Why Is Galaxy NGC 221 Exhibiting a Blue Shift in Its Light Spectrum?

AI Thread Summary
Galaxy NGC 221 is exhibiting a blue shift in its light spectrum, indicating it is moving towards Earth. The calcium line typically observed at 396.85 nm is detected at 396.58 nm, confirming this motion. To calculate the speed of the galaxy, the observer needs to apply the appropriate formula for redshift and blueshift. The initial attempts to find the speed using the wavelength ratio have led to confusion, resulting in incorrect values. Clarification on the correct application of the formula is sought for accurate speed determination.
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Homework Statement



The light from galaxy NGC 221 consists of a recognizable spectrum of wavelengths. However, all are shifted to the shorter wavelength end of the spectrum. In Particular, the calcium "line" ordinarily observed at 396.85nm is observed at 396.58nm. (a) is this galaxy moving towards or away from the earth? (b) at what speed?

Homework Equations



Fobs=fsourcesqrt(1-v^2/c^2)/(1+v/ccostheta)

The Attempt at a Solution


I think that the galaxy is moving toward the earth, but I'm not sure how to get what speed it's going at. I tried totake the ration of 396.58/396.85 to plug in so the frequencies would cancel out, but I'm getting a very small negative number. This doesn't seem right. Any help would be appreciated!
 
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Use the formula
fobs = fsourcesqrt[(c-v)/c+v)]
 
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