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Article: <5fhk32$l8r@dfw-ixnews12.ix.netcom.com>
From: saquo@ix.netcom.com(Nancy )
Subject: Re: IN SYMPATHY to the Hale-Bopp Cooperative
Date: 4 Mar 1997 16:53:54 GMT
In article: <5ffup8$be@news.Hawaii.Edu>
>>> I'm not aware of any size estimates from the IAU or
NASA or
>>> JPL.
>>> tholen@galileo.ifa.hawaii.edu
>
>> How soon we forget!
>
> I haven't forgotten any size estimates from the IAU or NASA
> or JPL, Nancy. Press releases from European Southern
> Observatory aren't from "IAU or NASA or JPL".
> tholen@galileo.ifa.hawaii.edu
Looking at your posting at face value, a reader might assume that I had responded with JUST a size estimate from the ESO. That posting was 3/4 filled with a size estimate posted by Ron Baalke of NASA. He thereby officiated it. You're avoiding again, David, because you'all are hoping not to have to reconcile what was said back then to the situation now. If all that supposed outgassing from a comet (when the ESO could find NO emissions) that was estimated to be of a monstrous size in order to produce such a show, then has Hale-Bopp gotten tiny now, that folks look up in the sky, see what appears to be a star, and have to assume the lack of anything that looks like a tail is because the tail is supposed to be pointing AWAY from the line of vision?
.........
Posted on sci.astro by baalke@kelvin.jpl.nasa.gov (Ron Baalke)
25 August 1995
A very unusual comet was discovered last month, on its way from the outer reaches of the solar system towards the Sun. Although it is still situated beyond the orbit of Jupiter, it is so bright that it can be observed in even small telescopes. It has been named 'Hale-Bopp' after the discoverers and is already of great interest to cometary astronomers. ... On this basis, Dan Green of the CBAT published a first, highly uncertain parabolic orbit. To some surprise, it showed that the comet was located at a heliocentric distance of no less than 1,000 million kilometres, well beyond the orbit of Jupiter! It was immediately obvious that it must therefore be intrinsically very bright. Indeed, it was about 250 times brighter than Comet Halley when this famous object was observed at the same distance in late 1987!
One possible cause for the unusual brightness of Comet Hale-Bopp at its present location, more than 200 million kilometres outside the orbit of Jupiter, is that it possesses a very large nucleus, that is the 'dirty snowball' of dust and ice at the centre of a comet. The larger the diameter of the nucleus, the more sunlight will be reflected from its surface and the brighter will it appear. A corresponding estimate indicates that the diameter of its nucleus would be nearly 100 kilometres, as compared to about 10 kilometres for Comet Halley.