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Comet 17P - Estimate of physical size
Estimate of physical size of Comet 17P:
2 arcmins = 120 arcsecs =~ dia. 142472 kilometers 3 arcmins = 180 arcsecs =~ dia. 213708 kilometers Computations - using the sine rule 1 a.u. = 149,597,870.691 kilometers ; wikipedia Distance Earth to Comet 17P Oct 25 = 1.637 a.u. ; NASA-JPL Near Earth Object simulator Distance Earth to Comet 17P Oct 25 = 244,891,714 ; Product Comet 17P object size: 2-3 arcmin ; my obs and other internet reports Physical diameter using the sine rule from object's diameter in arcsecs: Physical diameter = [ Deg2Rad( Objdiameter_arcsec / 3600#) ) * Distance_to-Object ] Results for 120 and 180 arcsecs: 120 arcsecs =~ 142472 kilometers 180 arcsecs =~ 213708 kilometers Diameter of major planets ; wikipedia Jupiter 142985 km Saturn 120534 km Worked example for 120 arcsecs: Objdia/3600 = 0.0333333 Deg2Rad ( Objdia/3600 ) = 5.8173 x 10^-4 = 0.00058173 Deg2Rad ( Objdia/3600 ) * Dist_to_object = 0.00058173 x 244,891,714 Deg2Rad ( Objdia/3600 ) * Dist_to_object =~ 142,462 - C |
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Comet 17P - Estimate of physical size
On Fri, 26 Oct 2007 12:19:31 -0700, canopus56
wrote: Estimate of physical size of Comet 17P: 2 arcmins = 120 arcsecs =~ dia. 142472 kilometers 3 arcmins = 180 arcsecs =~ dia. 213708 kilometers As of last night, I put the distinct coma size at 6 arcmin, with a diffuse coma extending to 17 arcmin. So I'd make those sizes several times larger. Intensity profiles from the last two nights are at http://www.cloudbait.com/gallery/comet/holmes.html _________________________________________________ Chris L Peterson Cloudbait Observatory http://www.cloudbait.com |
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Comet 17P - Estimate of physical size
On Oct 26, 2:20 pm, Chris L Peterson wrote:
As of last night, I put the distinct coma size at 6 arcmin, with a diffuse coma extending to 17 arcmin. So I'd make those sizes several times larger. snip Thanks, Chris. I have created a physical size reference table for 2 to 30 arcmins based on today's distance estimate here - http://www.utahastronomy.com/Current...e_of_Comet_17P - Canopus56 |
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Comet 17P - Estimate of physical size
On Fri, 26 Oct 2007 15:16:22 -0700, canopus56
wrote: Thanks, Chris. I have created a physical size reference table for 2 to 30 arcmins based on today's distance estimate here - http://www.utahastronomy.com/Current...e_of_Comet_17P Good thing. Before the snow rolled in this evening, I got more images. The coma is now well over 10 arcmin across. I've updated the profiles at http://www.cloudbait.com/gallery/comet/holmes.html ; it is now obvious that the nucleus has split, or that the coma is becoming significantly offset from the nucleus (can't really say which). _________________________________________________ Chris L Peterson Cloudbait Observatory http://www.cloudbait.com |
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Comet 17P - Estimate of physical size
Chris L Peterson wrote:
Good thing. Before the snow rolled in this evening, I got more images. The coma is now well over 10 arcmin across. I've updated the profiles at http://www.cloudbait.com/gallery/comet/holmes.html ; it is now obvious that the nucleus has split, or that the coma is becoming significantly offset from the nucleus (can't really say which). I think what we are seeing may simply be a projection effect: the bright elongated inner region may well be the tail seen extending behind the comet (and a bit to the side). The offset in general may be due to the approximately 15 degree viewing angle. One thing for su we don't get the chance to see bright active comes from the point of view very often. Clear skies, Greg -- Greg Crinklaw Astronomical Software Developer Cloudcroft, New Mexico, USA (33N, 106W, 2700m) SkyTools: http://www.skyhound.com/cs.html Observing: http://www.skyhound.com/sh/skyhound.html Comets: http://comets.skyhound.com To reply take out your eye |
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Comet 17P - Estimate of physical size
On Oct 26, 1:19 pm, canopus56 wrote:
snip all In a Cloudy Night's forum, someone pointed out that you can use the Google search box's built-in calculator to find the physical size of Comet 17P. In general - sin ( radians (your_arcmins arcmins) ) * 1.62900 [a.u.] * 149 597 871 = physical size 17P Get the current day's distance to Comet 17P from the NASA-JPL Near Earth Object orbit simulator - http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=17P&orb=1 An example of a string that is formated for use in the Google search box is: sin(radians * (10 arcminutes)) * 1.62900 * 149 597 871 which yields = 708 878.821 kilometers According to Allen's Astrophysical Quantities, typical comet coma physical diameters are 10,000 to 100,000 km. - Canopus56 |
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