What determines the magnitude of stars?
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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 spectrum indicates the chemical composition of each star. As the chemical composition changes, the spectrum changes. However, because of the huge mass of stars, these changes are so slow they are not being "observed" by human astronomers. The relative velocity between each star and us is responsible for a shift of the whole spectrum. If a star is "approaching us", the spectrum is shifted towards the blue part of the spectrum. If the star "moves away" the spectrum is redshift.
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The best way to compare other stars to the sun is to talk in terms of\n\nTheir size: how many solar diameters are they?\nTheir mass: how many solar masses are they?\nTheir brightness: how does their luminosity compare to the sun = 1?\n\nMorgan-Keenan spectral classification\nThis stellar classification is the most commonly used. The common classes are normally listed from hottest to coldest (with mass, radius and luminosity compared to the Sun) and are: \n\nClass Temperature Star colour Mass Radius Luminosity \nO 30,000 - 60,000 K Bluish ("blue") 60 15 1,400,000 \nB 10,000 - 30,000 K Bluish-white ("blue-white") 18 7 20,000 \nA 7,500 - 10,000 K White with bluish tinge ("white") 3.2 2.5 80 \nF 6,000 - 7,500 K White ("yellow-white") 1.7 1.3 6 \nG 5,000 - 6,000 K Light yellow ("yellow") 1.1 1.1 1.2 \nK 3,500 - 5,000 K Light orange ("orange") 0.8 0.9 0.4 \nM 2,000 - 3,500 K Reddish orange ("red") 0.3 0.4 0.04 \n\nThese classes are further subdivided by Arabic numerals (0-9). A0 denotes the hottest stars in the A class and A9 denotes the coolest ones. The sun is classified as G2.\n\nSpectral types\n\nClass O\nClass O stars are very hot and very luminous, being bluish in colour; in fact, most of their output is in the ultraviolet range. These are the rarest of all main sequence stars, constituting as few as 1 in 32,000. O-stars shine with a power over a million times our Sun's output. \n\nExamples: Zeta Puppis, Epsilon Orionis \n\nClass B\nClass B stars are extremely luminous and blue. As O and B stars are so powerful, they live for a very short time. They constitute about 0.13% of main sequence stars -- rare, but much more common than those of class O.(\n\nExamples: Rigel, Spica \n\nClass A\nClass A stars are amongst the more common naked eye stars. As with all class A stars, they are white or bluish-white. They comprise perhaps 0.63% of all main sequence stars.\n\nExamples: Vega, Sirius \n\nClass F\nClass F stars are still quite powerful but they tend to be main sequence stars. Their colour is white with a slight tinge of yellow. These represent 3.1% of all main sequence stars.\n\nExamples: Canopus, Procyon \n\nClass G\nClass G stars are probably the best known, if only for the reason that our Sun is of this class. Supergiant stars often swing between O or B (blue) and K or M (red). While they do this, they do not stay for long in the G classification as this is an extremely unstable place for a supergiant to be. These are about 8% of all main sequence stars. \n\nExamples: Sun, Capella \n\nClass K\nClass K are orangish stars which are slightly cooler than our Sun. Some K stars are giants and supergiants, such as Arcturus while others like Alpha Centauri B are main sequence stars.  These make up some 13% of main sequence stars.\n\nExamples: Arcturus, Aldebaran \n\nClass M\nClass M is by far the most common class if we go by the number of stars. All the red dwarfs go in here and they are plentiful; over 78% of stars are red dwarfs, such as Proxima Centauri. M is also host to most giants and some supergiants such as Antares and Betelgeuse, as well as Mira variables. \n\nThe red color is deceptive; it is because of the dimness of the star. When an equally hot object, a halogen lamp (3000 K) which is white hot is put at a few kilometers distance, it appears like a red star.\n\nExamples: Betelgeuse, Barnard's star \n\nSpectral types for rare stars\nA number of new spectral types have been taken into use for rare types of stars, as they have been discovered:\n\nW: Up to 70,000 K - Wolf-Rayet stars. \nL: 1,500 - 2,000 K - Stars with masses insufficient to run the regular hydrogen fusion process (brown dwarfs). Class L stars contain lithium which is rapidly destroyed in hotter stars. \nT: 1,000 K - Cooler brown dwarfs with methane in the spectrum. \nC: Carbon stars. \nR: Formerly a class on its own representing the carbon star equivalent of Class K stars, e.g. S C
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You first need to apply a mass - luminosity relationship. I believe Kepler suggests M = k L^3.5. My results show Gamma:Delta luminosity ratio is 1:3184.\n\nAs for absolute magnitudes you need to log things I believe.\n\nYou will need m - M = -5 * 5Log(Distance)\n\nThis sounds like first year astrophysics coursework. You should attend workshops if you are having trouble.
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i believe it's the magnification (or other distortion such as increased brightness) of the appearance of a star in the sky or through a telescope. the diffraction can be eliminated digitally, but other than that i'm not sure.
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Mark sections that are the same size on a map.  You can do this by drawing 1 in. by 1 in. squares.  Then, find the number of stars in one part of the sky.  On the map, estimate the stars in other parts of the sky, using the sample you had taken.  Multiply the number of stars in the sky by the sections you have number of sections you have labeled on the map.
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science_FREAK, you think the furthest star is just 82 million km away????!!!  That wouldn't even take us out of our own solar system!  In fact, our star, the Sun, is 150 million km away!\n\nIf you mean why do some stars "appear" brighter than others, then that is because stars are at different distances from the Earth, and they are different sizes.  IF you had 2 identical stars, but one was twice the distance from the Earth that the other, then the further away one would appear much dimmer in the sky.\n\nBut all stars shine with a slightly different brightness, I doubt that any two are identical.  So the appearance of some stars being brighter than others is down to size of stars and how far away from us that they are.
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There is a surprisingly simple answer to your great question: Each month we see different stars, so to answer for a specific night of the year at your specific location on Earth depending on your eyesight and how bright the city lights around you are might be hard to pin down. \n However there is a magnitude scale that astronomers use to describe how bright objects in the sky are. Without getting into details on how that works, the average human being can see down to about magnitude 6 ( brighter objects have lower magnitude until you reach zero. Then even brighter objects use negative numbers for their magnitudes which is a bit weird, isn't it?) Therefore, all you have to do is get a map of the whole sky showing anything brighter than magnitude 6 and count the stars. If you are fortunate to be away from bright city lights and you can see the Milky Way, you would be really surprised to know that you can only see about 6,000 stars. That's the number of stars above magnitude 6 in the entire sky.
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The number I usually see quoted is 4000, but checking with Google.....\n\nFrom my suburban location, without optical aid, I can see down to about magnitude 5 on a really good night around 2am when there's little traffic and stores are closed.  That's about 2822 (actually less, since  I never see some southern hemisphere stars).  In my binoculars, I see down to magnitude 8, or 77,627 stars.\n\nNow, out in the country, a person with good eyes on a dark clear night can see down to magnitude 6, which is 8768 stars total.   A person with a 6-inch refractor telescope can see down to about magnitude 13, which gives 15,431,076 stars.\n\nOn the other hand, I read a book by an astronomer who said he could see down to magnitude 8 on top of Mauna Kea breathing oxygen from a tank.  That's 77,627 stars with no optical aid.\n\nNow-- for stars seen and unseen, there are about 400 billion stars in our galaxy.  \n\nIn the known universe?  The CNN story linked below says 70 sextillion.  That's 7 with 22 zeros.\n\nIn the whole universe, known and unknown?  Nobody knows--we do not even know if the universe is finite or infinite.  The number could be "infinity".
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Like the number of grains of sand on the beach or angels that can dance on the head of a pin, the number of stars in the sky remains a great unknown. Discussing the number of stars in the Milky Way alone, astronomer William Keel, writing for the sci.astro Galaxies FAQ, claims that there are "about as many as the number of hamburgers sold by McDonald's." \nThen he elaborates. The usual way to determine the number of stars in the universe is to consider how many stars there are in the Milky Way, and then to multiply that number by our best guesstimate at the number of galaxies in the universe. This FAQ suggests there are probably about 400 billion stars in the Milky Way, although "a 50% error either way is quite plausible." As for the number of galaxies in the universe, well that's a whole separate mathematical puzzle. \n\nOther star enumerators we located on the Web offer numbers ranging from more than 200 billion stars in our galaxy to 3 thousand million billion stars (3 followed by 16 zeroes), in the universe. NASA alleges there are zillions of uncountable stars.
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Well if you look at the spectrum of a star you'll see a smooth continuum as well as the spectral lines.  Those lines are either absorbtion lines or emission lines of such things as Hydrogen, Helium, Calcium, Iron and a whole heap of others and we know the wavelength of those lines very well so by comparing what we measure them to be with what we have determined in the lab we can calculate how fast the star is moving towards or away us (radial velocity).\n\nThen once we know the radial velocity we just measure where the peak in the continuum is, correct for the radial velocity to find what the wavelength where the emission actually peaks and then since the star is very close to a blackbody we can calculate the temperature (a blackbody of a given temperature will peak at a given wavelength).
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It's the same way that scientists look at all massive measures: density*volume.  The density (ie the number of stars per square lightyear) is assessed by counting the frequency of galaxies and the size of galaxies.  The mass of galaxies can be inferred by the speeds of rotaion, and the mass will give you an idea as to how many stars there are in the galaxy by looking at the average mass of a star.  Then you get a sense of how many galaxies are in a given volume of space.  They use this, and extrapolate from the size of space (set by the tenets of general relativity, the Big Bang theory, the red-shift observed speed of expansion, etc), and they can thereby infer how many stars there are in the universe.\n\nIt's like the mass of the earth.  We can't figure it out with 10 kilograms, or even 100 kilograms, but we can get an idea as to the magnitude of the mass.  With magnitude, i mean the number of digits to the left of the decimal place.  We call the difference between 10 and 100 "one order of magnitude," and the difference between 100 and 100,000 "three orders of magnitude."  Such scales are commonly used in science for things where exact numbers are impossible to get, but the range of magnitude is important.  Some such commonly known scales are the measure of sound in decibles, the Richter scale for earthquake power, and the pH scale for acidity.  With a pH of seven, one can infer that a liter of water has 3,344,000,000,000,000,000 hydronium ions per liter, whereas it only has 3,344,000,000,000,000 hydronium ions per liter at a pH of 10.  In these cases, the magnitude, rather than the exact number, is the matter of interest.\n\nIt's the same in counting stars.  We can't know the exact number of stars, especially since they constantly form and die--but we can get a pretty good idea as to the magnitude of the number by looking at stellar density and extrapolating the size of the universe.
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It sounds like you need three things\n\nA starting point for each star.\n\nA vector for each star (that takes care of direction and speed)\n\nGravity (The more dense a star is in relation too its mass the greater its gravitational pull)\n\nOnce you have worked out the specific gravity for each object (star) the only things that vary are the vector of each star and thus its new position.\n\nGood luck!! I know any gravitational calculation with three or more object gets very complicated very quickly.
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Several different ways depending on the distances involved.\n\nFor close stars, we look at where the star appears to be in the sky at times about half a year apart. Think of looking at your outstretched thumb through your left eye, and then your right eye. The thumb appears to be in a different position with respect to a distant building. In the same way, a star will appear to be in a slightly different position when we look at it from different ends of the earth's orbit. The amount of shift depends on the distance to the star and that allows us to figure out the distance. This method is called paralax.\n\nFor slightly more distant stars, we look at clusters of stars and measure their apparent motion across the sky over a course of *years*. Just as train tracks appear to converge at the horizon, the motions of the star will appear to converge. The rate of convergence is related to how far away the cluster is.\n\nWith these methods, we get enough stars to do statistical analyses of the brightness of the stars versus their chemical composition and other aspects of their spectrum. With this knowledge, we can estimate the distances to further stars by just comparing their spectrum to that of already measured stars. Scientific models of stars are used at this stage.\n\nFarther away than this, we look for 'standard candles', that is, stars of known brightness. By comparing the brightness they appear to be versus their actual brightness, we can estimate their distances. A particular type of 'standard candles' are the Cepheid variables. Their actual brightness depends on how fast they vibrate. Since we can see these stars in other galaxies, we can use them to determine the distances to those galaxies.\n\nFinally, after we know the ditances to some galaxies, we can measure the rate at which they move apart as a function of distance. By measure red-shift (hence speed) of more distant galaxies, we can determine their distances.
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You can try to count the stars, but there are as many stars in the Universe as there are grains of sand on the beach.  It would be a very difficult task and take millions of lifetimes to complete.  Sorry.
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not at all. its crazy. why would it matter under what set of stars you where born under to set your life? i think it more so depends on what you were given in life and raised then the stars.
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A Star's Size:\n\nA star begins its "life" in a contracting nebula of gas and dust. As the density of the material increases under the influence of gravity, compression heats the material. If the material gets hot enough, hydrogen atoms begin fusing together to form helium atoms, and a star is born. A star will spend most of its life, called the main sequence phase, fusing hydrogen into helium.\n\n  \nIt's logical that a large nebula (one with a large amount of mass) will form a large star, and a small nebula will form a small star. However, in addition to a star's initial mass, a star's size also depends on the balance between the inward pull of gravity and the outward push of the energy produced by fusion. The entire sequence of a star's evolution can be described in terms of the changing balance between these two opposing forces.