 Photometric redshift

A photometric redshift is an estimate for the recession velocity of an astronomical object, such as a galaxy or quasar, without measuring its spectrum.The technique uses photometry (that is, the brightness of the object viewed through various standard filters, each of which lets through a relatively broad passband of colours, such as red light, green light, or blue light) to determine the redshift, and hence, through Hubble's law, the distance, of the observed object.