The Milky Way Wobbles
Our galaxy rotates around the supermassive black hole at its centre. But, as scientists describe online in the October 2013 issue of the Monthly Notices of the Royal Astronomical Society, it do not simply orbit the galactic centre in straightforward ellipses but bob up and down in complicated patterns – perpendicular to the galaxy’s main disk, or its plane. The three-dimensional analysis by the Radial Velocity Experiment revealed that while the Milky Way is rotating, its stars are sloshing in waves. Scientists don’t know why it does that yet. The galaxy’s spiral arms could be leaving a wake in which other stars bob, or the ripples could be remnants of the galaxy’s collision with a smaller galaxy earlier.