Readers ask about the Milky Way’s newfound ‘feather’, CT scan safety and more

Fine feather

A filament of cold, dense gas named the Gangotri wave may bridge two spiral arms near the Milky Way’s center, Lisa Grossman reported in “Scientists find the Milky Way’s first known ‘feather’ ” (SN: 12/18/21 & 1/1/22, p. 4).

Reader Doug Holcomb asked how this newfound “feather” differs from a galactic spur.