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Homework Help: Relativity aberration of light

  1. Feb 11, 2013 #1
    Hi everybody, I really need help and it's quite an emergency..
    I have this problem to do but i'm really stuck I don't know where I have to begin and I don't even understand what they're asking for:

    A star in the sky is observed from earth to describe an elliptical path whose minor axis subtends
    an angle of 36". What angle does the star make with the ecliptic?
    Suppose the apparent elliptical motion of part (b) were due entirely to the parallax effect.
    Approximately how far away (in light years) from the sun would the star be?

    Here it is ! I was trying to draw the situation but it's impossible, i'm not visualizing which angle I have to calculate and what does 36" represent exactly ? I just have the final result,but don't know how to get to it. If someone can explain and help me with a drawing it would be nice !

  2. jcsd
  3. Feb 12, 2013 #2


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    Science Advisor
    Homework Helper

    Welcome to PF!

    Hi Unicorn! Welcome to PF! :smile:

    If the star is stationary, so that the ellipse is entirely caused by parallax,

    then we can treat the earth as stationary instead,

    in which case the star must be following a circle with the same radius as the earth's orbit, and parallel to the ecliptic …

    that's the circle which (because we don't see it head-on) looks like the ellipse described in the question :wink:
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