A new 3D map reveals the hidden stuff of the universe

There is a huge amount of material in the universe that we can not see directly. But scientists can say that it is there. They call it dark matter.

They know it's there because their gravity pulls the stars and the galaxies that surround it, altering their motion. Dark matter also pulls light in passing, bending, a phenomenon called gravitational lens. And now, studying where this lens appears in the sky, an international team of scientists has released a detailed 3D map[BI1] of dark matter.

The biggest advantage of the cosmic map, published Monday, Sept. 24 in the arXiv preprint newspaper, is that it will help scientists determine exactly how and where dark energy – an invisible energy that permeates the universe and accelerates its expansion – operates in space, researchers said in a statement

"Our map gives us a better idea of ​​the amount of dark energy present and tells us a little more about its properties and how it accelerates the expansion of the universe." Rachel Mandelbaum, astronomer at Carnegie Mellon University in Pittsburgh in the survey, said in the statement.

To build the map, researchers carefully studied the shapes of more than 10 million galaxies, including those from far away in space, whose light created billions of years ago only reaches the Earth. [The 11 Most Beautiful Mathematical Equations]

They measured how much the shapes of these galaxies seemed to be distorted compared to what astronomers expect, then showed how much of these distortions were due to dark matter lenses rather than to the effects of the atmosphere or telescope and detector used. This difference allowed the researchers to deduce how much dark matter the light had to cross before reaching the Earth.

This map is drawn from the first of five years of observation of the Japanese Subaru telescope in Hawaii, as part of a project called "Hyper Suprime-Cam Survey" (HSC). The HSC will continue to scan the space for another four years to make its map more accurate and complete.

A first result: the HSC found evidence of a somewhat less dark energy in the universe than another previously conducted survey in Europe called the Planck survey. This study examined the weak traces of the Big Bang left by electromagnetic radiation, called the cosmic microwave background. The slight difference is small enough not to be statistically significant, which means there can be no real difference, but the difference is enticing, they said.