A 3-D map of the universe spanning 12 to 14.5 billion light-years. Image credit: NAOJ; partial data supplied by: CFHT, SDSS.By using the Fibre Multi-Object Spectrograph (FMOS) on the Subaru Telescope, an international team led by Japanese researchers has made a 3-D map of 3,000 galaxies 13 billion light-years from Earth. Based on this comprehensive survey — the first such study at this great distance — the team was able to confirm that Einstein’s general theory of relativity is still valid.
Since it was discovered in the late 1990s that the universe is expanding at an accelerated rate, scientists have been trying to explain why. The mysterious dark energy could be driving acceleration, or Einstein’s theory of general relativity, which says gravity warps space and time, could be breaking down.Teppei Okumura (left) and Chiaki Hikage. Image credit: Kavli IPMU.To test Einstein’s theory, a team of researchers led by Teppei Okumura (Kavli IPMU Project Researcher), Chiaki Hikage (Kavli IPMU Project Assistant Professor), and Tomonori Totani (University of Tokyo Department of Astronomy Professor), used FastSound Survey data on more than 3,000 distant galaxies to analyse their velocities and clustering. This survey is one of the strategic observation programs at the Subaru Telescope, and used 40 nights of its telescope time from 2012 to 2014.
Their results indicate that even far into the universe, general relativity is valid, giving further support that the expansion of the universe could be explained by a cosmological constant, as proposed by Einstein in his theory of general relativity.Experimental results looking at the expansion of the universe, in comparison to that predicted by Einstein’s theory of general relativity in green. Comoving distance is one of the distance scales used in cosmology. It is derived from the time taken for the object’s light to reach the observer, including the change caused by the expansion of the universe so far. Illustration credit: Okumura et al.“We tested the theory of general relativity further than anyone else ever has. It’s a privilege to be able to publish our results 100 years after Einstein proposed his theory,” said Okumura.
“Having started this project 12 years ago it gives me great pleasure to finally see this result come out,” said Karl Glazebrook, Professor at Swinburne University of Technology in Australia, who proposed the survey.
No one has been able to analyse galaxies more than 10 billion light-years away, but the team managed to break this barrier thanks to the FMOS on the Subaru Telescope, which can analyse galaxies 12.4 to 14.7 billion light-years away. The Prime Focus Spectrograph, currently under construction, is expected to be able to study galaxies even further away.
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