A group of scientists has discovered a huge gas filament extending through the Milky Way.
The huge filament of space gas is so large that, upon the discovery, the scientists were not certain what they were initially observing. Their research was accepted for publication in The Astrophysical Journal Letters, you can access it in preprint here.
The filament, called 'Cattail', has a structure that remains unknown, according to Science Alert. Another possibility is that Cattail forms part of the Milky Way's spiral arms.
The scientists from Nanjing University are puzzled as it is hard to determine whether Cattail is an independent gas filament or part of a larger spiral structure in the Milky Way. This is partly because it is incredibly difficult to measure the distance between Earth and other cosmic objects within our galaxy.
The scientists said in the paper:
"...it is puzzling that the structure does not fully follow the warp of the galactic disk."
They added:
"While these questions remain open with the existing data, the observations provide new insights into our understanding of the galactic structure."
[h/t: Futurism]
What the discovery paper actually describes
The Cattail study reports a structure detected through emission from neutral atomic hydrogen, often written as H I. Its title deliberately leaves two possibilities open: a very large gas filament or part of a previously unrecognized spiral arm. That is a question about the organization of gas within the outer Galaxy, rather than evidence for a separate, unidentified galaxy. The researchers combined position and velocity information to examine how the structure fits with the Milky Way’s known layout. Their uncertainty is part of the result, not an absence of measurable properties. Cattail discovery paper.
Why mapping our own galaxy is difficult
For a reader, the useful comparison is trying to understand a large building while standing inside one room. Looking through the Galactic disk places multiple structures along the same direction, so a striking shape on a map does not immediately establish a physical connection. Additional observations can test whether neighboring gas shares a coherent motion and location. Cattail is therefore valuable both as an object to investigate and as a reminder of how scientific classification develops: a measured feature can be real even while its relationship to a larger structure remains unresolved.
What astronomers measured
Cattail was found with the Five-hundred-meter Aperture Spherical Radio Telescope (FAST) in Guizhou province, China, combined with data from telescopes in Germany and Australia; Keping Qiu of Nanjing University led the observations, and the preprint was posted on 4 August 2021. The filament stretches across nearly 3,600 light-years and may be as long as 16,000 light-years. It lies about 68,000 light-years from Earth, roughly three times farther from the centre of the galaxy than the Sun, and contains about as much mass as 65,000 suns. “We don’t know how such a huge filamentary gas structure could form in such an extreme location,” Qiu said. The galaxy’s disc is thought to be warped at its edges, but Cattail does not seem to follow the warp, which the radio astronomer Felix Lockman of the Green Bank Observatory, who was not involved in the study, called strange.
Sources: Live Science, 23 August 2021: Mystery object in space could be a new arm of the Milky Way
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