The Milky Way is crowned with a “feather.”
Astronomers write in the Astrophysical Journal Letters on November 11 that a long, thin filament of cold, dense gas emerges jauntily from the galactic centre, linking two of the galaxy’s spiral arms. This is the first time such a structure has been discovered in the Milky Way, which resembles the barb of a feather branching out from the centre quill.
The Gangotri wave was called by the team who found our galaxy’s feather after the glacier that feeds India’s longest river, the Ganges. According to astronomer Veena V.S. of the University of Cologne in Germany, the Milky Way is known in Hindi and other Indian languages as Akasha Ganga, or “the river Ganga in the sky.”
She and her colleagues discovered the Gangotri wave in data from the APEX observatory in San Pedro de Atacama, Chile, by hunting for clouds of cold carbon monoxide gas, which is thick and simple to detect. The structure runs 6,000 to 13,000 light years from the Milky Way’s Norma arm to the 3-kiloparsec arm, a minor arm in the galactic core. In the Milky Way, all other known gas tendrils line with the spiral arms (SN: 12/30/15).
Another peculiar property of the Gangotri wave is its waviness. Over hundreds of light-years, the filament seems to waver up and down like a sine wave. According to Veena, astronomers aren’t sure what may be causing this.
Other galaxies have gaseous plumage, but she claims that mapping the Milky Way’s structure from the inside out is “very, very tough.” She expects to discover additional galactic feathers and other structural elements of our galaxy. “We’ll be able to chart the Milky Way one by one.”