What gas stream extends behind the Large and Small Magellanic Clouds?

The Magellanic Stream is a long gas stream extending behind the Large and Small Magellanic Clouds.

It consists mainly of high-velocity clouds of neutral hydrogen pulled from the two satellite galaxies as they orbit the Milky Way. The stream arcs across a huge section of the sky, passing through the region near the Milky Way’s south galactic pole. A related feature called the Leading Arm extends ahead of the Clouds in their motion.

Anomalous-velocity gas near the Magellanic Clouds was first noticed in 1965. The feature was mapped as neutral-hydrogen emission in the early 1970s, and its physical connection to the Clouds was established in 1974. Later observations showed that the stream is much more extensive than early maps suggested, stretching at least 180 degrees across the sky.

The stream is important because it records the interaction between the Magellanic Clouds and the Milky Way. Tidal forces and pressure from the Milky Way’s hot outer atmosphere likely both helped remove the gas. That material may eventually fuel future star formation in the Milky Way.