Astronomers love to remind us that there’s no up or down in space. Look out into the depths of the universe and you’ll see galaxies floating edge-on, face-on and at every angle in between. Look at planets circling stars within the Milky Way, and their orbits might be oriented in any direction at all.
But for one class of celestial objects this seems to be untrue: planetary nebulae, the gorgeous clouds of gas puffed by stars in their last, gasping moments of life, seem to be mysteriously aligned with the plane of the Milky Way—something that Bryan Rees, an astronomer at the University of Manchester in England, and lead author of a paper in an upcoming issue of Monthly Notices of the Royal Astronomical Society calls “quite unexpected.”
That’s putting it mildly. Most planetary nebulae are roughly spherical; they’re not visibly “aligned” with anything. One especially spectacular subclass, however, is more hourglass-shaped, and when Rees and his colleague Albert Zijlstra examined this particular kind, the long dimensions of the clouds pointed more or less in the same direction. “They’re not exactly aligned,” he says, “but they’re not random.”