Magellanic Stream

The Magellanic Stream is a long arc of gas trailing the Magellanic Clouds around the Milky Way. Gravitational tides and the Milky Way’s hot halo gas shaped its structure.

Tidal stripping: The removal of material from an astronomical body by another body's gravitational field. Gravitational encounters between the Clouds and the Milky Way can pull gas into extended streamers.
Large Magellanic Cloud: The largest satellite galaxy of the Milky Way and the more massive of the Magellanic Clouds. Its gravity and gas contribute to models of the Stream’s formation.
Neutral hydrogen: Hydrogen atoms that retain their electrons, detectable in space through their 21-centimeter radio emission. Radio maps of neutral hydrogen first revealed the Stream’s long gas trail.
Ionized gas: Gas whose atoms or molecules have lost or gained electrons. Most Stream material may be ionized, making its total mass difficult to measure.
Ram pressure stripping: The removal of gas from a moving galaxy by pressure from surrounding intergalactic or intracluster gas. The Clouds’ motion through the Milky Way’s hot halo pushes gas away and shapes the Stream.
Small Magellanic Cloud: A dwarf galaxy orbiting the Milky Way and interacting closely with the Large Magellanic Cloud. Its gas and past encounters with the Large Cloud are central to formation scenarios.
H-alpha emission: Red light emitted when hydrogen electrons transition from the third to the second energy level. Its detection shows that parts of the Stream are ionized and emitting light.
Galactic corona: The hot, diffuse outer atmosphere surrounding a galaxy. Its density and temperature determine how strongly it can reshape the Stream.
Milky Way circumgalactic medium: The diffuse, hot gas surrounding the Milky Way beyond its stellar disk. This halo supplies the pressure and material that interact with Stream gas.
First infall model: A model in which a satellite galaxy is making its first close approach to a larger host. It challenges older accounts that require the Clouds to have completed several Milky Way orbits.

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