The Magellanic Stream: Circumnavigating the Galaxy
  The Magellanic Clouds are surrounded by an extended network of gaseous
structures. Chief among these is the Magellanic Stream, an interwoven tail of
filaments trailing the Clouds in their orbit around the Milky Way. When
considered in tandem with its Leading Arm, the Stream stretches over 200
degrees on the sky. Thought to represent the result of tidal interactions
between the Clouds and ram-pressure forces exerted by the Galactic corona, its
kinematic properties reflect the dynamical history of the closest pair of dwarf
galaxies to the Milky Way. The Stream is a benchmark for hydrodynamical
simulations of accreting gas and cloud/corona interactions. If the Stream
survives these interactions and arrives safely in the Galactic disk, its cargo
of over a billion solar masses of gas has the potential to maintain or elevate
the Galactic star formation rate. In this article, we review the current state
of knowledge of the Stream, including its chemical composition, physical
conditions, origin, and fate. We also review the dynamics of the Magellanic
System, including the proper motions and orbital history of the Large and Small
Magellanic Clouds, the first-passage and second-passage scenarios, and the
evidence for a Magellanic Group of galaxies.
