Milky way “vibrating like a drum”

Our Milky Way galaxy is warped, and vibrates like a drum, because of the influence of two small companion galaxies, astronomers have found.

The researchers said the effect is due to the most prominent of the Milky Way’s satellite galaxies, a pair of galaxies called the Magellanic Clouds. They are stirring up with the Milky Way’s “dark matter,” an invisible substance that’s detectable only by its gravitational pull, the astronomers added.

Dark matter is thought to make up more then 90 percent of the weight of the universe.

The interaction creates a warp in the galaxy that has puzzled astronomers for half a century, the researchers continued. The warp, most obvious in the thin disk of hydrogen gas permeating the galaxy, extends across the Milky Way’s 200,000-light year width. A light year is the distance light travels in a year.

Leo Blitz, professor of astronomy at the University of California, Berkeley, and colleagues charted this warp and analyzed it in detail for the first time, based on a new galactic map of light given off by the hydrogen gas.

They found the gas layer is vibrating like a drumhead, and that the vibration consists almost wholly of three “notes,” also called modes. These notes would be unimaginably deep by human standards—some three million octaves, or scales, below the note called middle C on a piano.

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