An Erupting Classical Nova in a Globular Cluster of M87

Only one certain classical nova eruption has ever been detected inside a globular cluster—nova T Sco (observed in A.D. 1860) in M80. During a survey of M87 we have detected an erupting star coincident (to within 0.08 pixels) with a globular cluster of that giant elliptical galaxy. We are able to discount variables in the foreground or background of M87. The light curve and color of the erupting star match those expected for a nova at the distance of M87. The chance superposition of an M87 field nova on the globular cluster is very unlikely but cannot be completely ruled out. Our detection hints at a globular cluster nova frequency f ~ 0.004 nova per cluster per year, much higher than previous observations have suggested.