Stars Life Cycle

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

There are billions upon billions of stars in our galaxy but only about 2000 of those are visible to us at night. Although there is one star that we are able to see during the day, but only because it is the closest one to earth, this star is the sun. Because the brightness of the sun is so vast we cannot see other stars, but when the sun sets we can see an abundance of celestial objects. The sun appears to be what some would call “the largest star” but it is only an average sized star, there are a countless more that are hundreds times the size of our sun. When we look up into the night sky and focus our eyes on what appears to be a star we often notice it twinkling, this is caused by turbulence in earth’s atmosphere. The atmosphere is like a lens and makes a boiling effect causing stars to look like they’re twinkling. Astronomers have discovered clusters of stars forming patterns, we call them constellations and there are roughly eighty-eight in our night sky. Stars can come in all kinds of different shapes sizes and distances, which causes some stars to appear closer than others. Bigger stars tend to shine more brightly than smaller stars. Even though a star seems bigger and brighter than the others doesn’t actually mean it is, it could just be a star closer to earth than most. The closest star to us is Alpha Centauri and is approximately four light years from earth meaning it takes four years for the light from Alpha Centauri to reach

Many physical properties of stars can be found by using a little bit of light. One property of a star is luminosity. Luminosity is the quantity of energy created in a star and then released as electromagnetic radiation. The brightness of a star is a blend of luminosity and distance of a star and can also depend on the quantity of energy absorbed in the direction of a star. Another property of a star is distance. Astronomers use parallax to establish the distance to an object. As Earth travels around the Sun, they monitor neighboring stars from various positions. They are then able to measure how much the star seems to move to establish the distance to the star.

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.

After the core of a star has depleted all its hydrogen in fusion, it undergoes its final stages of its life, or in other words, its death. The process path of a dying star depends on its mass. Low mass stars, from about 0.4 up to 8 solar masses will evolve from a planetary nebula to a white dwarf. Stars with larger the 8 solar masses will form supernovae, than either a neutron star for intermediate stars (8-25 solar masses) or a black hole for high mass stars (greater than 25 solar masses).

Stars, such as our sun begin their life in an entirely different form from the one we come to recognize. Their lives begin in the bitter cold, around 10 degrees Kelvin, which is only a few degrees above the 3 degrees Kelvin temperature of the background of space itself. Their density is also extremely sparse, with a density of around 1 billion particles per cubic metre, which is only a wisp in comparison to the density of around 1410 kilograms per cubic metre that the sun like star will have during its time on the main sequence. Although they may be quite low in density, the clouds are absolutely enormous, spanning up to tens of parsecs (an astronomical unit of measurement that is determined to be around 19 trillion miles) across. In these clouds, there is an abundance of molecular and atomic gases of various types, which will serve as the rough material that will be used to create the stars and solar systems. Hydrogen is the most abundant element found within these clouds, although they can also contain many other trace elements of metals and gasses.

The deaths of normal stars give birth to neutron stars. Neutron Stars are products of the so called supernova. Supernovae transpire during the death of a highly developed star which occurs when there is not enough nuclear fuel to keep the pressure intact inside the core of a star (Gursky 1975). The aftermath of a supernova is crucial because it frees iron, carbon, copper, and oxygen along with other elements found in a star. This explosion completely demolishes the star and has the ability to transform into either a black hole or neutron star (Freddy 2006). These supernovae are extremely bright and every 200 years there is an explosion that happens to be big enough and bright enough to be seen from earth. Neutron stars are very significant within the universe. It is said that the neutron star was discovered before the before the neutron. It was Lev Landau who first wrote about and studied dense stars. He focused his research on the idea there were objects in the universe that were denser than but as small as white dwarfs and regular stars (Haensel 2007). This focus leads to the discovery of the fascinating and complicated neutron star. The end is only the beginning for neutron stars.

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

Most stars, around 70 percent, are red dwarves, which are less massive than the sun. These stars are immortal, to our purposes. Their lives are several orders of magnitude longer than the sun's. There are many more that aren't red dwarves but are still less massive than the sun. Most stars we can see with the naked eye, however, are more massive, and stellar lifetime decreases rapidly with mass. There isn't a red dwarf close enough to be seen naked eye. So most that you see in the

The universe is approximately 13.77 billion years old (1). There are two methods which researchers use to determine the age of the universe: observing the oldest stars; and using the Hubble’s constant (1). Observing stars does not necessarily mean going outside and looking up in the sky at night. By viewing into a telescope, researchers can look beyond the human eyes to see a more desirable view of reality in space. Thus, researchers can gather information and determine where the global cluster of stars is located in the universe. Hubble’s constant is an accepted measurement where modern society has come to accept and use; being a correct or incorrect measurement.

Stars change dramatically throughout their existence, due to the forces of gravity, in a process called stellar evolution. Stellar evolution describes how stars transform over time, from birth, through life which includes growth, and ending in death. This process can take billions of years, although the time scale depends on the mass of the star. Luminosity also plays a role in the evolution of a star.

For about another thirty million years, the star continues to contract and its central density, central temperature, and surface temperature increase; then it is a main sequence star where pressure and gravity are balanced and nuclear energy is being generated in the core. It takes forty to fifty million years for a star to reach this stage. The Sun is a main sequence star (McMillan, 2011).

About 90 percent of the stars in the universe, are main sequence stars. Stars start their lives off as big clouds of dust and gravity draws the clouds and forms them into one. Mark Morris, made a statement and said “Nature doesn’t form stars in isolation.” “ It forms them in clusters, out of natal clouds that collapse under their own gravity.”

Since we first gazed upon the heavens, man has been perplexed over where the bright lights in the sky have come from. This report will provide information for the birth and death of both low and high mass stars that is supported by scientifically proven statements and observations. It is the long held belief of many, that molecular clouds are the nurseries of stars. These dense clouds of gas are most often found in the spiral arms of galaxies. Obviously, smaller cloud produce low mass stars while large clouds produce high mass stars which collapse much faster than their smaller siblings during the protostar phase ( Washington). At this point, the cloud is cool with very low pressure. Once these clouds of gas become dense enough, they collapse to create the beginnings of a star know

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.