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Shoemaker-Levy 9, Impact Modeling |
 Apr 6 2006, 11:11 AM
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#1
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 Member  Group: Members Posts: 531 Joined: 24-August 05 Member No.: 471  |
- http://arxiv.org/abs/astro-ph/0604079 - Shoemaker-Levy 9 Impact Modeling: I. High-Resolution 3D Bolides
--- We have run high-resolution, three-dimensional, hydrodynamic simulations of the impact of comet Shoemaker-Levy 9 into the atmosphere of Jupiter. We find that the energy deposition profile is largely similar to the previous two-dimensional calculations of Mac Low and Zahnle (1994), though perhaps somewhat broader in the range of height over which the energy is deposited. As with similar calculations for impacts into the Venusian atmosphere, there is considerable sensitivity in the results to small changes in the initial conditions, indicating dynamical chaos. We calculated the median depth of energy deposition (the height z at which 50% of the bolide's energy has been released) per run. The mean value among runs is approx 70 km below the 1-bar level, for a 1-km diameter impactor of porous ice of density rho=0.6 g cm^{-3}. The standard deviation among these runs is 14 km. We find little evidence of a trend in these results with the resolution of the calculations (up to 57 cells across the impactor radius, or 8.8-m resolution), suggesting that resolutions as low as 16 grid cells across the radius of the bolide may yield good results for this particular quantity. --- -------------------- - blue_scape / Nico -
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Apr 7 2006, 11:40 PM
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#2
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 Senior Member Group: Members Posts: 2454 Joined: 8-July 05 From: NGC 5907 Member No.: 430 |
Speaking of comets breaking apart (if only we had a well-shielded probe
following this one. Who needs to make a crater with a copper ball when you've got the whole comet revealing its interior to you): Space Weather News for April 7, 2006 http://spaceweather.com Dying comet 73P/Schwassmann-Wachmann 3 continues to break apart. Astronomers are tracking at least 20 fragments approaching Earth for a harmless but beautiful close encounter in May. In particular, fragment B of the comet has brightened 15-fold since April 2nd. This signals a possible breakup of "73P-B" into even more fragments. Amateur astronomers with backyard telescopes and CCD cameras can monitor the ongoing disintegration. Visit Spaceweather.com for sky maps, images more information. -------------------- "After having some business dealings with men, I am occasionally chagrined,
and feel as if I had done some wrong, and it is hard to forget the ugly circumstance. I see that such intercourse long continued would make one thoroughly prosaic, hard, and coarse. But the longest intercourse with Nature, though in her rudest moods, does not thus harden and make coarse. A hard, sensible man whom we liken to a rock is indeed much harder than a rock. From hard, coarse, insensible men with whom I have no sympathy, I go to commune with the rocks, whose hearts are comparatively soft." - Henry David Thoreau, November 15, 1853 |
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Apr 11 2006, 03:02 PM
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#3
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Senior Member Group: Members Posts: 2454 Joined: 8-July 05 From: NGC 5907 Member No.: 430 |
Hybrid comet-asteroid in mysterious break-up
09:30 11 April 2006 NewScientist.com news service Jeff Hecht Something substantial has broken off an icy 50-kilometre object beyond the orbit of Saturn, leaving puzzled astronomers trying to figure out why. Comets have been seen breaking up before, but only after heating when passing close to the Sun or a gravitational disturbance following a close encounter with a planet. However, at 1.9 billion kilometres, this object is very far from the Sun. Another mysterious feature is that much more gas and dust is escaping from the breakaway fragment than from the parent body. The disintegration has created a dust cloud more than 100,000 km across and which is several times brighter than the original object was before the event. The object, called 60558 Echeclus, was discovered in 2000 and is a “centaur” - part rocky asteroid and part icy comet. Its new activity, revealed in images taken on 2 April, makes it look “really strange", says William Romanishen of the University of Oklahoma, US, one of the team that took the images. "The first thing that came to mind was a collision." Earlier observations showed Echeclus rotates about once every 26 hours, so a fragment would need a push to escape its gravity, says Paul Weissman of the Jet Propulsion Laboratory, who spotted the original cloud of gas and dust around Echeclus on 30 December 2005. Full article here: http://www.newscientistspace.com/article/d...us-breakup.html -------------------- "After having some business dealings with men, I am occasionally chagrined,
and feel as if I had done some wrong, and it is hard to forget the ugly circumstance. I see that such intercourse long continued would make one thoroughly prosaic, hard, and coarse. But the longest intercourse with Nature, though in her rudest moods, does not thus harden and make coarse. A hard, sensible man whom we liken to a rock is indeed much harder than a rock. From hard, coarse, insensible men with whom I have no sympathy, I go to commune with the rocks, whose hearts are comparatively soft." - Henry David Thoreau, November 15, 1853 |
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| Guest_BruceMoomaw_* |
Apr 11 2006, 08:29 PM
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#4
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Guests |
QUOTE (ljk4-1 @ Apr 7 2006, 11:40 PM)  Speaking of comets breaking apart (if only we had a well-shielded probe following this one. Who needs to make a crater with a copper ball when you've got the whole comet revealing its interior to you): Space Weather News for April 7, 2006 http://spaceweather.com Dying comet 73P/Schwassmann-Wachmann 3 continues to break apart. Astronomers are tracking at least 20 fragments approaching Earth for a harmless but beautiful close encounter in May. In particular, fragment B of the comet has brightened 15-fold since April 2nd. This signals a possible breakup of "73P-B" into even more fragments. Amateur astronomers with backyard telescopes and CCD cameras can monitor the ongoing disintegration. Visit Spaceweather.com for sky maps, images more information. This is the one which was supposed to be CONTOUR's second destination -- this year. (Or rather, one of its fragments was, to get just such a cross-sectional view.) It is, perhaps, the biggest scientific loss from that failure -- but the proposed CONTOUR-2 would also visit it, around 2020. The question is how much the Sun will have modified the exposed fresh surfaces by then. I was under the impression that the split had occurred recently, but one source I saw in passing a few days ago said that the first split into two pieces actually happened all the way back in 1930. I'll have to check on this. Anyway, a flyby in 2020 still sems worthwhile -- if, that is, SW-3 hasn't completely crumbled by then... |
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Apr 17 2006, 06:17 PM
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#5
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Senior Member Group: Members Posts: 2454 Joined: 8-July 05 From: NGC 5907 Member No.: 430 |
Fragmented Comet Will Sweep By Earth Next Month
http://www.spacedaily.com/reports/Fragment...Next_Month.html Boulder CO (SPX) Apr 17, 2006 - Astronomers tracking Comet 73P/Schwassmann-Wachmann 3 report that the near-Earth object continues to break apart, with at least 20 fragments now approaching the planet for a close encounter next month. -------------------- "After having some business dealings with men, I am occasionally chagrined,
and feel as if I had done some wrong, and it is hard to forget the ugly circumstance. I see that such intercourse long continued would make one thoroughly prosaic, hard, and coarse. But the longest intercourse with Nature, though in her rudest moods, does not thus harden and make coarse. A hard, sensible man whom we liken to a rock is indeed much harder than a rock. From hard, coarse, insensible men with whom I have no sympathy, I go to commune with the rocks, whose hearts are comparatively soft." - Henry David Thoreau, November 15, 1853 |
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| Guest_BruceMoomaw_* |
Apr 17 2006, 06:37 PM
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#6
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Guests |
That article confirms that it did break up very recently -- some time between 1990 and 1995. This makes CONTOUR's failure even more of a pity; it begins to look as though SW3 will crumble completely before any other mission can get a look at a cross-section of one of its fragments.
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Apr 19 2006, 02:51 PM
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#7
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Senior Member Group: Members Posts: 2454 Joined: 8-July 05 From: NGC 5907 Member No.: 430 |
IRON AND ICE
- Fragmenting Comet Flyby To Be Webcast http://www.spacedaily.com/reports/Fragment...Be_Webcast.html New York NY (SPX) Apr 18, 2006 - Slooh.com, an astronomical event Web site, said Tuesday it will begin live monitoring of the approach of Comet 73P Schwassmann-Wachmann, beginning this week at 9 p.m. Eastern Time. -------------------- "After having some business dealings with men, I am occasionally chagrined,
and feel as if I had done some wrong, and it is hard to forget the ugly circumstance. I see that such intercourse long continued would make one thoroughly prosaic, hard, and coarse. But the longest intercourse with Nature, though in her rudest moods, does not thus harden and make coarse. A hard, sensible man whom we liken to a rock is indeed much harder than a rock. From hard, coarse, insensible men with whom I have no sympathy, I go to commune with the rocks, whose hearts are comparatively soft." - Henry David Thoreau, November 15, 1853 |
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Apr 24 2006, 03:22 PM
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#8
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Senior Member Group: Members Posts: 2454 Joined: 8-July 05 From: NGC 5907 Member No.: 430 |
Thirty pieces and counting, some of which may reach magnitude 4.
I presume there is no way to get any space probes near one of these chunks? Is the HST scheduled to image any of them? Space Weather News for April 22, 2006 http://spaceweather.com COMET NEWS: Astronomers are now monitoring more than 30 fragments of dying comet 73P/Schwassmann-Wachmann 3, which is approaching Earth for a close encounter in mid-May. One of the brightest fragments, fragment B, is splitting in two in plain view of amateur astronomers using backyard telescopes. Visit Spaceweather.com for pictures of the breakup, sky maps and more. -------------------- "After having some business dealings with men, I am occasionally chagrined,
and feel as if I had done some wrong, and it is hard to forget the ugly circumstance. I see that such intercourse long continued would make one thoroughly prosaic, hard, and coarse. But the longest intercourse with Nature, though in her rudest moods, does not thus harden and make coarse. A hard, sensible man whom we liken to a rock is indeed much harder than a rock. From hard, coarse, insensible men with whom I have no sympathy, I go to commune with the rocks, whose hearts are comparatively soft." - Henry David Thoreau, November 15, 1853 |
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Apr 24 2006, 06:01 PM
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#9
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Member Group: Members Posts: 624 Joined: 10-August 05 Member No.: 460 |
Maybe it is time for an ice cream scoop theory: Comets shovel icy particulate picked up in the Kuiper belt into the inner solar system, dumping their load with every visit
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Apr 24 2006, 07:38 PM
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#10
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Member Group: Members Posts: 235 Joined: 2-August 05 Member No.: 451 |
Surely you are not saying that comets have any way to accumulate a significant amount of icy material when in the outer part of the Solar System each orbit.
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Apr 25 2006, 05:53 PM
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#11
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Member Group: Members Posts: 624 Joined: 10-August 05 Member No.: 460 |
No, but I think that it is interesting that only a couple of chunks of 73P/Schwassmann-Wachmann 3 behave like comets, and every comet we have looked at closely seems to be mostly black stuff. Extrapolating, is it reasonable to assume most 'comets' are invisible and we only see the occasional comet that has a enough moisture content near or on the surface to show its face? Extrapolating even more, this would mean there is a lot more stuff in the Kuiper belt and beyond than imagined. Are the contraints on possible Kuiper belt objects based upon forground or background observations?
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Apr 26 2006, 05:04 AM
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#12
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Senior Member Group: Members Posts: 1870 Joined: 20-February 05 Member No.: 174 |
"Black Stuff"....
Even though exposed comet nucleus material (at least in the inner solar system) is mostly as black as laserjet toner... about 4% reflectivity, it's not 0% reflective. It's *** ENORMOUSLY *** difficult to make anything signigicantly blacker. If bare comet nucleii had significant amounts of exposed water, like the water-bearing higher albedo exposures on a very limited fraction of Temple-1's surface, but much greater (enough to influence brightness), it would dramatically show up in the near and middle infrared spectrum. Generally, size/frequency distrubution limits based on brightnesses of observed populations use "best guess" albedo assumptions based on larger members of the population, but not the largest (whicy may be atypical) For comet nucleii, they're plugging in an albedo of around 4%. Also.. if there really were absolutely black objects, they'd show up perfectly well in the thermal infrared. a 4% and 0% reflectance black surface will heat up to essentially the same temperature, as long as they're not strongly heat absorbing |
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Apr 26 2006, 03:00 PM
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#13
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Member Group: Members Posts: 624 Joined: 10-August 05 Member No.: 460 |
QUOTE (edstrick @ Apr 25 2006, 11:04 PM) Also.. if there really were absolutely black objects, they'd show up perfectly well in the thermal infrared. a 4% and 0% reflectance black surface will heat up to essentially the same temperature, as long as they're not strongly heat absorbing ...which they are not, if Tempel 1 is typical. Thanks. (I will sleep better believing we are not be pummelled by unseen dark crusties loaded with alien DNA...) |
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Apr 27 2006, 06:41 PM
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#14
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Senior Member Group: Members Posts: 2454 Joined: 8-July 05 From: NGC 5907 Member No.: 430 |
Compare these new images of the Breakup Comet from HST:
http://hubblesite.org/news/2006/18 http://www.jhuapl.edu/newscenter/pressrele...2006/060427.asp http://www.spacetelescope.org With this one from a ground-base amateur astrophotographer via Spaceweather.com: http://spaceweather.com/swpod2006/27apr06/hergenrother1.gif The latter is a bit blurrier, but otherwise pretty darn good, showing quite a few of the new comet chunks. -------------------- "After having some business dealings with men, I am occasionally chagrined,
and feel as if I had done some wrong, and it is hard to forget the ugly circumstance. I see that such intercourse long continued would make one thoroughly prosaic, hard, and coarse. But the longest intercourse with Nature, though in her rudest moods, does not thus harden and make coarse. A hard, sensible man whom we liken to a rock is indeed much harder than a rock. From hard, coarse, insensible men with whom I have no sympathy, I go to commune with the rocks, whose hearts are comparatively soft." - Henry David Thoreau, November 15, 1853 |
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| Guest_BruceMoomaw_* |
Apr 27 2006, 11:12 PM
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#15
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Guests |
ESA has a new sequence of Hubble photos showing the really spectacular fireworks display that SW3 is turning into. It really starts to look as though nothing will be left by the time that a CONTOUR 2 spacecraft could get there.
http://sci.esa.int/science-e/www/area/index.cfm?fareaid=1 |
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Apr 27 2006, 11:14 PM
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#16
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Founder Group: Chairman Posts: 14457 Joined: 8-February 04 Member No.: 1 |
At the BAA Out of London meeting this weekend just gone ( a tie in with the 125th aniv of the Liverpool Astronomy Assoc ) - we had a half hour session on the Faulkes North scope....
http://www.britastro.org/baa/ http://britastro.org/baa/images/stories/ne...0060422_ftn.jpg Doug |
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May 17 2008, 09:30 AM
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#17
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 Senior Member Group: Members Posts: 1729 Joined: 3-August 06 From: 43° 35' 53" N 1° 26' 35" E Member No.: 1004 |
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May 17 2008, 03:03 PM
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#18
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 Interplanetary Dumpster Diver Group: Admin Posts: 4407 Joined: 17-February 04 From: Powell, TN Member No.: 33 |
Those are different transmissions of the raw frame. Here are the four raw transmissions.
Attached thumbnail(s)
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May 17 2008, 03:24 PM
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#19
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Senior Member Group: Members Posts: 1729 Joined: 3-August 06 From: 43° 35' 53" N 1° 26' 35" E Member No.: 1004 |
Yes, and I remember that the one with the fireball is the first, but I am not sure.
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