The origin of meteoroid streams

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The origin of meteoroid streams

Post  taixyz1992 on Thu Dec 16, 2010 4:50 pm


A meteor shower is the result of an interaction between a planet, such as Earth, and streams of debris from a comet.

Comets can produce debris by water vapor drag, as demonstrated by Fred Whipple in 1951 [2] , and by breakup. Whipple envisioned comets as "dirty snowballs," made up of rock embedded in ice, orbiting the Sun. The "ice" may be water, methane, ammonia, or other volatiles, alone or in combination. The "rock" may vary in size from that of a dust mote to that of a small boulder. Dust mote sized solids are orders of magnitude more common than those the size of sand grains, which, in turn, are similarly more common than those the size of pebbles, and so on. When the ice warms and sublimates, the vapor can drag along dust, sand, and pebbles. Each time a comet swings by the Sun in its orbit, some of its ice vaporizes and a certain amount of meteoroids will be shed. The meteoroids spread out along the entire orbit of the comet to form a meteoroid stream, also known as a "dust trail" (as opposed to a comet's "dust tail" caused by the very small particles that are quickly blown away by solar radiation pressure).

Recently, Peter Jenniskens [3] has argued that most of our short-period meteor showers are not from the normal water vapor drag of active comets, but the product of infrequent disintegrations, when large chunks break off a mostly dormant comet. Examples are the Quadrantids and Geminids, which originated from a breakup of asteroid-looking objects 2003 EH1 and 3200 Phaethon, respectively, about 500 and 1000 years ago. The fragments tend to fall apart quickly into dust, sand, and pebbles, and spread out along the orbit of the comet to form a dense meteoroid stream, which subsequently evolves into Earth's path.

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Re: The origin of meteoroid streams

Post  nirvana on Sat Dec 18, 2010 6:03 pm

Wikileaks: Sudan's President Bashir 'stole billions'
President Omar al-Bashir (file photo) Sudan has denied allegations that Mr Bashir stole public funds
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Sudanese President Omar al-Bashir has been accused of siphoning off up to $9bn of his country's funds and placing it in foreign accounts, according to leaked US diplomatic cables.

Diplomats quoted the chief prosecutor of the International Criminal Court (ICC) as saying that much of the money may be stashed in London banks.

The allegations released by the Wikileaks website have been published by the Guardian newspaper.

Sudan has denied the claims.

The cables quoted ICC chief prosecutor Luis Moreno Ocampo as telling US officials that some of the funds may be held by the part-nationalised Lloyds Banking Group. He reportedly said it was time to go public with the scale of Mr Bashir's theft.

"Ocampo suggested if Bashir's stash of money were disclosed (he put the figure at $9bn), it would change Sudanese public opinion from him being a 'crusader' to that of a thief," one report by a senior US official said.

"Ocampo reported Lloyds bank in London may be holding or knowledgeable of the whereabouts of the money," the cable said.

Lloyds has responded by saying it has no evidence of holding funds in Mr Bashir's name.

"We have absolutely no evidence to suggest there is any connection between Lloyds Banking Group and Mr Bashir. The group's policy is to abide by the legal and regulatory obligations in all jurisdictions in which we operate," the bank said.

Correspondents say that if Mr Ocampo's claim about Bashir's fortune is correct, the Sudanese funds being held in London banks amount to one tenth of the country's annual GDP.
Claims 'ludicrous'

Mr Ocampo is said to have discussed evidence of the stash with the Americans just days after issuing an arrest warrant for Mr Bashir in March 2009 - the first issued by the court against a serving head of state.

Mr Bashir was indicted last year for seven counts of war crimes and crimes against humanity in the Darfur region, with a further three counts of genocide added in July.

A spokesperson for the Sudanese government dismissed the claim, describing it as further evidence of the ICC's political agenda in discrediting the Sudanese government.

"To claim that the president can control the treasury and take money to put into his own accounts is ludicrous - it is a laughable claim by the ICC prosecutor," Khalid al-Mubarak, government spokesperson at the Sudanese embassy in London, told the Guardian.

"Ocampo is a maverick, and this is just part of his political agenda. He has failed miserably in all his cases and has refused to investigate Iraq or Gaza - he needs success and he has targeted Bashir to increase his own importance."

"Attempts to smear not only Bashir but Sudan as a whole are well known, and are clearly linked with anti-Arab sentiments and Islamophobia," Mr Mubarak said.





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On November 1

Post  be_map1512 on Tue Nov 01, 2011 3:10 pm

On November 1 the system evolved into a full-fledged hurricane with peak winds of 75 mph (120 km/h), although the National Hurricane Center left it unnamed to avoid confusion amid media interest in the predecessor extratropical storm. It later received the name "the Perfect Storm" after a conversation between Boston National Weather Service forecaster Robert Case and author Sebastian Junger. The system was the fourth hurricane and final tropical cyclone in the 1991 Atlantic hurricane season. The tropical system weakened, striking Nova Scotia as a tropical storm before dissipating.sydney strippers
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