What Are Redshifts?
An object whose light has been stretched since it was emitted is said to be “redshifted.” Conversely, if the wavelength of the light is reduced, the object is said to be “blueshifted.” A redshift does not mean that the object will necessarily appear red. It simply means the light wavelengths are longer (and thus appear “redder”) than they would otherwise be. So you can’t tell just by looking at a star whether it is redshifted or blueshifted. In fact, the overall color of a star indicates its temperature—it has virtually nothing to do with redshifts. To calculate redshift, astronomers break the light into a rainbow (a spectrum) and measure how certain spectral features have moved toward the red end of the spectrum. Several things can cause a redshift. One is velocity. If a star is moving away from us, its light beams become stretched due to the Doppler Effect. Stars within our own galaxy are redshifted or blueshifted due to their velocity relative to us. A second cause of redshift is gr
