Norma Arm

It is named for the Norma constellation, through which the Arm as seen from Earth passes.

Like many other galaxies of similar type, the Milky Way consists of a large mass of stars shaped into the form of a relatively flat disc by gravity.

The disc is rotating, with the dense central body of stars moving at greater speeds than those toward the rim of the disc.

As a result, the pattern of stars within the Galaxy as viewed from directly above or below the disc has formed into a spiral.

Because of localised gravitational variations, the spiral pattern has itself formed several distinct 'spiral arms', where particularly large numbers of stars can be found.