Dark matter "noodles" may be hiding in the milk path

25 A new discovery by Australian scientists challenges the conventional wisdom about the gas that fills the Milky Way. In an article published in Science, the scientists wrote that they discovered a large block of invisible gas and its existence was discovered as a result of its effect on radio radiation from a distant quasar

Invisible structures in the shape of noodles, lasagna or other formations hover in our galaxy and radically challenge our understanding of the gas in our Milky Way. Australian astronomers write in an article in the journal Science that the structures look like "lumps" in the thin gas between the stars in our galaxy. The observations were made possible by an innovative technique.

According to the paper's lead author Dr. Keith Bannister "so far we have deduced that the interstellar gas is constantly being recycled by the accretion or explosion of old stars and is used by future generations of stars."

Dr. Bannister and his colleagues described groundbreaking observations of one of these "lumps" that allowed them to make the first estimate of its shape. The observations were made possible by using CSIRO's Compact Array Telescope in Eastern Australia.

Astronomers got the first clues to the existence of the mysterious objects about 30 years ago after seeing unexplained changes in the radio waves coming from a quasar. They realized that this behavior was caused by the invisible "atmosphere" of our galaxy consisting of a gas of electrically charged particles that fills the space between the stars.

"These lumps in the gas act like focusing lenses and the lack of focusing of the radio waves alternately makes them weak and strong over a period of days, weeks or months," said Dr. Bannister. These clumps are very difficult to detect and many researchers have given up looking for it, but Dr Nister and his colleagues realized they could do it with CSIRO's compact array.

They observed through the telescope a quasar known as PKS 1939-315 in the Keshet group, they saw a year-long quenching event. The astronomers believe that the size of the gas lenses is roughly the diameter of the Earth's orbit around the Sun and they are about 3,000 light years away from us, a thousand times that of the nearest star - Proxma Centauri.

Until now they knew nothing about their shape, however, the team showed that this lens cannot be a solid lump or in the form of a bent sheet.

"We are probably looking at the edge of a flat sheet," said CSIRO team member Dr. Cormac Reynolds. "Or we can be seeing the bottom of a hollow cylinder like a noodle, or a spherical shell like a nut."

As the quenching event continued, members of Dr. Bannister's team observed the same quasar through another radio telescope as well as through optical telescopes. According to Dr. Bannister, the optical light from the quasar did not change during the radio decay. "This means that optical surveys that previously looked for dark clumps in space would not have been able to detect the clump that his group identified."

What are these lenses made of? One proposal talks about cold clouds of gas that stay together through their own gravity. If this model is correct, these clouds may account for a significant fraction of the Milky Way's mass.

"No one knows what the lenses look like. But these structures are real, and our observations are a big step forward in determining their size and shape," said Dr Bannister.