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

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SUMMARY

The galaxy NGC 221 exhibits a blue shift in its light spectrum, indicating it is moving towards Earth. The calcium line typically observed at 396.85nm is recorded at 396.58nm, confirming this motion. To calculate the speed of the galaxy, the formula Fobs = fsourcesqrt[(c-v)/c+v)] should be utilized, as the ratio of observed to source wavelengths can provide the necessary information. The discussion emphasizes the importance of correctly applying the Doppler effect equations to determine the velocity of celestial bodies.

PREREQUISITES
  • Understanding of the Doppler effect in astronomy
  • Familiarity with spectral lines and their significance
  • Basic knowledge of physics equations related to wave motion
  • Proficiency in algebra for manipulating equations
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  • Study the application of the Doppler effect in astrophysics
  • Learn how to calculate redshift and blueshift using spectral data
  • Explore the implications of galaxy motion on cosmology
  • Investigate the properties of light spectra from various celestial objects
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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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