New Delhi:
The first and largest map of the large-scale structure of the universe has been created by the astronomers. The largest map of the universe created ever is based entirely on the positions of quasars, the incredibly bright and distant points of light that are powered by super-massive black holes.
Ashley Ross of the Ohio State University in the US said quasars are the ideal objects that have helped in making the biggest map of universe yet, thanks to their brightness and visibility all across the universe.
"Because quasars are so bright, we can see them all the way across the universe," said Ross. "That makes them the ideal objects to use to make the biggest map yet," said Ross.
The super-massive black holes at the centre of the quasars provide the brightness to them. The quasar’s black hole heat up to incredible temperatures and begin to glow when the matter and energy fall into them. A dedicated 2.5-metre telescope on Earth detects this bright glow.
"These quasars are so far away that their light left them when the universe was between three and seven billion years old, long before the Earth even existed," said Gongbo Zhao from the National Astronomical Observatories of Chinese Academy of Sciences.
The Sloan Foundation Telescope was used by the scientists to create the map as they observed an unprecedented number of quasars.
Astronomers measured accurate three-dimensional positions for more than 147,000 quasars during the first two years of the Sloan Digital Sky Survey's Extended Baryon Oscillation Spectroscopic Survey (eBOSS).
The team obtained the distances of the quasars with the help of the telescope’s observations. They used it to create a three-dimensional map of where the quasars are.
However, they had to go a step further to use the map to understand the expansion history of the universe. For this, they used a clever technique involving studying "baryon acoustic oscillations" (BAOs). BAOs are the present-day imprint of sound waves which travelled through the early universe, when it was much hotter and denser than the universe we see today.
However, when the universe was 380,000 years old, conditions changed suddenly and the sound waves became "frozen" in place. These frozen waves are left imprinted in the three- dimensional structure of the universe we see today. The results of the new study confirm the standard model of cosmology that researchers have built over the last 20 years.
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In this standard model, the universe follows the predictions of Einstein's General Theory of Relativity - but includes components whose effects we can measure, but whose causes we do not understand.
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(With inputs from PTI)
