The tail of the comet stretches more than 7o across the sky, says Jäger. Its almost as wide as the bowl of the Big Dipper. Physically, ISONs tail is about 12 times wider than the sun. So, when the head of ISON plunges into the suns atmosphere on Nov. 28th, more than 15 million kilometers of the comets tail will still be jutting into space behind it. Because so much gas and dust is spewing from the comets core, it is impossible to see clearly what caused Comet ISONs outburst on Nov. 13-14. One possibility is that fresh veins of ice are opening up in the comets nucleus, vaporizing furiously as ISON approaches the sun. Another possibility is that the nucleus has completely fragmented. If so, it will still be several days before we know for sure, says Karl Battams, an astronomer with NASAs Comet ISON Observing Campaign. When comet nuclei fall apart, it’s not like a shrapnel-laden explosion. Instead, the chunks slowly drift apart at slightly different speeds. Given that ISON’s nucleus is shrouded in such a tremendous volume of light-scattering dust and gas right now, it will be almost impossible to determine this for at least a few days and perhaps not until the comet reaches the field of view of NASAs STEREO HI-1A instrument on November 21, 2013. We will have to wait for the chunks to drift apart a sufficient distance, assuming they dont crumble first. Monitoring is encouraged. Comet ISON rises in the east just before the sun. Amateur astronomers, if you have a GOTO telescope, enter these coordinates. Dates of special interest include Nov. 17th and 18th when the comet will pass the bright star Spica, making ISON extra-easy to find. Sky maps: Nov. 15, 16, 17, 18, 19. Realtime Comet ISON Photo Gallery Ephemerides: Comet ISON, Comet Lovejoy, Comet Encke, Comet LINEAR X1
Posted on: Mon, 18 Nov 2013 22:37:13 +0000
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