Some planetary nebulae found to align strangely

Despite having no interactions with each other, planetary nebulae of a certain shape seem to line up in the same way near the center of our galaxy. 

Bipolar planetary nebula Hubble 5.  (Image credit: NASA/ESA)

Planetary nebulae are one of the final stages of evolution for small to intermediate mass stars.  As these stars run out of hydrogen (their main source of energy) and begin to burn helium, they become very unstable and expand and contract.  These pulsations eventually cause the star to eject its outer layers, forming a planetary nebula.  These planetary nebulae come in all kinds of complex shapes - some are spherical, but others look like hourglasses or butterflies.  Our own sun will form a planetary nebula billions of years from now.

Astronomers found that, near the center of our galaxy, these "bipolar" planetary nebulae (those that resemble butterflies or hourglasses) all seem to align in the same way, along the disk of the galaxy.  This is very exciting because in order to create this kind of alignment, the stars that formed these nebulae had to have been rotating in a strange way.  As astronomers are wont to do when we discover something unusual, this has been attributed to magnetic fields.  It is thought that a strong magnetic field at the center of the galaxy could be the reason these planetary nebulae line up the way they do, similar to how iron filaments line up under the influence of a magnet.  

Bipolar planetary nebula M2-9. (Image credit: NASA/ESA)

Confusingly, planetary nebulae have nothing to do with planets.  When astronomer William Herschel observed them over two centuries ago, he thought the glowing blue and green nebulae he observed through his telescope resembled gas giant planets like Uranus. 

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