On the outskirts of our galaxy, a cosmic tug-of-war is unfolding—and only NASA’s Hubble Space Telescope can see who’s winning.

The  players are two dwarf galaxies, the Large Magellanic Cloud and the  Small Magellanic Cloud, both of which orbit our own Milky Way Galaxy.  But as they go around the Milky Way, they are also orbiting each other.  Each one tugs at the other, and one of them has pulled out a huge cloud  of gas from its companion.

Called  the Leading Arm, this arching collection of gas connects the Magellanic  Clouds to the Milky Way. Roughly half the size of our galaxy, this  structure is thought to be about 1 or 2 billion years old. Its name comes from the fact that it’s leading the motion of the Magellanic Clouds.

See： http://hubblesite.org/news_release/news/2018-15