Re: [Utah-astronomy] A 3D construction of Comet 17P
It would appear the situation has changed since 11-10 and my 11-10 based 3D construction. The tail light spot trailing the comet may now be showing a position angle off to one side of the medial center line of the comet. Amateur images published on the web through 11-11 were showing the disconnected tail about 34-35' behind the center of the coma, but at a line directly trailing the medial line of the coma and central condensation. A great triptych by John Wunderlin posted on Cloudy Nights and Spaceweather.com illustrates the situation on 11-10. http://spaceweather.com/comets/holmes/10nov07/John-Wunderlin1.jpg Based on the assumption that the position angle of the dust light spot trailing the comet on 11-10 was nearly on the sun-comet line, I prepared the 3D construction above. This assumption was questionable, because comet dust tails typically curve away from the comet, e.g as seen in comets McNaught in 2007 and Hale-Bopp in 1997 - http://en.wikipedia.org/wiki/Image:Comet_P1_McNaught02_-_23-01-07.jpg http://en.wikipedia.org/wiki/Image:Comet_Hale-Bopp.jpg An early 10-26 image and report by the professional astronomer Dr. Pierre Bastien of the Universite de Montreal suggested the then nascent tail may have been at an angle. See - http://www.spaceref.com/news/viewpr.html?pid=23901 As the tail grew, the did not appear to be any deviation in position angle of the tail relative the medial line of the comet, as shown in the amateur images above. But the 11-15 wide-field image posted on Cloudy Nights by "Hiro" may show a changed geometry. http://farm3.static.flickr.com/2100/2040106475_4557f789e6.jpg The light spot trailing the comet - now about 60' behind the comet - in "Hiro"'s 11-15 image appears to be slightly off-center from the medial line of the comet. This would be consistent with a far end of the disconnected tail drifting into a curved shape. Subsequent images may clarify if there is a trend. - Kurt _______________________________________________ Sent via CSolutions - http://www.csolutions.net
I took a look at the comet last night when I came home from work. With the naked eye I could barely see it -- so barely that I wasn't sure I really did. I went inside and got the powerful binocs Chuck sold me. The comet was dim but enormous, immediately north of Alpha Persei. Trying to estimate its size by that of the moon on the other side of the sky, I thought it looked like it was about three-quarters of the moon's diameter. Maybe it was even as large as the moon. It was hard to tell because of course I couldn't have them both in the same field of view. I'm hoping someone could calculate its general size, using that number of arc minutes projected out beyond Mars' orbit. Also, when it went in front of the star, which I understand it always has, I hope someone took a spectrum of the star so that we could see how it changed when the comet went in front. -- Joe
On Saturday night96-7pm) I held a star party for my sons Cub Scout den in our backyard, unfortunately it cloudy over completely after about 20 minutes so we only got some views of a hazy moon, a very distorted Jupiter and its moons that were hugging the horizon and hiding in some tree branches, and a quick peak of course at the "Cub Scout" star. And a few constellations pointed out with the green laser before we called it quits. After I had gotten the scope down and inside the sky cleared almost completely...typical!! I still had the 15x70mm binos out so I took a quick peek at the Comet and I was very surprised at it's low surface brightness, this thing is big and diffuse now, it extended over the bright star Alpha Persei(Mirfak). It seems to me that it's at least the size of the moon. not at all the same comet I observed a week ago, contrast against the starry background just isn't there anymore. I also took a look at the very dim blue dot of Neptune that was near the moon, something I had really wanted to show the scouts and their parents, oh well maybe next time! Howard --- Joe Bauman <bau@desnews.com> wrote:
I took a look at the comet last night when I came home from work. With the naked eye I could barely see it -- so barely that I wasn't sure I really did. I went inside and got the powerful binocs Chuck sold me. The comet was dim but enormous, immediately north of Alpha Persei. Trying to estimate its size by that of the moon on the other side of the sky, I thought it looked like it was about three-quarters of the moon's diameter. Maybe it was even as large as the moon. It was hard to tell because of course I couldn't have them both in the same field of view. I'm hoping someone could calculate its general size, using that number of arc minutes projected out beyond Mars' orbit. Also, when it went in front of the star, which I understand it always has, I hope someone took a spectrum of the star so that we could see how it changed when the comet went in front. -- Joe
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participants (3)
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Howard Jackman -
Joe Bauman -
Kurt Fisher