At around 10:30 p.m. on June 9, President Susan Hockfield flipped the switch turning on the 12 new fixtures that will illuminate the Great Dome, the Roman numerals that spell out 1916, and the façade of Building 10. The new lights, which use only as much electricity as two hair dryers, are indirectly powered by a 40-kilowatt photovoltaic array that will feed MIT’s grid three to four times as much energy as the fixtures use. The system replaces long-defunct roof fixtures, which lit the dome, and problematic fixtures that lit the façade from Killian Court trees. An anonymous donor and a Massachusetts Technology Collaborative grant provided funds for the system.