Discovering the structure, content and size of the objects in our galaxy taking into account that we are immersed in it, is not something easy . This newly discovered structure proves it. This gas giant is located 22 kiloparsecs from the center of the Milky Way and scientists are not quite sure what it is; but it is a curl of gas so large that it could even be a spiral arm of the galaxy, unknown until now. Either that, or the largest gas filament ever detected in the Milky Way.
It’s disconcertingly big
Our galaxy is quite unusual, of that there is no doubt. It is a typical barred spiral galaxy of about 1,150,000 to 200,000 light years in diameter and about 2,000 light years deep with more than 400,000 million stars, where the morphology of molecular clouds plays a very important role in the formation of stars.
Using the 500-meter aperture spherical radio telescope (FAST), a team of astronomers from Nanjing University (China) has discovered a very very massive elongated structure while searching for clouds of neutral atomic hydrogen (HI). It is the extension to the first galactic quadrant of the Shield-Centaur arm (Outer Scutum-Centaurus or OSC) and appears to be located far behind the OSC, which is a secondary spiral arm of the Milky Way. According to the calculations of the experts, it is 71,750 light years from the galactic center and its mass is approximately 6.5 × 104 solar masses . As the FAST data suggests, it is 3,590 light years long and 675 light years wide. An incredibly huge structure. But it could be even more so according to data from the HI4PI all-sky HI survey, which determines that it could be about 16,310 light years long; it could be larger than the Gould Belt , a bubble of stars whose structure was estimated to be 3,000 light-years long.
Will it be a structure yet to be discovered or the largest filament ever detected?
Cattail doesn’t seem to line up perfectly with any of the traditional explanations about our galaxy. Its alignment isn’t a perfect match with the rest of the Milky Way’s structure, so it wouldn’t have to be the largest and most far-reaching spiral arm in the galaxy. Although it is difficult for astronomers to determine what it really is.
“It is puzzling that the structure does not fully follow the deformation of the galactic disk.” “While these questions remain open with existing data. The observations provide new insights into our understanding of galactic structure,” explain the authors in the study published in The Astrophysical Journal Letters.
There are several reasons why it is difficult to map the Milky Way in three dimensions . One of them is that it is very difficult to calculate distances to cosmic objects. Another is that there are many objects, so it can be difficult to tell if something is a large grouping or just a random collection distributed along a line of sight.
What if it is a filament? If it is a filament, it is not known how it could form and remain beyond the familiar spiral arms of the Milky Way.
Referencia: The discovery of the largest gas filament in our Galaxy, or a new spiral arm? Chong Li, Keping Qiu, Bo Hu, Yue Cao The Astrophysical Journal Letters, 2021 arXiv:2108.01905 [astro-ph.GA]
