what is a planetary nebula, and how does it form?
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Planetary nebula are formed after a supernova explosion.\n The remains of a giant star that has consumed its fuel.
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A Planetary Nebula is a misleading name.  At the end of a lower mass star's life (for stars up to about 8 times the mass of the sun), the star puffs up, and loses the outer layers of gas surrounding it.  All this gas goes out into space where it can be seen as what we call a planetary nebula.\n\nOriginally the word "nebula" was applied to any astronomical object that was not a star or a memeber of our solar system (planets, asteroids etc), the word essentially means "cloud."\n\nAs telescopes got better people started to find many different types of nebulae. A Spiral Nebula looks like, well a spiral, today we know that these are spiral galaxies.  Planetary Nebula were named because the looked round, and a number of them had the same greenish color that Uranus had been seen to have by Hershel.
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We are all related.  You will see scientists, who mainly believe in the big bang theory, will often describe us as "stardust".  The reason for this is that when planetary nebula are being created, and a star results, the leftover matter from the new star is what planets condense from.  They are made of the same basic materials.  \n\nIn addition, every basic element on the periodic table from hydrogen to iron (including carbon; e.g. "carbon-based life forms" such as us) is naturally produced inside the sun, and every larger element can be produced from the same basic ingredients by other processes.  \n\nIt is no coincidence that we (and everything else) are made of the same elements as the rest of the solar system and much of the universe.
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Nubulas do not really have those wonderfull colors you see in photos made by the habbel telescope and such. Those colors are computer generated to facilitate recognizing the different regions and/or components of the nebulae.
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Astronomers, for the longest time, had been puzzled over some objects in the sky.  On photographic plates, there were stars, planetary nebulae, and some mysterious objects.  They wouldn't resolve themselves into singular stars.  And some of them were shaped like spirals.  This gave the mystery objects the name 'spiral nebulae'.  In the 1920s, Edwin Hubbell was examining one of those spiral nebulae called the 'Andromeda Nebula'.  He managed to find something that astronomers here had known for a while: a Cepheid variable.  This is a star that pulses very slowly.  These stars have very predictable pulsations.  The longer the pulsation period, the more bright the star is.  It's called the 'period-luminosity relationship'.  In any case, when he found a Cepheid variable, he was able to know what the absolute magnitude of the star should be.  So he was able to measure the apparent magnitude, and compare it to the predicted magnitude, and he got a distance of 2 million light-years (he used the distance modulus equation).  So he knew that this 'nebula' COULDN'T be in our galaxy, and that he had found a new 'island in the sky'.
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They start out as an enormous gas cloud. Gravity causes the parcicles in the cloud to spin around the point of center mass, and the velocity of the spin subsequently flattens it into a disk. That's how galaxies, and on a much smaller scale, planetary systems form.
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I am not quite sure what your asking.\n\nWhen the star is forming, it starts out as a gigantic cloud of mostly Hydrogen. As the stellar material coalesces, the material begins to heat up and the pressure at the center of what will become the new star increases dramatically.  The material becomes denser and is pulled together by its own gravity, heating up as the pressure rises.  Gravity is working to pull the star together, and eventually the ball of gas becomes so massive, that the pressure and heat at its core are sufficient to undergo nuclear fusion.  In order to counteract the force of gravity, the Hydrogen at the stars core undergoes fusion, in the process, producing Helium and a lot of energy.  It is this energy produced from nuclear fusion at the stars core that keeps the star from collapsing in on itself.
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Many of the most interesting infrared objects are associated with star formation. Stars form from collapsing clouds of gas and dust. As the cloud collapses, its density and temperature increase. The temperature and density are highest at the center of the cloud, where a new star will eventually form. The object that is formed at the center of the collapsing cloud and which will become a star is called a protostar. Since a protostar is embedded in a cloud of gas and dust, it is difficult to detect in visible light. Any visible light that it does emit is absorbed by the material surrounding it. Only during the later stages, when a protostar is hot enough for its radiation to blow away most of the material surrounding it, can it be seen in visible light. Until then, a protostar can be detected only in the infrared. The light from the protostar is absorbed by the dust surrounding it, causing the dust to warm up and radiate in the infrared. Infrared studies of star forming regions will give us important information about how stars are born and thus on how our own Sun and Solar System were formed.
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Actually the sun does not have enough mass to go supernova, after becoming a red giant its radius could actually get as big as earth's orbit, and once this happens it will lose its layers in what is called a "planetary nebula" which believe it or not has nothing to do with planets, and after this it will become a white dwarf and eventually burn out.
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First, our sun has a long time to go before it could possibly become a supernova, not for billions and billions of years, so don't worry about it, if you were worrying. OK?\n\nNow, the way a star burns is by fusion, which is building up heavier elements by fusing atoms of lighter elements together. The typical start starts out as hydrogen, and it fuses the hydrogens together into helium. \n\nWhat happens when a star runs out of hydrogen? It starts fusing the heliums together into heavier elements. In order to begin this process, the star has to contract, to squeeze everything together to make the core temperature hotter. \n\nNotice that when the star began to run out of hydrogen, it cooled off a little. So the temperature of the star fluctuates. Its size fluctuates too, since the heat energy partly counteracts the gravity that holds it together.\n\nSo, the star cools off a little, it contracts, and we call this a pulsating or variable star. (This is somewhat of an oversimplification; there are different types of variable stars. But I am ignoring them for purposes of this illustration.) Then the star begins fusing helium, and heats up again. The star expands. \n\nThe outer surface of the star explodes away in what we call a nova-- not a supernova, yet. Some of the gas rushes away and may form what is called a nebula, a cloud. some of thee nebulas give off pretty colors, because, just like a neon sign, the gas in them is excited by the energy of the star and glows.\n\nSo, after repeated cycles of this, and bazillions of years, the star is exhausted. When the star gets iron in its core, there is no turning back. You can't fuse iron into anything. \n\nBut, you say, what about those elements that are heavier than iron, like gold and mercury and uranium? Ah, I'm so glad you asked about that. That is where the supernova comes in. \n\nA supernova is the death of a star. A nova flares up and puts out lots of energy, but the supernova puts out as much energy as the star might have put out over its entire lifetime! The last time there was a supernova in our galaxy (the Crab Nebula was formed) in 1054 AD. The Chinese were the only ones whe were doing much astronomical observation then. \n\nBut it was visible in broad daylight! From LIGHT YEARS away!\n\nWhat happens is this: the star begins to contract one final time. Most of the star blows away, making a really, really impressive nebula. All the elements that were built up in the final explosion-- all the heavy elements beyond iron-- get flung out into space, where they might meet with other elements and form planets and things.\n\nWhat happens to the rest of the star? One of three things, depending on how big it is. If it is little, it may form a white dwarf, a little star that is not so big but is now mostly hydrogen and helium and will last a long time. I think they are supposed to expand into red giants when they are about to burn out, but I don't remember for sure. \n\nIf the star is medium sized, it may become a neutron star. It is no longer buring with fusion like a regular star. The nuclear particles in its core are squeezed together so that protons and electrons have lost their identities and everything is neutrons. This is as solid and dense as matter can get, neutronium. It has an incredibly strong magnetic field, bazillions of times anything on earth.\n\nThe star's axis of rotation may not line up with the magnetic poles (just the way Earth's magnetic poles are not right at the true north and true south poles.) If this hapens, and the magnetic poles are pointed in the right direction, then every time it points our way, we see a little 'flash' of magnetic energy, and we call these 'pulsars'. The first time anybody detected them, they thought they were radio signals from people in space, because they were so regularly-spaced. It is a good thing there are no pulsars near Earth, because the flashes of intense magnetic fields would fry us lik
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Up until the time that the earth started forming, the sun had time (I can't speculate, but probably a few billion years) to begin it's nuclear fusion and begin burning. Sol would have been surrounded by thick clouds of dust, ice and gases (see planetary nebulae). The particles of gas and dust began to clump together into larger and larger pieces and began spinning around the sun either falling in their maintainable orbits or falling back into the sun. These clumps continued to come together and the planets were formed in their respective distances around the sun.
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when a meteoroid enters the atmosphere and burns up it produces a meteor.\n\nhttp://en.wikipedia.org/wiki/Meteor
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During a supernova, all matter is reduced to its smallest particles.  The smallest being the electrons and Hydrogen ion(H+). At a signifigant distance from "Ground 0," there occures a cooling phenominom that is a naturalphysical event.  Thus heat is an extensive physical property of most matted.  At this point electrons and H+ begin unifying into Hydrogen atoms.  At an even greater point two Hydrogen atoms fuse to product a Helium atom.  So on and so forth.  When these select few elements getr far enough from, "Ground 0" they are cooled to the point that fussion is no longer a natural phenominon.  At this distance in this time, of the story, things like planets, astroids and meteors form in extremely large massed of these elements to form minerals.  When these stellar bodies form H2O (water) they are capable of forming gassious H2O, CO2, H2, O2 and vary importantly C-4.  This place is called Earth any you are there. For further tutorial an planetary evolution e-mail me at melecrs@yahoo.com
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The most abundant element in the universe is hydrogen.  Nebulae are made up most of that and "dust".
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Check the link below.  It can be formed through volcanic activity as well as crystallizing out of mineral rich water deposits.  It is almost pure iron that is oxidized.
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A little more specifically, meteorites contain little inclusions called "chondrules" which have not been melted and reformed since they first formed in the proto-planetary disk around our sun.  All rocks we find on Earth or any other world have been formed since that time; the "fingerprint" of what conditions were like in space before becoming part of a planet is lost. This is not the case for chondrules in meteorites.\n\nChondrules give us insight into the sorts of particles that were available for larger bodies (and eventually planets) to form from.\n\nYou can read about chondrules on wikipedia.\nhttp://en.wikipedia.org/wiki/Chondrule\n\nAsteroids are examples of the smallest gravitationally bound objects in the solar system.  These are possible building blocks of protoplanets (enough of them stick together and you can have enough gravity to start pulling dust and even gas right out of the proto-solar disk).  By understanding their characteristics, we can more accurately model the formation of protoplanets.
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No one knows.  It is believe it formed from photons of light.  However, scientist are not puzzled on how it happened but rather its byproducts, matter and anti-matter.  For every particle, there is an anti-particle.  In theory, if anti-matter comes in contact with matter, it cancels itself out.  Meaning, if anti-matter existed in our Universe, we wouldn't be here.  Our Universe seems to made only of matter.  So where is this anti-matter?  \n\nI read an article that there was some evidence to prove that matter pops into our Universe seemingly out of nowhere.  I wish i could find more information on it but I can't.  Below is an easy to read article.  It's all fascinating stuff and it is written in easy to understand language.  \n\nhttp://www.pbs.org/wnet/hawking/mysteries/html/gleiser-1.html\n\nhttp://www.pbs.org/wnet/hawking/html/