Question about Our Motion Through Our galaxy

[dmill1220]

Hi Folks!
I have been discussing this topic on my clubs private forum, and I have yet to receive any response.
A club member and Myself want to know how Astronomers have accurately measured Our Oscillation thru the Galactic plane.
I found this link which explains our motion, but does not give any links as to how this result has been obtained, Maybe I'm just too curious by nature for my own good!
Here is the Link http://curious.astro.cornell.edu/que...php?number=402 Please give credit to Curious about Astronomy or ask an astronomer for this link.
I understand Parallax measurements and the Red shifting of spectra or the Doppler effect, But is it a combination of techniques (Spectral & Parallax) or something altogether different? I am assuming that Parallax would only work for stars very close to us, and would involve a long period of observation.
Dennis

[dmill1220]

oh No for some reason or another this link has been changed or removed but here is what I got from this site
Quote:
U = 10 km/s (radially inwards)
V = 5 km/s (in the direction of Galactic rotation)
W = 7 km/s (northwards out of the plane of the Galaxy)

Of course the Sun won't keep on going in this direction forever. In fact we approximate it's motion by an 'epicycle' on top of the mean motion around the Galaxy. The period of oscillation in and out of the plane of the galaxy (up and down) is about 70 million years. This means that we pass through the Galactic midplane about every 35 million years . end quote.
OK this is weird the link now seems to be working!
Please give credit to Curious about Astronomy, or Ask an Astronomer for this Link and Quote
Dennis

[Dragon Star]

I think they apply all of those things, redshift, blueshift, exc...to arrive at a more precise analysis. But the method I hear of the most is we use the distance to a globular cluster to calibrate the distances to a number of other globular clusters. By determining the center of their distribution, we get an estimate of the distance to the center of the Galaxy.

http://heasarc.gsfc.nasa.gov/docs/co...yway_info.html

http://www.astro.washington.edu/labs...er_galaxy.html

http://fuse.pha.jhu.edu/outreach/kit1/trig.html

Hope that helps.

[dmill1220]

Hi Dragon!
Thanks amigo!
I already knew about how they have measured our distance to the Center, its the Up and down Cyclic movement that I'm wondering about.
Im assuming that they are pulling all the stops out on this calculation,
Proper Motion, Spectral Analysis, triangulation, Momentum, Gravity, and the past Geologic record, but I really cant seem to find the specific Formula or sets of Formulas that they used to determine Our cylcic rate thru the Galactic Plane. but Your link did help a to get a better grasp though! Very good links too!
I am waiting for either a response from Ask An Astronomer or in BAUT.
I am curious if this is a concretely proven fact, thru Observation, or just a Mathematical and Geological theory, and how long they took to arrive at the Up and down Cyclic Galactic Plane Motion, conclusion.
But you do Rock dude!
Dennis

[dmill1220]

Hey Dragon !
After some more careful thought and actually reading the whole link given at BAUT, from what I understand its more of a Calculated Mathematical theory from Red Clusters Instead of Globs!
Check this out and tell me that my MS isnt playing with my head please!
http://cat.inist.fr/?aModele=afficheN&cpsidt=17432332
Dennis

[Dragon Star]

Oh, sorry. Misunderstood your post. I've had a rough day.

But yes, it appears you're right. But don't take my word for it right now, I have a smashing headache.

*runs for some aspirin*

[stuart]

Originally Posted by dmill1220

its the Up and down Cyclic movement that I'm wondering about. ... I really cant seem to find the specific Formula or sets of Formulas that they used to determine Our cylcic rate thru the Galactic Plane.

I'm pretty sure that if you assume simple harmonic motion (a spring), that if you have the current position, the velocity vector, and the potential (gravitational pull from the Galaxy), then you can calculate a simple formula for our system.

[dmill1220]

Thanks Stuart!
that is an excellent Logical approach!

I am trying to find out though how much is Assumption, the accuracy of the different Models used, and the Probablities of the numbers bieng correct, It seems they have two Models that assume two different results, one has to do with our present position, the model they used by studying the Red Clusters in our Galaxy, which are, they way I understand, some of the oldest in our System.
it does appear from what I have gathered so far, that the time cycle has some very large differences and, are based or extrapolated using one model, if our Velocity, Vectors, and, present Position is accurate.

There is a Society Club member at the local club that I belong to who is a Biology Major, that questions both our Movement and, epicyclic time periods.
He assumes 100 mil yrs based on his Knowledge or assumptions from the Paleo Biological records of previous Extinctions.
He may be right if our present position is not accurate and, our Models are using incorrect Positional or outdated Data.
of This I have no Idea or, knowledge, as far as his correlations with the Paleo Biologic Data, that he is refering to, he just doesnt belive in the accuracy of the time periods given. and the way they got those figures.
I now am in Doubt also
When I get a result from Ask An Astronomer I will post it unless you can enlighten or correct this line of thinking?
Please excuse my verbal or writing skills! My MS sometimes wreaks havoc on my cognitive ability!
Do you have any thoughts or corrections to my line of thinking?
I greatly value your input.
Dennis

[Dragon Star]

Originally Posted by dmill1220

My MS sometimes wreaks havoc on my cognitive ability!

I have yet to see a sliver of evidence for this. You are a good guy, and really the only thing you have wrong with you is that you use exclamation points too much!

Lighten up old man, you are better off then most and you know it.

[dmill1220]

Thanks Dragon,
For your kind thoughts, but I really do have to struggle most of the time to keep thinking straight. I have lost quite a bit of memory and, sometimes my logic is scatter brained and, I don't make any sense. I can safely say that I've lost half of what I used to know, or would come naturally to me. sometimes I don't even know what I am doing or saying ,so I have to be checked quite often.
MS, S**ks, it creates havoc with my logic and, motor skills and has left me with a permanent leg brace and Arm Brace, sometimes I'm OK, other times I can sound like a babbling fool. or forget how to even spell, and slur my words or even drool.
I used to have a high IQ, but I can guarantee you that it is not the case any more, at least I know this and, I am struggling with it.
but my spirits are high and I refuse to let it get me down. I will never surrender and I will never quit! sometimes that is not so good since I tend to over due things, and I end up in the hospital every 3 to 4 months for about a week or so being pumped with steroids to reduce the swelling in my Brain and nervous system. I now have a permanent Iv tap in my chest.
I have a head like a rock!
LOL!
I appreciate your thoughts
Dennis