Astronomers Create 3D Map of Dark Matter
Astronomers have mapped the positions of vast, invisible isles of dark matter in the sky, within which normal “bright” matter galaxies are embedded like glittering gems. The three-dimensional map [image] spans not only space, but also time, and stretches back to when the universe was only about half its present age.
Dark matter is a mysterious hypothetical substance [image] that is thought not to interact with light photons and is thus invisible to current detection instruments.
Scientists first invoked the concept in the 1930s to explain why fast-spinning galaxies with relatively little mass don’t break apart. The unusual solution: They contain a large amount of invisible matter whose heft and gravity hold the galaxies together. Scientists have since estimated that only about one-sixth of the matter in the universe is visible, and that the rest is dark matter.
Some of the strongest evidence for dark matter’s existence was announced last year, and even that was highly debated.
Even though dark matter can’t be seen directly, some scientists say its presence and distribution in the universe can be observed indirectly by the way its gravity distorts the light of distant galaxies streaming toward us.
“We look at galaxies which are behind the dark matter that we’re interested in,” explained study team member Richard Massey of Caltech. “The light from these distant galaxies doesn’t travel in a straight line because space itself is distorted and bent, and the light follows that distortion.”