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Post by Guest Wed Apr 22, 2009 9:16 pm

couldnt print at home so im posting it here so i can from the school computer, sorry u guys have to see my half ass school work, but i got to do it.

The Life and Times of a Star

By Dylan Starr

All in all, stars are very interesting and mysterious entities. Without them, everything we know would not exist, including human life itself. They are very difficult things to study, and actually, though we have collected tons upon tons of data on them, not much is really know about them. However, what we do know about them is also filled with uncertainties and guess work for they can not be studied as other things can be. No one has touched a star, and it would be impossible to make definite observations due to the fact that we are millions of miles away from even the closest one, our son. Anything we use as fact we are only really 99% sure of, for the most part anyway.

Our sun itself is extremely small in comparison to most other stars scattered throughout our universe. Our galaxy, and even our universe is a very vast expanse of nothingness and yet everything that is virtually inconceivable to the human brain. Our own earth seems very large. Yet when compared the vastness of our other planets, it is really rather small. And even these planets pale in comparison when compared to the star they circle, which in turn is tiny when compared to some of the other stars. And believe it or not, the stars that cast a shadow over the sun, are even yet outmatched in size by others that drift through space and have for innumerable amount of years

Stars are formed from large masses of dust and particles and heat known as nebula. More so actually, whole galaxies are formed from a single nebula. There are many nebula that have been viewed scattered through out the universe which are beginning the birth of new stars and galaxies. There are not many though, when compared to the overall amount of mass that the universe is comprised of, which is to say that there have been a lot of galaxies and stars already formed. This indicates that the universe has been around for a very, very, very long time, as one would expect. This, however, gives you a better scope of the actual age of the universe, for there are actually quite a numerous amount of nebula located through out its dark depths, and yet still only comprise a small fraction of it. This can also be an indicate to the vastness of space, which is largely incomprehensible to most.

Stars begin to form from these nebula when the particles located through out it began to attract one another through the force well known as gravity, which everything has. As the particles and dust begin to come together, they form balls of extremely hot sphere masses. At first they are nothing, but eventually they begin to form a substance know as a protostar. A protostar is the fetus stage of a star and is the true beginning of the birth of a star. Not much is largely known about these masses, because there are not all that many to study at this point in the universes history. Less is actually known about them then the enigma known as the black hole. They do however, hold many keys to the secrets of stars and could unlock a whole new understanding of these celestial bodies.

Now depending on the size the protostar achieves before it begins to fully fluctuate into a full grown star, will dictate which path the star takes during its whole life time. The size of stars are measured in solar masses. One solar mass is equal to the total mass of our sun which is roughly 2 nonillion kilograms. A single nonillion is equal to the value of 10 to the thirtieth power. In relation to ourselves, two nonillion is equal to the product of the mass of our earth and the numeral 332,950, which is quite a considerable amount, and makes our own measurement of size seem virtually non existent. Protostars are split into two groups, protostars with a mass of less than eight solar masses and protostars that have more than eight solar masses. First we shall follow the path of the first group, (protostars with a mass less than eight solar masses, since our own star, the sun, is obviously a part of this group.

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Post by Guest Wed Apr 22, 2009 9:18 pm

When a protostar begins to age into a full grown star and has a solar mass of less than eight, it begins to form what is called a main sequence star. A typical main sequence star is our sun, which is again the exact equivalent to a single solar mass. It is also a fairly small main sequence star. This is not to say that a main sequence star will never exceed more than 8 solar masses, for the largest known sequence star is measured between 120-200 solar masses. Again, our own sun is tiny when compared to the other celestial bodies in the universe. It is in this first stage that a star gets its classification from humans. We generally classify it in terms of heat and how fast they spin around. Scientists can tell how hot a star is by the color that it shines. The weakest color in terms of thermal in energy for a star is red, and blue is the strongest. The temperatures ranging between these two extremes in order from indication of coldest to warmest are orange, yellow, and white. In total there are five classes and our own sun is only in the second coldest region, orange, though it appears yellowish white from the earth. viewed from space it is clearly a mass of orange burning gasses.

The second classification of stars, which is highly less important, is how fast a star spins. For many years scientists have troubled over why some stars spin at a faster rate than others, for their size seemed to have little to no effect on the matter. After careful study though, a conclusion was reached, though it is still mostly just speculation and further research is needed to back it up enough for it to be considered scientific fact. It has been noted that stars which have had planets form around them spin with less speed than a star with out planets. This is thought to be due to the contrasting gravitational pulls, and while the gravitational pull of a planet is minuscule when compared to the star it orbits, it could very well be enough to be the cause of a slowing of the speed of its revolutions.

The whole time a star is in its main sequence stage, it is converting the hydrogen within it into helium. After all of the hydrogen has been converted, the star begins to heat and expand at a very large rate. The star takes on a red color, hence its name, which indicates that though it has grown vastly in size, it has cooled by a large amount in reference to human standards. Our own sun will eventually become a red giant, though it will not happen in our life time. It is expected to begin its expansion in about five million years, the time when it will literally become a monster. It has been estimated that it will expand to AT LEAST two hundred times its current size. This means will expand out to such a size that the two most inner most planets, Mercury and Venus, will be engulfed and cease to exist. The sun will be nearly touching our own planet, the earth. Life here will become an impossibility, that is assuming that the earth will survive to be this age. The whole process should last about one million years. All of our water sources will have evaporated and the surface will be molten rock. Our atmospheric condition will be similar to the current one of Venus.

After many, many years, the red giant will slowly begin to enter yet another phase and is nearing the end of its life. As it burns up all of its fuel it will slowly begin to die. The outer layers are thrust out into space due to a strong pulsating of the star and an increase in the intensity of its solar winds. This is comparable to the star puking up a lot of its mass as a sick cancer patient would, another analogy to the fact that star has begun to in fact die. Eventually the star will have expelled all of its gasses into the surrounding space. This does not mean, however, that it is mass that is lost. Due to the strong gravity and magnetic fields left over, the gasses will typically continue to remain in a spherical shape. It takes on the appearance of on of our solar systems gas giants. This is where the name planetary nebula is derived from. The nebula are generally one light year across. It is this stage of stars that are responsible for the evolution of the universe as we know it. Initially the only two elements that the universe consisted of were helium and hydrogen. In this stage, elements undergo serious nuclear fusion. It is from these processes the elements carbon, nitrogen, and oxygen come from, which are the three main elemental components of life.

Eventually, the gravity holding the large gas cloud known as the planetary nebula will form once more into a single massive ball of hot gasses, formed by the force of gravity still in existence from the original starr. Most commonly, white dwarfs are very small, averaging to be about the size of the sun. Due to the fusion indicated during the previous stage, white dwarfs are made of carbon and oxygen. There have also been rare reports of white dwarfs created of oxygen, neon, and magnesium as well as some, even more extremely rare, that are comprised mainly of helium. The make up will depend on the events the star undertook as a planetary nebula White dwarfs, as indicated by the name, are extremely hot and radiate the color white. However, it has no source of energy to keep it going and so is the final stage of a low mass star. It will slowly burn off all its remaining fuel as well as begin to cool down. This means that it will slowly turn to yellow, orange, red, and finally, when it is all said and done. It will lose all source of light and become a cold and dead black dwarf.

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Post by Guest Wed Apr 22, 2009 9:19 pm

Black dwarfs are by far the most difficult stellar object to study, as none actually exist in the universe yet. The calculated time to create a black dwarf is longer than the total age of the predicted universe itself, so their existence in current time is an impossibility, though a future appearance is very probable. It is created when a white dwarf cools and expels the bulk of its matter due to thermal radiation. Their estimated average size is thought to be between eight and ten solar masses. A black dwarf is comprised of electron-degenerate matter. It is unsure of when a star can reach this stage or if it is even possible. It is linked also to the substance known as dark matter of which little is also known. It is speculated that they will be observable by a still exiting gravitational pull, much like a black hole. This is the end of a star that began as a proton star of eight solar masses or less.

Should a proton star began to mature in to an actual star with a mass higher than eight solar masses, it will enter a stage known as, and well named, a massive star. Massive stars do not much differ from main sequence stars except the fact that they are much, much larger, and are typically in the white and blue range temperatures. The largest star known to man is roughly between 1800 and 2100 solar masses large. In other words, it is roughly 1950 times larger than our own sun, which is quite a considerable comparison. If our sun was replaced with this star, known as Canis Majoris, it would extend out all the way, and possibly past the planet Saturn. It is so large that it would take you 162,000 years to walk across it, which is way more than a single human life times. Canis Majoris is in fact one of the few known stars which can be called a hyper giant. It has entered the super red giant phase, but keeps its blue color due to its vast mass and temperature and is a true phenomenon. These two stages are just like the two stages of low mass stars, except they are considerably larger in size and typically much, much hotter.

A super red giant, or hyper giant in the case of Canis Majoris, never achieves the stage of planetary nebula. In fact, for a star that began as a protostar with a solar mass of over 15, this will be the last stage as an actual star for it. When a super red giant has reached its limit, it undergoes yet another phenomenal transformation of which its wonders outshine, quite literally in fact, the monsters known as super red giants. This stage is known as the supernova, a tremendous explosion that not even the force of an atomic bomb could rival. It is one of the most devastating creations that this universe has produced. The blast sets out so much radiation that a single supernova has the potential to outshine an entire galaxy. This is the most extreme and also the shortest lived of all star stages, lasting only between a few weeks or months. Despite the rapid life of this stage, as much energy is produced from this event as our sun will create in its entire life time. It is set off by the sudden ending of energy produced by nuclear fusion with in the star, creating a sudden gravitational collapse. The inward collapse of such a large mass and intense heat is the initial cause of the monstrous explosion known as a supernova.

From here, one of two things can happen, either way, the star has one final stage it will partake in. Both of these stages begin forming at the time of gravitational collapse within the super red giant. Once again this depends on the size of the proton star at the beginning of the cycle. If the proton star was between eight and fifteen solar masses large, it will become a mass known as a neutron star. It is formed by the colliding and canceling out of electrons (negative charge) and protons (positive charge). This creates a large accumulation of neutrons whose numbers will equal half that of the total protons and electrons in the original star. Neutrons are neutral meaning that they posses neither a negative or positive electrical charge. This kind of star is incapable of collapsing unlike the super red giant it was produced from thanks to the Pauli exclusion principle. This is a scientific rule stating that no two neutrons are able to occupy the same quantum state, which means that they can not collide and fuse like protons and electrons can. Ironically, they are one of the smallest celestial objects, despite being created by the largest ones. They have a solar mass ranging between 1.35 solar masses and 2.1 solar masses. They average about 12 kilometers in radius. This is slightly less then seven and a half miles. In comparison to the sun, the sun is 60,000 times as big as a normal neutron star. Do to its small size, and the force of the supernova that created it, it has insanely high rotation speeds. These last anywhere between 1.4 milliseconds and thirty seconds, depending on age because they do lose momentum as time goes on, as all things do. It also has a very large gravity despite its large size which is ten to the eleventh power greater than our own.

The second thing that can come out of a supernova, is a black hole. For this to occur, the proton star that created it has to exceed fifteen solar masses. This is extremely rare. Black holes are true monsters. They are by far, the single most greatest powerful object in the history of their universe. They are lethal to everything, including the essence of light itself. They can be best described as large rips through space in which everything nearby gets sucked in from the tremendous gravitational pull. They are impossible to see since not even light can escape and show off no physical body. They are detectable though by the rapid disappearance of matter around it. The easiest scenario to detect them is in binary stars. Binary stars are comprised of two separate stars that formed relatively close to each other and orbit each other do to each others gravitational pull. At least one of these stars must be a massive star to start out with, when the one becomes a black hole, the other gets sucked in which is clearly visible to us through powerful telescopes through which we can view the gasses of the star being sucked into a portion of space which appears non existent.

Black holes are enigmas that have baffled humans for many of years. No one can tell what goes on inside a black because there is no way of observing it. Since not even light can escape it, appears as just a rip through space. It is however, known that black holes do eventually wither away and die into nothingness. What is done with the matter sucked up in it is still unknown. What is known, and is a very disturbing thought is that there is a super massive black hole with in the heart of every galaxy, including our own. It is thought to have slowed down, or weakened as of late, but in years to come is expected to rear up again, taking in large amounts of light and energy at a very quick pace. When this happens it could very well be the end of the milky way galaxy.

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