Science reports that the Milky Way isn’t quite as flat, edge-on, as we thought. It’s got a slight but detectable S-curve, like a piece of warping plywood:
To make the map, astronomers looked to its bright, pulsing stars called cepheids. These stars burn up to 10,000 times more brightly than the sun so they are visible from across the galaxy and through interstellar clouds of gas and dust. Crucially, cepheids are “standard candles”: Their light waxes and wanes at a rate that corresponds to their inherent brightness. Astronomers can combine their true brightness with their apparent brightness, measured from Earth, to calculate how far away they are. Using a 1.3-meter telescope at Las Campanas Observatory in Chile, astronomers monitored the steady pulses from more than 2400 stars and pinpointed their location on a 3D model of the galaxy.
The cepheid stars cluster along an S-shaped curve, showing that the Milky Way’s disk is more warped than previously thought.
You can read more about the 3D map here, in Science.