Star Cluster's Extreme Speed Puzzles Astronomers

Now I'm not an Astrophysicist but I would like to know how an earth based telescope over the course of four years of our own motion through space can measure an object's motion 25000 light years away with a degree of certainty down to 7 millionths of a degree. I would really like it if someone could explain that to me (I'm not being sarcastic...I really do want to know).

Thanks for that, now I want to know.....

I'm guessing you look at motion against background objects - the same way planetary objects are seen. The hook seems to be their method of canceling out the atmospheric turbulence, so that you get enough detail to resolve the displacement.

Maybe its all done with "smoke and mirrors".

I am no rocket scientist either but just a keen amateur.

It seems to me that , as has been the case so often with these blogs, that the initial report has less than desirable accuracy and science in its story. I have commented on this in the past as I do not understand why we are fed blogs that are written by people that clearly do not like the subject and therefor show no profound interest in it. This taints the science badly.

I believe the full story should have elaborated more on the possibilities for errors as they undoubtedly are there. They cannot even guarantee that level of accuracy with 2 independent measurements with the same telescope, let alone 2 different telescopes at different locations after a period of more than 4 years. I realise they know the earths movements rather precisely but still.

One suggested they look at background motion and this is essentially correct but you need to know the background motion before you can do that. How do they know the background of an object that is this far away? They cannot make me believe that they know the further lying objects precisely enough to say anything worthwhile about the closer object. They do these measurements with comets and asteroids and as these are relatively close by, the accuracy is incredible. Here the margin for error has got to be enormous in my mind.

If we do have a proper scientist in the room I would love to see some credible explanation of these matters.

Astronomical speed has always puzzled me. It seems to me that there are too many variables to profess the certainty of relative speed as so many do.

If there are eddy type currents of mass moving this could cause anomalies showing up as inaccurate speed calcs.

After all speed is relative in its measurement is it not?

I recall many years ago in the Texas outlands, my cousin and I climbed into the crow's nest of a railroad signal post. My cousin lived in the area and had done this before. At the very first, and faintest sound of a train whistle (horn) we raced to a VERY remote crossing late at night. On the horizon my cousin pointed out the tiny speck,that at first I mistook for a low star, as the trains light. It grew larger. Slowly. After about an hour the light had doubled in size. After another half hour double that. About two hours into this I could clearly see it was in fact a single point of moving light with vector and such. A few minutes more and the silent light showed it's true make up; three individual headlights. From the time that the three lights were discernible to the time the train was a visible outline a hundred yards or so away was quick. During these hours of silence and I mean dead silence, save the occasional horn blast, time was very deceptive with regard to what was about to happen. The now shadowy outline hit upon us in a blast of energy, rumbling noise wind and shaking and thunder that I was ill prepared for. The shear mass of this thing was enormous. A herd of Bison numbering the thousands might match this power. Then in a moments time the energy gave way to the bobbing trailing of a red light on the end car (no caboose), which displayed a completely different nature than the approaching train at any point or the directly passing locomotive.

I know of the origins of relativity and that they too relate to the train and its observer. But I am sure that the Universe does not travel on a pair of tracks. Neither does the ocean. Neither does the wind. I suspect if a comparison should be made that the Universe is more like a body of gas (oxymoronic - body of gas) than a train. If the earth is the fixed point from which calcs are made, the datum, then upon which fixed point is is that based? It seems there are no fixed points in a fluid/dynamic/gaseous Universe littered with the little specks of known matter that make up planets and such from which true accuracy may be established. I just can not (with my limited understanding) buy into accuracy assertions made upon such a degree of variables.

cr3

I agree with your sentiment. Although with my rationale I have to conclude that they DO KNOW about certain things. The landings on moon and mars as well as all the other planet probes, needed a level of accuracy that boggles most peoples minds, mine included.

These measurements can be made accurately as it is close by. This is where I loose the plot with regards to these deep space guestimates.

With regards to refference point you are right. They do know however that speed of light is always what it is, this is constant so maybe they do use some of that as well?

I dunno, that's why I asked for a real scientist, not another monkey!

Only kidding you "hauw" (Chinese pronounciation of your avatar)

I agree that the farther away an observer is from what they are observing, the more difficult any assessment will be. As far as the whole speed of light thing goes...remember that the speed of light is only constant in a given medium, if it passes through a gas cloud or something, then its speed will change. Light is also affected by gravity (I don't believe its speed is, but its path is definitely affected...they call it gravitational lensing I believe), so I'm sure they use a lot of fancy math to make an approximation (which is fine) but I guess my biggest problem (as seems to be yours) is that I would like to see some error analysis of the data. If when all the possible errors have been accounted for, the speed is 200000km/s +/- 150000km/s then I don't think that's even worth mentioning, but if the error term is +/- say only 10% then maybe that is good enough of a guess. It just seems like a little too much "dumbing down" in the article to give anyone truly interested in the information a good enough explanation to satisfy a curious mind.

Dear C Rummel3, I had not read your interesting discussion until I noticed your reply to Jorrie. You bring some interesting observations to the table with some very literate descriptions.

Since any discussion regarding Dark matter, Dark Energy, Zero point Energy, et.al. is founded in speculation, any postulations are acceptable for this discussion. I would like to hear more since we seem to be in agreement regarding the fluxual state of the universe.

Also I admit to making some totally "off the wall" comments in hopes they may provoke clarifying logical responses from better minds than mine (and there are many in this forum) LOL.

Hi taejonkwando, you wrote: "Since any discussion regarding Dark matter, Dark Energy, Zero point Energy, et.al. is founded in speculation, any postulations are acceptable for this discussion."

Wow! I would not concede to simply "founded in speculation", but I'll agree to the "any postulations" bit. One can obviously postulate, but science will eventually require some observation and analysis to support those postulates...

Jorrie

Hi CR3, you wrote: "Astronomical speed has always puzzled me."

This is true for many of us! Astronomers have a very accurate method of measuring radial speeds (towards or away from us) in terms of ordinary old Doppler shift of the spectral lines of known elements, e.g. hydrogen.

Transverse speed is a lot more difficult for distant objects. One can measure movement against the very distant background stars, but one also needs to know the distance to the star under consideration. All these parameters have measurement uncertainties, but we know more or less how uncertain.

The popular press normally neglects to quote the tolerances of the measurements, but scientists are quite adamant about having 'error bands'. In the case of a 200 km/s transverse speed measurement, I would guess the errors to be 10% max. But 180 km/s is still a very fast speed!

Jorrie

Since they used 2 telescopes, and a fake star was made with a laser for reference, it occurs to me that there were 2 fake stars (one for each telescope), and they may not have been in the same place. Thus it would be measurement error. However, a speed of 200 kilometers per second is not really so awesome, is it?