Question

Using the distance-redshift relationship, if a galaxy is observed to have a redshift (z) of 0.1, what is its approximate recession velocity as a fraction of the speed of light?

Accepted Answer

To calculate the recession velocity of a galaxy at low redshift, we use the formula v equals z times c, where v is the recession velocity, z is the redshift, and c is the speed of light. Redshift represents the phenomenon where light from an object moving away from an observer is stretched to longer, redder wavelengths. The speed of light, c, is approximately 300,000 kilometers per second. For a galaxy with a redshift of 0.1, you multiply 0.1 by the speed of light. This results in a recession velocity of 0.1c, or 10 percent of the speed of light. This linear approximation is valid for relatively nearby galaxies where the velocity is significantly less than the speed of light. At higher redshifts, the relationship becomes non-linear and requires the use of general relativity to account for the expansion of space itself rather than simple motion through space.

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Using the distance-redshift relationship, if a galaxy is observed to have a redshift (z) of 0.1, what is its approximate recession velocity as a fraction of the speed of light?

To calculate the recession velocity of a galaxy at low redshift, we use the formula v equals z times c, where v is the recession velocity, z is the redshift, and c is the speed of light. Redshift represents the phenomenon where light from an object moving away ....