Comments on: Happy Fourth of July! http://www.universetoday.com/2009/07/02/happy-fourth-of-july/ Space and astronomy news Sun, 21 Mar 2010 02:48:47 +0000 http://wordpress.org/?v=2.9.2 hourly 1 By: Kaizadhttp://www.universetoday.com/2009/07/02/happy-fourth-of-july/comment-page-1/#comment-68244 Kaizad Sat, 04 Jul 2009 21:13:22 +0000 http://www.universetoday.com/?p=33948#comment-68244 Thanks for the link Jon, I went through it when you posted it. Thanks for the link Jon, I went through it when you posted it.

]]> By: Jon Hanfordhttp://www.universetoday.com/2009/07/02/happy-fourth-of-july/comment-page-1/#comment-68241 Jon Hanford Sat, 04 Jul 2009 14:46:47 +0000 http://www.universetoday.com/?p=33948#comment-68241 @Kaizad, from the paper cited above and other sources, it appears that the knots are composed of clumps of molecular gas clouds and dust, some apparently quite dense. Researchers are still unsure of when these knots were formed and exactly how to interpret various features seen in them ( i.e. the reason for their cometary or 'head-tail' appearance). The paper I linked to has many wonderful images of specific knots in various wavelengths and several interpretations of their appearance. The authors relate that their observations will probably not answer the question of the knots' origin but may be useful in developing a cohesive model of the evolution and fate of the knots, so I would guess that information on the age of the Helix might also be deduced from their observations. Hope some of this has made sense :) . Btw, the short paper has many references to earlier work on the origin, age and evolution of the knots. @Kaizad, from the paper cited above and other sources, it appears that the knots are composed of clumps of molecular gas clouds and dust, some apparently quite dense. Researchers are still unsure of when these knots were formed and exactly how to interpret various features seen in them ( i.e. the reason for their cometary or 'head-tail' appearance). The paper I linked to has many wonderful images of specific knots in various wavelengths and several interpretations of their appearance. The authors relate that their observations will probably not answer the question of the knots' origin but may be useful in developing a cohesive model of the evolution and fate of the knots, so I would guess that information on the age of the Helix might also be deduced from their observations. Hope some of this has made sense :) . Btw, the short paper has many references to earlier work on the origin, age and evolution of the knots.

]]> By: Jon Hanfordhttp://www.universetoday.com/2009/07/02/happy-fourth-of-july/comment-page-1/#comment-68231 Jon Hanford Fri, 03 Jul 2009 15:07:29 +0000 http://www.universetoday.com/?p=33948#comment-68231 A preprint of the paper with MANY color and B&W images can be found here: http://arxiv.org/PS_cache/arxiv/pdf/0906/0906.2870v1.pdf . There are some pretty cool comparison pix with previous HST observations of these knots in different wavelengths. A preprint of the paper with MANY color and B&W images can be found here: http://arxiv.org/PS_cache/arxiv/pdf/0906/0906.2870v1.pdf . There are some pretty cool comparison pix with previous HST observations of these knots in different wavelengths.

]]> By: Kaizadhttp://www.universetoday.com/2009/07/02/happy-fourth-of-july/comment-page-1/#comment-68227 Kaizad Fri, 03 Jul 2009 12:37:37 +0000 http://www.universetoday.com/?p=33948#comment-68227 Nice work.I'm curious though, what exactly is a knot? A clump of hydrogen shielded by dust etc ? Since these knots are slowly destroyed, or pushed away, by stellar wind, can their density and/or distance from the star be any indicator of the age of the nebula? Nice work.

I'm curious though, what exactly is a knot? A clump of hydrogen shielded by dust etc ? Since these knots are slowly destroyed, or pushed away, by stellar wind, can their density and/or distance from the star be any indicator of the age of the nebula?

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