Stellar Evolution

When stars died, chemicals other than hydrogen and helium formed, which led to the next level of complexity—Heavier Chemical Element. Most stars spent about 90% of their life over billions of years on during protons and hydrogen nuclei into helium nuclei. When they run out of fuel, the furnace at the center of the star stopped supporting the star, and gravity took over. Small stars did not have much pressure at the center. They burned hydrogen slowly over billions of years at relatively low temperatures. When they died, they would slowly fade away. However, great stars had so much mass that they can create enormous pressures and temperature, and when the giant stars ran out of hydrogen, the temperature got cranked up even higher, which led the star to collapse. The high temperature that the collapse caused was able to make helium nuclei fuse into nuclei of carbon. When a star used up its helium, it collapsed again, and the cycle started over. The star heated up and began to fuse carbon to form

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

Soon after the big bang the cosmic dust as well as gases combined and cooled off together to form stars. The nuclear fusion in stars converts hydrogen into helium and is a continuous process in the stars until hydrogen runs out at the core of the star. When hydrogen runs out, helium atoms fuse to form carbon atoms. Massive stars can synthesize heavier elements such as

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

- Because the interior of a less massive star doesn’t reach sufficiently high temperature and pressure to fuse helium. So the only energy source is hydrogen.

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.

Comparing red giants to the sun, they are about 1000 times larger. Compared to the sun’s temperature, a red giants temperature is about half as much. This is because the same amount of energy has to be spread out across a much more massive star causing it to be cooler than it was before. The name red giant was given to these stars because the change in temperature causes the star to shine in the redder part of the spectrum. Stars can spend anywhere between 1000 years and one billion years in the red giant phase. After a certain amount of time, the helium finally runs out and fusion stops. Since there is no more helium, gravity pushes the star inward. The stars outer atmosphere is then blown out into huge clouds of gas and dust which is known as planetary nebulae. These clouds of gas and dust are then made to make new stars. As for the core of the star, it is still there. The star is now a white dwarf. White dwarf stars occur when the red giant loses its outer atmosphere. White dwarf stars are extremely hot because they are composed of only the core of the star which is the hottest

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

One day the universe will turn dark forever as the last star fizzles out and that star will most likely be a red dwarf. When a red dwarf star forms it possesses important properties that give it the potential to host rocky planets similar to Earth. Therefore the creation and resulting properties of red dwarfs form stars that can provide energy to planets which may one day be hospitable to life forms. First the process of formation of red dwarfs will be explained. Then, the properties of these stars will be examined. Finally, the importance of red dwarf stars’ existence will be considered.

A star has 5 definite stages and 3 stages which can vary between stars. The 5 definite stages are a Nebula, a Star, a Red Giant, a White Dwarf and a Red Dwarf. The stages that can vary are a Supernova, a Neutron Star and a Black hole. As the star goes through each stage, it can change size dramastically. An example of this is a Red Giant, which is 100 time the size of the Sun, compared to a Red dwarf, only 1 tenth the size of the sun (Life cycle). An interesting fact is “The closest star to Earth is Proxima Centauri, located 4.2 light-years away. In other words, it takes light itself more than 4 years to complete the journey from Earth. If you tried to hitch a ride on the fastest spacecraft ever launched from Earth, it would still take you more than 70 000 years to get there from here.” (Interesting facts)

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.