Sequence Star will stay in its newborn state for about 90% of its life however when it is time to return to the universe, it must go through many stages before its final curtain call.
This causes the ball, now a star, to shine. Depending on the mass of the star, they can reach different types of fusion. Normal stars that have a mass of up to 4 times the sun can only have hydrogen fusion, helium fusion, and carbon fission. Stars with a bigger mass is classified as a massive star, and they undergo multiple stages. They start out similar to the normal stars with hydrogen fusion, helium fusion and carbon fission, but continue over to oxygen fusion, and silicon fusion. The end product of Silicon is Iron. No star can fuse Iron, it will die. How much gas and dust is collected during the star’s formation determines the size and colour of the star. As time passes by, stars fight the inward pull of the force of gravity. The outward pressure created by the nuclear reactions pushing away from the star's core keeps the star whole. However, these nuclear reactions require hydrogen. Eventually the supply of hydrogen in the core runs out and the star begins to
After approximately 10 billion years after the star is considered to be a main sequence star, the hydrogen at the center of the core is depleted. This causes the nuclear fusion which had been previously fueling the star to die out. Helium replaces the hydrogen in the core, and the inner core begins to shrink due to gravity. This process speeds up once all the hydrogen is completely used up. The radius of the star has increased
Stars go through phases with each one altering the star. They start as a protostar then ignite to
Stars generate energy via nuclear fusion of elements. Stars of the magnitude great enough to become type II supernovae possess the mass needed to fuse elements that have an atomic mass greater than hydrogen and helium. The energy generated by these fusion reactions is large enough that it is able to counter the force of gravity and prevent the star from collapsing, maintaining stellar equilibrium. The helium produced in the core builds
Main sequence stars like our own sun enduring in a state of nuclear fusion during which they will produce energy for billions of years by replacing hydrogen to helium. Stars change over billions of years. When their main sequence phase ends they pass through other states of existence according to their size and other characteristics. The larger a star's mass, the shorter its lifespan is. As stars move toward the end of their lives, much of their hydrogen will be converted to helium. Helium sinks to the star's core and raises the star's temperature—causing its outer shell to expand. These large, puffy stars are known as Red Giants. The red giant phase is actually a prelude to a star shedding its outer layers and becoming a small, dense body called a White Dwarf. White dwarfs cool down for billions and billions of years, until they finally go dark and produce no energy at all. Once this happens, scientists have yet to observe, such stars become known as Black Dwarfs. A few stars avoid this evolutionary path and instead go out with a bang, exploding as Supernovae. These violent explosions leave behind a small core that will then turn into something called a Neutron Star or even, if the remainder is large enough, it is then turned into something called a Black Hole.