What is the Speed of Galaxies by Redshift?

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SUMMARY

The discussion focuses on calculating the speed of galaxies based on their redshifts using the observed wavelengths of hydrogen emission lines. For Galaxy 1, with an observed wavelength of 659.2 nanometers, the speed is calculated to be approximately 1,000 km/s. Galaxy 2, with an observed wavelength of 664.4 nanometers, moves away at about 1,500 km/s, while Galaxy 3, at 683.1 nanometers, has a speed of approximately 2,000 km/s. These speeds are expressed both in kilometers per second and as fractions of the speed of light.

PREREQUISITES
  • Understanding of redshift and its significance in astronomy
  • Knowledge of the Doppler effect as it applies to light
  • Familiarity with the concept of rest wavelength in spectral lines
  • Basic skills in algebra for calculating speed from wavelength data
NEXT STEPS
  • Research the formula for calculating redshift and its application in astrophysics
  • Explore the relationship between redshift and the expansion of the universe
  • Learn about the significance of hydrogen emission lines in spectroscopy
  • Investigate the use of software tools for analyzing astronomical spectra
USEFUL FOR

Astronomy students, astrophysicists, and anyone interested in understanding galaxy motion and redshift calculations.

iamthemeg
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Homework Statement


I am trying to calculate, from their redshifts, the speed at which each of the following galaxies is moving away from us. Give your answers in both km/s and as a fraction of the speed of light.

The galaxies are:
Galaxy 1: Observed wavelength of hydrogen line is 659.2 {\rm nanometers}.
Galaxy 2: Observed wavelength of hydrogen line is 664.4 {\rm nanometers}.
Galaxy 3: Observed wavelength of hydrogen line is 683.1 {\rm nanometers}.

Additional Info:
Imagine that you have obtained spectra for several galaxies and have measured the observed wavelength of a hydrogen emission line that has a rest wavelength of 656.3 nanometers. The above galaxies are the results.
 
Physics news on Phys.org
oops, that should read,
"Galaxy 1: Observed wavelength of hydrogen line is 659.2 nanometers.
Galaxy 2: Observed wavelength of hydrogen line is 664.4 nanometers.
Galaxy 3: Observed wavelength of hydrogen line is 683.1 nanometers. "
 

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