Understanding gravity and inflation with SKA and other telescopes

The Square Kilometre Array (SKA) project’s 2016 science conference, “Science for the SKA Generation”, is currently taking place in Goa, India. 

SKA-mid artist impression
Artist's impression of the SKA-MID telescope (Credit: SKA Organisation)

Some 200 astronomers from around the globe have travelled to attend the week-long conference, which this year is focusing on bringing early career and senior researchers together to develop new collaborations and preview the science that SKA will do in 2023 and beyond.

Stefano Camera, Research Associate in Theoretical & Observational Cosmology at the Jodrell Bank Centre for Astrophysics, presented his work on how observations conducted with the SKA and other upcoming cosmological surveys will provide scientists with valuable insights into the behaviour of gravity on very large scales in the early stages of the Universe. This will allow them to refine our current models and better understand the process of inflation that is thought to have driven this early evolution.

The work is based on a statistical analysis of the distribution of galaxies, to be obtained with large-scale surveys conducted using the SKA dishes (SKA-mid) in South Africa.

“We need a census of hundreds of millions of galaxies, stretching as far away as possible and covering almost the whole sky for the analysis to be relevant” explained Stefano.

Current optical facilities can only look at small areas of the sky at a time to get enough depth to see very distant galaxies, or map large areas superficially. “SKA-mid is uniquely suited to go beyond the current capabilities. With its sensitivity and survey speed we’ll be able to create large but accurate maps of the temperature of neutral hydrogen in galaxies, effectively surveying an unprecedented volume of the Universe.”

The distances of galaxies, however, are hard to measure using solely their radio wave emissions, hence the need for synergy with other facilities. To get this information, Stefano would use data produced by the upcoming Euclid spacecraft and conduct a similar survey with the Large Synoptic Survey Telecope (LSST) in Chile. Euclid is a European Space Agency mission to map the geometry of the Dark Universe and understand the evolution of cosmic structures in the optical/near-infrared, due to launch in 2020. LSST is a wide-field optical survey telescope being built in Chile and due to start operating in 2019.

“Thus, by combining observations from different experiments at different wavelengths, we can obtain extra information and get the full picture on how cosmic structures evolved on extremely large scales”, he added.

“At such large scales, we can still detect an imprint of the early inflation of the Universe, the mysterious phase of accelerated expansion which set the stage for the formation of galaxies and all the structures in the cosmos.”

Stefano concluded, “For the first time, we will be able to compare predictions of how Einstein’s theory of gravity works on these large scales with actual observations. If the predictions and the data match, it’ll be a further beautiful confirmation of the theory of general relativity, but if they don’t, it could be a tell-tale sign that we need a different theory. This is very exciting as it will eventually lead us to a better understanding of gravity as a fundamental force of Nature, allowing us to extend our understanding of the history of the Universe back to the Big Bang itself!”

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