Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Galactic structure

  1. Mar 2, 2008 #1
    when astrophysicists study the structure and rotation of galaxies do they take into account that we are seeing the stars in it where they were at different times, we aren't seeing them where they actually are now? Say stars on the closest edge are 100,000 light years away but stars on the furthest edge are 165,000 light years away so that the current structure of that galaxy would look different than what we are actually seeing? Does that make sense to anyone?
  2. jcsd
  3. Mar 2, 2008 #2


    User Avatar
    Staff Emeritus
    Science Advisor

    Well the distances to individual stars does affect 'when' we see the light, but those distances will depend not on the dimensions of the galaxy, but the angle (orientation) of the galactic plane with respect to us (the observers).

    I believe astronomers favor those galaxies whose planes are perpendicular to us. As the galactic planes tilt away, then the time differential of observed light increases in width with the angle, so one would have to consider that.

    However, looking at galaxies in the 'most favorable' orientation, one may notice little change over some length of time.

    The caveat is that we haven't really looked very long at the universe with respect to cosmological times, and we only started look way far away (Hubble Ultra Deep Field) in 2003.


    What will be interesting is to look at HUDF in 100, 200, . . . 1000 years to see what has changed. However, none of us will be around.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook