An invisible force affects our universe. We can not see it and can not see it – but we can observe how it interacts gravitationally with the things we can see and recognize, such as light.
An international team of astronomers has now used one of the world's most powerful telescopes to analyze this effect over 10 million galaxies related to Einstein's general theory of relativity. The result? The most comprehensive map of dark matter in the history of the universe.
The peer review is ongoing, but the map has suggested something unexpected – that dark matter structures may develop more slowly than previously thought. 19659003] "If further data show that we are definitely correct, then this indicates that our current understanding of the Standard Model and General Theory of Relativity is lacking," said the physicist Chiaki Hikage of the Kavli Institute of Physics and Mathematics of the Universe.
We do not know what dark matter is. What we do know is that the effects of gravity that we see in the universe can not be explained by observable matter alone. For example, the rotational speed of galaxies would be quite different if it relied only on the gravitational force of observable mass.
We also know that gravity can bend the path of light as we see it with gravitational lenses. This effect can also be used to map dark matter – if you subtract the gravitational effect of visible matter, the gravity effect of dark matter remains.
This is a common way to find dark matter, and that's what the Hikage team used. They used the 870-megapixel hyper-suprime cam of the 8.2-meter Subaru telescope to reach galaxies billions of light-years away.
Because it took their light so long to reach us, we see that they exist billions of years ago. Which means that the map covers a large area of the universe's history, so that astronomers can observe how dark matter is has developed over billions of years.
The resulting 3D map shows the ragged layout of the dark matter of the Universe in line with the results of previous research – with the exception of the speed with which the structures develop. After this new map, this is slower than predicted by previous results.
Not much, but enough to turn out to be weird. That is, the jury is not yet clear what it means. This could indicate that something is missing in the standard model, which would be quite amazing. or it could indicate a statistical fluctuation in the data.
It might take a while to figure it out. The team has been working on this project since 2014, using only observations from the first year or 11 percent of the survey of Hyper Suprime-Cam that are ongoing. Photographing is expected to be completed in 2020.
Let's not be too excited – there is still a lot of mothership at work. But it is still a fascinating result, and we expect more information with bated breath.
"If we can achieve better accuracy with a little more work, we might be able to find something concrete," Hikage said. "This is a big motivation factor for me."
The team's research was included in the publication of the Astronomical Society of Japan and can be read in full on the pre-print server arXiv.