We Have A New Map Of Dark Matter In The Universe... But It Doesn't Match The Last One

Monday, 01 October 2018 - 12:05PM
Astronomy
Physics
Space
Monday, 01 October 2018 - 12:05PM
We Have A New Map Of Dark Matter In The Universe... But It Doesn't Match The Last One
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NASA JPL
A few years ago, the Planck survey gave scientists a picture of where dark matter might be lurking across the universe. That survey was based on monitoring the cosmic background radiation (or CBR) but, like an invisible kid on a trampoline, scientists still can't observe dark matter directly – they can only measure its effects. Now, a new survey conducted by Japan's Subaru Telescope, called the Hyper Suprime-Cam survey, has created a new, 3D map of all that dark matter... But the two versions don't quite match up.

What's interesting is that the HSC survey isn't using the same method as Planck. Instead of monitoring the CBR to create its map, it relied on the phenomenon of gravitational lensing, which occurs when light is bent by gravitational forces. Astronomers have already used gravitational lensing to peer at distant galaxies, but in the case of the HSC survey, the key was to estimate the shape of a galaxy and see how distorted its image was when observed by the telescope. After factoring in all the regular variables, like the effects of the atmosphere and the telescope itself, the distortion left over was credited to dark matter, which the light would have to pass through to get to Earth.



The map created by the HSC survey is strikingly similar to Planck's but seems to reflect less dark energy than expected. The difference isn't statistically significant, but something similar happened in 2013 when the Planck satellite released its findings: there was a little less dark energy and dark matter than expected. Still, it's an exciting day for physicists and astronomers looking to pin down what exactly makes up 95% of the universe.

According to Rachel Mandelbaum, an astronomer associated with the study: "Our map gives us a better picture of how much dark energy there is and tells us a little more about its properties and how it's making the expansion of the universe accelerate."
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