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 Post subject: Re: Comet ISON
PostPosted: Thu Dec 05, 2013 8:35 pm 
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The December edition of The Sky At Night was devoted to comets:
http://www.bbc.co.uk/iplayer/episode/b03kkykg
The team (including our friend Dr. Chris North) visited the La Palma observatories to observe three comets (including ISON) from there.

And here is the definitive video from the LASCO C3 camera showing ISON's perihelion passage and its subsequent demise:
http://www.antarctica.ac.uk/met/jds/2012S1%20C3.gif

According to the BAA Comet Section:
Quote:
2012 S1 (ISON) continued brightening until about 12 hours prior to perihelion, then faded. The brightest portion of the comet become elongated. It showed two tails, the longest over 4° long. A tail feature survived perihelion, and then the comet reappeared as a bright, well condensed object on November 29. On November 30, the comet appeared very diffuse and significantly fainter and it faded and became more diffuse.
A possible explanation is that the intense solar wind and radiation when very near the Sun stripped all material from the nucleus, causing the fade. As the thermal wave penetrated the bare nucleus it disintegrated, leaving a ghostly remnant.


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 Post subject: Re: Comet ISON
PostPosted: Sat Dec 07, 2013 2:35 pm 
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ISON Update (from the Hubble Blog)

People are writing loving obituaries for Comet ISON, the sungrazer who lived life a little too close to the edge. Is that it? Are we ISON'ed out? In a post-ISON era? Adrift and alone in a universe bereft of ISONs?

Probably, but Hubble is planning to do one more observation in late December, to try to get a glimpse of the remains.

So what will it see? Well, possibly nothing. The pieces could be so small that they don't reflect light, or they could be slightly off the expected trajectory after breaking apart. (Hubble will have to follow the expected path unless Earth-bound observatories can help pinpoint the comet bits -- otherwise the telescope would just be guessing at a location.) Some people have wondered whether there's a danger from the fragments. The answer is no -- they still follow the general trajectory, and they're still extremely far away from Earth.

Best case scenario, Hubble sees something like a coma, an expanding cloud of diffuse particles, or some bits of rubble that were once a nucleus.

So there may be a little – very little – more ISON in your life sometime in the next several weeks. Hubble can't look right now -- the comet is still so close to the Sun that an observation would damage Hubble's optics. Hubble actually has safeguards that shut the telescope down if it tries to gaze at an object too close to the Sun. Ground observatories are also unable to view whatever's left of the comet at this point due to its location near the Sun -- by the time it would be in view, the sky is too bright.

If Hubble does observe ISON, astronomers will be able to do things like estimate the size of the particles, and judge the speed at which the comet is disintegrating -- which will help us learn about ISON's composition and structure. Now, like a team of forensic examiners at the scene of the crime, it's time for astronomers look back on the data they've collected and figure out how and why ISON went to pieces, and what that means about Oort Cloud objects, sungrazers, and comets in general.


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 Post subject: Whatever became of Comet ISON?
PostPosted: Sat Dec 21, 2013 3:35 pm 
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The Bradford Robotic Telescope has been out of action for a few days (extreme weather on Mount Teide knocked out the power and made the road impassible), but it finally came back on-line last night, and this morning took some images of the area of sky where any remnants of Comet ISON should be located:
Attachment:
File comment: Stack of 5x 60-sec images from BRT Cluster Camera (a 180mm lens) on the morning of 21-Dec.
ison_21dec.jpg
ison_21dec.jpg [ 142.8 KiB | Viewed 2314 times ]

Whatever's left of it should be near the centre of that (4-degree) field.


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