Astronomers may have found part of a never-before-seen arm of the Milky Way galaxy. This huge stream of gas 鈥� named Cattail because of its long, thin shape 鈥� is the largest and most distant gas filament ever spotted in our galaxy.
at Nanjing University in China and his colleagues found one end of Cattail using the Five-hundred-meter Aperture Spherical radio Telescope (FAST) in China. They then searched data from the HI4PI survey, an all-sky search for hydrogen gas, to confirm it and detect the rest of the huge structure.
The researchers found that it is more than 16,000 light years long and about 675 light years wide, with a mass around 65,000 times the mass of the sun. It is nearly 72,000 light years away from the centre of the galaxy, placing it right on the edge of the Milky Way.
Advertisement
While Cattail鈥檚 mass may seem huge, its density is so low that it is probably mostly made of gas alone. 鈥淭he gas density of this structure is way too low to form a star,鈥� says Qiu. If it is just a filament of gas, it is unclear how it could have been formed 鈥� astronomers don鈥檛 know of any way to make such a filament so far from a galaxy鈥檚 centre.
It is also possible that Cattail could be a new outer arm of the spiral galaxy, although it doesn鈥檛 have quite the same shape as the four known arms.鈥淚f Cattail is part of a new spiral arm, it means that we might know less than what we thought, especially if it could not be traced back or connected to a known major arm,鈥� says Qiu.
鈥淚f the structure is part of a new arm, it鈥檚 puzzling that it doesn鈥檛 fully follow the warped pattern of the Galactic disc,鈥� he says. We will need more observations of Cattail鈥檚 entire length to be sure.
Reference:
Sign up to our free Launchpad newsletter for a voyage across the galaxy and beyond, every Friday
