Light Eyes Opening

Ancient sea mud records supernova blast

lighteyes7701@yahoo.com — Sun, 25 Nov 2007 18:38:09 GMT

It is the oldest telescope in the world - and it lies at the bottom of the ocean. Ancient sea floor sediments have revealed that a supernova exploded during the Pliocene era and may have caused a minor extinction event on Earth.

Levels of radioactive iron-60 suggest the supernova was between 60 and 300 light years away, says Brian Fields of the University of Illinois at Urbana-Champaign. "It didn't hit us or we wouldn't be here." Radiation from the blast could have weakened Earth's atmosphere, he says, exposing organisms to the sun's ultraviolet radiation. This coincides with an extinction peak, but Fields says there is no direct evidence of a link. The work was reported at a meeting of the Geological Society of America in Denver, Colorado, this week.

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Real Flying Saucer Eyed by Defense Dept.

lighteyes7701@yahoo.com — Sun, 25 Nov 2007 18:38:09 GMT

Oct. 12, 2007 — Think "flying saucer" and UFOs or 1950s B movies come to mind (see "Earth vs. the Flying Saucers" or "The Day the Earth Stood Still"). But now researchers have built an unmanned aerial vehicle that looks and acts like the imagined thing.

The disc-shaped device can take off vertically from any surface, land practically anywhere, and if it accidentally contacts a building or cliff, it won't explode into a fireball, like those rascally helicopters.

These features could make the aircraft uniquely suited to flying in urban war zones, aiding with search and rescue in disaster areas, inspecting crops and pipelines, and taking aerial photographs.

"You can take it down to a foot in diameter and we are told it is fully scaleable up to a large-sized craft," said David Steel, director of GFS Projects in Peterborough, England.

"GFS" stands for Geoff's Flying Saucer, after Geoff Hatton, the engineer and inventor who originally conceived of the idea.

Although flying saucers are a favorite among extra terrestrials, Earthbound engineers have had a more difficult time getting the vehicles off the ground.

Some designs will hover, but they can't move up or down to navigate over a hill or building, for example. Other designs do not lend themselves to maneuverability or steering.

Hatton's design accomplishes both.

The vehicle looks something like an upside-down bowl with a propeller on top. When the propeller spins, air gets pushed down over the outer surface of the bowl. That action creates lower air pressure on top of the craft and higher air pressure below, giving the vehicle lift.

The design makes it easy to incorporate a large payload at the center of gravity, said Holger Babinsky, associate professor of aerodynamics at the University of Cambridge in Cambridge, England.

"You can do it in a helicopter, but you have the blades that stick out a long way and if you want to maneuver in a tight terrain, that's dangerous," he said.

Air flaps around the edge of the saucer prevent it from spinning like a top and allow the controller to steer it.

According to Steel, the saucer is more stable and easier to fly than a helicopter and because it has fewer moving parts than a helicopter, it's easier to build and maintain.

But fuel efficiency could be an issue, said Holger. "That is the number one killer," he said.

The reason is that the fan is relatively small and in a confined space and needs to produce high volumes of air.

"The batteries don't last as long because the amount of power you convert into thrust is not so great because the efficiency is low," he said.

The U.S. Department of Defense has its eye on the saucer and earlier this year awarded GFS with a contract to demonstrate that the craft could hover and maneuver. In fact, the flying saucer did both, flying in winds of more than 10 mph.

This past September, the U.K. Ministry of Defense selected GFS as one of six teams to compete in the Grand Challenge Program, a competition next July for autonomous vehicles. The saucer will be equipped with cameras and infrared technology to find hidden threats along a designated course.

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Dazzling comet outburst continues to mystify

lighteyes7701@yahoo.com — Sun, 25 Nov 2007 18:38:09 GMT

The comet that suddenly became about a million times brighter nearly two weeks ago continues to "shine" with abnormal luminosity, leaving observers puzzled over what caused the outburst and whether the comet will perform an encore in the coming months.

Comet 17P/Holmes is normally an invisible runt of a comet, about 3.3 kilometres across and about 25,000 times too faint to be seen with the naked eye.

But following its sudden brightening on 23 October, the comet's coma, a surrounding shell of gas and dust, has been expanding at a rate of about 0.5 kilometres per second, making the comet appear as a fuzzy "star" that can be seen with the naked eye in the constellation Perseus (see image at right and watch a video of dust streaming off the comet's icy body, or nucleus).

The comet was actually discovered during a similar, but less spectacular, brightening event in November 1892. It faded after a few weeks, only to dramatically brighten again in January 1893.

The comet orbits the Sun every seven years on a path that takes it from the distance of Jupiter's orbit to about twice that of Earth's. Interestingly, in both the 1892 event and the recent one, the comet initially brightened about five months after reaching perihelion – its closest approach to the Sun.

"It's curious that the outburst came in the same period of orbit," says Brian Marsden, former director of the Minor Planet Center at the Harvard-Smithsonian Center for Astrophysics in Massachusetts, US. "It will be interesting to see if it behaves in the same general way [this time as before]."

The common timing of the two mega-outbursts following perihelion suggests that the intensity of the Sun's radiation is a key factor in the brightening. But that alone is not enough, as the comet reaches perihelion every seven years and hasn't produced such an outburst in 115 years. There are also plenty of comets that make closer approaches to the Sun than Comet 17P/Holmes without brightening nearly as much.

"The fact that it's brightened by a factor of a million is just incredible," says David Jewitt at the University of Hawaii in Honolulu, US. "What's special about this one? We don't know."

Michael Mumma, director of the Goddard Center for Astrobiology in Greenbelt, Maryland, US, and colleagues are observing the comet with the 10-metre Keck II telescope's infrared vision.

They find that the comet is still actively releasing gas. Most of it is composed of water vapour, but ethane, acetylene and hydrogen cyanide have also been seen in trace amounts. "We hope to learn a great deal about the material that was once in the interior of the comet nucleus," Mumma told New Scientist.

The standard explanation of comet outbursts says that a sudden event exposes fresh ices from within the nucleus to solar radiation. This causes them to vaporise, dragging dust along with them. Sunlight reflecting off that dust then magnifies the comet's brightness.

Built-up pressure

In an electronic telegram distributed by the International Astronomical Union, Zdenek Sekanina of NASA's Jet Propulsion Laboratory in Pasadena, California, US, suggests that a flattened layer that was once part of the nucleus could have broken off and completely disintegrated to produce the outburst. The idea, which has not been peer-reviewed, is partially based on an estimate of the mass of particles in the coma.

Another hypothesis suggests that pockets of volatile gas somehow get trapped in the nucleus. Eventually, built-up pressure causes the surface to rupture, producing large outbursts.

Tom Van Flandern of Meta Research in Sequim, Washington, US, suggests a more outlandish possibility. He argues that comets are orbited by satellites and that occasionally a satellite crashes into its host comet, producing an outburst.

A similar idea was put forward more than 20 years ago by astronomer Fred Whipple, who suggested that the 1892 outburst of Comet Holmes was caused by a satellite grazing the surface of the nucleus and that the second brightening in 1893 was the result of the satellite crashing into the comet's surface.

Race against the clock

Jewitt says the recent recurrence of the comet's brightening strongly argues against the satellite model. "The fact that this has happened after 115 years – with nothing in the intervening years – makes the model more ad hoc," he told New Scientist.

Marsden agrees, and believes that whatever caused the comet to suddenly brighten has to be intrinsic to the comet. "We need to continue observations and see how it goes," he adds.

Mumma says the comet could fade at any time. In the case of the event 115 years ago, the comet rapidly faded after the second outburst. "That's part of the challenge – to try to learn as much as we can before the darn thing vanishes," he says.

Fortunately, the fading itself can also shed light on what caused the outburst. The comet is currently in the main asteroid belt, at a distance from the Sun of about two and a half times that of Earth (or 2.5 astronomical units). Water ice can no longer sublimate beyond about 3 astronomical units, so if the comet is still active past that point, something more volatile than water ice must be driving its activity.

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