  Objects of known brightness, like Type Ia supernovae (SNIa), can be used to
measure distances. If a massive object warps spacetime to form multiple images
of a background SNIa, a direct test of cosmic expansion is also possible.
However, these lensing events must first be distinguished from other rare
phenomena. Recently, a supernova was found to shine much brighter than normal
for its distance, which resulted in a debate: was it a new type of
superluminous supernova or a normal SNIa magnified by a hidden gravitational
lens? Here we report that a spectrum obtained after the supernova faded away
shows the presence of a foreground galaxy--the first found to strongly magnify
a SNIa. We discuss how more lensed SNIa may be found than previously predicted.
