LIFE CYCLE OF A STAR
Stars are formed in nebulae, interstellar clouds of dust and gas (mostly hydrogen). These stellar nurseries are abundant in the arms of spiral galaxies.
In these stellar nurseries, dense parts of these clouds undergo gravitational collapse and compress to form a rotating gas globule.
The globule is cooled by emitting radio waves and infrared radiation. It is compressed by gravitational forces and also by shock waves of pressure from supernova or the hot gas released from nearby bright stars. These forces cause the roughly-spherical globule to collapse and rotate. The process of collapse takes from between 10,000 to 1,000,000 years.
A Central Core and a Protoplanetary Disk:
As the collapse proceeds, the temperature and pressure within the globule increases, as the atoms are in closer proximity. Also, the globule rotates faster and faster. This spinning action causes an increase in centrifugal forces (a radial force on spinning objects) that causes the globule to have a central core and a surrounding flattened disk of dust (called a protoplanetary disk or accretion disk). The central core becomes the star; the protoplanetary disk may eventually coalesce into orbiting planets, asteroids, etc.
Protostar:
The contracting cloud heats up due to friction and forms a glowing protostar; this stage lasts for roughly 50 million years. If there is enough material in the protostar, the gravitational collapse and the heating continue.
If there is not enough material in the protostar, one possible outcome is a brown dwarf (a large, not-very-luminous celestial body having a mass between 1028 kg and 84 x 1028 kg).
A Newborn Star:
When a temperature of about 27,000,000°F is reached, nuclear fusion begins. This is the nuclear reaction in which hydrogen atoms are converted to helium atoms plus energy. This energy (radiation) production prevents further contraction of the star.
Young stars emit jets of intense radiation that heat the surrounding matter to the point at which it glows brightly. These narrowly-focused jets can be trillions of miles long and can travel at 500,000 miles per hour. These jets may be focused by the star's magnetic field.
The protostar is now a stable main sequence star which will remain in this state for about 10 billion years. After that, the hydrogen fuel is depleted and the star begins to die.
Life span:
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...densities are shown as numbers on the the central line that defines the Main Sequence (M.S.) of stars. Most known stars lie along this line; they describe a stage in which a star reaches some fixed size and mass and commences burning of most of its hydrogen before changing to some other star type off the sequence. Star types, which are defined on the basis of stellar surface temperatures (page 20-7), are shown by the letters (O, B,...etc.) assigned to each group and evolutionary pathways for some are indicated. This particular plot also shows along the right ordinate the total time that Main Sequence stars of different masses spend on that sequence before evolving along the several principal pathways (see below); as far as we now know, stars do not completely vanish, but survive as dwarfs or Black Holes ( but the latter in principle can disappear by evaporation as Hawking radiation). Temperatures were obtained using Chandra X-ray data.
BILBLIOGRAPHY www.enchantedlearning.com/subjects/astronomy/stars/lifecycle/ imagine.gsfc.nasa.gov/docs/teachers/lifecycles/LC_main_p1.html hubblesite.org/newscenter/newsdesk/archive/releases/1999/20/ map.gsfc.nasa.gov/m_uni/uni_101stars.htm
Cinderella is about a beautiful young girl that is mistreated by her step family. They give her the worst chores, make her sleep in a very dirty room up in an attic, and even give her the name “Cinderella” because they say she is always playing in the cinders of the fire. Cinderella is different though because despite being mistreated, she is still very nice and warmhearted. She represents how you should act in a world full of hate. If you are nice to everyone despite their rudeness and hate you will be rewarded in the end. Since Cinderella was so nice to her step sisters throughout her whole life, when she wanted to go to the ball her fairy godmother granted her wish. Cinderella got to go to the ball and looked absolutely beautiful, beautiful enough to catch the attention of the prince. While at the ball she was still very nice to her stepsisters, giving them food and telling them how nice they looked. When the stepsisters got home from the ball that night, they explain how lovely the mysterious princess was and how they thought she was so beautiful, not knowing that the mysterious princess was Cinderella. Cinderella played it off like she knew nothing of the princess but agreed with them that she must have been very beautiful. The next day came around and the stepsisters returned to the ball the
All these effects were the cause of the discovery of nuclear fission and its properties. Nuclear Fusion Nuclear fusion is the process used by the sun and the stars in our solar system to produce their energy. Fusion involves smashing hydrogen atoms together at high velocities to form helium, and the matter is made into energy.
Written by author Tim O’Brien after his own experience in Vietnam, “The Things They Carried” is a short story that introduces the reader to the experiences of soldiers away at war. O’Brien uses potent metaphors with a third person narrator to shape each character. In doing so, the reader is able to sympathize with the internal and external struggles the men endure. These symbolic comparisons often give even the smallest details great literary weight, due to their dual meanings. The symbolism in “The Things They Carried” guides the reader through the complex development of characters by establishing their humanity during the inhumane circumstance of war, articulating what the men need for emotional and spiritual survival, and by revealing the character’s psychological burdens.
For immigrant, minority, or English learning student, name has historical and hereditary significance. They may have stories behind their name which are suppressed when they are regularly compelled to adjust to an “Americanized” setting. However, that transition forces students to take name that do not define them. Yee Wan moved to United States from China when she was 17. When she enrolled to a school at United States, she was forced to change her name-- she had to decide whether to keep her native name or change to American name so that it would be easier for her teachers to pronounce her name. Realizing that there was no choice, she had to change her name to Winnie. (McLaughlin 1). Similarly, Michelle-Thuy Ngoc is a US born teen
Stars are born and reborn from an explosion of a previous star. The particles and helium are brought together the same way the last star was born. Throughout the life of a star, it manages to avoid collapsing. The gravitational pull from the core of the star has to equal the gravitational pull of the gasses, which form a type of orbit. When this equality is broken, the star can go into several different stages. Some stars that are at least thirty times larger than our sun can form black holes and other kinds of stars.
Solar nebula is a rotating flattened disk of gas and dust in which the outer part of the disk became planets while the center bulge part became the sun. Its inner part is hot, which is heated by a young sun and due to the impact of the gas falling on the disk during its collapse. However, the outer part is cold and far below the freezing point of water. In the solar nebula, the process of condensation occurs after enough cooling of solar nebula and results in the formation into a disk. Condensation is a process of cooling the gas and its molecules stick together to form liquid or solid particles. Therefore, condensation is the change from gas to liquid. In this process, the gas must cool below a critical temperature. Accretion is the process in which the tiny condensed particles from the nebula begin to stick together to form bigger pieces. Solar nebular theory explains the formation of the solar system. In the solar nebula, tiny grains stuck together and created bigger grains that grew into clumps, possibly held together by electrical forces similar to those that make lint stick to your clothes. Subsequent collisions, if not too violent, allowed these smaller particles to grow into objects ranging in size from millimeters to kilometers. These larger objects are called planetesimals. As planetesimals moved within the disk and collide with one another, planets formed. Because astronomers have no direct way to observe how the Solar System formed, they rely heavily on computer simulations to study that remote time. Computer simulations try to solve Newton’s laws of motion for the complex mix of dust and gas that we believe made up the solar nebula. Merging of the planetesimals increased their mass and thus their gravitational attraction. That, in turn, helped them grow even more massive by drawing planetesimals into clumps or rings around the sun. The process of planets building undergoes consumption of most of the planetesimals. Some survived planetesimals form small moons, asteroids, and comets. The leftover Rocky planetesimals that remained between Jupiter and Mars were stirred by Jupiter’s gravitational force. Therefore, these Rocky planetesimals are unable to assemble into a planet. These planetesimals are known as asteroids. Formation of solar system is explained by solar nebular theory. A rotating flat disk with center bulge is the solar nebula. The outer part of the disk becomes planets and the center bulge becomes the sun.
Black holes were originally thought to have only mere mathematical concepts. There was seemingly no possible way to compress any object into a space small enough to equal to its schwarzschild radius. Later however, astronomer Subrahmanyan Chandrasekhar calculated that stars much larger than our own sun should theoretically be able to collapse into a black hole (UTFC). A star is like a blown up balloon with the force of gravity trying to compress the balloon inwards and the air trying to push the balloon outwards. Likewise, stars are held in balance by gravity trying to collapse the star inwards going against the outwards pressure of the internal reactions of the star called nuclear fusion. If the star is big enough and the pressure inside quickly disappears, gravity would and should slingshot the star into a tiny point with near infinite density with an extremely strong gravitatio...
Shklovskii, Iosif S. Stars: Their Birth, Life, and Death. Moscow: Central Press for Literature in Physics and Mathematics, 1975.
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is a disciplined process of inquiry conducted by and for those taking the action. The primary reason for engaging in action research is to assist the “actor” in improving and/or refining his or her actions.
Astronomers believe that most galaxies consist of a supermassive black hole at the center, which attracts all constituents of galaxies such as, dust, gases (mainly Hydrogen and Helium), atoms, stars, interstellar clouds and planets to the center by force of gravity, but are not sure whether all galaxies contain a black hole in the center. Galaxies keep moving in relative motion to one another and intermittently can come so close that the force of gravitational attraction between the galaxies may become strong enough to cause a change in the shape of the galaxies, while in exceptional cases, the galaxies may collide. If two galaxies collide, they may pass right through without any effect or may merge, forming strands of stars, extending beyond 100,000 light years in space (World Book Online Reference Centre, 2005). Hence, neighboring and often other colliding galaxies induce the sha...
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