ISON UPDATE FROM SKY and Telescope UPDATES: November 30, 9 a.m. EST: Fading continues; no activity. Filip Fratev posts again (at 8:15 UT this morning), just measured another drop of 0.5 magnitude for the last 11 hours (20:30 – 7:18 UT). Thus it is in the range of magnitude 3.1–3.6, probably more close to 3.5. The later LASCO C3 image from 12:54 UT shows the fading very obviously. He posts again at 15:29 UT; ISONs brightness has dropped rapidly. I estimated the comet as between about 4.5-5.0m. Magnitude decrease was almost 0.1m per hour. Jacob Czerny notes that the comet remnant is fading at the rate expected of a simple, inactive debris cloud moving farther from the Suns illumination. In addition it is expanding, which means its surface brightness is dimming even faster than its total brightness. As for what looks like a new comet tail? That turns out to be well modeled by the trajectories of particles that ceased to be emitted at perihelion two days ago. Explains Hermann Böhnhardt (Max Planck Institute for Solar System Research), If we assume in our calculations that the comet has emitted dust at perihelion, we can reproduce the current images quite well. Heres the latest blog article from the indefatigable cometary scientist Karl Battams: In ISONs Wake, a Trail of Questions. With great new movies from the STEREO A and B coronagraphs. Key takeaway: It does seem unlikely that there will be much to see in the night sky. I suspect that some of the outstanding astrophotographers around the world will be able to get something, but I doubt it will be as spectacular as before perihelion. I hope Im wrong though. November 29, 10:30 p.m. EST: A fading ghost. At 19:54 UT Filip Fratev (Bulgarian Acadamy of Sciences) wrote, ISON [has] started to fade.... [In] the last four hours it faded by more than 2 magnitudes and obviously is less bright... I estimated the comet to be between 2.6 and 3.1 magnitude now. Four hours later Karl Battams of the Comet ISON Observing Campaign tweeted, We cant tell if #ISON is in one piece or many. Its about mag 5 now and fading. Dust swarm or not, whats left of ISON has grown a tail thats sweeping around the way it was supposed to (simulation video). The times and dates in all spacecraft images are Universal Time; subtract 5 hours to get Eastern Standard Time. SOHOs LASCO C3 coronagraph took this image 19 hours after perihelion. See its 30 most recent images. NASA / SOHO Consortium
Posted on: Sat, 30 Nov 2013 19:30:08 +0000
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