(ORDO NEWS) — Astronomers have used distant galaxies for the first time to find and identify some of the missing Milky Way matter.
For decades, scientists have been puzzling over why they cannot explain all matter in the universe as the theory predicts. While most of the mass in the universe is considered mysterious dark matter and dark energy, 5% is “normal matter” that makes up stars, planets, asteroids, peanut butter and butterflies. It is known as baryonic matter.
But direct measurements only explained half of the expected baryonic matter.
Yuanming Wang, a doctoral student at the University of Sydney School of Physics, has developed an ingenious method to help find the missing substance. She used her technique to pinpoint a hitherto undetected flow of cold gas in the Milky Way about 10 light-years from Earth. The cloud is about a trillion kilometers long and 10 billion kilometers wide, but weighs as much as our moon.
“We suspect that most of the ‘missing’ baryonic matter is in the form of clouds of cold gas, either in galaxies or between galaxies,” Wang said. “This gas cannot be detected using traditional methods because it does not emit its own visible light and is too cold to be detected by radio astronomy.”
Astronomers looked for radio sources in the distant background to see how they flicker.
“We found 5 twinkling radio sources on a giant line in the sky. Our analysis shows that their light passed through the same cold blob of gas,” Wang said.
Just as visible light distorts as it travels through our atmosphere, causing stars to twinkle when radio waves pass through matter, this also affects their brightness. It is this “flicker” that Wang and her colleagues discovered.
Dr. Artem Tuntsov, a co-author at Manly Astrophysics, said: “We’re not entirely sure what this strange cloud is, but chances are it could be a hydrogen snow cloud destroyed by a nearby star to form a long thin clot of gas.”
Hydrogen freezes at a temperature of about minus 260 degrees, and theorists have suggested that some of the missing baryonic matter of the Universe may be trapped in these hydrogen “snow clouds”. They are almost impossible to detect directly.
“But now we have developed a method for identifying such clumps of ‘invisible’ cold gas using background galaxies,” said Ms. Wang.
Wang’s supervisor, Professor Tara Murphy, said: “This is a brilliant result for a young astronomer. We hope that the methods developed by Yuanming will allow us to find more of the missing substance.”
The data for the search for the gas cloud were obtained using the CSIRO Australian Square Kilometer Array Pathfinder (ASKAP) radio telescope in Western Australia.
Wang’s discovery complements a growing toolbox for astronomers in their search for the universe’s missing baryonic matter. This includes a method published last year by Jean-Pierre Maccard of Curtin University, who used the ASKAP CSIRO telescope to estimate the fraction of matter in the intergalactic medium, using fast radio bursts as “space weighing stations.”
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