Thursday, December 28, 2006

New Way To Form Black Hole Uncovered

Nature has again thrown astronomers for a loop. Just when they thought they understood how gamma-ray bursts formed, they have uncovered what appears to be evidence for a new kind of cosmic explosion. These seem to arise when a newly born black hole swallows most of the matter from its doomed parent star.
Gamma-ray bursts (GRBs), the most powerful explosions in the Universe, signal the formation of a new black hole and come in two flavours, long and short ones. In recent years, international efforts have shown that long gamma-ray bursts are linked with the explosive deaths of massive stars (hypernovae).
Last year, observations by different teams - including the GRACE and MISTICI collaborations that use ESO's telescopes - of the afterglows of two short gamma-ray bursts provided the first conclusive evidence that this class of objects most likely originates from the collision of compact objects: neutron stars or black holes.
The newly found gamma-ray bursts, however, do not fit the picture. They instead seem to share the properties of both the long and short classes.
"Some unknown process must be at play, about which we have presently no clue," said Massimo Della Valle of the Osservatorio Astrofisico di Arcetri in Firenze, Italy, lead author of one of the reports published in this week's issue of the journal Nature. "Either it is a new kind of merger which is able to produce long bursts, or a new kind of stellar explosion in which matter can't escape the black hole."
One of the mysterious events went bang on 14 June 2006, hence its name, GRB 060614. The gamma-ray burst lasted 102 seconds and belongs clearly to the category of long GRBs. As it happened in a relatively close-by galaxy, located only 1.6 billion light-years away in the constellation Indus, astronomers worldwide eagerly pointed their telescopes toward it to capture the supernova, watching and waiting as if for a jack-in-the-box to spring open.
The MISTICI collaboration used ESO's Very Large Telescope to follow the burst for 50 days. "Despite our deep monitoring, no rebrightening due to a supernova was seen," said Gianpiero Tagliaferri from the Observatory of Brera, Italy and member of the team. "If a supernova is present, if should at least be 100 times fainter than any other supernova usually associated with a long burst."
The burst exploded in a dwarf galaxy that shows moderate signs of star formation. Thus young, massive stars are present and, at the end of its life one of them could have uttered this long, agonising cry before vanishing into a black hole. "Why did it do so in a dark way, with no sign of a supernova?" asked Guido Chincarini, from the University of Milano-Bicocca, Italy, also member of the team. "A possibility is that a massive black hole formed that did not allow any matter to escape. All the material that is usually ejected in a supernova explosion would then fall back and be swallowed."
The same conclusion was previously reached by another team, who monitored both GRB 060614 and another burst, GRB 060505 (5 May 2006) for 5 and 12 weeks, respectively. For this, they used the ESO VLT and the 1.54-m Danish telescope at La Silla.
GRB 060505 was a faint burst with a duration of 4 seconds, and as such also belongs to the category of long bursts.
For GRB 060505, the astronomers could only see the burst in visible light for one night and then it faded away, while for GRB 060614, they could only follow it for four nights after the burst. Thus, if supernovae were associated with these long-bursts, as one would have expected, they must have been about a hundred times fainter than a normal supernova.
"Although both bursts are long, the remarkable conclusion from our monitoring is that there were no supernovae associated with them," said Johan Fynbo from the DARK Cosmology Centre at the Niels Bohr Institute of the Copenhagen University in Denmark, who led the study. "It is a bit like not hearing the thunder from a nearby storm when one could see a very long lasting flash."
For the May burst, the team has obtained deep images in very good observing conditions allowing the exact localisation of the burst in its host galaxy. The host galaxy turns out to be a small spiral galaxy, and the burst occurred in a compact star-forming region in one of the spiral arms of the galaxy. This is strong evidence that the star that made the GRB was massive.
"For the 5 May event, we have evidence that it was due to a massive star that died without making a supernova," said Fynbo. "We now have to find out what is the fraction of massive stars that die without us noticing, that is, without producing either a gamma-ray burst or a supernova."
"Whatever the solution to the problem is, it is clear that these new results challenge the commonly accepted scenario, in which long bursts are associated with a bright supernova," said Daniele Malesani, from the International School for Advanced Studies in Trieste, and now also at the DARK Cosmology Centre. "Our hope is to be able to find more of these unconventional bursts. The chase is on!"

Tuesday, December 26, 2006

Pinpoint Sound Beams Hunt Buried Land Mines

Researchers at MIT's Lincoln Laboratory are developing a highly pinpointed sound beam that can detect buried land mines from a safe distance. The new beam will use sound to seek out land mines like a bat uses sonar to hunt its prey.

The researchers built a prototype detector and tested it at the Cold Regions Research and Engineering Laboratory Army Corps of Engineers land-mine facility in New Hampshire. They were able to detect both metal and plastic mines but said that the system will have to get a major boost in acoustic power before minefield searchers can use it safely.

Robert W. Haupt, a technical staff member at Lincoln Lab, explores innovative ways to find and reduce the large number of land mines abandoned in war-torn countries. An estimated 26,000 people are killed or maimed every year by 60 to 70 million undetected land mines in 70 countries. Those casualties include military troops but most are civilians--half of them children under age 16--who step on uncleared minefields after a war.

Many existing prototype mine detection systems can detect only metal, have limited range or are impractical in the field. "Reliable methods that quickly and accurately locate land mines made of metal and plastic, unexploded ordnance and other mine-like targets are desperately needed," Haupt said.

Haupt and fellow Lincoln Lab staff member Ken Rolt developed a high-powered sound transmitter that looks like a stop sign studded with 35mm film canisters or prescription pill containers. This is called a parametric acoustic array, and Haupt and Rolt have built one of the most powerful ones around.

The array is made up of ceramic transducers--devices that emit a powerful narrow acoustic beam at ultrasonic frequencies. One meter away, the ultrasonic pressure level measures 155 decibels--more acoustic power than a jet engine. Immediately outside the beam, the acoustic intensity dies away to almost nothing.

By a process know as self-demodulation, the air in front of the acoustic beam converts the ultrasound to much lower frequency audible tones that sound like extremely loud tuning forks. Unlike ultrasound, the low-frequency sound can penetrate the ground, causing detectable vibrations in the mine's plungers and membranes.

"The use of ultrasound allows us to make a very narrow and highly directional beam, like a sound flashlight," Haupt said. It would take a huge number of conventional loudspeakers to do the same trick, and they would weigh too much, take up too much space and use too much power to be practical, he said. Plus, they would deafen anyone within earshot. "Using a narrow sound beam, we can put sound just where we want it, and we can minimize sound levels outside the beam to avoid harming the operators or people nearby," he said.

Once the sound beam "hits" buried ordnance, the vibrations from the mine, resonating from the sound waves, push up on the ground and can be measured remotely with a laser system called a Doppler vibrometer. The sound signature of a mine looks like a mountain range of spikes compared with the flat-line response of the rocks and dirt around it.

"It turns out that mines will vibrate quite differently from anything else," Haupt said. "You can determine what types of mines there are--and which countries made them--by their unique signatures."

Haupt also is working with Oral Buyukozturk, professor of civil engineering at MIT, to tailor the system to detect damage in cement bridge piers from as far away as the shore.

Monday, December 25, 2006

Research Yields Optical Buffer Memory

U.S. scientists, using state-of-the-art semiconductor manufacturing technology, said they created an optical buffer memory on a miniature silicon chip.
The device -- a temporary storage area for light signals -- works by slowing down the light signals, said Yurii Vlasov of the IBM Thomas J Watson Research Center, Yorktown Heights, N.Y.
The optical buffer was made by connecting a string of up to 100 tiny silicon ring waveguides -- tiny oval "racetracks" with a perimeter of just 55 micrometers, Vlasov said. By experimenting with various designs, the team created the buffer that could store up to 10 bits of information at data rates of up to 20 gigabits per second, he said.
While silicon ring waveguides were reported before, Vlasov said his team is the first to show it is possible to use a large number of rings to create the device and test its compatibility with real data at gigabit speeds.
Noting further testing is needed, Vlasov said such a buffer could help future optical networks synchronize different data streams without converting the signals into the electronic domain.
His team's findings were published in Nature Photonics.

Saturday, December 23, 2006

'Invisible' Transistors Developed

Futuristic "invisible" electronics may appear sooner rather than later, thanks to U.S. researchers developing transparent, high-performance transistors.

The transistors can be assembled inexpensively on glass and plastic, creating high quality displays on car windshields, goggles or billboards, the Northwestern University researchers said.

Developing new types of displays powered by electronics without visible wires has been going on for years. But no one could develop materials for transistors that could both be "invisible" and maintain a high level of performance, the university said in a news release.

"Our development provides new strategies for creating transparent electronics," said Tobin J. Marks, professor of materials science and engineering at Northwestern, who led the research. "You can imagine a variety of applications for new electronics that haven't been possible previously -- imagine displays of text or images that would seem to be floating in space."

To create the transistors, Marks' team combined films of the inorganic semiconductor indium oxide with a layer of self-assembling organic molecules that provides insulation. The films can be fabricated at room temperature, allowing the transistors to be produced at a low cost.

Thursday, December 21, 2006

Magnetic Whirlpools Feed Earth's Magnetosphere

Giant whirlpools of electrically charged gas, some 40,000 kilometres across, have been witnessed above the Earth by a team of European and American scientists. Using data from ESA's Cluster quartet of spacecraft, the researchers have shown that these whirlpools inject electrified gas into the magnetic environment of the Earth.

The magnetic field generated inside the Earth protects the planet from the electrically charged particles given out by the Sun. However, it is only a partially effective shield.

In the same way that a car can only travel along roads, electrically charged gas, known as plasma, can only travel along magnetic field lines, never across them. For a car to suddenly change direction, it has to use a road junction.

For a particle of plasma to suddenly jump onto a different field line, there has to be a reconnection event. In a reconnection, magnetic fields lines spontaneously break and then join up with other nearby lines. In doing so, the plasma is suddenly redirected along new routes.

Scientists know this happens in Earth's magnetosphere because of changes to the plasma sheet. This is one of the inner regions of the Earth's magnetic field. Plasma in the sheet is usually hot and tenuous, whereas the solar wind is cooler and denser. At certain times, the sheet fills with cooler and denser plasma over the course of a few hours.

For this to happen, the solar wind plasma must somehow be able to cross the Earth’s magnetic boundary, known as the magnetopause. Yet, until now scientists had no observational evidence that reconnection inside whirlpools contribute to this process. "Wondering how the solar wind could get into the plasma sheet is how I became interested in this problem," says Katariina Nykyri, lead author of the results, from the Imperial College, London, UK.

Together with colleagues, Nykyri began investigating a strange event recorded by Cluster on 3 July 2001. At this time, Cluster was passing the dawn side of the Earth. In this region of space, the solar wind is sliding past the Earth's magnetopause, in roughly the same way as wind blows across the surface of an ocean.

A previous Cluster observation had shown that whirlpools of plasma can be whipped up by this configuration. Such whirlpools are known as Kelvin-Helmholtz instabilities and scientists suspected them of being the location of magnetic reconnection but no one had found any conclusive evidence that this was the case.

Cluster can recognise magnetic reconnection because of what researchers call 'rotational discontinuities'. These show up as sudden changes in the direction of the plasma flow and magnetic field. After a painstaking analysis, Nykyri found just such rotational discontinuities in the data for 3 July 2001. To be certain of her result, she reanalysed the data four times.

Then she developed a computer model to simulate the event. The computer showed that the Cluster data was only understandable if the whirlpools were causing magnetic reconnection to take place. In these reconnections, plasma was being fed down through the magnetic boundary of Earth and into the magnetosphere.

The work does not stop there. Nykyri and colleagues are now developing more sophisticated computer simulations to understand the whirlpools’ three-dimensional behaviour. "This is a very big challenge," she says, because of the additional numerical processes involved.

She also plans to search the Cluster data archive for more examples of these events.

Tuesday, December 19, 2006

Reading Shakespeare Has Dramatic Effect On Human Brain

Research at the University of Liverpool has found that Shakespearean language excites positive brain activity, adding further drama to the bard's plays and poetry.

Shakespeare uses a linguistic technique known as functional shift that involves, for example using a noun to serve as a verb. Researchers found that this technique allows the brain to understand what a word means before it understands the function of the word within a sentence. This process causes a sudden peak in brain activity and forces the brain to work backwards in order to fully understand what Shakespeare is trying to say.

Professor Philip Davis, from the University’s School of English, said: “The brain reacts to reading a phrase such as ‘he godded me’ from the tragedy of Coriolanus, in a similar way to putting a jigsaw puzzle together. If it is easy to see which pieces slot together you become bored of the game, but if the pieces don’t appear to fit, when we know they should, the brain becomes excited. By throwing odd words into seemingly normal sentences, Shakespeare surprises the brain and catches it off guard in a manner that produces a sudden burst of activity - a sense of drama created out of the simplest of things.”

Experts believe that this heightened brain activity may be one of the reasons why Shakespeare’s plays have such a dramatic impact on their readers.

Professor Neil Roberts, from the University’s Magnetic Resonance and Image Analysis Research Centre, (MARIARC), explains: “The effect on the brain is a bit like a magic trick; we know what the trick means but not how it happened. Instead of being confused by this in a negative sense, the brain is positively excited. The brain signature is relatively uneventful when we understand the meaning of a word but when the word changes the grammar of the whole sentence, brain readings suddenly peak. The brain is then forced to retrace its thinking process in order to understand what it is supposed to make of this unusual word.”

Professor Roberts and Professor Davis together with Dr Guillaune Thierry, from the University of Wales, Bangor, monitored 20 participants using an electroencephalogram (EEG) as they read selected lines from Shakespeare’s plays.

In this initial test electrodes were placed on the subject’s scalp to measure brain responses.

Professor Roberts said: “EEG gives graph-like measurements and when the brain reads a sentence that does not make semantic sense it registers what we call a N400 effect – a negative wave modulation. When the brain reads a grammatically incorrect sentence it registers a P600 effect – an effect which continues to last after the word that triggered it was first read.”

Researchers also found that when participants read the word producing the functional shift there was no N400 effect indicating that the meaning was accepted but a P600 effect was observed which indicates a positive re-evaluation of the word. The team is now using magnetoencephalography (MEG) and functional magnetic resonance imaging (FMI) to test which areas of the brain are most affected and the kind of impact it could have in maintaining healthy brain activity.

Professor Davis added: “This interdisciplinary work is good for brain science because it offers permanent scripts of the human mind working moment-to-moment. It is good for literature as it illustrates primary human thinking. Through the two disciplines, we may discover new insights into the very motions of the mind.”

Sunday, December 17, 2006

Space Dust Reveals Solar System Clues

Microscopic space dust from the comet Wild 2 reveals clues that seem to run counter to the basic theories of the solar system's origin, U.S. scientists say.

Samples of dust, gathered from the Stardust mission, indicate the comet formed in the Kuiper Belt, outside Neptune's orbit, and only recently entered the inner areas of solar system, Lawrence Livermore National Laboratory scientists said in California. During its lifetime the comet gathered material that formed much closer to the sun.

"We're talking about a mineral that forms around 3,000 degrees Kelvin, which means it formed close to the hot infant star," said John Bradley, director of the lab's Institute for Geophysics and Planetary Physics and the head of the Livermore Stardust team. "If we found it in the comet, then how the heck did it get out there."

The mineral is osbornite, which has been found in Russia. Finding osbornite in the comet indicates that the solar system was more volatile during its infancy than originally thought, Bradley said.

The comet samples also had pre-solar materials that were transported beyond the orbit of Neptune by some process capable of moving particles, Bradley said.

Saturday, December 16, 2006

Anti-aging ingredient ready for market

A new anti-aging ingredient developed by university researchers in Australia may be available in skin products as soon as next year.

Known as GGC, the ingredient is a forerunner for the anti-oxidant glutathione and has a number of possible health benefits, the University of New South Wales researchers said. Glutathione is a defense for detoxifying harmful compounds implicated in cancer, diabetes, aging and other diseases and degenerative conditions in the body.

University researchers said after nine years they developed a new, cost-effective way to manufacture GGC, which has been licensed to Biospecialties Australia.

Researchers said they expected the ingredient would be used in foods, health and beauty products, dietary supplements and anti-aging creams.

Natural dietary sources of GGC are available, including milk whey protein and garlic in diluted concentrations, researchers said. The new GGC product could allow for more effective doses.

Thursday, December 14, 2006

Crop may mean groundwater changed Mars too

A crop of "blueberries" found on Mars' Victoria Crater by a NASA rover may indicate ground, not surface, water altered the area, U.S. space officials said.

NASA officials said they thought the "blueberries" were formed by iron-rich minerals when groundwater percolated through sediment. The spheres were scattered across the surface almost everywhere the Opportunity rover trekked from its landing site to the crater.

The crater's rim was "full of great big, juicy blueberries," the rover's chief scientist Steven Squyres said during the American Geophysical Union's meeting in San Francisco. "That was a surprise to us."

Because the "berries" form underground as groundwater rises through the soil, the finding suggests the water rose to a certain level then stopped without reaching the surface, Squyres said.

The finding was unexpected because Opportunity earlier found ripples in the nearby Endurance Crater -- indicating that water occasionally flowed on the surface.

Just how far deep the water level is won't be known until Opportunity descends into the crater in a few months.

"As we go down, we'll cross a bathtub ring," marking the highest level the water reached, Squyres said.

Tuesday, December 12, 2006

Mechanical Motion Used To 'Spin' Atoms In A Gas

For the first time, mechanical motion has been used to make atoms in a gas "spin," scientists at the National Institute of Standards and Technology (NIST) report. The technique eventually might be used in high-performance magnetic sensors, enable power-efficient chip-scale atomic devices such as clocks, or serve as components for manipulating bits of information in quantum computers.

The NIST team used a vibrating microscale cantilever, a tiny plank anchored at one end like a diving board, to drive magnetic oscillations in rubidium atoms. The scientists attached a tiny magnetic particle--about 10 by 50 by 100 micrometers in size--to the cantilever tip and applied electrical signals at the cantilever's "resonant" frequency to make the tip of the cantilever, and hence the magnetic particle, vibrate up and down. The vibrating particle in turn generated an oscillating magnetic field that impinged on atoms confined inside a 1-square-millimeter container nearby.

The electrons in the atoms, acting like tiny bar magnets with north and south poles, responded by rotating about a static magnetic field applied to the experimental set-up, causing the atoms to rotate like spinning tops that are wobbling slightly. The scientists detected the rotation by monitoring patterns in the amount of infrared laser light absorbed by the spinning atoms as their orientation fluctuated with the magnetic gyrations. Atoms absorb polarized light depending on their orientation with respect to the light beam.

Micro-cantilevers are a focus of intensive research in part because they can be operated with low power, such as from a battery, and yet are sensitive enough to detect very slight changes in magnetic fields with high spatial resolution. The NIST team noted that coupling between cantilever motion and atomic spins is easy to detect, and that the atoms maintain consistent rotation patterns for a sufficiently long time, on the order of milliseconds, to be useful in precision applications.

For instance, by comparing the oscillation frequency of the cantilever to the natural rotation behavior of the atoms (determined by measuring the extent of the wobble), the local magnetic field can be determined with high precision. Or, arrays of magnetic cantilevers might be constructed, with each cantilever coupled vibrationally to the others and coupled magnetically to a unique collection of atoms. Such a device could be used to store or manipulate binary data in a quantum computer. In theory, the coupling process also could work backwards, so that atomic spins could be detected by monitoring the vibrational motion of the cantilevers.

Sunday, December 10, 2006

A Whole Library On One Disc!

Imagine taking the entire collection of historical documents at the Smithsonian National Air and Space Museum and storing it on a single DVD.

University of Central Florida Chemistry Professor Kevin D. Belfield and his team have cracked a puzzle that stumped scientists for more than a dozen years. They have developed a new technology that will allow users to record and store massive amounts of data -- the museum's entire collection or as many as 500 movies, for example -- onto a single disc or, perhaps, a small cube.

Belfield's Two-Photon 3-D Optical Data Storage system makes this possible.

"For a while, the community has been able to record data in photochromic materials in several layers," Belfield said. "The problem was that no one could figure out how to read out the data without destroying it. But we cracked it."

Think of it this way. Television viewers can tape a show on a VHS tape. They can use the tape several times. But each time the same segment of the tape is used, the quality diminishes as the tape wears out. Eventually, the data is lost. The same is true of recordable DVDs.

Belfield's team figured out a way to use lasers to compact large amounts of information onto a DVD while maintaining excellent quality. The information is stored permanently without the possibility of damage.

The process involves shooting two different wavelengths of light onto the recording surface. The use of two lasers creates a very specific image that is sharper than what current techniques can render. Depending on the color (wavelength) of the light, information is written onto a disk. The information is highly compacted, so the disk isn't much thicker. It's like a typical DVD.

The challenge scientists faced for years was that light is also used to read the information. The light couldn't distinguish between reading and writing, so it would destroy the recorded information. Belfield's team developed a way to use light tuned to specific colors or wavelengths to allow information that a user wants to keep to stay intact.

Once the technology is fine-tuned, it could be used to store historical documents or create complicated databases that could give decision-makers quick access to critical information, Belfield said.

Blu-Ray Disc Association and industrial leaders in computer and other media recently commercially introduced Blu-Ray Disc technology that allows for storage of 25 gigabytes (GB) on a single layer of a disc and 50 GB on two layers. It has been referred to as the next generation of optical disc format, and it offers high-definition quality.

Belfield's technique allows for storing on multiple layers with the capacity of at least 1,000 GB and high-definition quality.

The UCF team has received a $270,000, three-year grant from the National Science Foundation to continue its work. The team will focus on making the technique even more efficient, partly by reducing the required laser power.

The team's work with lasers and lights has other practical applications. Belfield and his colleagues in the Department of Chemistry are exploring the use of light to detect and treat certain types of cancer.

Belfield's research team is creating chemical agents that, after being injected into patients, will travel within the bloodstream to find and bind with cancer cells. Using light, doctors would then be able to see if and where a patient has cancer cells. Another agent could be injected that would then destroy the cancer cells when activated by light, without damaging other healthy cells.

Friday, December 08, 2006

Better Bulb Discovered By US Team

A team of scientists at Vanderbilt University have been given an award from Popular Mechanics magazine for a discovery that could someday replace the common light bulb, the researchers say. Led by Vanderbilt associate professor Sandra Rosenthal, the team nearly a year ago discovered a new way to make solid-state lights that produce white lights. They say the finding could replace the common light bulb and cut the world's electricity consumption in half. " We were actually working on something else when this discovery was made, " Rosenthal said. "But I think good accidents happen in science a lot more often than scientists want to admit. "

Wednesday, December 06, 2006

NASA Telescope Sees Black Hole Munch On A Star

A giant black hole has been caught red-handed dipping into a cosmic cookie jar of stars by NASA's Galaxy Evolution Explorer. This is the first time astronomers have seen the whole process of a black hole eating a star, from its first to nearly final bites.

For perhaps thousands of years, the black hole rested quietly deep inside an unnamed elliptical galaxy. But then a star ventured a little too close to the sleeping black hole and was torn to shreds by the force of its gravity. Part of the shredded star swirled around the black hole, then began to plunge into it, triggering a bright ultraviolet flare that the Galaxy Evolution Explorer was able to detect.

Today, the space-based telescope continues to periodically watch this ultraviolet light fade as the black hole finishes the remaining bits of its stellar meal. The observations will ultimately provide a better understanding of how black holes evolve with their host galaxies.

"This will help us greatly in weighing black holes in the universe, and in understanding how they feed and grow in their host galaxies as the universe evolves," said Dr. Christopher Martin of Caltech, a co-author of the paper and the principal investigator for the Galaxy Evolution Explorer.

In the early 1990s, three other resting, or dormant, black holes were suspected of having eaten stars when the joint German-American-British Röntgen X-ray satellite picked up X-ray flares from their host galaxies. Astronomers had to wait until a decade later for NASA's Chandra X-ray Observatory and the European Space Agency's XMM-Newton X-ray observatory to confirm those findings, showing that the black holes' X-rays had faded dramatically -- a sign that stars were swallowed.

Now, Gezari and her colleagues have, for the first time, watched a similar feeding frenzy unfold, as it happens, through the ultraviolet eyes of the Galaxy Evolution Explorer. They used the telescope's detectors to catch an ultraviolet flare from a distant galaxy, then watched the flare diminish over time, as the galaxy's central black hole consumed the star. Additional data from Chandra, the Canada France Hawaii Telescope in Hawaii and the Keck Telescope, also in Hawaii, helped the team chronicle the event in multiple wavelengths over two years.

Black holes are heaps of concentrated matter whose gravity is so strong that even light cannot escape. Supermassive black holes are believed to reside at the cores of every galaxy, though some are thought to be more active than others. Active black holes drag surrounding material into them, heating it up and causing it to glow. Dormant black holes, like the one in our Milky Way galaxy, hardly make a peep, so they are difficult to study.

That's why astronomers get excited when an unsuspecting star wanders too close to a dormant black hole, an event thought to happen about once every 10,000 years in a typical galaxy. A star will flatten and stretch apart when a nearby black hole's gravity overcomes its own self-gravity. The same phenomenon happens on Earth every day, as the moon's gravity tugs on our world, causing the oceans to rise and fall. Once a star has been disrupted, a portion of its gaseous body will then be pulled into the black hole and heated up to temperatures that emit X-rays and ultraviolet light.

"The star just couldn't hold itself together," said Gezari, adding, "Now that we know we can observe these events with ultraviolet light, we've got a new tool for finding more."

The newfound feeding black hole is thought to be tens of millions times as massive as our sun. Its host galaxy is located 4 billion light-years away in the Bootes constellation.
Additional information about Galaxy Evolution Explorer can be found here.

Monday, December 04, 2006

Study Chips Into Pyramid Stone Theory

A study chips away at the theory that Egypt's pyramids were built of solid stone, with French and U.S. scientists saying concrete was used for some blocks.

The research promotes the theory that ancient Egyptian craftsmen had the skills and materials to cast the pyramids' huge blocks. Egyptologists reject the claim, insisting that the 2-ton stones were carved then dragged up the pyramids for placement, the Times of London said.

But a study of the Giza pyramids found two types of stone -- one from quarries and one man-made.

"There's no way around it. The chemistry is well and truly different," Gilles Hug of the French National Aerospace Research Agency said. The study by Hug and Michel Barsoum of Philadelphia's Drexel University will appear in the Journal of the American Ceramic Society.

The researchers used X-rays, a plasma torch and electron microscopes to compare small fragments from pyramids with stone from the Toura and Maadi quarries. They said they found "traces of a rapid chemical reaction which did not allow natural crystallization."

Hug and Barsoum said they believe the concrete method was used only for the stones on the higher levels.

Saturday, December 02, 2006

Ancient Astronomical Calculator Demystified

An international team has unravelled the secrets of a 2,000-year-old computer which could transform the way we think about the ancient world.

Professor Mike Edmunds and Dr Tony Freeth, of Cardiff University led the team who believe they have finally cracked the workings of the Antikythera Mechanism, a clock-like astronomical calculator dating from the second century BC.

Remnants of a broken wooden and bronze case containing more than 30 gears was found by divers exploring a shipwreck off the island of Antikythera at the turn of the 20th century. Scientists have been trying to reconstruct it ever since. The new research suggests it is more sophisticated than anyone previously thought.

Detailed work on the gears in the mechanism shows that it was able to track astronomical movements with remarkable precision. The calculator was able to follow the movements of the moon and the sun through the Zodiac, predict eclipses and even recreate the irregular orbit of the moon. The team believes it may also have predicted the positions of some or all of the planets.

The findings suggest that Greek technology was far more advanced than previously thought. No other civilisation is known to have created anything as complicated for another thousand years.

Professor Edmunds said: "This device is just extraordinary, the only thing of its kind. The design is beautiful, the astronomy is exactly right. The way the mechanics are designed just makes your jaw drop. Whoever has done this has done it extremely well."

The team was made up of researchers from Cardiff, the National Archaeological Museum of Athens and the Universities of Athens and Thessaloniki, supported by a substantial grant from the Leverhulme Trust. They were greatly aided by Hertfordshire X-Tek, who developed powerful X-Ray computer technology to help them study the corroded fragments of the machine. Computer giant Hewlett-Packard provided imaging technology to enhance the surface details of the machine.

The mechanism is in over 80 pieces and stored in precisely controlled conditions in Athens where it cannot be touched. Recreating its workings was a difficult, painstaking process, involving astronomers, mathematicians, computer experts, script analysts and conservation experts.

The team is unveiling its full findings at a two-day international conference in Athens from November 30 to December 1 and publishing the research in the journal Nature. The researchers are now hoping to create a computer model of how the machine worked, and, in time, a full working replica. It is still uncertain what the ancient Greeks used the mechanism for, or how widespread this technology was.

Professor Edmunds said: "It does raise the question what else were they making at the time. In terms of historic and scarcity value, I have to regard this mechanism as being more valuable than the Mona Lisa."