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Doppler shift question (galaxy movement)

  • Thread starter psych2012
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  • #1
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Homework Statement



In a distant galaxy, an emission line of hydrogen that has a rest wavelength of 656 nm has an observed wavelength of 662.6 nm. Is the galaxy moving away from us or toward us? How fast is it moving in (km/sec)?


Homework Equations



velocity = ((shifted wavelength - rest wavelength)(c)) / rest wavelength

The Attempt at a Solution



velocity = ((6.626 x 10^-10 km - 6.56 x 10^-10 km)(3 x 10^5 km)) / 6.56 x 10^-10 km = 3018 km/sec

My answer is: the galaxy is moving away from us at 3018 km/sec. I'm hoping someone can tell me if this answer is correct. My instructor assigned this as a homework question and will be using it as a quiz question as well, so it's a double whammy if I don't have the right answer.
 

Answers and Replies

  • #2
Delphi51
Homework Helper
3,407
10
Correct!
 

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