This weird, hourglass-shaped structure is a planetary nebula, the not entirely accurate name given to the clump of gas that forms after a dying sun ejects it outer layers. Astronomers recently looked at over a hundred of these nebulae in the Milky Way's galactic center. Shockingly, a huge number of the nebulae appear to be pointing the same way.
Researchers using the Hubble Telescope and the European Southern Observatory's New Technology Telescope examined 130 such nebulae in our galaxy's central bulge, where stars are packed together in much higher concentrations than they are elsewhere in the Milky Way. While two types of planetary nebula pointed in random directions, the nebulae of one specific type — the bipolar planetary nebula, which forms the hourglass-like shape above — appeared to all be aligned in the same direction in the sky. Bryan Rees and Albert Zjistra, both of the University of Manchester, explain further:
Rees: This really is a surprising find and, if it holds true, a very important one. Many of these ghostly butterflies appear to have their long axes aligned along the plane of our galaxy. By using images from both Hubble and the NTT we could get a really good view of these objects, so we could study them in great detail.
Zjistra: While two of these populations were completely randomly aligned in the sky, as expected, we found that the third — the bipolar nebulae — showed a surprising preference for a particular alignment. While any alignment at all is a surprise, to have it in the crowded central region of the galaxy is even more unexpected.
Rees: The alignment we're seeing for these bipolar nebulae indicates something bizarre about star systems within the central bulge. For them to line up in the way we see, the star systems that formed these nebulae would have to be rotating perpendicular to the interstellar clouds from which they formed, which is very strange.
The best explanation so far is that the central bulge as a whole might be responsible for the alignment of the nebula. The idea is that the bulge's rotation around the galactic center creates magnetic fields powerful enough to force these particular nebulae to all line up in the same direction. That explanation would suggest magnetic fields in the center of the Milky Way far, far more powerful than any we experience in our neck of the woods. Whatever's going on here, it's already a good reminder of just how strange and mysterious even relatively well-explored corners of our universe can be.
For more, check out the ESO website. Image of bipolar planetary nebula NGC 6537 — which was not part of this study — via the ESO.