Describe the stages in thelife of a Sun-like star, from its birth in the ISM to its ultimate collapse to a?
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The conversion of light elements into heavy elements, hydrogen into helium and on right up to iron, by atomic fusion. This is how a star shines. When the iron stage is reached the Sun has run out of fuel and the equilibrium between thermal forces and gravity is lost and gravity wins, resulting in the collapse into a white dwarf after going Nova and spreading its heavy elements into space. That's right we are all made of star stuff! JULES
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Heres a web site that discusses the fate of stars of 20 solar masses and up:\n\nhttp://observe.arc.nasa.gov/nasa/space/stellardeath/stellardeath_3.html
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It's going to be difficult to tell you more than I know, but I'll give it my best shot.\n\nThe sun is big and bright and hot.  It is a giant fusion reactor creating energy by fusing atoms of matter together.  The energy is transmitted out into space as photons of light.\n\nIt is a medium sized yellow star which began making energy about 4 billion years ago and is estimated to have about 5 billion years left before its fuel begins to run out.
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No, main sequence stars (like our sun) last for about 10 billion years. It has lived for about 5 billion years or so, which means the sun has another 5 billion more years to live. After those 5 billion years are over the fusion process is stopped (due to the lack of hydrogen). The star collapses on itself and makes the star even hotter. All that heat fuses the helium and the star expands into a red giant. It will last in this form for another 100 million years or so. Then the outer layers of the red giant comes of creating a planetary nebula. Then after that gas is gone all that is left is the hot core or the white dwarf. The white dwarf cools and becomes a cold dead core (Black Dwarf)
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The Sun's current age, determined using computer models of stellar evolution and nucleocosmochronology, is thought to be about 4.57 billion years.[4]\n\nThe Sun is about halfway through its main-sequence evolution, during which nuclear fusion reactions in its core fuse hydrogen into helium. Each second, more than 4 million tonnes of matter are converted into energy within the Sun's core, producing neutrinos and solar radiation. The Sun will spend a total of approximately 10 billion years as a main sequence star.\n\nThe Sun does not have enough mass to explode as a supernova. Instead, in 4-5 billion years, it will enter a red giant phase, its outer layers expanding as the hydrogen fuel in the core is consumed and the core contracts and heats up. Helium fusion will begin when the core temperature reaches about 3×108 K. While it is likely that the expansion of the outer layers of the Sun will reach the current position of Earth's orbit, recent research suggests that mass lost from the Sun earlier in its red giant phase will cause the Earth's orbit to move further out, preventing it from being engulfed. However, Earth's water and most of the atmosphere will be boiled away.\n\nFollowing the red giant phase, intense thermal pulsations will cause the Sun to throw off its outer layers, forming a planetary nebula. The only object that remains after the outer layers are ejected is the extremely hot stellar core, which will slowly cool and fade as a white dwarf over many billions of years. This stellar evolution scenario is typical of low- to medium-mass stars.[5][6]
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(1) white dwarf (...how our own sun will end up)\n(2) neutron star (...almost but not quite a black hole)\n(3) black hole
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the sun will eventually become a white dwarf, but the most violent explosive event may be the helium flash.  this occurs after the sun's core have compressed and heated and its outer layers have expanded and cooled and helium fusion begins.
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The Sun, in 4.5 billion years supposedly, WILL start to swell. It will get bigger, and en-gulp Mercury and Venus. The atmosphere will evaporate, water will melt, and life will be gone. The sun will swell enough to devour the earth, then shrink, grow, Turn into a planetary nebula, then shrink, for the last time, into a white dwarf. Then In a few billion years, cool down to a black dwarf.\n\nThe reason the sun expands, In case you want to know, Is because of its fuel supply. The energy from the sun comes from nuclear fusion of Helium. When the helium supply runs out, The sun has to fuse hydrogen, therefore making the sun swell. The sun then will Shrink, once its helium supply is restored, grow again, then cast out a planetary nebula (For what a planetary nebula looks like, Look up the ring nebula) then it wont have enough hydrogen to grow back to the normal size...and become a white dwarf. Eventually, it will cool into a black dwarf and die.
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sun....its a star btw but there are stars bigger than the sun
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Our Sun will "burn out" in about 4.5- to 5.0-billion years from now.\n\nRight now the Sun is converting hydrogen into helium at a rate of some 600-MILLION metric tons per second. Once this main fuel source is exhausted, the Sun will begin fusing helium, and once that's gone it will "burn" progressively heavier and heavier elements. Each change in fuel will be accompanied first by a diminishment in size, then a period of swelling. Mercury, Venus, and Earth will be consumed. Finally nothing but iron will be left to burn in the Sun, and since the energy required for that is higher than the Sun can generate, it will gradually dwindle more and more in size until it will become what's called a 'white dwarf' star.
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The star begins as a cool cloud of gas, well to the right Under its own gravity, the cloud begins to collapse. As it collapses, it releases its gravitational energy as radiation. So a young star is cool but bright. We usually don't see these proto-stars, however, because they are generally shrouded in dust and only give off light in the far infrared part of the spectrum. \n\nThe proto-star continues to collapse, and as it does, it gets hotter and hotter. "Stars" less than a percent of the Sun's mass eventually halt their collapse due to gas pressure. These stars are "brown dwarfs" or "giant planets," like Jupiter. They never ignite their hydrogen, and gradually dim away.\n\nStars larger than about 0.05 to 0.07 solar masses contract, getting hotter and hotter, until their cores are hot enough to begin burning hydrogen. When a star "turns on" its hydrogen-burning phase, we say that it has reached the main sequence, and is a true star, not a protostar, brown dwarf, or planet. The main sequence is a line of stars plotted on the HR-diagram, which represent stars which are burning hydrogen, fusing it into helium. The fusion process in the core releases heat and light, supporting the star against further gravitational collapse, and making it shine. Stars spend most of their life in one spot on the main sequence. Very massive stars live at the top of the main sequence, shining very blue and very bright, while low-mass stars are dim and red. The sun is between these two extremes. \n\nEventually, the hydrogen in the core whose fusion supports the star begins to run out. The core becomes mostly helium (the product of hydrogen fusion), and hydrogen burning moves out away from the core, forming a burning shell around the core. When this happens, the core begins to collapse again, but the outer regions of the star are pushed outwards. The star becomes brighter and cooler. This is the Red Giant stage. When the sun reaches the Red Giant stage, 5 billion years from now, it will likely grow to engulf Mercury, Venus, and the Earth. \n\nIf the star has little mass, it may end its life here, throwing off its outer layers, creating a planetary nebula out of its atmosphere, and a hot, dense "white dwarf" out of its core. The white dwarf shines only by residual left-over heat, and will eventually fade into a mere cinder. Cores of stars at least half as massive as the sun, however, will eventually collapse and heat enough to start burning helium in their cores. Once helium-burining starts, the star decends the giant branch again, reverses its swelling a bit, and lives happily fusing helium in its core, and hydrogen in a shell around the core. \n\nThen the giant dance begins again. The core helium runs out, and the star once again becomes a red giant. Stars like the sun get off the bus here, and become planetary nebulae and white dwarfs. Heavier stars begin burning carbon. This happens over and over again with heavier and heavier elements. The star ascends and descends the giant branch many times. Lighter stars that don't get hot enough in their cores to burn the next element become planetary nebulae and white dwarfs. Stars that are heavy enough eventually heat their cores enough to begin the next stage of burning and descend the giant branch for a while. For each element, the process is quicker and quicker. A star might burn Hydrogen on the main sequence for billions of years, but once this process gets to, say, silicon, the star might burn silicon for only a few days. \n\nA very massive star, more than 5-10 times solar mass, will ascend and descend the giant branch many times, until the star is ready to burn iron. But iron fusion doesn't release energy; it sucks it up. So what happens is that the star is ascending the giant branch, its iron core is collapsing and heating, until iron is ready to fuse. As soon as it does, though, it absorbs all of the heat around it, chilling the core. A
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...when it has degenerated & becomes dead.\n\nA white dwarf is what stars, like our Sun, become when they have exhausted their nuclear fuel. Near the end of its nuclear burning stage, such a star expels most of its outer material (creating a planetary nebula), until only the hot core remains, which then settles down to become a very hot (T > 100,000K) young white dwarf. Since a white dwarf has no way to keep itself hot unless it is accreting matter from a nearby star (see Cataclysmic Variables), it cools down over the course of the next billion years or so. Many nearby, young white dwarfs have been detected as sources of soft X-rays (i.e. lower-energy X-rays); recently, soft X-ray and extreme ultraviolet observations have become a powerful tool in the study the composition and structure of the thin atmosphere of these stars.\n\nA typical white dwarf is half as massive as the Sun, yet only slightly bigger than the Earth. This makes white dwarfs one of the densest forms of matter, surpassed only by neutron stars.\n\nBecause a white dwarf is no longer able to create internal pressure, gravity unopposedly crushes it down until even the very electrons that make up a white dwarf's atoms are mashed together. In normal circumstances, identical electrons (those with the same "spin") are not allowed to occupy the same energy level. Since there are only two ways an electron can spin, only two electrons can occupy a single energy level. This is what's know in physics as the Pauli Exclusion Principle. And in a normal gas, this isn't a problem; there aren't enough electrons floating around to completely fill up all the energy levels. But in a white dwarf, all of its electrons are forced close together; soon all the energy levels in its atoms are filled up with electrons. Well, if all the energy levels are filled, and it is impossible to put more than two electrons in each level, than our white dwarf has become degenerate. For gravity to compress the white dwarf anymore, it must force electrons where they cannot go. Once a star is degenerate, gravity cannot compress it any more because quantum mechanics tells us there is no more available space to be taken up. So our white dwarf survives, not by internal combustion, but by quantum mechanical principles that prevent its complete collapse.\n\nDegenerate matter has other unusual properties; for example, the more massive a white dwarf is, the smaller it is! This is because the more mass a white dwarf has, the more its electrons must squeeze together to maintain enough outward pressure to support the extra mass. There is a limit on the amount of mass a white dwarf can have, however. It was found by Subrahmanyan Chandrasekhar to be 1.4 times the mass of our Sun, and is is call the "Chandrasekhar limit" after its discoverer. \n\nWith a surface gravity of 100,000 times that of the earth, the atmosphere of a white dwarf is very strange. The heavier atoms in its atmosphere sink and the lighter ones remain at the surface. Some white dwarfs have almost pure hydrogen or helium atmospheres, the lightest of elements. Also, the very strong gravity pulls the atmosphere close around it in a very thin layer, that, if were it on earth, would be lower than the tops of our skyscrapers! \n\nUnderneath the atmosphere of many white dwarfs, scientists think there is a 50 km thick crust, the bottom of which is a crystalline lattice of carbon and oxygen atoms. One might make the comparison between a cool carbon/oxygen white dwarf and a diamond! (After all, a diamond is just crystallized carbon!)
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Usually what happens is a large event such as a supernova will destroy an old star, kicking out elements. Here's how it's believed to have happened before this solar system was formed, since it's believed that the sun is only a 500 million years older than the planets:\n\nWhen a star is about to die, its last stages of life consume a lot of different materials (this is assuming this star is large enough to create a supernova).  When it runs out of hydrogen, it begins to fuse helium, when that runs out, it goes to lithium, then on down the periodic table, until iron, which requires too much energy to fuse, and the fusion within the star ceases.  What happens here is tight . . . lets establish this first:\n\nStars are composed of mostly hydrogen and helium, little bit of lithium, and much much less of the heavier elements . . .  \n\nWhen the iron is left to fuse and it can't be done, the internal pressure from the core, which is generated by fusion, is lost, and the top shell of the sun is left to be supported but, since the fusion pressure has ceased, there's nothing to keep it up, and the outer shell of the star collapses.  This massive collapse of all that material to the leftover core compresses the inward falling material, increasing pressure and when that material hits the inner core, it 'bounces' back out violently, releasing massive amounts of energy, shooting the entire outer portion of the star into space. This is the moment in which heavy elements are made, in supernova events. The universe at one point did not have much by way of heavy elements, but as more and more stars collapse and supernova, they create more and more heavier elements; the origin of the diversity of the periodic table is here.\n\nFrom this you could assume, that as the universe gets older, stars are going to be creating and spitting out more and more heavy elements, and since stars cannot really use heavier elements to fuse, the number of stars over billions of years will slowly start to decline.
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Birth and death of stars is an interesting subject, IMO.\n\nHere are some starting points:\n\nhttp://en.wikipedia.org/wiki/Star\nhttp://en.wikipedia.org/wiki/Hertzsprung-Russell_diagram\nhttp://en.wikipedia.org/wiki/Supernova\nhttp://aspire.cosmic-ray.org/labs/star_life/starlife_main.html\nhttp://www.windows.ucar.edu/sun/Solar_interior/Nuclear_Reactions/Fusion/Fusion_in_stars/star_life.html
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main sequence stars are at their most stable, during their main sequence lifetime when they are just burning hydrgen\n\nhope this is as specific as you need.
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The Sun moves quite fast around the center of our Galaxy, at a speed of about 800,000 kilometers per hour (500,000 miles per hour).  Even still, it takes the Sun about 250 million years to complete one orbit!\n\nA few years ago, the most massive star was the Pistol star.  It's about 100 times more massive than the Sun is.  In fact, any star that massive won't be stable.  The Pistol star got its name because it is the source of the Pistol nebula - the Pistol star is unstable and is constantly blowing off material, material we see as the Pistol nebula.\n\nWhen a star begins to "die" it expands into a red giant or red supergiant.  The largest (in size) supergiants can be larger than the size of Jupiter's orbit.  Such a star won't last too long (only a few million years, if that) before it explodes as a supernova.
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The sun is the closest star to Earth.