Newly discovered invisible structures shaped like noodles or sheets of lasagna could drastically our understanding of gas conditions in the Milky Way, experts at the Commonwealth Scientific and Industrial Research Organization (CSIRO) in Australia report in a new study.
CSIRO astronomer Dr. Keith Bannister and his colleagues, who published a paper detailing their findings Thursday in the journal Science, explained that these structures look like “lumps” in the thin interstellar gas found throughout the galaxy. For the first time, they were able to observe one of these lumps, which has enables them to predict its shape.
Thanks to a new technique, Dr. Bannister’s team was able to use the Compact Array telescope in eastern Australia to monitor a quasar known as PKS 1939-315 in the constellation of Sagittarius. While observing PKS 1939-315, they witnessed a lensing event that continued for an entire year, and which involved lenses roughly the size of Earth’s orbit around the sun.
These lenses are believed to be approximately 3000 light-years away, or 1000 times more distant than the closest star, Proxima Centauri. Previously, their shape was unknown, but thanks to these new observations, they know that it could not have been a solid lump or a bent sheet.
Lumps could be gravitationally-bound gas clouds
The first signs of these mysterious objects were detected by astronomers three decades ago, as they noticed radio waves from a quasar that fluctuated significantly in terms of strength. It was determined that the behavior was due to the Milky Way’s so-called “invisible atmosphere,” the thin gas of electrically charged particles that makes up the space in between stars.
“Lumps in this gas work like lenses, focusing and defocusing the radio waves, making them appear to strengthen and weaken over a period of days, weeks or months,” said Dr. Bannister. Such observations were difficult to come by, causing many researchers to abandon the search, but the CSIRO team realized that they could pull them off using the Compact Array.
In light of their observations of PKS 1939-315, they believe that the shape of these lenses could be like looking at “a flat sheet, edge on,” like “looking down the barrel of a hollow cylinder like a noodle,” or like “a spherical shell like a hazelnut,” CSIRO team member Dr. Cormac Reynolds explained. Additional observations will “definitely sort out the geometry,” he added.
In addition, Dr. Bannister and his colleagues observed the lensing event with other optical and radio telescopes, and found that there was little to no variation in the optical light from the quasar during that time. This indicates that previous optical surveys searching for the dark lumps would not have spotted this one, which the CSIRO team believes could be cold gas clouds held together by the force of their own gravity.
It remains unclear how these invisible lenses form, but Dr. Bannister said that these structures “are real, and our observations are a big step forward in determining their size and shape.” He added that the discovery “could radically change ideas about this interstellar gas, which is the Galaxy’s star recycling depot, housing material from old stars that will be refashioned into new ones.”
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Feature Image: CSIRO’s Compact Array in Australia is shown under the night lights of the Milky Way. (Credit: Alex Cherney)
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