Giant band of galactic gas likely has dual origin

Giant band of galactic gas likely has dual origin

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An enormous ribbon of gas that threads through the thinner gas of the Milky Way’s halo is the result of a gravitational tug-of-war between the two Magellanic clouds1, 2, the brightest satellite galaxies orbiting our own.

The Magellanic Stream, as the ribbon is known, stretches for hundreds of thousands of light years, with a small arm poking out ahead of the two galaxies and a long tail following behind them. The stream was discovered in the 1970s, and recent theoretical models suggest that it is caused by the gravitational pull of the Large Magellanic Cloud tearing gas out of its lesser sibling, the Small Magellanic Cloud. This stripping, the result of tidal forces, would have begun some 2 billion years ago, and together with an interaction with the Milky Way’s halo it would have spread the gas into its current shape.

But, in 2007, astronomer David Nidever, now at the University of Michigan in Ann Arbor, and his collaborators defied conventional wisdom by proposing that part of the Magellanic Stream came from the Large Magellanic Cloud, as stellar winds and supernovae blew gas out3.

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