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Homework Help: Transverse velocity

  1. Mar 26, 2008 #1
    Hi, I've been asked to find the transverse velocity of a star. It has a proper motion of 0.249 arcsec/yr and it is at a distance of 23.8 parsecs.

    Now im happy with the formula to use (vt = d x sin(mu)) but im not sure of the units im supposed to be using. I've plugged these values straigh in but the result doesn't seem correct.

    Can anyone perhaps tell me what units are supposed to be used here?

  2. jcsd
  3. Mar 26, 2008 #2

    Chi Meson

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    1 Parsec = 3.086 × 10^16 meters

    Make a right triangle with one angle of 0 degrees, 0 minutes, and 0.249 seconds (0.249"). The length of hypotenuse will be essential the same as the length of the adjacent side, so it doesn't matter which one you choose to be the distance to the star (oh, meters or km works fine). Do a little trig to find the distance the star moves in a year.

    Units could be m/s, km/year, m/year.
  4. Mar 26, 2008 #3


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    … Au … ?

    Hi grscott_2000! :smile:

    I suspect you're supposed to do it in AU (astronomical units) … see:

    Last edited: Mar 26, 2008
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