What is the redshift?
The redshift of an object is the amount by which the spectral lines in the source are shifted to the red. That is, the wavelengths get longer. To be precise, the redshift is given by z = [λobs-λem]/λem where λem is the emitted wavelength of a line, which is known from laboratory measurements, and λobs is the observed wavelength of the line. In an expanding Universe, distant objects are redshifted, with z = Ho D/c for small distances. This law was discovered by Hubble and Ho is known as the Hubble constant. Back to top. Are quasars really at the large distances indicated by their redshifts? The short answer is Yes! Stockton (1978, ApJ, 223, 747) observed faint galaxies near in the sky to bright quasars at moderate redshifts. He chose quasars with moderate redshifts so he would still be able to see galaxies at the redshift of the quasar. He found that a good fraction of the redshifts of the faint galaxies agreed with the redshifts of the quasars. In other words, quasars are associated wi
