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A cosmic illusion revealed

A team of researchers led by Robert Quimby at the Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU) has announced the discovery of a galaxy that magnified a supernova thirtyfold via gravitational lensing. This is the first example of strong gravitational lensing of a supernova and confirms the team’s previous explanation for the unusual properties of this supernova. The team has also shown how such discoveries of objects of known brightness, like type Ia supernovae (SNIa), could become far more common than previously thought possible. A SNIa supernova seen through gravitational lenses can be used to make a direct measurement of the universe’s expansion rate (the Hubble parameter), so this discovery may have a significant impact on how cosmic expansion is studied in the future. Supernovae of Type Ia (SNIa) are also very useful to understand the mysterious components of the Universe such as dark energy and dark matter. SNIa have strikingly similar peak luminosities, regardless of where they happen in the Universe. This property allows astronomers to use SNIa as standard “candles” to measure cosmological distance independent of the Universe’s expansion. Distance measurement with SNIa was key to the discovery of accelerating expansion of the Universe (2011 Nobel Prize in Physics). In 2010, a supernova named PS1-10afx was found that demonstrated the same color and light curve (the change in brightness over time) as a Type Ia supernova, but its peak brightness was 30 times greater than expected. This discovery was made using the Panoramic Survey Telescope & Rapid Response System 1 (Pan-STARRS1, a telescope located in Hawai’i that can image the entire visible sky several times each month). This anomaly led some to conclude that it was a completely new type of superluminous supernova. “PS1-10afx looked a lot like a Type Ia supernova, ” says Quimby, “but it was just too bright.” “In the future, when a target is identified as a possible lensed Type Ia supernova,” says Quimby, “high-resolution follow-up observations can be taken to resolve the individual image components.” Each image comes from the same source but travels a different path length on its way to the observer, so there is an arrival time difference between these multiple supernova images. If this “time delay” can be measured, a direct test of cosmic expansion is possible, faster expansion leads to shorter time delays. By timing the delays precisely and comparing these to the delay expected from the geometry of the lens, expansion history of the Universe can be directly inferred. Quimby continues, “The discovery and selection method we have crafted may thus soon improve our understanding of our expanding universe.” via KurzweilAI.

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