Comets
A rare meteor shower predicted to hit Earth on 1 September should give astronomers only their second chance to study an ancient comet's crust. It could also help them develop a warning system against an otherwise insidious threat - a comet aimed at Earth from the dark fringes of the solar system.
For the first time, there is solid data to refute a popular theory that life came to Earth aboard a comet, Rutgers researchers say.
Deteriorated DNA from microbes, frozen for millions of years in the Antarctic ice, shows that organisms could not have survived the bombardment of cosmic radiation during deep space travel from outside the solar system, said Paul Falkowski, a Rutgers biologist and oceanographer.
Deteriorated DNA from microbes, frozen for millions of years in the Antarctic ice, shows that organisms could not have survived the bombardment of cosmic radiation during deep space travel from outside the solar system, said Paul Falkowski, a Rutgers biologist and oceanographer.
Since 1986, four different comets -- Halley, Borrelly, Wild 2 and Tempel 1 -- have been examined in impressive detail by a wide variety of American, European and Russian spacecraft, including one that has actually returned a small dust sample to Earth and another that crashed a large piggyback spacecraft into a comet's nucleus to try and reveal some of its subsurface structure. And in 2014, the still more ambitious European "Rosetta" mission will rendezvous with the nucleus of a fifth comet (Churyumov-Gerasimenko), examine it from just 25 kilometers away (or less) for over a year and a half, and even drop a small survivable lander onto the nucleus' surface.
All this attention is entirely justified, given the fact that comets are the only preserved pieces of the "planetesimals" that were made by accretion out of the initial dust, ices and gas of the primordial pre-Solar System nebula itself, and which in turn merged together to form the planets.
All this attention is entirely justified, given the fact that comets are the only preserved pieces of the "planetesimals" that were made by accretion out of the initial dust, ices and gas of the primordial pre-Solar System nebula itself, and which in turn merged together to form the planets.
It was so faint amid the star-freckled blackness that professional star-gazer Lin Chi-sheng missed it as he photographed the heavens from Lulin Observatory, Nantou County, earlier this month.
Luckily, Lin's camera, recording time-lapse images of space through the observatory's telescope, didn't miss it -- a mighty chunk of ice and rock "a few kilometers" in diameter and hurtling toward Earth: "Asteroid C/2007-N3."
Luckily, Lin's camera, recording time-lapse images of space through the observatory's telescope, didn't miss it -- a mighty chunk of ice and rock "a few kilometers" in diameter and hurtling toward Earth: "Asteroid C/2007-N3."
1862: American astronomer Lewis Swift discovers the presence of a large comet that will soon bear his name. Three days later, another American astronomer, Horace Tuttle, makes the same sighting. So this heavenly body comes down to us as the Comet Swift-Tuttle.
Based on their observations, and those of other astronomers who began tracking the comet's highly elongated orbit, it was calculated that Swift-Tuttle would make its next appearance during the 1980s. They were close. Japanese astronomer Tsuruhiko Kiuchi rediscovered the comet in 1992.
Based on their observations, and those of other astronomers who began tracking the comet's highly elongated orbit, it was calculated that Swift-Tuttle would make its next appearance during the 1980s. They were close. Japanese astronomer Tsuruhiko Kiuchi rediscovered the comet in 1992.
Comet LINEAR (C/2006 VZ13), now crossing through Draco and Boötes, has far exceeded expectations. It was originally predicted to peak in brightness around magnitude 10, a pleasant spectacle for people who enjoy viewing faint comets through telescopes. But the latest magnitude estimates range from 7.5 to 8.0, making it an easy sight through 10×50 binoculars in a dark, transparent sky.
A dying comet has prompted astronomers to take issue with a mainstream theory about the impact of "space weather" on these enigmatic wanderers of the Solar System.
A comet theory put forth by a group of 25 geo-scientists suggests that a massive comet exploded over Canada, possibly wiping out both beast and man around 12,900 years ago, and pushing the earth into another ice age.
University of South Carolina archaeologist Dr. Albert Goodyear said the theory may not be such "out-of-this-world" thinking based on his study of ancient stone-tool artifacts he and his team have excavated from the Topper dig site in Allendale, as well as ones found in Georgia, North Carolina and Virginia.
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| Site where most pre-Clovis work is being done. |
University of South Carolina archaeologist Dr. Albert Goodyear said the theory may not be such "out-of-this-world" thinking based on his study of ancient stone-tool artifacts he and his team have excavated from the Topper dig site in Allendale, as well as ones found in Georgia, North Carolina and Virginia.
Investigations of a buried layer at sites from California to Belgium reveal materials that include metallic microspherules, carbon spherules, nanodiamonds, fullerenes, charcoal, and soot. The layer's composition may indicate that a massive body, possibly a comet, exploded in the atmosphere over the Laurentide Ice Sheet 12,900 years ago. The timing coincides with a great die-off of mammoths and other North American megafauna and the onset of a period of cooling in Northern Europe and elswhere known as the Younger Dryas Event. The American Clovis culture appears to have been dramatically affected, even terminated, at this same time. Speakers discuss numerous lines of evidence contributing to the impact hypothesis. The nature and frequency of this new kind of impact event could have major implications for our understanding of extinctions and climate change.
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Part 1
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| The eagle screams,
And with pale beak tears corpses. . . . Mountains dash together, Heroes go the way to Hel, And heaven is rent in twain. . . . All men abandon their homesteads When the warder of Midgard In wrath slays the serpent. The sun grows dark, The earth sinks into the sea, The bright stars From heaven vanish; Fire rages, Heat blazes, And high flames play 'Gainst heaven itself" R.B. Anderson, "Norse Mythology," 1875 |
NASA seems to spend a lot of time looking for and thinking of ways to divert errant asteroids that might possibly hit earth. However, they keep reassuring the public that the probability of actually being hit by an asteroid is extremely small. So why all the attention?
