NASA & ESA and P. Kelly (University of California, Berkeley), CC BY 3.0 <https://creativecommons.org/licenses/by/3.0>, via Wikimedia Commons
NASA & ESA and P. Kelly (University of California, Berkeley), CC BY 3.0 <https://creativecommons.org/licenses/by/3.0>, via Wikimedia Commons

Light from this exploding star may tell us how fast the universe is expanding

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Images of an exploding star whose light was distorted by gravity may help us pin down just how fast the universe is expanding, according to Australian and international research. Scientists currently use two methods to try to measure the expansion of the universe, known as the Hubble constant, but these two methods have produced different results. This new research uses a new technique that involved looking at five images of a distant supernova, called N Refsdal, which is located about 9.3 billion light-years away from Earth. The light from this exploding star was warped by gravity as it travelled different paths to Earth creating 5 different images. By looking at the different images the researchers were able to measure how much the Universe had grown.

Journal/conference: Science

Link to research (DOI): 10.1126/sciadv.abh1322

Organisation/s: The Australian National University, ARC Centre of Excellence for All Sky Astrophysics in 3D (ASTRO 3D), University of Minnesota, USA

Funder: N/A

Media release

From: AAAS

Gravitational lensing of a supernova provides a measurement of the Hubble constant

Science

The time delays between multiple images of Supernova Refsdal, produced by gravitational lensing, provide a new measurement of the expansion rate of the Universe, according to a new study. The Hubble constant quantifies the expansion rate of the Universe; its value is debated, with different methods giving inconsistent results. In principle, the time delays between multiple images of a strongly lensed supernova could provide an independent method of measuring the Hubble constant. However, this approach – known as time-delay cosmography – has not been applied to a supernova. Here, Patrick Kelly and colleagues study multiple images of the gravitationally lensed Supernova Refsdal, which was discovered using the Hubble Space Telescope in 2014. Supernova Refsdal appears in multiple images, produced through gravitational lensing by a massive foreground galaxy cluster. As predicted by models of the galaxy cluster, a new image of the supernova appeared in 2015. Monitoring the brightness of each image for multiple years has allowed the time delays between them to be measured to within 1.5%. Kelly et al. combine that measurement with lens models of the foreground cluster to make a blinded measurement of the Hubble constant, finding a value of ~66.6 kilometers per second per megaparsec. According to the authors, this value is more consistent with the Hubble constant value derived from the cosmic microwave background measurement than that from the cosmic distance ladder method.

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