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Huge comet outburst reported, 17P/Holmes
stevesliva
post Oct 24 2007, 08:24 PM
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Spaceweather has started coverage... nice photo of exactly where it is.
http://spaceweather.com/archive.php?view=1...0&year=2007
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ngunn
post Oct 24 2007, 08:50 PM
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I went out for a look about an hour ago. Slight haze and lots of moonlight so I used binoculars. I found a 'star' in the position indicated (using ephemeris position and Norton's Star Atlas) not a lot fainter than Delta Persei. I'd guess about magnitude 3.5. I've never seen a comet looking like a fairly bright star before so I retired indoors puzzled as clouds overtook the scene. Checked here and - well it seems that was it! I wonder how long it will remain so bright and starlike? I look forward to following its progress if weather allows.
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nprev
post Oct 24 2007, 11:41 PM
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Pics, please, gentlemen, if you can...not only am I in LA, but the whole area's covered with smoke from these damned wildfires (cough, cough...)


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MizarKey
post Oct 25 2007, 07:23 AM
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I just saw it a few minutes ago...WOW! What an odd duck this comet is...my very first impression: like looking down on Saturn. The nucleus is bright and orangeish and the coma is nearly pefectly round and grey like fog. I used 20X80 binoculars and I'm in central California under clear skies with a bright moon.
Locating it was easy if you know how Perseus is supposed to look...the comet stands out.

Worth a look!


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ugordan
post Oct 25 2007, 08:37 AM
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QUOTE (nprev @ Oct 25 2007, 01:41 AM) *
Pics, please, gentlemen, if you can..

Via SpaceWeather.com comes this one:
http://www.spaceweather.com/comets/holmes/...Eric-Allen1.jpg

It really looks like an instantaneous, symmetrical release of volatiles which are now slowly expanding to form a visible coma. The comet's brightness might stay the same (or even increase a bit) until this coma dissipates and changes the comet's appearance from a star-like object to a fuzzy, dim blob.

I can't imagine what could have triggered such an event. An impact comes to mind, but are we really expected to see such a rare event, statistically speaking?
Was it a simple case of falling apart under thermal stress?

Who needs Deep Impact when you've got this. smile.gif


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ngunn
post Oct 25 2007, 09:17 AM
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QUOTE (ugordan @ Oct 25 2007, 09:37 AM) *
An impact comes to mind, but are we really expected to see such a rare event, statistically speaking?


I was wondering that too. It seems to have been so sudden. Most comet break-ups are protracted, multi-staged affairs. You'd need a huge build-up of internal pressure to produce a single explosive event as this seems to have been. A collision could certainly do it. It's only a single event so maybe statistics are a poor guide. Let's hope observations can narrow down the possibilities.
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ugordan
post Oct 25 2007, 09:23 AM
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Are there any constraints about its rotational period? I'm wondering if a fast enough rotation would homogenize the coma even with a directional outburst. An impact would probably not be symmetric unless the whole thing got blown up. We'll need some more observations to see if there's a directional component to the outgassing.


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ngunn
post Oct 25 2007, 09:32 AM
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QUOTE (ugordan @ Oct 25 2007, 10:23 AM) *
An impact would probably not be symmetric unless the whole thing got blown up.


Interesting, but maybe that depends on whether or not the bright centre we see now actually corresponds to the position of the nucleus.
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ngunn
post Oct 25 2007, 10:37 AM
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From the account here
http://www.ast.cam.ac.uk/~jds/per01.htm
it seems that this comet did something similar at the time of its discovery in 1892.

So probably no collision, just an unusually tough crust.
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MizarKey
post Oct 25 2007, 01:40 PM
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QUOTE (ugordan @ Oct 25 2007, 01:37 AM) *


That picture is very good, but with the naked eye it appears orangeish yellow. When I first went out to look at it I was holding the binocular in my hands (20x80 binocs are pretty heavy and you get tired of holding them up quick). I first looked at the Pleiades to make sure the focus was good. At the time I had only a rough idea where the comet was (near Mirfak according to Phil Plait - the bad astronomer). When I found the comet I thought the focus had gone out and I tried refocusing...with no luck of course. Even though he had mentioned it was mag. 3 or so, I was surprised at how bright and round it was. I might even get my little telescope out of storage for this one...


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Guest_PhilCo126_*
post Oct 25 2007, 02:35 PM
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more info and pictures: http://www.aerith.net/comet/catalog/0017P/2007.html
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Holder of the Tw...
post Oct 25 2007, 03:49 PM
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Stepped outside last night at local midnight and looked straight up. It took almost no time at all to see there was something "wrong " with Persues. The extra "star" was very visible and unmistakeable.

I got out my little trusty Astroscan on low magnification (16X). Took awhile to aim it, given the angle, but finally found it. Even at low magnification, there was nothing starlike about it at this point. Looked like a little bright tan blob, with a distinct core and an even, thin, circular, bright fuzzy haze around the the core . It may have been my eyes, or the telescope, or both, but I think there was a short and faint tail starting to develop.

My observations were made from Tulsa, Oklahoma in the US.
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Holder of the Tw...
post Oct 25 2007, 04:25 PM
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Deep Impact is schedueled to fly by earth December 31st to be targeted to comet Beothin. I know it's a long shot, but does anyone know if it would be possible to retarget the spacecraft to Holmes instead? Just as a possible option, I'm not saying they should if they can.
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djellison
post Oct 25 2007, 05:07 PM
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The chances of the mechanics working are near zero I would have thought. Holmes is quite far out of the ecliptic.

Meanwhile the clouds here are strengthening my belief that there is a direct correlation between the UK climate and transient astronomical phenomenon.

Doug
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Stu
post Oct 25 2007, 05:42 PM
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QUOTE (djellison @ Oct 25 2007, 06:07 PM) *
Meanwhile the clouds here are strengthening my belief that there is a direct correlation between the UK climate and transient astronomical phenomenon.

Doug


Oh Doug, I think that was first proved about a decade ago when I organised half a dozen "Skywatch" nights to show people Comet Hale-Bopp and it was cloudy for every one of them... mad.gif ( Clear the nights either side, of course...!!) And I can guarantee that if there's a meteor shower due, or a spectacularly bright Iridium flare, or a meteor storm, clouds will roll across a clear blue sky at twilight like that scene in INDEPENDANCE DAY. I managed to glimpse Comet McNaught just 3 times before it dropped behind the horizon, and on each of those nights I just caught it thru a gap in the cloud...

Up here in Kendal tonight the cloud cover is thicker than Jade Goody, and I've about as much chance of seeing Holmes as I have of hearing a knock on my door and opening it to find a rain-soaked Keira Knightley standing there, shivering, asking if she can beg a towel because she's just moved in next door and has locked herself out... laugh.gif


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