Multiple Images of a Highly Magnified Supernova Formed by an Early-Type Cluster Galaxy Lens

TL;DR

This paper reports the discovery of a gravitationally lensed supernova with multiple images, enabling measurements of cosmic expansion and matter distribution in the lensing galaxy and cluster.

Contribution

First observation of a supernova with multiple images caused by gravitational lensing in a galaxy cluster, confirming Refsdal's hypothesis and providing a new tool for cosmology.

Findings

Four images of a supernova forming an Einstein cross around a galaxy

Multiple images of the host galaxy observed, with future supernova images expected

Magnifications and time delays used to probe cosmic expansion and matter distribution

Abstract

In 1964, Refsdal hypothesized that a supernova whose light traversed multiple paths around a strong gravitational lens could be used to measure the rate of cosmic expansion. We report the discovery of such a system. In Hubble Space Telescope imaging, we have found four images of a single supernova forming an Einstein cross configuration around a redshift z=0.54 elliptical galaxy in the MACS J1149.6+2223 cluster. The cluster's gravitational potential also creates multiple images of the z=1.49 spiral supernova host galaxy, and a future appearance of the supernova elsewhere in the cluster field is expected. The magnifications and staggered arrivals of the supernova images probe the cosmic expansion rate, as well as the distribution of matter in the galaxy and cluster lenses.