March 5, 2015: Three-leaf clover plants abound everywhere: on lawns, in gardens, and in forests. But spotting a four-leaf clover is a rare, lucky find. Astronomers using the Hubble Space Telescope have found the equivalent of a four-leaf clover with the discovery of four images of the same supernova. The images are arranged around a giant foreground elliptical galaxy embedded in a cluster of galaxies. The arrangement forms a cross-shaped pattern called an Einstein Cross. The powerful gravity from both the elliptical galaxy and its galaxy cluster magnifies the light from the supernova behind them in an effect called gravitational lensing. The elliptical galaxy and its galaxy cluster, MACS J1149.6+2223, are 5 billion light-years away from Earth. The supernova behind it is 9.3 billion light-years away.
Once the four images fade away, astronomers predict they will have a rare opportunity to
watch a rerun of the supernova's appearance. Computer models of the cluster predict
that another image of the stellar blast will appear within five years. Astronomers may
have missed an earlier appearance of the supernova in 1995. These multiple appearances
of the exploding star are due to the various paths its divided light is taking
through the maze of clumpy dark matter in the galactic grouping. Each image takes a
different route through the cluster and arrives at a different time, due, in part, to
differences in the length of the pathways the light follows to reach Earth.
Join Hubble astronomers during the live Hubble Hangout discussion at 3pm EST on Thurs., March 5, to learn still more.