The Milky Way’s giant gas bubbles were seen in visible light for the first time
The new technique could map the velocity of gas in the towering structures called Fermi bubbles

Giant bubbles of expanding gas that surround the Milky Way have been seen in visible light for the first time. The gas’s motion shifts the light’s wavelength, as depicted in this illustration. Emission from gas moving toward the solar system (bright spot at middle right) appears slightly bluer, while gas moving away appears redder.
HST/NASA, and A. Field/STScI