Public Release: 

Seeing quadruple: Four images of the same supernova, a rare find

American Association for the Advancement of Science

Galaxies bend light through an effect called gravitational lensing that helps astronomers peer deeper into the cosmos. Now, researchers have detected an extreme case of this phenomenon where a fortuitously aligned galaxy has magnified a Type Ia supernova by roughly 50 times. The researchers report acquiring four images of this supernova event; to date, acquiring multiply imaged lensed supernova has been extremely difficult, in particular for Type 1a supernovae, which are important to study as indicators of distance in cosmology. One of the foundations of Einstein's theory of general relativity is that matter curves the surrounding space-time. This curve can create a "lens," deflecting the path of passing light and magnifying any objects on the other side. Yet, for astronomers to benefit from this phenomenon, a sufficiently massive foreground object must align precisely with the background target they wish to study. If the target is fleeting, as with a supernova, it must be spotted and studied quickly. In September 2016, using the intermediate Palomar Transient Factory in California, Ariel Goobar and colleagues detected a new Type Ia supernova that appeared to have the correct alignment with a foreground galaxy. Moving quickly, they were able to utilize several other telescopes to make detailed measurements of the supernova, called iPTF16geu. High-resolution data showed that the light from the supernova had been split into four images by the lens, which also magnified it by a factor of about 50. Because Type Ia supernova explode in a very predictable and consistent manner, comparing the four separate images could help scientists to determine the expansion rate of the Universe or other cosmological parameters.

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