Introduction

When you look up at the night sky you will see many stars witch look like points of light because you are so far away. But, what are stars?  Why do they exist? Are they all the same where do they come from? Many questions like these have been asked and as technology becomes better we learn more and more about them. Some thing that we learned are how they are born. We also learned that stars come in many colours and sizes. Before we thought that stars where the only thing space but in 1995 when the Hubble space telescope was invented it took detailed pictures of nebulas which are left over by a dieing star. 
What is a star?
They all look the same but no two stars is alike (Star, 2007). Stars can range from very big to very small. The smallest ones are only 0.08 the size of the sun (Talcott, 2006). The biggest stars can be as big as 250 times the suns size or 250 solar masses. The colours of a star can be red, yellow or blue. Stars are mainly composed of gasses and metals The two main gasses that are needed for a star to survive are Hydrogen of Helium. There is more hydrogen in a star then helium. The reason a star shines is because of the nuclear fusion that occurs in its core, this is called nucleosynthisis. There are two processes of nucleosynthisis. The first process happens when hydrogen is converted into helium. The second process is when helium is converted into carbon. In every star there are traces of metals like iron (Star, 2007).
Types of Stars
No two stars are alike, everyone is different in terms of size colour and chemical composition. There are seven main classifications of stars. The first type is type O. A type O star are big and bright stars. Since class o stars are so big, bright, and hot they have a surface temperature of 60000K, they burn through there hydrogen supply very quickly and only live up to 6 million years(Talcott,2006). These stars are blue and are around 20-120 the size of our sun. Since they are so big there own gravity squeezes the stars core over its life time until it explodes and a forms a black hole. Class b stars are bluish white and have a surface temperature of 10,000-31,000K. They have life span of 300 million to 1.8 billion years and they are 4-20 times the size of our sun. These stars die like a class o star but instead of a black hole being formed a neutron star is formed. Class f stars are whitish yellow are only 1.05 to 2 times the size of our sun. They have a surface temperature of 6,000 to 7,400K and live from 1.8 billion to 8.8 billion years. These stars die in the way of a planetary nebula. Class g stars are yellow and are about 0.8 to 1.05 the size of our sun. There life time spans from 8.8-17 billion years and they have a surface temperature of 5,300 to 6,000K. Our sun is a class g star. When a class g star dies it expellees its outer layers and forms a planetary nebula and the star core turns into a white dwarf star. Class k stars are orange and have a surface temperature of 2,200-3,900K. They live from 17 to 55 billion years and are about 0.5 to 0.8 the size of our sun. These stars die the same way as a class g. Class m stars are red and have a temperature of 2,200 to 3,900K. They are 0.08-0.5 times the size of our sun and live from 55 billion to 5.5 trillion years. Any class m star that has ever been created is still living to day because our universe is only 13.7 billion years old. Since none of them have died scientists dont know how these stars die yet.
Death and Birth of Stars
Every Star is born the same way. In space there are large clouds of dust and gas. Gravity begins to pull these large clouds of dust and gas together and they form clumps of gas called globules. The globule gets squeezed really hard and the center begins to heat up. When the center heats up enough nuclear fusion begins to occur and a protostar forms. The gas that didnt become a protostar begins to orbit around it. The gas orbiting it is called a protoplanetaryy disc. As the star matures most of the gasw ill absorb into it (Iben, 2002). Not all stars die the same way. There are two ways a star can die. These two ways are called a supernova and a planetary nebula. Class O, B and A type stars die in a the supernova. These stars will expand to 10 times there size during there life time. The key factor of a supernova is sound.  After 6 million years the star's own gravity will begin to squeeze the its core. The core will collapse and it will re release a sound wave. The sound wave will be bounced back by the surrounding gas will hit the core or by this time a protoneutron star. The waves that keep bouncing back become faster and stronger until the waves combine into one huge shockwave. The shockwave is much too strong to be concealed by the gas so the shockwave is released and that causes the star to explode or become a supernova (Reddy, 2007). A supernova is like when sonic boom happens just on a much larger scale. Class F, G and K type stars die in the same way. These stars remain the same colour for about a few billion years. When these stars begin to run low on hydrogen they begin to heat up, turn red and expand to 100 times there original size(Dickinson,2004). These star become so hot that they stop converting hydrogen into helium and convert helium into carbon. The star eventually uses up all its helium available and its core collapses into a white dwarf. The white dwarf is dense and emits so much radiation that it pushes the remaining gas into space and forms a bubble. This is called a planetary nebula and has nothing to do with planets (Dickinson, 2004).
Nebula
A nebula is a large cloud of dust and gas in space which are left over from dying stars. The word nebula comes from the Latin word which means cloud. Nebulas are composed of two main gasses hydrogen and oxygen. There are four types of nebulas. . The first type of nebula is called an emission nebula because of its hydrogen atoms absorb radiation from nearby stars and reemit as light. These types of nebulas look red. The second type of nebula is called a reflection nebula because its atoms take nearby light and reflect it. These nebulas have the colour blue. The third type of nebula is called a planetary nebula. These nebulas regularly symmetrical and can come in all colours of the spectrum. . They are formed when a star like are sun ejects its outer layers. The fourth type of nebula is called a dark nebula. These nebulas are black and restrict light. They do not reflect or emit light. From a telescope, these nebulas look like holes in space. Some peculiar nebulas have been found containing alcohol and methane (Bakich, 2007).
Gilles Fontaine
Gilles Fontanne is worlds for most expert of the class D star. His famous quote states I wanted to know how stars die. His first interest took place when he became a star gazer when he was a teen. Gilles Fontaine then pursued his interest in stars and became astrophysics and the University of Rochester. Gilles fountain then took a very strong interest in the white dwarf. In 1980, he made a very big discovery. He used some instruments that he created and calculated that the universe was around 12 billion years old. Fontaine created many devices that could calculate the dimension, surface temperature, internal chemical composition, period of rotation and, distance from the sun of a star. Most of these devices are still used today. Fontaine has written over 200 major articles for magazines and news papers. Gilles Fontanne has won many awards like the BSC Physics award at Laval University in 1969 and the Marie-Victorian Award by the government of Quebec in 1999(Science,2007).
Conclusion
Stars sure are something where theres more than meets the eye because stars are not just tiny points of light in the sky. They have different nuclear fusions that happen inside them. Sometimes the smallest of stars are the hottest and emit the most radiation. There are huge colourful nebulas that have been left over by old dying stars. There are some stars that are only due to dye at 55 trillion years old. Some stars are weird because they are so big and massive. Even as technology improves we keep on learning more and more about stars.
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