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Life cycle of stars


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  • 1. The Life Cycle of Stars Sample Student Paper (names removed)
  • 2. The Birth of a StarIn order for a star to go through the process of nuclear fusion, it needs fuel. These fuels are mostly Hydrogen and Helium, also accompanied by discrete amounts of Carbon, Nitrogen, and Oxygen. While a Star is using up one type of fuel, it must change its size and pressure in order to use another fuel. Making these changes is a very gradual process which usually happens over the course of millions to billions of years. The Star is born in an immense cloud of gas and dust known as a Nebula.
  • 3. NebulaThe word Nebula in latin means cloud,which is perfectly suited for what it is. ANebula is a cosmic cloud of dust and gasfloating in space. All the elements neededfor a Star are stored within the Nebula.They are Hydrogen, Helium, and smallamounts of Oxygen, Carbon, and Nitrogen,which are called heavier elements The Crab Nebulacompared to Hydrogen and Helium. About90% of the Nebula is Hydrogen, about 10% isHelium, and about 0.1% are heavierelements as mentioned before. Nebulae areamong the largest objects in space. In fact,many Nebulae are at least dozens, if nothundreds of light years wide. There are alsofive different types of Nebulae, EmissionNebulae, Reflection Nebulae, Dark Nebulae,Planetary Nebulae, and Supernova Nebulae.By the way, Planetary Nebulae have nothingto do with planets! The Eagle Nebula
  • 4. Nebula to StarIn order for the new-born Star to go froma Nebula to a Star, it must reach a criticalMass of approximately 80 times Jupiters,due to accretion of matter. Once thisoccurs, the internal pressure raises thecore temperature high enough to beginnuclear fusion. Dust, gas, and othermaterials gradually wait in the Nebula forany gravitational disturbance to passthrough or by the Nebula. Once thishappens, it causes ripples and a processcalled accretion. Accretion is growth insize or extent. This means the Stars growlarger.
  • 5. StarA Star is a bright globe of gas whichproduces heat and light by nuclearfusion. Stars consist mostly ofHydrogen and Helium. Surfacetemperatures of a Star vary from2000o C to 30,000o C, depending uponthe content and size of the Star. The A Star named Electrahottest Stars tend to be a blue-whitecolor while red Stars are typically thecooler Stars. The smallest Masspossible for a Star is 155950.3608kgbecause if it is any less, nuclearfusion can not occur, thereforecausing the object to become a very Our Sundim object, or very large planet.
  • 6. Star to Red GiantAs a few billion years pass, a Starruns out of its protons. The result isa core left with alphas. Even thoughthe outer layers still containHydrogen, they arent hot enough tofuse. Without fuel, the Star beginsto cool and contract. The outerlayers sink into the core due toGravity, which causes them to heatup. The Star now has a source ofenergy. The core is now hotter thanit was during its normal life. Theheat causes the Star to swell andexpand. By the time the radiationreaches the surface of the Star, ithas become weak. Weak radiation A Red Giant is a bright, immense Starmakes the Star red, as the Star with a low mass nearing the end of itsgrows huge. I think its obvious evolution.where they got the name from.
  • 7. Red GiantRed Giants are very bright, redStars (hence the name) that arenot very hot. Red Giants literallyblow up like a balloon because allof the Helium that it possesses.The size of a Red Giant can be 10to 100 times the diameter of ourSun. Red Giants of, formerly, Betelgeuse (a Red Giant in thelarge Stars are sometimes called constellation Orion)Super Giants and can be up to1000 times the diameter of ourSun. They also have luminositiesof often 1,000,000 times greaterthan that of our Sun.
  • 8. Red Giant to White DwarfOnce a small Red Giant runs out of fuel,it begins to cool down and contract dueto gravity. The inner parts of the Starcontract which gives off heat and causesthe outer parts to expand. Theexpansion of the outer parts causesthem to slowly separate and form aPlanetary Nebula. The inner parts of thestar continue to contract until it reachesthe size of Earth. Electrons begin tooverlap due to the atoms being crushed This picture depicts the Suntogether. Since two Electrons cannot as a white dwarf star and thetake up the same space, they begin to Sun now. The size difference is quite obvious.repel. This forms a small sphere ofmatter, which is called a White-Dwarfstar.
  • 9. White Dwarf A White Dwarf is a verysmall, hot Star and is thelast stage of the life cycle for a Star such as our Sun. White Dwarfs have a similar mass to our Sun,except a White Dwarf is about 1% of the Suns diameter. Approximately, Comparison between Earth and a a White Dwarf is the size of Earth. White Dwarf White Dwarfs have a surface temperature of 8,000o C or more, but being small and hot costs the White Dwarf a bright luminosity. White Dwarfs have the luminosity of 1% of our Suns luminosity. A White Dwarf in Space
  • 10. Red Giant to SupernovaMost small Red Giants die as a WhiteDwarf, but the massive Red Giants diein a more spectacular way, aSupernova. After the fuel in a RedGiant is exhausted, the core becomescooler and the internal pressure beginsto decrease, causing contraction. Formassive Red Giants, this is a disastrousevent which leads to the collapsing ofthe Star. The outer layers start to gainheat as they fall. This heat ignitesnuclear fusion in the outer layers This is Keplers Supernova. This Supernova occurred inwhich causes them to explode. This is the Milky Way and is thecalled a Supernova. For a few days, most recent Supernova tothis explosion is brighter than a whole be seen by the naked eye.galaxy!
  • 11. Supernova A Supernova is an explosive death of a massive Star. At its height, a Supernova can be as bright as 100 million bright Stars. Supernovae have been accounted for creating heavier elements than Hydrogen and Helium. Over the years, two types of Supernovae have been found. Keplers Supernova.Type I: A Supernova which happens in a binary star system. It occurs by gas from one Star falling onto a White Dwarf, causing it to explode.Type II: A Supernova which occurs when a humongous star, at least ten times more massive than our Sun, explodes because of malfunctioning internal nuclear reactions towards the end of its life. These large explosions either create a Neutron Star or a Black Hole. A Supernova captured in real time in August of 2006 through a gamma telescope.
  • 12. Supernova to Neutron Star After the spectacular explosion of aSupernova, the outer layers are blastedoff into space and form a Nebula. Thecore is shrunk by gravity and condensedinto a sphere shape approximately thesize of Manhattan. TheElectromagnetic(EM) force keeps theelectrons out of the nucleus. Since theEM force is the only thing that matters,the Star wouldnt be able to shrink tosuch a size simply because of the Massand number of atoms. However, because A Neutron Star is formedof the Stars Mass, Gravity defeats the EM when a massive Starforce. Since the EM force is now broken, collapses, or in this case,the protons and electrons combine to explodes.make neutrons. All that is left areneutrons, and the Neutron Star is formed.
  • 13. Neutron StarNeutrons Stars are stars that are mostly made up of Neutrons, hence the name,and areproduced by the massive explosion of a Supernova. Neutron Stars are very dense, thereforethey have a larger Mass compared to Stars such as our Sun. Typical Neutron Star have a Mass A Neutron Star namedof three times our Suns, but a diameter of only 20 km! If the Mass of a Neutron Star is greater RS 9862-81-8-9325421- 0 A.than 3 times that of our Suns, then the gravity will be so strong that it will shrink into itselfand become a Black Hole. The remains of a Supernova with a Neutron Star in the middle.
  • 14. Supernova to Black HoleAs we just learned, a Neutron Star is madefrom a Supernova explosion. Also, NeutronStars can create Black Holes. If the NeutronStar becomes too big, the gravitationalforces become too much for the pressuregradients and the collapse cannot bestopped. The Neutron Star continues toshrink until finally it becomes a Black Hole.
  • 15. Black Holes Little is known about BlackHoles, not even their Density. Ofthe information that we do knowabout them, Black Holes are theremnants of the most massiveStars in the universe. The Cygnus X-1, a Black Hole which is located 6,070 light years away.gravitational pull of a Black Holeis so great that nothing canescape from it, not even light,therefore they are black.BlackHoles are believed to distort thespace around them, and also suckin surrounding objects. The youngest Black Hole hole known to man, SN1979C.
  • 16. Work CitedStages of a Star- The Life Cycle of a Star [Internet]. cited 2012 Jan 3] . Available from: Nebulae [Internet]. cited 2012 Jan 3] . Available from: Birth of a Star- Tangen KT, Weiss MW. Life Cycle of a Star [Internet]. Mohegan Lake(NY):Oracle ThinkQuest; cited 2013 Jan 3] . Available from: to Star- Stellar Birth [Internet].[2006 Jan 7, cited 2013 Jan 3] . Available from: to Red Giant- Seagrave WK. Red Giant [Internet]. :Penny Press Ltd.; [2012, cited 2013 Jan 3] . Available from: