Lead author of the study, PhD student Yuanming Wang. Photo: Louise Cooper
Astronomers have for the first time used distant galaxies as “twinkling pines” to locate and identify a piece of matter that is missing from the Milky Way.
For decades, scientists have been baffled as to why they could not explain all the matter in the universe as predicted by the theory. Although it is believed that most of the mass of the universe is mysterious dark matter and dark energy, 5% is “normal matter” that forms stars, planets, asteroids, peanut butter and butterflies. This is known as baryonic matter.
However, the direct measurement has only accounted for about 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 locate the missing subject. He has applied his technique to identify a hitherto undetected cold gas stream in the Milky Way, about 10 light-years from Earth. The cloud is about a trillion miles long and 10 billion wide, but it only weighs on the mass of our Moon.
The results, published in Monthly notices from the Royal Astronomical Society, offer a promising way for scientists to locate the missing topic of the Milky Way.
“We suspect that much of the‘ missing ’baryonic matter is in the form of cold gas clouds in or between galaxies,” said Ms Wang, who is pursuing her PhD at the Sydney Institute of Astronomy.
“This gas cannot be detected by conventional methods because it does not emit visible light of its own and is too cold to be detected by radio astronomy,” he said.
What astronomers did is look for radio sources on a distant background to see how they “shone.”
“We found five flashing radio sources on a giant line in the sky. Our analyzes show that its light must have passed through the same cold gas group, ”Wang said.
Just as visible light is distorted as it passes through our atmosphere to give a twinkle to the stars, when radio waves pass through matter, it also affects their brightness. It was this “scintillation” that Ms. Wang and her colleagues detected.
Dr. Artem Tuntsov, co-author of Manly Astrophysics, said: “We don’t know at all what the strange cloud is, but one possibility is that it could be a hydrogen ‘snow cloud’ interrupted by a nearby star to form a long , fine mass of gas. “
Hydrogen freezes at about 260 degrees and theorists have proposed that some of the baryonic matter missing in the universe could be trapped in these “snow clouds” of hydrogen. They are almost impossible to detect directly.
“However, we have now developed a method to identify these“ invisible ”cold gas groups using background galaxies as pines,” Wang said.
Ms. Wang’s supervisor, Professor Tara Murphy, said, “This is a brilliant result for a young astronomer. We hope that the pioneering Yuanming methods will allow us to detect more missing matter.”