Is there proof that the red shift measures velocity of remote stars, and not also due to gravity red shifts?
596163
Yes there is.\n\nSupernova decay curves show the time dilation that would be expected from rapid motion (i.e. taking the redshift as a doppler velocity) so we know it isn't tired light.\n\nA lot of other methods of measuring distance have been developed and those are used to calibrate the redshift measurements (by finding the Hubble Constant).
811109
You misunderstand Einstein's Theory of Special Relativity. It doesn't say that you can't have something move faster than the speed of light. Only "information" can NOT move faster than the speed of light. By information, I mean any "signal", like electromagnetic waves (which includes light, radio waves, etc. etc.). Any material object within the Universe are also restricted by Special Relativity, since material objects also carry "information".\n\nFor the Universe or the fabric of spacetime to be expanding faster than the speed of light is NOT a violation of Special Relativity, and the Universe will not be moving backwards in time.\n\n--------------------------------------------------------\n\nEdit - Ok, here let me clarify why I said that Special Relativity (SR) does NOT apply to the expansion of the Universe:\n\nVelocity of something depends on which definition of distance we use. So, if we assume that the distance of an object at time t is the distance from our position at time t to the object's position at time t measured by a set of observers moving with the expansion of the Universe, and all making their observations when they see the Universe as having age t, then the velocity (change in D per change in t) can definitely be larger than the speed of light. This is not a contradiction of special relativity because this "distance" is not the same as the spatial distance used in SR, and the age of the Universe is not the same as the time used in SR.\n\nIn the special case of the "empty Universe", where one can show the model in both special relativistic and cosmological coordinates, the velocity defined by change in cosmological distance per unit cosmic time is given by v = c ln(1+z), where z is the redshift, which clearly goes to infinity as the redshift goes to infinity, and is larger than c for z > 1.718.\n\nFor the "critical density Universe", this velocity is given by v = 2c[1-(1/sqrt(1+z))], which is larger than c for z > 3. \n\nFor the "concordance model" based on CMB data and the acceleration of the expansion measured using supernovae, a flat Universe with Omega = 0.27 (this would be our Universe), the velocity is greater than c for z > 1.407\n\nAll this just means that for any expanding universe, there will be a value of z (i.e., redshift or cosmological distance) that will give the appearance of galaxies moving at velocities greater than c.
1160107
Since we can't actually see a planet orbiting a distant star, the way we can look for planets is by their influence on the star they orbit. This influence is due to the force of gravity. Even though a planet may be small in comparison to its star, it will nonetheless exert a gravitational force, gently "tugging" at its star. As the planet(s) orbit the star, they will tug at it from different sides. The net effect then, if we carefully watch this star for many years, is that we will see this star "wobble" back and forth! \n\nThere are two basic methods of detecting a planet's gravitational influence on its star: \n\n\n  a. Astrometric Detection \n  b. Radial Velocity Detection \n\n\nThe first method - Astrometry - was hinted at in the previous paragraph. We observe a star and measure its position relative to distant background stars (hence the word "metric" in the name). As an orbiting body tugs at its companion star, we observe a change in position of the star. Measurements of a periodic change in position, back and forth, can indicate that something is possibly orbiting the star. Careful analysis of these measurements can tell us about the orbiting object. \n\nThe second method - Radial Velocity - is a completely different kind of measurement, but relies upon the same principle. That is, gravity. As an orbiting body tugs on its companion star, the light from the star will experience a Doppler shift. If the planet pulls the star slightly away from us on Earth, the starlight will be shifted towards longer wavelengths and appear more red; pulled slightly towards Earth, the starlight is shifted towards shorter wavelengths to appear more blue. To accurately measure this Doppler shift, we chose a known spectral line and observe its shift from red to blue and back. \n\n\n\n\ncheck in here.....I think you'll have your questions answered.\nTo my knowledge,  have been discovered 197 planets out of our solar system until now (update 16 june 2006)\n\nhttp://exoplanet.eu/catalog.php\n\nhttp://isi9.mtwilson.edu/~david/planets.html
977701
I found this interesting article about an ancient black hole scientists have located near our solar system.  They determined the exact route and speed at which this monster has been traveling.\n\nConducting a bit of astronomical archaeology, researchers have dug up 43-year-old photographic evidence of an ancient black hole and used the information to learn that the object has been wandering at high speed on an odd, looping path through the Milky Way Galaxy for 7 billion years.\n\nThe study, discussed in the Sept. 13 issue of the journal Nature, represents the first measure of a black hole's movement through space, said researchers involved in the work.\n\nThe object's travels take it above and below the main plane of the galaxy, where the Sun and most other stars reside and orbit around the galactic center in relatively orderly fashion. The wayward black hole zooms along at 90 miles per second (145 kilometers per second) relative to the Earth, currently carving an arc up and over our solar system.\n\nIn pinning down the vagabond's trajectory and piecing together a picture of its past, researchers say they are adding pages to at least one chapter in the book that explains how the galaxy formed. \n\nThe object is estimated to have been around more than 2 billion years before our Sun was born, a time when the Milky Way was a toddler of a galaxy.\n\n"We believe that hundreds of thousands of very massive stars formed early in the history of our Galaxy, but this is the first black hole remnant of one of those huge primeval stars that we've found," said lead researcher Felix Mirabel, an astrophysicist at the Institute for Astronomy and Space Physics of Argentina and the French Atomic Energy Commission.\n\nAccording to what I read, I would have to assume that the rate and speed at which a black hole travels has much to do with its' size.\n\nI would recommend you finish reading the article.  It is very interesting. Thanks for your question.
1046890
Through the study of other stars 'wobble' within our own galaxy, we have detected planets larger than Jupiter, we believe.  Though, this is through a calculation with the doppler effect.  So to play it safe, as far as we know now it is Jupiter.  But to say that this will always be true would be bold and naive.
356302
The doppler effec refers only to the velocity of the object, as seen by your current position. The contribution of the expansion of the Universe is usualy noted as REd- SHifting. Note that there is also another effect, which adds to the doppler effect, and that is the lorentz factor.
123325
Yes, think stars.  VISION doesn't travel; LIGHT does.  So the question is how far can light travel, and there are no real limits to this--apart, perhaps, from the fact that light gets stretched by the expansion of the universe, and the red-shift "horizon" is at about 14 billion light years away.  But since there is nothing bright enough that the unaided eye can see, in practice it's less than that for things you can actually--rather than theoretically--see.
454817
the doppler effect means that if an object is moving away from us the light it is sending out is slightly more red than normal (the wave length is longer)-a red shift, if it is moving towards us the light from it is slightly more blue(wavelength is shorter)- a blue shift. Most of the galaxies we see in space are red shifted so everything is moving away from everything else. This proves that so far the universe is expanding. If gravity gets the better of us and all the galaxies begin to move in on each other then they would be blue shifted. This may well happen in the far off future- we can't tell yet, but Even if this was happening they wouldn't all meet in a 'big crunch' (the opposite of the big bang) for a few billion years so it's not really anything to worry about!
605687
The stars do move. The motion of a star in space is measured by astronomers in two ways. They use a spectrograph to measure the Doppler shift of the Star's light to determine the redial velocity, which is how fast the star is moving toward or away from the Earth. And they take careful position measurements with telescopes to determine the proper motion, which is the sideways motion in the sky. The star with the fastest proper motion is Barnard's Star, which is only moving at 10.3 arc seconds per year. That is only one degree every 350 years. Yet the star's speed though space is 750,000 miles per hour! It just looks slow from Earth since it is so far away.
585869
No, otherwise similar phenomena would be observed on Earth. Redshift is caused by the lengthening of the light waves - the peaks and troughs are at relatively the same place on the wave compared to locally generated light, but the length has been "stretched". The amount it is "stretched" depends on how fast ourselves and the object are moving apart - generally, objects at greater distance are moving apart more rapidly, so we see more shift. If matter caused this, it would be constant.\n\nThe opposite is true of distant matter moving towards us. For example, the galaxy of Andromena is moving towards our galaxy, and the light we see from this experiences "blue shift" - ie, the shortening of the light waves.\n\nIf red shift could be explained by interaction with matter, then we would not see blue shift. Or if both were caused by interactions with matter, they would cancel each other out, or we would see a steady "equilibrium" situation with the stretching, where all light reaching us from distance would be shifted by the same amount.\n\nSo no, nice theory though, keep plugging away, we need people to question these assumptions to further develop and refine the theories, or to disprove them if they are false!
104087
Have a look here,\nhttp://outreach.physics.utah.edu/labs/star_life/starlife_main.html
1147922
The expansion of the universe is the main reason. Yes, there are certainly stars in every direction, most of them contained within other galaxies. At extreme ranges (about 13.7-billion light years) those galaxies are moving away from us so fast that their light is effectively red-shifted out of sight.
448439
T Tauri stars have bipolar outflows, to the best of my knowledge.  They form Herbig-Haro Objects when the collide with slower matter from the interstellar medium.  They might not always show up with T Tauri stars because of nearby nebula, but my astronomy professor (James Kaler, UIUC) assures me that they are there.\n\nIf you're talking about mass outflows that the T Tauri stars outputs in addition to the bipolar flows, then I'm sure Doppler shifting can be used.  The speeds for the regular outflows should be pretty similar to that of the T Tauri itself, whereas the bipolar flows (depending on orientation to earth, of course) should be much higher.  I hope this helped!
928062
Well you can use spectroscopy to find out the composition of distant objects in space.  IE if a star emits light near (usually a slight red shift from distant objects) the emission lines of helium or mercury you could conclude that those elements are present.\n\nMike
267839
The universe is expanding more quickly the farther one gets toward the edge. \n\nWe know this because objects seen moving away from us through radio telescopes exibit a red shift, depending upon how fast they are moving away. The light from stars that are farther away from earth show more red shift than those close to earth, indicating that they are moving faster from us then their closer neighboors.\n\nThis implies that the forces of expansion are greater than those of contraction (gravity), and that the fate of the universe is not cyclical (no more big bangs), and that black holes, while locally dense, will never exert enough influence to contribute to large scale contraction of the universe.
880277
It has to do with the light it recieves from the nearby stars but it also depends on what the gas cloud is made of.  Hydrogen emits (and blocks) red light.  Other forms of light are also reradiated as red.  As the temperature of the gas cloud increases (due to recieving radiation) infrared emissions would increase also.
914780
Well, we look at the light and determine "this light is about a million years old." :-) Not really, but that's the general idea.\n\nFor galaxies of very large distance, we can determine how fast the galaxy is receding from us. The easiest way is the Doppler shift - we can see the galaxy (obviously) and therefore astronomers can determine how big it is, what type of stars must be in them, and therefore what color light we should see. However, the light is slightly redder than what models predict (and what nearby galaxies have). We can measure this "red shift", plug it into Doppler's equation, and determine how fast the galaxy is moving. (This is similar to how when a police siren passes you, it drops its pitch - and how much it changes is proportional to how fast the police car is going.)\n\nThen there's a nice relationship called Hubble's Law, which states that the farther a galaxy is from us, the faster it's receding. This is a consequence of the Big Bang, and indeed the constant in this equation must be the reciprocal of the age of the universe. So we can then estimate (within a few thousand years or so) how far the galaxy must be from us.\n\nFor closer galaxies, there are some other techniques. There are certain types of variable stars (stars that, every few hours or days, increase and decrease their brightness) that in order to be stable must vary between two known brightnesses. Of course the brightness isn't exact, but the average among the thousands of variables in a galaxy is very close to exact. Now when we measure brightness (actually, apparent magnitude) from Earth, we see stars dimmer if they're farther from us. But because we know the absolute magnitude of these variables, and we can measure their apparent magnitude, we can calculate the distance we must be for them to become this much dimmer.\n\nThere are actually a lot of techniques, which work better for certain distance ranges. Look up the "distance ladder" if you're interested.