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Thread: Andromeda Galaxy Blueshift

  1. #1

    Andromeda Galaxy Blueshift

    It is thought that the Andromeda Galaxy is moving towards the Milky Way. Does anyone know any supporting evidence for this, aside from the Blushifting?

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    I would imagine the blue shift would be the primary evidence. I don't think there's been enough of a temporal baseline to look for actual changes in distance measurements, like Cepheids. One would have to figure out how far it would have to move to get a measurement that was larger than the errors. Then you could figure out how long that would take given the velocity implied by the blue shift. I'm sure someone around here probably has the necessary figures to do such a calculation.

  3. #3
    Quote Originally Posted by Amber Robot View Post
    I would imagine the blue shift would be the primary evidence. I don't think there's been enough of a temporal baseline to look for actual changes in distance measurements, like Cepheids. One would have to figure out how far it would have to move to get a measurement that was larger than the errors. Then you could figure out how long that would take given the velocity implied by the blue shift. I'm sure someone around here probably has the necessary figures to do such a calculation.
    Thanks. So basically you say that there is nothing else at all but the blueshift. Interesting.

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    At the approach rate indicated by the blueshift, my rough estimate is that several hundred years would be needed to increase the angular diameter of the galaxy by 1/1000 of an arcsecond. That is beyond the capabilities of any astrometric methods we have at the present time.

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    Much is known of the motion of our galactic neighbours. The local group is moving towards the Virgo super cluster.

    Andromeda seems to be the only galaxy that is coming towards us,.

    While we all know this by means of red and blue shift and a understanding of that science. I know of no other method used.

  6. #6

    Lightbulb Milky Way vs M31

    Quote Originally Posted by stardad View Post
    It is thought that the Andromeda Galaxy is moving towards the Milky Way. Does anyone know any supporting evidence for this, aside from the Blushifting?

    I don't see why the blueshift should not by itself be quite convincing. Until fairly recently, observational data were not precise enough to measure the proper motion. However, this should be doable with HST and a proposal to that effect came forward in 2008 (van der Marel, 2008), but I can find no indication of any published results, and I don't even know if the proposal was accepted. Darling, et al., 2010 claim they should be able to measure the proper motion of M31 within 2-3 years using precision radio astrometry of water masers in the spiral arms of the galaxy.

    While the blueshift provides a clear indication of radial velocity (i.e., velocity along the line of sight), it provides no indication of transverse velocity (i.e., velocity perpendicular to the line of sight). There have been some efforts to learn something about the transverse velocity without the necessarily precise proper motion measurement (e.g., Loeb, et al., 2005; van der Marel, et al., 2008) but they produce limits on the transverse velocity more efficiently than they produce reliable estimates of the transverse velocity.

    Cox & Loeb, 2008 uses the best available data to predict the particulars of an M31 - Milky Way collision, which they think likely within the next few billion years.

  7. #7
    Quote Originally Posted by Hornblower View Post
    At the approach rate indicated by the blueshift, my rough estimate is that several hundred years would be needed to increase the angular diameter of the galaxy by 1/1000 of an arcsecond. That is beyond the capabilities of any astrometric methods we have at the present time.
    OK, so you confirm that there in NOTHING else.

  8. #8
    Quote Originally Posted by astromark View Post
    Much is known of the motion of our galactic neighbours. The local group is moving towards the Virgo super cluster.

    Andromeda seems to be the only galaxy that is coming towards us,.

    While we all know this by means of red and blue shift and a understanding of that science. I know of no other method used.
    Ok. So you also confirm it. Thanks.

  9. #9
    Quote Originally Posted by Tim Thompson View Post
    I don't see why the blueshift should not by itself be quite convincing.
    No? That's Ok. No need to get into that.




    Until fairly recently, observational data were not precise enough to measure the proper motion. However, this should be doable with HST and a proposal to that effect came forward in 2008 (van der Marel, 2008), but I can find no indication of any published results, and I don't even know if the proposal was accepted. Darling, et al., 2010 claim they should be able to measure the proper motion of M31 within 2-3 years using precision radio astrometry of water masers in the spiral arms of the galaxy.
    So maybe in a few years. OK. How long is Hubble good for? What is the basis for this measurement exactly you hope may come online?

    While the blueshift provides a clear indication of radial velocity (i.e., velocity along the line of sight), it provides no indication of transverse velocity (i.e., velocity perpendicular to the line of sight). There have been some efforts to learn something about the transverse velocity without the necessarily precise proper motion measurement (e.g., Loeb, et al., 2005; van der Marel, et al., 2008) but they produce limits on the transverse velocity more efficiently than they produce reliable estimates of the transverse velocity.
    So it is not known at all. OK. Thanks. It amazes me how little we know.

    Cox & Loeb, 2008 uses the best available data to predict the particulars of an M31 - Milky Way collision, which they think likely within the next few billion years.
    Likely is no better than what we know makes it likely. I think you can relax.

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    As has been said above, we do not know whether Andromeda will hit the Milky-Way or not.

    We know that M31 is getting closer (blueshift), rather than getting further away (redshift), but we do not yet have enough data to conclude how closely it will pass the Milky-Way.

    What we know for sure is that Doppler shift allows us to determine whether a galaxy is moving towards us or away from us. M31 is moving towards us.

  11. #11
    Quote Originally Posted by speedfreek View Post
    As has been said above, we do not know whether Andromeda will hit the Milky-Way or not.
    Not sure who the "we" is? Nasa claims to know, and so do millions of other sites.

    "Our galaxy, the Milky Way, has collided with another galaxy, called Andromeda. Although the two galaxies are passing through each other at a million miles an hour, the whole process will take many millions of years to complete. And when everything settles down, the two galaxies will have merged into one. "
    http://www.nasa.gov/audience/forstud...s_Collide.html

    We know that M31 is getting closer (blueshift), rather than getting further away (redshift), but we do not yet have enough data to conclude how closely it will pass the Milky-Way.
    OK, so we have the blue shift. Got it. Nothing else. OK. As long as it means what you think it means in deep space I guess it would mean what you claim. By the way, have we any evidence that laws there are the same as here?

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    Well, when we view the spectra of distant objects, the absorption lines show us they are "made of the same stuff" as locally...

    http://www.universetoday.com/15220/a...-the-universe/
    http://www.mpifr-bonn.mpg.de/public/pr/pr-munh3-en.html

    According to Michael Murphy, Swinburne astrophysicist and lead author of the study, it is an important finding, as many scientists debate whether the laws of nature may change at different times and in different places in the Universe. "We have been able to show that the laws of physics are the same in this galaxy half way across the visible Universe as they are here on Earth," he said.
    Original paper:
    http://arxiv.org/abs/0806.3081

    And rather than being halfway across the universe, M31 is only a couple of million light-years away. We have no evidence that the laws of physics would be any different there.

    (And I use "we" as in the knowledge of humanity, through science)

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    Quote Originally Posted by stardad View Post
    Not sure who the "we" is? Nasa claims to know, and so do millions of other sites.
    Note that the page you linked to is aimed at young students (I don't know what grade 5-8 means, I guess 10 to 13 years old?) and therefore it keeps it simple, omitting all the caveats and uncertainties that normally accompany any scientific information.

    More on the uncertainties here: http://en.wikipedia.org/wiki/Androme...on#Uncertainty for example.

    OK, so we have the blue shift. Got it. Nothing else.
    What is the significance of "nothing else"?

  14. #14
    Quote Originally Posted by speedfreek View Post
    Well, when we view the spectra of distant objects, the absorption lines show us they are "made of the same stuff" as locally...

    http://www.universetoday.com/15220/a...-the-universe/
    http://www.mpifr-bonn.mpg.de/public/pr/pr-munh3-en.html
    In your links I did not see the details on the claim.

    "The astronomers determined this by effectively looking back in time at a distant quasar, labeled B0218+367. The quasar’s light, which took 7.5 billion years to reach us, was partially absorbed by ammonia gas in an intervening galaxy. "

    The question arise, how do they know it was ammonia gas? How do they know it partially absorbed the light?




    And rather than being halfway across the universe, M31 is only a couple of million light-years away. We have no evidence that the laws of physics would be any different there.

    (And I use "we" as in the knowledge of humanity, through science)
    We shall see. You need to flesh out the claims a bit, so far it seems thin.

  15. #15
    Quote Originally Posted by Strange View Post
    Note that the page you linked to is aimed at young students (I don't know what grade 5-8 means, I guess 10 to 13 years old?) and therefore it keeps it simple, omitting all the caveats and uncertainties that normally accompany any scientific information.
    Right. I t was not meant to illuminate the caveats and be a marvelous article. It was meant to show what is being claimed to kids and in millions of other links to everyone....that a crash up is not a maybe...they claim it outright.

    More on the uncertainties here: http://en.wikipedia.org/wiki/Androme...on#Uncertainty for example.

    What is the significance of "nothing else"?
    True, that in more detailed articles they hedge their bets a little. I see this one gives it about 50/50. I suppose if we got one even more detailed, it would include...'we don't know'.

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    Quote Originally Posted by stardad View Post
    In your links I did not see the details on the claim.

    "The astronomers determined this by effectively looking back in time at a distant quasar, labeled B0218+367. The quasar’s light, which took 7.5 billion years to reach us, was partially absorbed by ammonia gas in an intervening galaxy. "

    The question arise, how do they know it was ammonia gas? How do they know it partially absorbed the light?
    As explained in the original paper, they used spectroscopy.

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    Ten to thirteen is a good estimate for grades 5 through 8. In the state where I live, about half the first grade pupils will be five on the first day of school (typically about Sept 1).

    As for uncertainties, I know that Doppler shift will only show the radial component of the velocity, so the tangential component could be anything that is too small to measure by astrometry. I believe Hipparcos can achieve milli-arcsecond precision when targeting stars, so that sort of precision is possible, at least when looking at what are, essentially, quite nearby points, but just as a wag1, the achievable precision for a diffuse object like a galaxy is at least an order of magnitude worse.


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  18. #18
    Quote Originally Posted by speedfreek View Post
    As explained in the original paper, they used spectroscopy.
    Yes, I figured that much. But that doesn't give details of how they figure ammonia is there and the light is being affected by it..?

  19. #19
    Quote Originally Posted by swampyankee View Post
    Ten to thirteen is a good estimate for grades 5 through 8. In the state where I live, about half the first grade pupils will be five on the first day of school (typically about Sept 1).
    A good age to be told the truth to, wouldn't you think?

    As for uncertainties, I know that Doppler shift will only show the radial component of the velocity, so the tangential component could be anything that is too small to measure by astrometry.
    Well if you claim it shows the radial component that is a good start. Explain the difference briefly between radial and tangential, and how the blue shift is determined for what we think it is determined for..

    I believe Hipparcos can achieve milli-arcsecond precision when targeting stars, so that sort of precision is possible, at least when looking at what are, essentially, quite nearby points, but just as a wag1, the achievable precision for a diffuse object like a galaxy is at least an order of magnitude worse.
    Oh dear, that is another topic. Distance. Alas I am not a believer in the standard model, so that would take a little bit of discussion. It is my feeling so far that size and distances to stars are actually not known at all. But as I said, that is another story.
    1: Widly Approximate Guess.
    ? For what?

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    Quote Originally Posted by stardad View Post
    Quote Originally Posted by stardad
    And rather than being halfway across the universe, M31 is only a couple of million light-years away. We have no evidence that the laws of physics would be any different there.

    (And I use "we" as in the knowledge of humanity, through science)
    We shall see. You need to flesh out the claims a bit, so far it seems thin.
    Which claims, and exactly what about those claims do think we need to flesh out?

    Do you have any evidence that the laws are any different there, than they are here?

    Although you don't think we need to get into it, exactly why you don't think the blueshift should be convincing?

  21. #21
    Quote Originally Posted by Tensor View Post
    Which claims, and exactly what about those claims do think we need to flesh out?
    As I mentioned, they refer to ammonia out there and light passing through it...
    Do you have any evidence that the laws are any different there, than they are here?
    I don't make a claim, so the evidence required is for those that do make a science claim. I merely point out that it seems to actually be not known.

    Although you don't think we need to get into it, exactly why you don't think the blueshift should be convincing?
    Well, that depends on where we see it. If it is beyond the range of earth, and area, then what we see may not be what we think we see. That is why it is a good thing to try to determine what is actually known.

    If we get to the point where it is admitted that nothing else exists but the blue shifted light, then we can proceed from there. If there are good evidences beside that, then we can chalk it up as something that is known by several different methods.

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    Quote Originally Posted by stardad View Post
    Yes, I figured that much. But that doesn't give details of how they figure ammonia is there and the light is being affected by it..?
    Do a search on Absorption Line Spectra. You will find several quite detailed explanations. For a quick example, Ammonia(as every other element) has it's own, very specific energy levels that will absorb photons of a very specific energy. Absorbtions appear as dark bands (known as Fraunhofer lines, for the person who discovered them in 1814)in a spectrum. If a spectrum is observed to have dark lines, and they match the lines of ammonia (which can, and have, been produced on Earth for comparison), then the light has passed through ammonia.

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    Quote Originally Posted by stardad View Post
    As I mentioned, they refer to ammonia out there and light passing through it...
    See post #22. The lines appear exactly as they do from samples on Earth.

    Quote Originally Posted by stardad View Post
    I don't make a claim, so the evidence required is for those that do make a science claim.
    Not quite. Here in Q and A, answers are required to be mainstream answers. If you disagree or don't like that answer fine, but if you want to question that answer, you need to take it to ATM. However, there is ample evidence. Feel free to look up Oklo, astronomic spectroscopy(both emission and absorption), Stellar orbits around Sagittarius A*, etc, etc, etc.

    Quote Originally Posted by stardad View Post
    I merely point out that it seems to actually be not known.
    That is your claim whether you want to look at it that way or not. Feel free to explain exactly why a spectrum from another galaxy would have the exact same absorption lines for ammonia, if the light hadn't passed through ammonia. Or why helium absorption lines were found on the Sun 14 years before the exact same lines were found on Earth, when light was passed through Helium.

    Quote Originally Posted by stardad View Post
    Well, that depends on where we see it. If it is beyond the range of earth, and area, then what we see may not be what we think we see. That is why it is a good thing to try to determine what is actually known.
    Since a Helium absorption line was found on the Sun, I would think that you would include the Sun in the area, right? Does area go out to Jupiter? How about Neptune? Further? How far? How about you define area for us?

    Quote Originally Posted by stardad View Post
    If we get to the point where it is admitted that nothing else exists but the blue shifted light, then we can proceed from there. If there are good evidences beside that, then we can chalk it up as something that is known by several different methods.
    Let's start with the basics. Do you agree that red/blue shift of a spectrum are an indication of motion?

  24. #24
    Quote Originally Posted by Tensor View Post
    See post #22. The lines appear exactly as they do from samples on Earth.
    No doubt. But what I want to see is that ammonia exists in and permeates the Andromeda Galaxy? Not whether it gives off a certain light signature here. Then, what light from where is going through it?

    Not quite. Here in Q and A, answers are required to be mainstream answers. If you disagree or don't like that answer fine, but if you want to question that answer, you need to take it to ATM. However, there is ample evidence. Feel free to look up Oklo, astronomic spectroscopy(both emission and absorption), Stellar orbits around Sagittarius A*, etc, etc, etc.
    Answers can be mainstream, as long as they are not vague, and have evidence. Not sure why you tossed out Oklo, and etc and mentioned there is ample evidence....for what?? Andromeda ammonia? The light that passes by the galaxy and has to pass through the ammonia? Where has the spectral lines representing ammonia been seen? All through that galaxy? Where is the light coming from that passes through it? How do you know?


    That is your claim whether you want to look at it that way or not. Feel free to explain exactly why a spectrum from another galaxy would have the exact same absorption lines for ammonia, if the light hadn't passed through ammonia.
    Thanks. OK, I will feel free just as soon as we see where this ammonia is supposed to be and what passes through it from where...is that fair??
    Or why helium absorption lines were found on the Sun 14 years before the exact same lines were found on Earth, when light was passed through Helium.
    Not an issue. Last I checked the sun was in our system.


    Since a Helium absorption line was found on the Sun, I would think that you would include the Sun in the area, right? Does area go out to Jupiter? How about Neptune? Further? How far? How about you define area for us?
    Well for now as far as the Andromeda galaxy.


    Let's start with the basics. Do you agree that red/blue shift of a spectrum are an indication of motion?
    Where? Here near earth? Of course.

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    Quote Originally Posted by stardad View Post
    No doubt. But what I want to see is that ammonia exists in and permeates the Andromeda Galaxy? Not whether it gives off a certain light signature here.
    Can you explain why something that looks exactly like ammonia wouldn't be ammonia, just because it is further away? Why would spectra be different in different locations?

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    Points of clarification, stardad:

    As mentioned, the Space/Astronomy Q&A forum is where people come to get mainstreams answers to their questions. One may not argue against the mainstream answers in Q&A. One may not develop an against-the-mainstream position in Q&A. If you want to argue an ATM theory, that must be done in the ATM forum. If you want to pursue more in-depth discussion of the mainstream, there are more appropriate forums for that, as well.
    Brett's the name. Peters Creek is the place.
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  27. #27
    Quote Originally Posted by Strange View Post
    Can you explain why something that looks exactly like ammonia wouldn't be ammonia, just because it is further away? Why would spectra be different in different locations?
    Well, not sure I would want to do that, or need to. So where is the ammonia located exactly? All through through the galaxy? I kind of like to look at what we know.

  28. #28
    Quote Originally Posted by PetersCreek View Post
    Points of clarification, stardad:

    As mentioned, the Space/Astronomy Q&A forum is where people come to get mainstreams answers to their questions. One may not argue against the mainstream answers in Q&A. One may not develop an against-the-mainstream position in Q&A. If you want to argue an ATM theory, that must be done in the ATM forum. If you want to pursue more in-depth discussion of the mainstream, there are more appropriate forums for that, as well.
    No arguing against mainstream ideas here. OK. So this is a good place to just find out what the 'mainstream' position is. (Not that this doesn't change faster than a march hare)

  29. #29
    Quote Originally Posted by Strange View Post
    Can you explain why something that looks exactly like ammonia wouldn't be ammonia, just because it is further away? Why would spectra be different in different locations?
    No. You see this is not the place to question a mainstream answer.

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    Quote Originally Posted by stardad View Post
    Well, not sure I would want to do that, or need to. So where is the ammonia located exactly? All through through the galaxy? I kind of like to look at what we know.
    Ammonia should be present in molecular clouds.

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