University of Sydney Student Develops Ingenious Technique to Find Missing Matter

Astronomers now have a new method for detecting missing matter, using distant galaxies as "scintillating pins" to identify these mysterious materials.

One of the persisting questions in astronomy is how to account for all the matter in the universe as predicted in theory. Actual attempts to measure always end up with an inexplicable loss, leading to the proposal of dark matter and dark energy. Only five percent of the known universe is made up of so-called normal matter - those that are found in physically observable parts of the universe from living beings to stars. This normal matter is also known as baryonic matter, and only half of it has been found via direct measurement.

Tracking Down Missing Matter

Yuanming Wang, a Ph.D. candidate from the University of Sydney's School Physics, has developed a novel strategy of locating and identifying this missing matter. Her new technique was used to accurately point the location of a previously undiscovered cold gas stream in the Milky Way about 10 light-years away from earth. The gas cloud extends about a trillion kilometers long and close to ten billion kilometers wide. However, it only weighs about as much as the earth's moon.

Details of their new method appear in the journal Monthly Notices of the Royal Astronomical Society.

"We suspect that much of the 'missing' baryonic matter is in the form of cold gas clouds either in galaxies or between galaxies," Wang said in a press release from the University. She is currently pursuing her doctorate at the Sydney Institute. She also adds that the gas is undetectable using conventional detection methods since the cloud does not emit visible light on its own and that it is too cold to be detected by radio astronomy equipment.

To detect the massive gas cloud, researchers looked for other radio sources in the background and inquired how these sources shone light. They found five radio sources following a giant line in the sky, with further analysis of these light sources showing that light must have "passed through the same cold clump of gas." In the same way as visible light appears to "twinkle" as it passes through the Earth's atmosphere, radio waves are also affected as it passes through matter. There is an observable difference in their brightness, which the University of Sydney researchers used to detect the gas cloud.

Identifying the Gas Cloud

According to Dr. Artem Tuntsov, a co-author of the study from an astronomy-focused institute Manly Astrophysics, while they are not sure what the gas cloud exactly is, it could possibly be a "hydrogen snow cloud" that was disrupted by a nearby star, forming a long, thin strand of gas.

Hydrogen gas starts to freeze at about minus 260 degrees Celsius, leading theorists to suggest that the previously unaccounted baryonic matter could be trapped inside the hydrogen snow clouds which are, as Wang mentioned, difficult to detect using conventional methods.

"This is a brilliant result for a young astronomer. We hope the methods trailblazed by Yuanming will allow us to detect more missing matter." said professor Tara Murphy, Wang's supervisor.

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