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At rest, hydrogen has a spectral line at 126 nm. If this line is observed at 141 nm for the star Sirius, how fast is Sirius moving in km/s?

 Jan 31, 2021
edited by Skatergoat  Jan 31, 2021
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z = (obs - emit )/emit

  =  (141-126)/126 = .119    (positive =   red shift)

 

if v is much less than c then   z~~ v/c

.119 = v/3x10^8

v = 3.57 x 107 m/s = 3.57 x104 km/s       (ignoring the Lorentz factor)

 Feb 1, 2021
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Thank you bro!!!

Skatergoat  Feb 1, 2021

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