I Need the Precise Size of An Average Supergiant Star?
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Size of Star depends on how it was formed originally. I don't think it could be said precisely. U can take the size of our sun as a measure. Radies=6400kms
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This should help you:  http://www.le.ac.uk/physics/faulkes/web/stars/o_st_overview.html
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All kinds of answers.  A red supergiant will go supernova, then leave you with either a neutron star or black hole.\n\nA red giant turns into a white dwarf.
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A basic observable quantity for a star is its brightness. Because stars can have a very broad range of brightness, astronomers commonly introduce a logarithmic scale called a magnitude scale to classify the brightness.\nThe Magnitude Scale:\nThe magnitudes m1 and m2 for two stars are related to the corresponding brightnesses b1 and b2 through the equation:\nm1-m2=2.5(logb1-logb2)=2.5log(b1/b2)\nwhere "log" means the (base-10) logarithm of the corresponding number; that is, the power to which 10 must be raised to give the number. Because this relation is logarithmic, a very large range in brightnesses corresponds to a much smaller range of magnitudes; this is a major utility of the magnitude scale.\nThe preceding equation gives us a way to relate the magnitudes and brightnesses of two object, but there are several ways in which we could specify the brightness and this leads to several different magnitudes that astromers define. One important distinction is between whether we are talking about the apparent brightness of an object, or its "true" brightness. The former is a convolution of the true brightness and the effect of distance on the observed brightness, because the intensity of light from a source decreases as the square of the distance (the inverse square law). The apparent magnitude of an object is the "what you see is what you get" magnitude. It is determined using the apparent brightness as observed, with no consideration given to how distance is influencing the observation. Obviously the apparent magnitude is easy to determine because we only need measure the apparent brightness and convert it to a magnitude with no further thought given to the matter. However, the apparent magnitude is not so useful because it mixes up the intrinsic brightness of the star (which is related to its internal energy production) and the effect of distance (which has nothing to do with the intrinsic structure of the star).Clearly, a star that is very bright in our sky could be bright primarily because it is very close to us (the Sun, for example), or because it is rather distant but is intrinsically very bright (Betelgeuse, for example). It is the "true" brightness, with the distance dependence factored out, that is of most interest to us as astronomers. Therefore, it is useful to establish a convention whereby we can compare two stars on the same footing, without variations in brightness due to differing distances complicating the issue. \nAstronomers define the absolute magnitude to be the apparent magnitude that a star would have if it were (in our imagination) placed at a distance of 10 parsecs (which is 32.6 light years) from the Earth. I can do this if I know the true distance to the star because I can then use the inverse square law to determine how its apparent brightness would change if I moved it from its true position to a standard distance of 10 parsecs. There is nothing magic about the standard distance of 10 parsecs. We could as well use any other distance as a standard, but 10 parsecs is the distance astronomers have chosen for this standard. A common convention, and one that we will mostly follow, is to use a lower-case "m" to denote an apparent magnitude and an upper-case "M" to denote an absolute magnitude. \nNotice the very important point that I can determine the apparent magnitude m of a star simply by measuring how bright it appears to be, but to determine the absolute magnitude M the distance to the star must also be known. As we shall see, determining distances to stars is a quite non-trivial matter in the general case.You might think that introducing the apparent and absolute magnitudes would resolve ambiguities about what we mean when we refer to the brightness of a star, but there is a further complication. The brightness of an object (whether apparent or absolute) depends on the wavelength at which we observe it, as we saw clearly in the discussion of
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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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I googled "biggest star" and the first hit was the one below. The answer is the Pistol Star, which I never heard of before. Wikipedia also mentions Eta Carinae, which I have heard of before.
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type of star\nspectral type\ndistance from star to Earth
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Many stars are between 1 billion and 10 billion years old. Some stars may even be close to 13.7 billion years old, which is the observed age of the universe. (See Big Bang theory and stellar evolution.) They range in size from the tiny neutron stars (which are actually dead stars) no bigger than a city, to supergiants like the North Star (Polaris) and Betelgeuse, in the Orion constellation, which have a diameter about 1,000 times larger than the Sun—about 1.6 billion kilometers. However, these have a much lower density than the Sun.\n\nOne of the most massive stars known is Eta Carinae, with 100–150 times as much mass as the Sun. Recent work by Donald Figer, an astronomer at the Space Telescope Science Institute in Baltimore, Maryland, suggests that 150 solar masses is the upper limit of stars in the current era of the universe. He used the Hubble Space Telescope to observe about a thousand stars in the Arches cluster, a massive young star cluster near the core of the Milky Way, and found no stars over that limit despite a statistical expectation that there should be several. The reason for this limit is not precisely known, but the Eddington limit is part of the answer. The very first stars to form after the Big Bang may have been larger, up to 300 solar masses or more, due to the complete absence of elements heavier than lithium in their composition. This generation of supermassive stars is long extinct, however, and currently only theoretical.\n\nWith a mass only 93 times that of Jupiter, AB Doradus C, a companion to AB Doradus A, is the smallest known star undergoing nuclear fusion in its core. Smaller bodies are brown dwarfs, which occupy a poorly-defined grey area between stars and gas giants. The minimum mass a star can have is estimated to be in the vicinity of 75 Jupiters.
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The only way that I know to do this with a normal telescope is to compare the star with others nearby of known magnitude and try to decide if it's brighter or dimmer until you find the same.\n\nOtherwise you'd need to measure the amount of light that comes from it, and I think you need computers to do that.\n\nThe magnitude scale is exponential, so deciding a magnitude ain't that simple. (ie a star of magnitude +2 is ten times brighter than a star of magnitude +3)
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The offical SI base unit would be meters. \n\nProbably centimeters works best for an average plant.
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You don't really need the Star's speed, only it's spectral class. The spectral classes are O, B, A, F, G, K and M, with O being the brightest and M the dimmest. If you know how bright the star is intrinsically from it's spectral class, then you can calculate how far away it is from it's apparent brightness in the sky. But this method if fraught with difficulties. Red giants and white dwarfs are off the main sequence of stars. That means that a red star may be much brighter that it's spectral type would indicate and a white dwarf is much dimmer than it's spectral class would indicate. Also, there may be interstellar dust and gas between you and the star that makes it look dimmer that it would through clear space. But if you are careful, all these factors can be taken into account and you can get an approximate distance.\n\nFor the distance to a remote galaxy that is too far away for individual stars to be seen, the red shift of the overall glow of the galaxy can be measured and used to determine the galaxies radial velocity, or the speed at which it is moving away from you. Multiplying that by the Hubble constant gives you an approximate distance.\n\nIf you want a really accurate distance to a star, the only sure way is by measuring it's parallax. But this can only be done for comparatively nearby stars. The Hipparcos satellite measured thousands of stellar parallaxes to a precision not obtainable from the ground, and the catalog is freely available online.
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It depends on how massive the star is:\n\nFor stars of less than 8 times the mass of the sun:\nMain Sequence -> Red Giant -> (planetary nebula)-> White Dwarf\n\nFor stars with 8 to about 18 times the mass of the sun:\nMain Sequence -> Red Giant -> (supernova) -> Neutron Star\n\nFor stars with more than about 18 times the mass of the sun:\nMain Sequence -> Red Giant -> (supernova) -> Black Hole\n\nNote that for the massive stars I've simplified things into the "red giant" term, high mass star evolution is pretty complex, and many high mass stars can transition between red and blue supergiants several times during ther brief lives.
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click first here:http://en.wikipedia.org/wiki/Sagittarius_%28astrology%29
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Largest Star (By Size) - VV Cephei - 1900 times diameter of sun\n\nMost Luminous Star - LBV 1806-20 - 40,000,000 times luminous than the sun\n\nHowever, the brightest objects in our universe are the quasars... Check the links below for more info\n\nI hope these were the answers u were lookin for...
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Our sun is solidly in the average category. The exact average star is about 1,000,000 miles in diameter.\n\nMany other stars are spectacularly larger or smaller.\n\nThe lifespan of larger stars is shorter.  Srars become brighter at the end of their life, when hydrogen nuclei have been exhausted.  \n\nWhen stars become supernovae, other elements are created, the last one being iron, and much material is blown off.\n\nThen you have a dying monarch of light.  Red and white drwarfs.\n\nSites for stellar evolution info:\nhttp://search.yahoo.com/search?fr=ks&p=stellar+evolution\n\nOur sun has a remaining life span at current luminosity of 25 billion years.  That should give us enough time to figure out what to do when it goes into the ending processes.\n\nDetailed information about our sun and neighborhood:\nhttp://www.urantia.org/papers/toc.html\ngo to Paper 41 and Paper 57
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You'd need either the OFFICIAL name/designation of the star, or its celestial coordinates (right ascension and declination). Even then, you may have picked a star that's never been catalogued and there'd be no data on it. If you do have the star's celestial coordinates, try this website --> http://www.telescope.org/\n\nThe website gives free access to their telescope so that users can remotely photograph celestial objects they're interested in.
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This sounds like a homework question?  Maybe I shouldn't give you the whole answer, so you can learn something on your own.\n\nYou are describing a Cassegrain telescope.  You can use the mirror formula to calculate the image plane for the first optic (the concave mirror) and then use that as the object plane for the second optic (the convex mirror) to get your final focal image plane.\n\nMirror Equation:  (1/So) + (1/Si) = -2/R\n\nSo = object plane (distance from object to mirror)\nSi = image plane (distance from image to mirror)\nR  = radius of curvature of mirror\n\nThe hardest part of these calculations is to use the right sign convention and to remember that the stars (initial object plane) can be treated as at infinity.