An intriguing filamentous structure discovered at the edge of the Milky Way

Would the Milky Way be different from the representations we know about it? A team of researchers from Nanjing University in China discovered thanks to the powerful radiotélescope spherical with an opening of 500 meters (Fast for Five-hundred-meter Aperture Spherical radio Telescope), a filamentous structure extending in a region far from the center of the galaxy, at 71.754 light years. A study, published in preprint August 5, was carried out on this discovery, leading to two hypotheses that could explain the existence of this mysterious cloud : an immense filament of gas in a neighborhood extremely close to the Milky Way or a galactic spiral arm remained undetected to this day.

A massive enigma

The origin of this filament, named Cattail (or “Quenouille” in French), therefore remains to be determined. But the astronomers have developed two hypotheses that could explain the existence of this gas cloud, revealed by chance while scientists observed Cygnus X radio source, in the constellation Cygnus. First, Cattail could be a large molecular filament made up of gases such as hydrogen, about 5 kiloparsecs long. It would then constitute one of the most imposing molecular clouds visible near the Milky Way. On a comparative scale, 5 kpc is equivalent to 16,307.8 light years. A light year is equal to 9.460 billion kilometers, and our solar system only covers 20 billion kilometers.

Chinese astronomers looked at the velocity of the filament, and their study highlights how fast it moves, at a speed oscillating between 160 and 140 kilometers per second. The structure is located behind an arm extending long from the center of the Milky Way, called Écu-Croix. Its proximity and speed have long made researchers hesitate: a galaxie woman remained invisible? By carrying out additional observations, the second most probable theory would be that of a new arm of our galaxy, that radio telescopes and other instruments could not have detected for lack of power. If this hypothesis is confirmed, it would mean that this new “branch” of the Milky Way would be located in the outer region of the galaxy named in English Extreme outer galaxy. This possibility turns out to be interesting for scientists, the sectors furthest from galactic centers being veritable nurseries for young people. stars.

Fast in support

The use of the Fast radio telescope was essential in this discovery. The instrument, installed in China’s Guizhou province, was declared operational in 2020, despite initial observations dating back to 2016. Forming a dome 500 meters in diameter, like of feu Arecibo, Fast is composed of 4,500 panels of metal picking up signals on different wavelengths, varying from 70 megahertz to 3 gigahertz. Thanks to its precision, the radio telescope has in particular become a staple in the hunt for pulsars: in May 2021, it had discovered 201.

Fast’s precision could explain such a late detection of an arm of the Milky Way, where other older radio telescopes could not have detected an element diffuse or concealed by another. However, there is no doubt that astrophysicists from Nanjing University should turn their eyes and Fast’s parable to Cattail in order to unravel the riddle of this strange gas structure.