Is dark energy accelerating at a faster speed? 

Manasi Saraf Joshi
Wednesday, 26 September 2018

“By using the Hyper Suprime-Cam Survey, which uses the 820 mega-pixel Hyper Suprime-Cam attached to the 8.2 metre Subaru telescope at the summit of Maunakea, allowed researchers to study galaxies billions of light years away. These galaxies existed billions of years ago but their light only reached Earth today,” .-Surhud More said

Pune: Scientists world over are trying to solve the mystery of dark energy and dark matter which together make up 95 per cent of our universe. Dark matter is responsible for the formation of galaxies in the universe while dark energy is responsible for the acceleration in the universe’s ongoing expansion.

To know what exactly is dark matter and dark energy, a group of scientists have surveyed and made the world’s deepest, yet a wide map of dark matter. Associate Professor at Inter-University Centre for Astronomy and Astrophysics (IUCAA), Surhud More said, “Previous studies have measured the amount of cosmic structure when the universe was young. Dark energy can affect the growth rate of these structures at a later time, closer to today. Scientists are just starting to measure the growth of these structures by studying dark matter in the later universe and thus using it to learn about dark energy.” 

“By using the Hyper Suprime-Cam Survey, which uses the 820 mega-pixel Hyper Suprime-Cam attached to the 8.2 metre Subaru telescope at the summit of Maunakea, allowed researchers to study galaxies billions of light years away. These galaxies existed billions of years ago but their light only reached Earth today,” he said.

He added, “Einstein’s general theory of relativity has helped us measure the lumpiness of dark matter in our universe today by analysing images of 10 million distant galaxies and further use it to understand dark energy.” Einstein had predicted gravitational lensing in his theory of general relativity, where gravity can bend the path of light, making faraway galaxies appear distorted to the observers on the Earth. “With this method, astronomers make a new, sharp and wide 3-dimensional dark matter map of the universe that reveals the lumpiness of the universe. Secondly, comparisons to the young universe could shed light on the nature of dark energy,” he said. 

Since 2014, researchers from Japan, Taiwan and the US, led by Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU) Project Assistant Professor Chiaki Hikage and a collaboration group co-chaired by Surhud studied these minute distortions caused by gravitational lensing to reconstruct where matter is distributed in the universe. Now, the team can see how fluctuations of dark matter across the sky have changed over billions of years and how dark energy has influenced this growth of structure. “Fluctuations measured by Planck are like a precise arrow shot from the early universe and we have measured where the arrow landed with Hyper Suprime-Cam instrument of the Subaru Telescope,” said 
Surhud.Luckily, there is more data for the team to analyse in the future. This result uses only 11 per cent of the full survey, because the Hyper Suprime-Cam is still taking images, and is scheduled to finish around 2020. “LSST will survey 100 times more area within the next decade with about a 100 times more galaxies to map out the unseen dark matter and the properties of dark energy,” he said.

Originally from Dehugaon, 34-year-old Surhud was brought up in Mushet, Alibaug before he moved out for his research work. He was an associate professor at Kavli, IPMU and currently holds an affiliate position there.

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