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New Radial Velocity Experiment (RAVE) Data Release

  1. Sep 22, 2016 #1
    The RAVE project site: https://www.rave-survey.org/project/

    In the above image taken from one of the RAVE DR5 video, surveyed stars are shown in 3D and color coded according to their positive or negative radial velocity relative to the Sun.

    I'm a bit puzzled that stars on one 'side' tend to run away from us whereas on the other 'side' they tend to come toward us. If the Sun is moving around the galactic center "with the flow" there should not be such a bias? Does that mean that the Sun moves noticeably faster (or slower) then the other stars or is this expected from the way velocities have been measured or computed?

    Looking closer at the stars in one of the fly through video we can see that not all stars follow the same trend. Some go one way while others in the same vicinity go the other way. This reminds me of another video i saw a few years back showing a simulation of stars formation in a dust cloud where you could see them 'dancing' around in very chaotic orbits - a bit like fire flies above a camp fire.

    If we keep surveying those stars, i guess that at some point in the future we will have enough data to actually infer their orbits - and create fascinating movies. :smile:
  2. jcsd
  3. Sep 27, 2016 #2
    Thanks for the thread! This is an automated courtesy bump. Sorry you aren't generating responses at the moment. Do you have any further information, come to any new conclusions or is it possible to reword the post? The more details the better.
  4. Sep 28, 2016 #3


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    No bias would require the same angular velocity for all stars. Stars closer to the galactic center have a larger angular velocity: if they are "behind" us (relative to the orbital direction), they are approaching us, if they are "ahead" of us, they move away from us. The opposite happens to stars further away from the center.

    There is a also some dipole effect from the random motion of our sun relative to the average flow of stars around us.
  5. Sep 28, 2016 #4
    Thanks for the hint. That makes sense, and it should produce a cross pattern - like the BMW logo. However the RAVE survey only covers a portion of one hemisphere (looking back apparently) so we don't get the whole pattern, but a top view from one of the video does indeed show a 'blue shift' for stars closer to the galactic center as you explain it:

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