Observations of Doppler shifts toward the center of the galaxy show on one side hydrogen clouds are blueshifted while on the other side hydrogen clouds are redshifted.This is the pattern of the rotation velocity of a:

Question

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The pattern observed in the Doppler shifts of hydrogen clouds is consistent with the rotation velocity of a disk-shaped object. Specifically, the blueshifted clouds suggest that material on that side of the disk is moving toward us and therefore rotating in the same direction as us, while the redshifted clouds suggest that material on the other side of the disk is moving away from us and therefore rotating in the opposite direction. This is a common pattern observed in spiral galaxies like our own Milky Way, which are disk-shaped structures.

Observations of Doppler Shifts Toward the Center of the Galaxy