High-velocity cloud

Large collections of gas found in the galactic halo of the Milky Way

High-velocity clouds (HVCs) are large accumulations of gas with an unusually rapid motion relative to their surroundings. They can be found throughout the galactic halo of the Milky Way. Their bulk motions in the local standard of rest have velocities which are measured in excess of 70–90 km s−1.

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