As an astronomer, there is no better feeling than achieving “first light” with a new instrument or telescope. It is the culmination of years of preparations and construction of new hardware, which for the first time collects light particles from an astronomical object.

This is usually followed by a sigh of relief and then the excitement of all the new science that is now possible.

On October 22, the Dark Energy Spectroscopic Instrument (DESI) on the Mayall Telescope in Arizona, US, achieved first light. This is a huge leap in our ability to measure galaxy distances – enabling a new era of mapping the structures in the Universe.