Astronomers using the Hubble Space Telescope have captured four images of the same supernova, but they all appeared in different places. How? The light from that distant stellar explosion was redirected by a galaxy between Earth and the supernova,
Astronomers using the Hubble Space Telescope have captured four images of the same supernova, but they all appeared in different places. How? The light from that distant stellar explosion was redirected by a galaxy between Earth and the supernova, in one of the clearest examples of gravitational lensing ever observed.
Scientists have theorized for decades that it would be possible to observe the light from a supernova in this way, but this is the first observed instance of it. There are a number of examples of gravitational lensing for other objects, like stars and quasars — the Einstein Cross is a particularly good example.
The supernova observed by Hubble was named SN Refsdal in honor of the famed Norwegian astrophysicist. The stellar detonation, which was spotted on Nov. 11, 2014, is located 9.3 billion light years away from Earth. That’s very near the edge of the observable universe. In the middle of that 9.3 billion year journey here, the light from SN Refsdal passed through a giant cosmic lens caused by the gravity from a large cluster of galaxies called MACS J1149.6+2223. The four lights appeared separately over the course of several weeks, as light can take different paths through a lens the size of a galaxy.
The discovery of this object comes quite close to the 100-year anniversary of Einstein’s theory of general relativity, which predicted gravitational lensing long before we had the tools to observe it. Among relativity’s numerous predictions is the idea that even light must obey gravity. The gravity of a very massive object like a star or, as in this case, a cluster of galaxies, is sufficient to bend light as it passes by. Light rays passing through an area of space that has been curved