Reposted from the University of Portsmouth News:
Cosmologists from the University of Portsmouth are among those preparing to make the biggest map of the Universe ever created.
Scientists from Portsmouth’s Institute of Cosmology and Gravitation are part of an international team setting out their plans for the giant cosmic atlas to be made by sweeping the sky and combining signals from hundreds of radio dishes.
Researchers from the Cosmology Science Working Group of the Square Kilometre Array (SKA) have worked out how to use the world’s largest telescope for the task.
Professor Roy Maartens, from Portsmouth and the University of the Western Cape, in South Africa, announced the plans for a new mammoth survey today.
He said: “The team has produced an exciting collection of cutting-edge ideas that will help shape the future of cosmology.
“These are ideas and questions which astrophysicists have had rattling round their minds for decades.”
Dr David Bacon, Dr Gongbo Zhao and Dr Alkistis Pourtsidou, all from the Institute of Cosmology and Gravitation, are also part of the team, along with cosmologists from Australia, France, Germany, Italy, Japan, the Netherlands, Norway, the UK and the USA.
A computer generated image of the SKA-MID, with 15m wide dish telescopes to track objects. When it is built, the field will also include aperture array telescopes, able to electronically point at multiple regions of the sky simultaneously. CREDIT: SKA Organisation
The SKA will be a collection of thousands of radio receivers and dishes spread across two sites in South Africa and Western Australia. When the first phase is completed in 2023, the SKA will have a total collecting area equivalent to 15 football pitches, and will produce more data in one day than several times the daily traffic of the entire internet. A second phase, due in the late 2020s, will be ten times larger still.
The standard way to map the positions of galaxies is to painstakingly detect the faint signals from many individual galaxies, staring at them for long enough to measure properties like their distance. Though time consuming, this method is the most accurate, allowing highly detailed 3D maps of the matter distribution to be made. By the late 2020′s, the researchers hope to have found almost a billion galaxies in this way; in comparison, the largest galaxy surveys to date have mapped the positions of only around a million galaxies.
An alternative option being developed by SKA researchers, and others, is to rapidly scan the telescopes across the sky, sacrificing accuracy but surveying a much larger area in a short period of time.
This will give a low-resolution map, but enough information to start answering questions about the geometry of the Universe and the nature of gravity. The results from this type of ‘intensity mapping’ survey could be ready as early as 2025.
For the astrophysicists, some of the biggest questions relate to dark energy, an enigmatic substance that appears to be making the Universe expand at an ever faster rate. The SKA will allow the most precise investigations of dark energy to date. By using 3D maps of the distribution of galaxies, they will be able to study dark energy and test Einstein’s theory of General better than any experiment so far.
Dr Zhao said: “Testing Einstein’s theory is a top priority for cosmologists. We will be able to shed light on whether there is a ’5th force’ of nature. Seeing it would be the smoking gun revealing that General Relativity is breaking down over cosmological distances.”
Such a huge atlas of the distribution of matter in the Universe will also open a new window to investigate the first moments after the Big Bang, which will help shed light on how the new-born Universe behaved when it was only a fraction of a second old. The measurements will allow researchers to more closely scrutinise “cosmic inflation”, the process that is believed to have sown the seeds of structures like galaxies and superclusters that we see today.
Dr Bacon said that in addition to 3D maps of the hydrogen radio emission, the SKA will also make two-dimensional maps using the total radio-wave emissions of galaxies. The 2D maps will also provide a new way of seeing how light rays are bent by gravity – an early prediction of Einstein’s theory that was first measured during a solar eclipse in 1919.
He said: “By measuring tiny distortions in the shapes of galaxies, we hope to track the evolution of structures in dark matter over cosmic time.”
The researchers hope that this will provide more vital clues about the nature of dark energy, and how structures formed in the Universe.
A range of experiments scheduled to begin in the next decade will provide a wealth of astrophysical information to complement and check the SKA’s findings.
