Largest gas filament discovered in our Milky Way

It appears to be so far the furthest and largest giant filament in the galaxy.


Milky Way, our home galaxy, is a typical barred spiral galaxy about 1150,000 to 200,000 light-years across, about 2,000 light-years deep. It is believed to have more than 400 billion stars.

Throughout the Milky Way, molecular clouds typically appear filamentary, and mounting evidence indicates that this morphology plays an important role in star formation.

Astronomers have long realized that our home galaxy Milky Way is unusual. Recently, Using the Five-hundred-meter Aperture Spherical radio Telescope (FAST), astronomers spotted an unusual structure in our milky way. That structure called Cattail may be the largest filament of gas in our galaxy discovered to date, suggests a new study.

The structure- that appears as a long curl of gas– is so massive that the scientists initially thought it might be part of our galaxy’s spiral arms. It is the extension into the Galactic first quadrant of the Outer Scutum-Centaurus (OSC) arm and appears to be located far behind the OSC.

This elongated structure, found by astronomers from Nanjing University in China, has a velocity of 71,750 light-years from the galactic center. Astronomers calculated its mass to be 6.5 × 104 M☉. As FAST’s data suggests, it is 3,590 light-years in length and 675 light-years in width.

When astronomers combined the data with the HI4PI all-sky HI survey, they found that the Cattail could be even longer: as long as 16,300 light-years.

Astronomers said, “The question about how such a huge filament is produced at the extreme Galactic location remains open. Alternatively, Cattail might be part of a new arm beyond the OSC, though it is puzzling that the structure does not fully follow the warp of the Galactic disk.”

Journal Reference:
  1. Chong Li, Keping Qiu e al. The discovery of the largest gas filament in our galaxy, or a new spiral arm? arXiv: 2108.01905
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