Comets


Meteor

England: Whitchurch, Shropshire - 2 Large 'fireballs' seen, one resembling a comet without a tail


UK UFO Sightings
Thu, 30 Jul 2009 15:03 UTC
Posted: July 30, 2009

Location of Sighting: Blackpark Road, Whitchurch, Shropshire
Date of Sighting: Saturday 4th July 2009
Time: 11.20-11.30

Witness Statement: Whilst sitting in the hot tub, looking up at the stars, we both noticed a bright light, which looked similar to a large Chinese lantern, it sort of drifted across the sky in a northerly direction, it suddenly changed direction and headed south east and upwards quite quickly, the light appeared to be a ball of fire, and we watched it for about 4-5 minutes.
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Blackbox

Go Back To Sleep - Comet Collisions Won't Spark The End Of The World


Red Orbit
Fri, 31 Jul 2009 01:42 UTC
Hale Bopp
© UnknownComet Hale-Bopp.
Evidence indicates that it is highly unlikely that a comet crash would result in Earth's demise, researchers at the University of Washington said on Thursday.

Writing in Science Express, the online edition of the journal Science, researchers acknowledged that while most scientists agree that an asteroid collision 65 million years ago caused the mass extinction of the dinosaurs, they tend to differ in opinion on how many other mass extinctions have resulted from similar events.

Researchers used computer models to simulate the formation of comet clouds in the solar system for 1.2 billion years. They pinpointed a body called the Oort Cloud as the source for many long-period comets that find their way into Earth's path.

Formed 4.5 billion years ago from the nebula that formed our solar system, the Oort Cloud spans from about 93 billion miles from the sun to about three light years away. Scientist said the Oort Cloud could contain literally billions of comets, many of which are so small and distant to be seen.

Comment: Regarding the claim that "the gravitational pulls of Jupiter and Saturn act as comet deflectors", let's see what Clube and Napier, British astronomers and writers of The Cosmic Serpent, have to say:
The giant comets normally reside far beyond the planets, in a spherical cloud surrounding the Sun, called the Oort cloud. There is also evidence for a flattened disk of comets closer to the inner solar system, called the Edgeworth/Kuiper belt. What prompts members of either of these comet repositories to enter the realm of the planets? Clube and Napier suggest a galactic influence. The solar system periodically passes through the plane of the galaxy as the Sun (and the solar system with it) orbits the galactic center. Each passage may dislodge giant comets and divert them closer to the Sun. The outer planets, particularly Jupiter, may then perturb some of these giant comets into orbits which enter the inner solar system. These comets, stressed both by gravity and by heat from the sun, may fragment into a cloud of smaller objects with dynamically similar orbits.

Chiron offers a good example of a giant comet as called for by Clube and Napier's giant comet hypothesis. Chiron is somewhere between 148 and 208 kilometers in diameter. Currently Chiron's unstable "parking orbit" lies mostly between Saturn and Uranus. Chiron may end up injected into the inner solar system within a hundred thousand years, or ejected from the solar system on a similar time scale. It is also possible that Chiron has already visited the inner solar system.

The Taurid complex and the Kreutz sungrazer group are two families of objects which most likely represent the fragmented remains of two giant comets in the current era. SOHO has recently discovered many new members of the Kreutz group which were previously unknown.

The Kreutz progenitor was injected into a retrograde orbit and attained the sungrazing state at a high inclination to the ecliptic. Hence the debris of its "children" does not pose a threat to the Earth. The Taurid progenitor on the other hand ended up in a short-period low-inclination prograde orbit. This is why the Earth can encounter its debris with potentially calamitous results.

What would happen should the Earth pass through the orbit of a disintegrating giant comet just before or after the comet passes that same point? Since larger fragments tend to cluster close to the nucleus of the comet, chances would increase that the Earth would be bombarded by these larger fragments. The severity of this comet fragment shower would far exceed any ordinary meteor shower. Not only would "shooting stars" and bright fireballs caused by small debris appear, but so too would large airbursts and possibly ground impacts. These would result in significant destruction should they occur over an inhabited area. If a large enough fragment struck in the ocean -- say, 200 meters or so in diameter -- it would raise tsunamis even at a great distance that would sweep away coastal habitations.

Duncan Steel, a colleague of Clube and Napier, refers to this process as coherent catastrophism. Widespread destruction derives from the coherent arrival of many impactors within a few days, as opposed to the sporadic arrival of objects spread randomly in space. The shower repeats for a period of years until the cometary orbit precesses so that the Earth no longer encounters the dense part of the debris field. (Of course, sporadic debris unrelated to the disintegrating comet may impact at any time as well.)


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Meteor

Comets, Not Asteroids, to Blame for Moon's Scarred Face

Hazel Muir
New Scientist
Tue, 28 Jul 2009 00:29 UTC
Moon
© NASAA new study suggests comets gouged out the vast majority of craters on the moon.
Icy comets - not rocky asteroids - launched a dramatic assault on the Earth and moon around 3.85 billion years ago, a new study of ancient rocks in Greenland suggests. The work suggests much of Earth's water could have been brought to the planet by comets.

"We can see craters on the moon's surface with the naked eye, but nobody actually knew what caused them - was it rocks, was it iron, was it ice?" says Uffe Gråe Jørgensen, an astronomer at the Niels Bohr Institute in Copenhagen, Denmark. "It's exciting to find signs that it was actually ice."

Evidence suggests that the Earth and moon had both formed around 4.5 billion years ago. But almost all the craters on the moon date to a later period, the "Late Heavy Bombardment" 3.8 to 3.9 billion years ago, when around 100 million billion tonnes of rock or ice crashed onto the lunar surface. The Earth would have been pummelled by debris at the same time, although plate tectonics on our restless planet have since erased the scars.
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Meteor

Jupiter increases risk of comet strike on Earth

David Shiga
New Scientist
Mon, 27 Aug 2007 06:47 UTC
Image
© Julian BaumEarth experienced an especially heavy bombardment of asteroids and comets early in the solar system's history.
Contrary to prevailing wisdom, Jupiter does not protect Earth from comet strikes. In fact, Earth would suffer fewer impacts without the influence of Jupiter's gravity, a new study says. It could have implications for determining which solar systems are most hospitable to life.

A 1994 study showed that replacing Jupiter with a much smaller planet like Uranus or Neptune would lead to 1000 times as many long-period comets hitting Earth. This led to speculation that complex life would have a hard time developing in solar systems without a Jupiter-like planet because of more intense bombardment by comets.

But a new study by Jonathan Horner and Barrie Jones of Open University in Milton Keynes, UK, shows that if there were no planet at all in Jupiter's orbit, Earth would actually be safer from impacts.

The contradictory results arise because Jupiter affects comets in two different, competing ways. Its gravity helps pull comets into the inner solar system, where they have a chance of hitting Earth, but can also clear away Earth-threatening comets by ejecting them from the solar system altogether, via a gravitational slingshot effect.
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Meteor

California's Channel Islands Hold Evidence of Clovis-Age Comets


PhysOrg
Mon, 20 Jul 2009 22:41 UTC
California
© NOAA and UC Santa BarbaraThis map shows California's Channel Islands with the islands of the previously combined islands of Santarosae encircled at the top.
A 17-member team has found what may be the smoking gun of a much-debated proposal that a cosmic impact about 12,900 years ago ripped through North America and drove multiple species into extinction.

In a paper appearing online ahead of regular publication in the Proceedings of the National Academy of Sciences, University of Oregon archaeologist Douglas J. Kennett and colleagues from nine institutions and three private research companies report the presence of shock-synthesized hexagonal diamonds in 12,900-year-old sediments on the Northern Channel Islands off the southern California coast.

These tiny diamonds and diamond clusters were buried deeply below four meters of sediment. They date to the end of Clovis -- a Paleoindian culture long thought to be North America's first human inhabitants. The nano-sized diamonds were pulled from Arlington Canyon on the island of Santa Rosa that had once been joined with three other Northern Channel Islands in a landmass known as Santarosae.
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Telescope

Subaru Telescope observes Comet-shaped Knots inside the Helix Nebula


ScienceDaily.com
Thu, 16 Jul 2009 06:05 UTC
near-infrared image of the Helix Nebula
© Subaru Telescope, NAOJNew near-infrared image of the Helix Nebula, showing comet-shaped knots within. These features look like a fireworks display in space.
The Helix Nebula, NGC 7293, is not only one of the most interesting and beautiful planetary nebulae; it is also one of the closest nebulae to Earth, at a distance of only 710 light years away. A new image, taken with an infrared camera on the Subaru Telescope in Hawaii, shows tens of thousands of previously unseen comet-shaped knots inside the nebula. The sheer number of knots -- more than have ever been seen before -- looks like a massive fireworks display in space.
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Telescope

Cosmic surprise: Many asteroids are comets


Agence France-Presse
Thu, 16 Jul 2009 05:45 UTC
meteor streaking across the sky
© AFP/NASA-HO/FileThis November 2000 NASA file image shows a meteor streaking across the sky during the Leonid meteor shower. Many of the primitive bodies wandering the asteroid belt between Mars and Jupiter are former comets, tossed out of orbit by a brutal ballet between the giant outer planets, say a team of astrophysicists.
Many of the primitive bodies wandering the asteroid belt between Mars and Jupiter are former comets, tossed out of orbit by a brutal ballet between the giant outer planets, say a team of astrophysicists.

A commonly accepted theory is that the asteroid belt is the rubble left over from a "proto-planetary disk," the dense ring of gas that surrounds a new-born star.

But the orbiting rocks have long been a source of deep curiosity. They are remarkably varied, ranging from mixtures of ice and rock to igneous rocks, which implies they have jumbled origins.

The answer to the mystery, according to a study published by the British journal Nature on Wednesday, is that a "significant fraction" of the asteroid population in fact comprises ex-comets.

Famously described as "dirty snowballs" of ice and dust, comets are lonely, long-distance wanderers of the Solar System whose elliptical swing around the Sun can take decades.

Researchers in France and the United States ran a mathematical model of the development of the early Solar System, when the planets were accreting from clustering masses of dust and gas.
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Telescope

Meteor shower, comet highlights in July

Bernie Reim
Morning Sentinel
Sat, 27 Jun 2009 13:32 UTC
Summer is now upon us and this will be a good month to enjoy the sky in spite of the short nights. The bright planets are evenly split this month, with the gas giants Saturn and Jupiter visible in the evening sky and our neighboring terrestrial planets, Venus and Mars, visible in the morning sky.

There will be two more very exciting celestial events taking place this month, but only one of them will be visible for us in New England. The annual Delta Aquarid Meteor Shower will peak during the morning hours of July 28. This shower actually begins around the middle of July and blends right into the famous Perseid Meteor Shower, which starts at the end of July and peaks on August 12.

Caused by Comet Machholz, you can expect around 15 to 20 Delta Aquarids per hour that morning. The moon will be first quarter and will set around midnight. Meteor showers are usually better after midnight, anyway, since that is when the earth is spinning directly into the meteors, like snowflakes on the front windshield of your car during a snowstorm. The whole earth can be seen as a little spaceship continually orbiting the sun at 18.6 miles per second, or 67,000 miles per hour.
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Meteor

Comets Seeded Earth's Early Atmosphere


Technology Review
Wed, 01 Jul 2009 07:21 UTC
The ratio of nitrogen isotopes in several comets almost exactly matches the ratio on Earth, implying that our early atmosphere probably came from a cometary bombardment.

Astrobiologists have long puzzled over the origin of Earth's oceans. But they've dwelt a little less long over a related question: where does the nitrogen in our atmosphere come from? Now a new analysis by Damien Hutsemekers and pals at the Universite de Liege, in Belgium, suggests an answer to both questions.

One of the most attractive theories of the origin of our water is that Earth was once bombarded by icy comets that left a watery residue. The trouble is that the ratio of deuterium to hydrogen in water on Earth is much lower than it is in the few comets we've been able to measure it in (i.e., Halley, Hyakutake, Hale-Bopp, and C/2002 T7 LINEAR). So if these types of comets, which we know came from the Oort Cloud, did supply Earth's water, it must have mixed with water already on Earth that had a very low deuterium content.
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Hourglass

Comets, Meteors & Myth: New Evidence for Toppled Civilizations and Biblical Tales

Robert Roy Britt
Space
Tue, 13 Nov 2001 18:25 UTC
"...and the seven judges of hell ... raised their torches, lighting the land with their livid flame. A stupor of despair went up to heaven when the god of the storm turned daylight into darkness, when he smashed the land like a cup."

-- An account of the Deluge from the Epic of Gilgamesh, circa 2200 B.C.
If you are fortunate enough to see the storm of shooting stars predicted for the Nov. 18 peak of the Leonid meteor shower, you'll be watching a similar but considerably less powerful version of events which some scientists say brought down the world's first civilizations.

The root of both: debris from a disintegrating comet.

Biblical stories, apocalyptic visions, ancient art and scientific data all seem to intersect at around 2350 B.C., when one or more catastrophic events wiped out several advanced societies in Europe, Asia and Africa.

Increasingly, some scientists suspect comets and their associated meteor storms were the cause. History and culture provide clues: Icons and myths surrounding the alleged cataclysms persist in cults and religions today and even fuel terrorism.
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