Comet chunks to fly by Earth

michaelmozina · May 4, 2006

From the link Calli posted earlier: <blockquote>In reply to:<hr />Zoom from a ground-based view of Comet 73P/Schwassmann-Wachmann 3's fragments B, G and R to a close-up of fragment B. Observations taken April 18 to 20, 2006, with Hubble's Advanced Camera for Surveys reveal that the fragment is continuing to break into smaller chunks. Several dozen house-sized "mini-fragments" are found trailing behind the main fragment.<hr /></blockquote> From watching the mpg images, I'd say the comet is breaking up in typical comet style. Most of the house sized particles will continue to disintegrate in the coma behind the core. <div class="Discussion_UserSignature"> It seems to be a natural consequence of our points of view to assume that the whole of space is filled with electrons and flying electric ions of all kinds. - Kristian Birkeland </div>

dmjspace · May 4, 2006

CalliArcale said: What did I edit out??? Are you seriously accusing me of censorship? Sorry. That came across a bit harsh. I simply meant that this crucial point was not addressed in your posts. You said: it is unreasonable to expect the dirty snowball model to make predictions about exactly when a particular comet will fracture. Here are some relevant portions from the former head of the USNO's Celestial Mechanics Branch Tom Van Flandern's book on the subject: When a comet splits, the separation velocities are amazingly small--generally less than one meter per second, even though orbital velocities around the Sun are typically 50,000 m/s.... This observation is entirely consistent with the multiple-nuclei interpretation of the EPH, but not the dirty snowball model. Why? Because to get such gentle splitting, the dirty snowball model must insist that comets are smaller than actually observed and much lower density than observed (i.e. they must have exceedingly low escape velocity). The EPH has no such restrictions. It says that comet "splitting" is merely the result of nuclei that were previously bound now wandering outside the group's gravitational sphere of influence (now altered by the Sun). A study of comet splitting conducted by Sekanina showed the EPH be to more accurate in predicting when a comet's nuclei should separate than any other competing model. But you won't hear about that from the dirty snowball guys. They're too busy inventing reasons for splits after-the-fact, and insisting that the split couldn't have been predicted because of all the unknown variables! TVF notes additional mysteries (to the dirty snowball model) that are elegantly explained by the EPH's satellite model for comets: 1. Comets split preferentially before perihelion...but not in general afterwards. 2.

CalliArcale · May 4, 2006

Phew, I'm glad you didn't think I was going around censoring people. That's a big relief. Apology definitely accepted. I did not intentionally avoid any questions. I've just been very busy this week and have not had time to thoroughly go through all of the posts. If I miss something, it's not out of malice. Just ask me again. Sometimes my brain needs a jog. <blockquote>In reply to:<hr />When a comet splits, the separation velocities are amazingly small--generally less than one meter per second, even though orbital velocities around the Sun are typically 50,000 m/s.... This observation is entirely consistent with the multiple-nuclei interpretation of the EPH, but not the dirty snowball model. Why? Because to get such gentle splitting, the dirty snowball model must insist that comets are smaller than actually observed and much lower density than observed (i.e. they must have exceedingly low escape velocity). <hr /></blockquote> Now we're getting down to brass tacks! <img src="/images/icons/wink.gif" /> Thank you. This is much better than saying "scientists are such idiots". This is explaining *why* you think they're wrong. I'm not so sure that the slow separation is a problem, though. Based on what I've absorbed about rocketry, I wouldn't think that water vapor outgassing would have a whole lot of thrust. One meter per second seems pretty reasonable to me, assuming they're only being propelled apart by water vapor and the occasional ion stream. BTW, don't be confused by the orbital velocity of the comet. It is actually irrelevant to their relative separation rate. It doesn't matter whether the comet is moving 50,000 m/s or some other speed. And Von Flandern ought to know that; it's basic celestial mechanics. What matters in studying a comet which broke apart spontaneously is how fast the objects separate relative to one another, and the overall comet's velocity arou <div class="Discussion_UserSignature"> "People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff." -- The Tenth Doctor, "Blink" </div>

cyclonebuster · May 4, 2006

Well since all those 60 three mile wide or greater fragments are to make it past us in 6 days from the 11th through the 17 th has any one figured out how far apart they are from one another?

sponge · May 5, 2006

After all that has been said in this post what chance in percent if any, is there of a piece of this comet striking the earth, simple answer please. <div class="Discussion_UserSignature"> SPONGE </div>

derekmcd · May 5, 2006

zero <div class="Discussion_UserSignature"> <div> </div> <div>"If something's hard to do, then it's not worth doing." - Homer Simpson</div> </div>

harmonicaman · May 5, 2006

In 2022 we may have a better chance, depending on how far the footprint of the debris field spreads out; but as it spreads out it becomes more diffuse, so the likelihood of us getting hit by something bigger than a refrigerator is still remote... Space is big. You just won't believe how vastly, hugely, mind- bogglingly big it is. I mean, you may think it's a long way down the road to the chemist's, but that's just peanuts to space. - Douglas Adams (1952 - 2001), The Hitchhiker's Guide to the Galaxy

cyclonebuster · May 5, 2006

Fragment count up to 61 now. They are finding more of these every day now.Up to 61 now. http://neo.jpl.nasa.gov/cgi-bin/db_s...&search=Search Seems like they are finding more everyday now. Ever hear of "Murphys Law"? "If something bad can happen it will happen!"How many have not been detected and where are they? Look how close the first fragment can come to us. Who's to say there are not any others we can not see? http://neo.jpl.nasa.gov/cgi-bin/neo_...t_min&sdir=ASC

dmjspace · May 5, 2006

Some might ask what the big deal is about which model is correct, the dirty snowball (DS) or the satellite model (a corollary of the EPH). A large part of it is whether the pieces of the comet are essentially ice-like or rock-like. The DS model insists a broken-up comet's pieces melt away because they're ice. The EPH, on the other hand, maintains that comets and asteroids have similar densities. Therefore, the fragments of 73P are not melting away, they are simply separating and escaping from each other's gravitational influence. They are basically turning into what we think of as asteroids--hard to detect, dark *rocks*. The implications of the EPH are that the fragments are still there: they're not evaporating. If we can see 61 fragments, you can bet there are a whole lot more that we cannot see. We can use this fundamental difference between models to predict meteor storms. In fact, when certain meteor storms have been predicted based on EPH premises, the EPH model has outperformed all competitors. See, for example, this discussion of the 1999 Leonids storm predictions, which were accurately modeled by the EPH, whereas DS models missed storm peak and intensity badly. Later storms were also modeled accurately by the EPH. It doesn't matter if the EPH offends scientists because it seems unbelievable or if they are so married to the DS model they can't consider another. What matters is how well competing models predict.

thepiper · May 5, 2006

There are other alternate theories to those two, most notably the Electric Universe model, which has already made some successful predictions with the Deep Impact mission. The thunderbolts site linked above is set to present its set of predictions for Schwassmann-Wachmann 3 this coming Monday. I have not heard of any NASA predictions, so I'm sure we can expect the usual "astronomers were surprised to discover" and "we will have to re-think certain aspects of comet theory" in their press releases. <img src="/images/icons/smile.gif" />

dmjspace · May 5, 2006

That's right. I'm not as familiar with the Electric Universe model, though I have read about Alfven's plasma theories. The EU model does seem to have a good prediction record.

harmonicaman · May 6, 2006

ThePiper - It was my understanding that the EU predictions for Deep Impact were way off the mark. After the results were in; the EU "Predictions" were revised to fit the actual results of the experiment. The EU model predictions included a vigorous electrical discharge that was not observed... To be valid, predictions must be made before an event occurs -- you can't revise it after the fact and still claim it was a prediction...

thepiper · May 6, 2006

The EU predictions for Deep Impact were not "way off the mark" at all and were not "revised" after the fact. For example, Electrical theorist Wallace Thornhill predicted two blasts. From the standard viewpoint that was an absurd prediction when considering an impactor being hit by a body at 23,000 miles per hour in “empty” space. But this is what makes such predictions so valuable. And here is what happened in the words of NASA investigator Peter Schultz, describing the event recorded from the spacecraft: "What you see is something really surprising. First, there is a small flash, then there's a delay, then there's a big flash and the whole thing breaks loose”. They also successfully predicted the release of copious x-rays, a much more energetic flash than that anticipated by NASA, and the initiation of new jets on the nucleus by the impact.

CalliArcale · May 8, 2006

Okay, folks, time to rein in the off-topic discussion. This thread is about the impending flyby of Comet 73P. Let's stick to that, okay? Start a separate thread for other more general comet discussions. <div class="Discussion_UserSignature"> "People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff." -- The Tenth Doctor, "Blink" </div>

CalliArcale · May 8, 2006

Last night, one of the fragments (fragment C) passed near the Ring Nebula as observed from Earth. http://spaceweather.com/ has some lovely images of the event from amateur astronomers. Check it out! (Alas, it was hazy with scattered clouds here in Minnesota. I didn't even try to see it; there was no point.) <div class="Discussion_UserSignature"> "People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff." -- The Tenth Doctor, "Blink" </div>

edawg · May 8, 2006

has anyonje caculated the chances of a fragmeant hitting the moon??? that would be a big wake up call

CalliArcale · May 9, 2006

Should be nil as well; judging by the spread of visible debris, it's not expanding fast enough for any of it to hit the Moon -- at least on this pass. There are no certainties for future passes. Update on the comet: Fragment B is reported to have suddenly increased in brightness again, to 5th magnitude. This probably signals more fragmenting. So, is anybody planning on hauling out the backyard scopes to take a look? <img src="/images/icons/wink.gif" /> The full moon will be an unfortunate competitor this weekend, but it should still be possible to see the fragments. <div class="Discussion_UserSignature"> "People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff." -- The Tenth Doctor, "Blink" </div>

edawg · May 10, 2006

but .03 Au fromt he moon is pretty close,and the biggest chunks we can see are 3mi across.im gonna pick up a cheap scope for this 1

CalliArcale · May 10, 2006

Fragment B is apparently now at fifth magnitude -- barely visible to the naked eye from rural areas with clear, dark skies. Binoculars will also be able to see the pieces. You can get free starmaps from Heavens Above. Click on Comet Schwassmann-Wachmann 3. You can also get starmaps at SpaceWeather.com, along with lovely astrophotos of the comet's larger fragments. <div class="Discussion_UserSignature"> "People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff." -- The Tenth Doctor, "Blink" </div>

CalliArcale · May 11, 2006

Lovely! Thanks for sharing that gorgeous Spitzer pic. <img src="/images/icons/wink.gif" /> <div class="Discussion_UserSignature"> "People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff." -- The Tenth Doctor, "Blink" </div>

CalliArcale · May 16, 2006

Swift has also imaged the comet. During closest approach, the comet was moving so fast it could be perceived to be in motion by a human eye through a modest telescope. Only one space telescope was up to the task of imaging it at this point: Swift. Swift has remarkable slewing capabilities, built into it primarily for the purpose of rapidly imaging GRB sites. In this case, the capability was exploited to track the comet. It imaged it simultaneously in both ultraviolet and x-rays. This appears to be the brightest comet yet imaged in x-ray, perhaps as a consequence of its breakup exposing more material to the ionizing effects of the solar wind. Check out the picture in this article. It shows Fragment B near the Ring Nebula. X-rays fly as cracking comet streaks across the sky <div class="Discussion_UserSignature"> "People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff." -- The Tenth Doctor, "Blink" </div>

spiritualspaceman · May 18, 2006

Comet B is nothing to be concerned with according to Eric Julien but Flagment S is the one that he says might impact the Atlantic Ocean and create according to his site and information a 200 meter wave

cyclonebuster · May 19, 2006

JPL Has the Earths center of mass passing .00001AU or 930 miles from the "S" fragment orbital plane. The intersection will happen Between June12th through June13th. http://neo.jpl.nasa.gov/cgi-bin/db_shm?rec=900458 Not good news with a fragmenting comet.

spacechump · May 20, 2006

I don't see where that information is shown.

edawg · May 20, 2006

is appears fema is planning a tsunami exercise...on may 23.what an odd cownkie-dink... Pacific Peril" - 3 Day Multi-State Tsunami Exercise Begins 23 May, 2006 Release Date: May 8, 2006 Release Number: R10-06-011 » 2006 Region X News Releases SEATTLE, Wash. -- The U.S. Department of Transportation in cooperation with Federal, State, local, and Canadian partners will host PACIFIC PERIL 06 from 23-25 May 2006 at Camp Rilea on the NW Oregon Coast. The three-day event will consist of a “training day” presenting earthquake and tsunami hazards and response plans, a full day Command Post Exercise (CPX) and a final table top review. The exercise play postulates a catastrophic seismic event that triggers a massive tsunami that devastates Pacific coastal communities from British Columbia to northern California. The Government of Canada, including the Province of British Columbia and the City of Vancouver, are also engaged in exercise play. According to Federal Aviation Administration Regional Administrator and Regional Emergency Transportation Coordinator (RETCO) Douglas R. Murphy, the exercise is designed to challenge participants with a high consequence scenario in order to better assess the effectiveness of existing response plans. “Experts agree that the likelihood of a massive earthquake and tsunamis wave is very real, and speak in terms of not if, but when. Our critical infrastructure is vulnerable, and advance preparation is the key to a successful response,” said Murphy. U.S. Department of Homeland Security FEMA Regional Director John Pennington agrees. “Emergency incidents are handled on a daily basis at the local level, but the challenges of responding to truly catastrophic disasters rapidly exceed the capabilities of any one community or state,” said Pennington. “In any disaster, coordination, planning, and unity of response are the key determinates of success. Exercises like PACIFIC PERIL help us valid

Comet chunks to fly by Earth

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