Four ways of looking at a supernova
Lenses make things look big. When the lens is the size of a galaxy, things look very big indeed.
WHEN ASTRONOMER ARIEL GOOBAR at the Intermediate Palomar Transient Factory in California looked at the image recorded by the facility’s camera, he knew he had to sprint. Incredibly, he was looking at something simultaneously massive, spectacular, new, short-lived and a triumphant demonstration of the theory of general relativity.
The camera had captured a new supernova – dubbed iptf16geu – exactly as it exploded. That was extraordinary enough, but there was something even weirder: the supernova looked 50 times larger than it should, given that it was one billion light-years away from Earth.
Goobar realised he was witnessing a phenomenon called “gravitational lensing”, predicted by Einstein but rarely seen. In this case, it was all due to a large galaxy situated between Earth and iptf16geu.
The galaxy was curving the space-time surrounding it. Light travelling through the curvature acted as a lens, enlarging the appearance of the distant explosion. It was a once-in-a-century opportunity. Goobar hit the phones, and organised extra images from the Hubble Telescope, the Very Large Telescope in Chile, and the Keck Observatory in Hawaii. The result? Supernova, four ways.
supernova iptf16geu in background galaxy multiple images of the supernova and background galaxy