introducing myself and got a good fun question :)

[Cpickens89]

Hey first off would like to say ive been coming here for a bit and decided to join up . The site's just awsome , im pretty much in love with astronomy from the simple fact that we never stop learning about this amazing universe . Going on 20yrs i could say ive loved it for all 20 of them

Ive got kind of a weird thought pop into mind

If we havent been out of the solor system we call home or out of the milky way for that matter,


how in the world do we know what our galaxy looks like ? course i know we can see others but how to we get a visual of ours. ?

 

[yevaud]

Welcome to SDC. Btw, there's an "introduce yourself" thread in "Free Space," if you want to introduce yourself properly.

We can image stars in all directions. We can image a star, determine what it's output and spectroscopic signature is; we can also determine it's redshift. Between these, we can place it's distance relative to us. Do this enough times, and you have an accurate map of our galaxy.

For example: we can image a red giant, and know it's output and magnitude would be detected as "X" at a certain distance. We then look at it's spectrograph, and tell it's redshift. Between these two, distance can accurately be determined.

Is this what you meant?

 

[MeteorWayne]

Hi cpickens99
Welcome to SDC. In addition to what yevaud said, for closer stars in addition to detemining distance from redshift, we have been able to detect the motion sideways as we orbit the Milky Way together, each on our own orbit. Also the observations extend well beyond visible stars to X-rays, infrared observation etc, whch show us gases, other high energy particles, and have let us peer us right to the edge of the black hole at the center of the Milky Way. Stars near the center orbit the MW so fast we have now recorded more than one orbit for some! Knowing where the center is helps put the rest of the obervations in context.

Wayne

 

[Cpickens89]

Thanks guy's , its just always been a little confusing to me how we mapped it out , being were right down inside of it . I was just curious as to how they figured out its shape an all . Thanks for replying .

 

[SpaceTas]

The local region of the galaxy was mapped using distance measurements to individual stars, and star clusters, combined with radial velocity (measuring motion toward/away from observer ie blue and red shifted spectral lines) and proper motion (across line of sight; sideways motion). The closer stars are measured using trigonometric parallax ie measuring position of star relative to background stars as the Earth moves about Sun. You can get a sense of this by holding out finger in front of your face and looking at it with one eye at a time. Hipparcos satellite is the latest example of these measurements. At greater distances, more indirect, but reliable methods are used (moving cluster, Cepheid variables ...)

But the overall shape was/is measured using radio observations of the hydrogen in the dark clouds. The velocity of each cloud is measured and a map formed. Here the resulting map:

There is also a general set of lecture notes including a local map at the same sitehttp://abyss.uoregon.edu/~js/ast123/lectures/lec10.html

 

[Cpickens89]

that actually helped out a bit guy's thanks , i got alot of learning to do to catch up with most of ya but its all good lol the more i learn the better