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The Great Christmas Comet of 2011, 2011 W3 (Lovejoy)
ElkGroveDan
post Dec 24 2011, 04:13 PM
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QUOTE (elakdawalla @ Dec 24 2011, 08:03 AM) *
Mongo, I just want to say thanks for these summaries -- it's great to have a single, concise source for the latest comet visibility news! Though it's making me very jealous of our southern hemisphere friends.


Ditto. I've been thinking about driving to Argentina. It's only 6451 miles.


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Explorer1
post Dec 24 2011, 06:46 PM
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That would be rather tricky, considering the Darien Gap...
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Mongo
post Dec 24 2011, 07:42 PM
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Christmas Eve image of comet Lovejoy by Scott Alder:

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nprev
post Dec 25 2011, 01:36 AM
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W O W ! ! !


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Mongo
post Dec 25 2011, 02:08 AM
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Yes, I think that Lovejoy has done quite well for a comet that was not supposed to survive perihelion.
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Mongo
post Dec 25 2011, 02:55 PM
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From comet-ml post #19078 by David Seargent:

QUOTE
I thought that the tail was somewhat less intense but longer than on the previous 2 mornings and the head (which was very indistinct and essentially just a lower terminus of the tail) about magnitude 4.8. By the way, the 15 degrees I gave as the tail length for Dec. 21 should read 21 degrees. I left out a term in the formula used for calculating angular distances on the sky (OK, math was never my strong point. If it had been, I probably would have studied Physics instead of Philosophy and become a professional astronomer!). In any case, this mornings tail length was measured as 28 degrees.


QUOTE
The length, shape and general morphology of the tail looked very similar to that of Ikeya-Seki when observed the same number of days after perihelion. Yet, I-S was definitely more intense; I would guess from memory about 2 magnitudes brighter. Also, the terminus of the tail seemed to end more suddenly than that of Lovejoy (the last 5 degrees or so of W3's tail grew very faint and difficult with the naked eye and could not be traced in the telescope). But the biggest difference was the head. At this point in its orbit, the head of the earlier comet was also about 2 magnitudes brighter and appeared in the 20x65 binoculars that I was then using as a very distinct, almost disk-like object; rather like a very bright and compact planetary nebula.
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Mongo
post Dec 25 2011, 07:41 PM
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From comet-ml post #19088 by Robert McNaught:

QUOTE
On Sun, 25 Dec 2011, [iso-8859-2] Jakub Černý wrote:

> Actually I do not think that nucleus has dissipated. Activity just fade
> quickly, but apparently there is still something huge producing much more
> material into tail and coma, unlikely swarm of debries.

Thanks Jakub,

I tend to agree that there is an "invisible" mass responsible for the hood and spine. The tail is showing no signs of becoming a ghost. I've put up a processed Uppsala image from last night (Dec 24.7UT).

http://msowww.anu.edu.au/~rmn/C2011W3.htm

It continues to show a well defined parabolic hood and the spine narrowing basically to an "empty" point pretty much on the edge of the parabola. Trying to image it now, but there is cloud and I can't get a focus sequence.

My astrometry of the tip-of-the-spine will perhaps tell one way or another whether this is a substantial mass or displaying significant short-term non-gravitional effects. Give it a week and we should a good handle on the dynamics.

The tail continues to fade (Dec 25.7UT) and is very significantly less bright than on Dec 21. There was quite a similarity to Hyakutake tonight, partly due to the tail being so long, narrow and "ghostly". There is no real comparison though, as there is no coma and condensation, which were both prominent in Hyakutake. On Dec 21 though, the tail surface brightness was sufficient to put it in the "awesome" category for me. Very much on par with Hyakutake, Hale-Bopp and Bennett. Tonight it was much more Halleyesque. I'll reply to the great comet listing thread in a day or so as I've been keeping such a list (and noting other folks lists) for a couple of decades.
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Mongo
post Dec 26 2011, 02:30 PM
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Comet-ml post #19096 by Rob Kaufman:

QUOTE
Here's a rough composite showing the growth of Lovejoy over the last 4 days, using some images kindly lent to me as I've only had one fine morning to observe it since it hit dark skies again. The various images were resized to the same scale. Don't place too much credence in the actual degree length stated as there are lots of variables that determine how much will be showing in any particular image. For this morning, the 30-degree tail length is based on several photographs that appear to show very faint extensions out to that length.



Anyway, the massive expansion is pretty clear. Hoping to get another great view of this 'megacomet' in the morning.

Cheers -

Rob Kaufman
Bright, Vic, Australia
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Mongo
post Dec 26 2011, 02:35 PM
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Comet-ml post #19100 bt Dave Herald, regarding the visual brightness of comet Lovejoy:

QUOTE
IMHO, most of the images that have been posted over the last few days reflects the true visual appearance. Specifically, in dark skies you can see the tail to the same extent as is shown in the images.

The main issue is how you might represent the brightness of the comet's tail. I think the best way to describe this is that the comet is currently close to one of the brighter parts of the Milky Way, and compared to the milky way at the same altitude, the surface brightness of the majority of the tail is somewhat brighter than the brighter parts of the Milky Way.


Dave Herald
Murrumbateman, Australia
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Mongo
post Dec 26 2011, 02:37 PM
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Comet-ml post #19101 by Rob Kaufman:

QUOTE
Hi Frans. I can only speak for the 23rd (24th here), but the visual view was very much the same as the photograph shown in the composite. In darker skies the tail was quite bright and prominent. I made out 20 degrees of tail visually, but didn't see the head or last couple of degrees of tail rise because daylight washed it out. The ion tail on the 23rd was quite prominent visually and the extent of faint end of the tail visible matched the photograph quite well.

Cheers -

Rob
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Mongo
post Dec 26 2011, 08:37 PM
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From comet-ml post #19115 by Jim Gifford:

QUOTE
As the comet's tail rose tonight it was at first hard to pick against the Milky Way background. The higher it rose the easier it became because of the straight edges of the tail. It has faded considerably since I observed it last on the 24th December but is now much longer at 28 degrees. It became striking to observe only when its full length was above the horizon and it stood vertically below the Southern Cross. All the intensity has gone out of the head and tail.
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Stu
post Dec 26 2011, 09:07 PM
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Latest ISS shots put together...

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Mongo
post Dec 26 2011, 09:28 PM
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From comet-ml post #19117 by Rob Kaufman:

QUOTE
Nice report Jim. I too observed it this morning, starting earlier at 1:30am (UT+11) with a fair bit of the fainter tail showing. I had also observed it on the 24th (23rd UT) and this morning it was considerably fainter, and longer. I could imagine that now, combined with interference from the Milky Way, it might be difficult to see in light-polluted skies. Nonetheless, I found it quite impressive still from my very dark sky site. Gone are the 'ribbon' structures and the ion tail evident on the 24th, and the tail (naked-eye, binoculars & photographic) shows no structure. The tail appeared fairly bright for the first 10-deg or so, but naked eye the exact position of the head was difficult to make out as the tail narrowed down to nothing. Not so with binoculars or photographically.

As the tail fanned out the surface brightness diminished although it was quite clear as far as the top Pointer, a distance of 28-deg. Naked-eye I could make it out faintly to halfway between the top Pointer & the Southern Cross, about 33-deg. Nothing could be seen there with binoculars - in fact even the section adjacent to the Pointers was difficult to make out with binoculars. Photography seems to show some faint hints of dust extending to adjacent to the Cross (perhaps 38-deg) but I need to check some reference images to see if it's just fortuitously aligned bright patches.

Was it John Bortle who predicted the comet would expand & dim to became a huge 'ghost'? Because that's the impression I got. The comet would still be a striking sight away from the Milky Way, but even in amongst it I found the sight of this great ghost transfixing, a true wonder!


He also posted this image:

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Mongo
post Dec 26 2011, 10:57 PM
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Comet-ml post #19119 by John Bortle:

QUOTE
--- In comets-ml@yahoogroups.com, "Rob" <Rob.Kau@...> wrote:
>
> Was it John Bortle who predicted the comet would expand & dim to became a huge 'ghost'? Because that's the impression I got. The comet would still be a striking sight away from the Milky Way, but even in amongst it I found the sight of this great ghost transfixing, a true wonder!
>
> Rob Kaufman
> Bright, Vic, Australia
>

At this time I would hasten to point out that based on descriptions of the Post-T evolution so far, 2011 W3 is almost precisely mimicing the physical appearance of the Great Southern Comet of 1880 during it apparition.

If this continues I would predict that by about next weekend 2011 W3's tail will have assumed essentially the same low level of brightness over virtually its entire length. As it fades toward obscurity, it will attain a maximum length between 50 and 60 degrees as seen from the darkest observing sites, but be exceedingly faint and ghostly in its appearance. At the same time the head will fade way completely, the sunward end of the tail simply fading to nothingness against the sky.

Incidentally, my main computer is down and I'm working from a tiny and frustrating laptop, so please forgive typing errors. I'm also unsure just how much I will be able to participate on the forum this week until my big machine returns.

J.Bortle
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Mongo
post Dec 27 2011, 02:47 AM
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Comet-ml post #19122 by David Seargent

QUOTE
Hi all,

This morning (Dec. 26, 1600-1650 UT) about 37 degrees of tail could be seen from Cowra, reaching up to the outer edges of the Southern Cross. Interestingly, this was the first time that something that could be called a "head" was discernible in the 25x100 BT. At the end of the tail, there was a small (approx 4 arcmin) very diffuse, transparent nebulous blob slightly brighter than the adjoining tail (m = 5.3). The distinction between "head' and "tail end" was more apparent using averted vision, but it was truly there! The two earlier sungrazers that I saw developed in a similar way, albeit much later after perihelion. Ikeya-Seki about 7 weeks after perihelion and White-Ortiz-Bolelli about 3. I would guess that the early diffusing of 2011 W3 probably signifies a small comet shutting down whilst still closer to the Sun rather than one that is disintegrating. On the other hand, the tail (although much fainter) is still very distinct and remains impressive in a dark sky. The length is truly amazing ... lengthening even while it fades!

Cheers,
David
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