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View Full Version : Planets Might Actually Shape Planetary Nebulae (plus a gallery)



Fraser
2008-Mar-10, 07:20 PM
Despite the name, a "planetary nebula" has nothing to do with planets. They were given the confusing name 300 years ago by William Herschel because they looked like planets in their early, rudimentary telescopes. They're really the glowing shells of gas and dust puffed out by stars nearing the end of their lives. But wait, [...]

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Noclevername
2008-Mar-10, 08:24 PM
How much of a role does the rotation of the star itself contribute to the shape of the nebula?

trinitree88
2008-Mar-11, 06:23 PM
How much of a role does the rotation of the star itself contribute to the shape of the nebula?

Noclevername. Not as much as you would expect. We launch satellites and space shuttles from latitudes near the equator to take advantage of the Earth's rotation, using less fuel to get them into orbit. So, you'd think that a star giving off it's outer layers, it would balloon out in a squashed spherical shape...like an orange you stepped on . That's an oblate spheroid. But, they don't. The planetary nebula forms by preferential ejection along the spin axes at the two poles of the star.
While some astronomers believe that a torus of earlier ejection gathers around the star's equator...hindering the equatorial burgeoning, and forcing the gas to seek the polar zones, there's a simpler explanation. Parity effects.
Stellar fusion is a weak interaction, and stars have magnetic fields. In a magnetic field weak interactions are not symmetrical, and a polar asymmetry is present in supernovae remnants, planetary nebulae, even the solar wind....faster at the poles. Much simpler explanation for the hourglass shapes so often seen.

see:http://www.sciencemag.org/cgi/content/summary/278/5337/387a

see:http://www.space.com/spacewatch/space_weather_glossary.html pete

eburacum45
2008-Mar-12, 06:17 PM
There's that spooky parity stuff again. The Left Handed Universe...
This might be relevant:
http://query.nytimes.com/gst/fullpage.html?sec=health&res=9A0DE0DB113AF936A15752C1A960948260

trinitree88
2008-Mar-12, 06:52 PM
There's that spooky parity stuff again. The Left Handed Universe...
This might be relevant:
http://query.nytimes.com/gst/fullpage.html?sec=health&res=9A0DE0DB113AF936A15752C1A960948260

eburacum. Yep. I once heard T.D.K.Lee speak on the history of the weak interaction at MIT. One of the best talks ever...funny, illuminating, surprising...all at once. Here was the guy at the heart of the controversy showing alternately how experiment & theory marched hand in hand for forty years, confirming certain suspicions, and denying others. I had been in the Physics Library reading preprints....before NASA Astrophysics Database, and Arxiv...and overheard two young students discussing whether or not they would go to the Physics Colloquiem talk....and they concluded they were too busy.
The text "Mirror Asymmetry & Time Reversed Worlds" by Martin Gardner is a readable take for a bright high school physics kid....and walks you through the rationale nicely. Ultimately parity effects determine our definition of up, down, magnetic North & South, left and right, and the helicity of right & left handed screws....and works its' way into neutrinos/antineutrinos. It was Gardner's book, pointing out that the effect had been present not only in every experiment involving weak decays, but in every run of every experiment, that led me down the parity path in astrophysics 25 years ago. Nobody had checked the data when Lee and Yang made their surmise in the fifties, and it had been generally waived aside in a lot of other areas....very surprising.
Lee, a very likeable chap...is famous for showing up at Columbia straight out of high school, and inadvertently enrolling straight into the graduate program....without ever taking the undergrad course....and then winning the Nobel. :dance::clap::eek: Heady stuff. pete