The galaxy ESO510-13 exhibits a pronounced warp in its disk.
Credit: STScI/NASA

Up to 50% of all disk galaxies (including both the Milky Way and Andromeda (M31) galaxies) exhibit a warping of their disks in the outer regions. Although the origins of these warps are not fully understood, possible causes include:

• A gravitational instability in the disk, perhaps induced by spiral arm or bar activity,
• Gravitational interactions with a companion or satellite galaxy,
• The accretion of dwarf galaxies or gas clouds from the galaxy’s environment, causing gravitational instability in the disk.