The enormous shell rests silently in an oak-studded plaza. You can’t miss it. In fact, Marc Quinn’s “Spiral of the Galaxy” is likely the most easily spotted work of art on the verges of the University of Texas campus, second only to Ellsworth Kelly’s “Austin,” the building-as-art at the Blanton Museum of Art. That’s because most of the school’s legacy art, as well as newer works planted by UT’s nationally acclaimed Landmarks public art program, are found deeper inside the urban campus. In part because the bronze surfaces of the shell readily catch the light during the day and night, passersby in cars automatically glance in its direction. On a fine day — absent a pandemic — “Spiral of the Galaxy” can be seen surrounded by people lingering at more than a dozen tables and ledges in the plaza outside Dell Medical School’s trim and shiny Health Learning Building, opposite the Dell Seton Medical Center on Red River Street.