The team, led by Dr Stanislav Shabala of the University of Tasmania, Dr Mark Crockett of the University of Oxford, and Dr Sugata Kaviraj of Imperial College, London, publish their results in the journal Monthly Notices of the Royal Astronomical Society.

Black holes at the centre of galaxies 'switch on' from time to time, driving material around them into outflows that can stretch for millions of light years. The flows plough through galactic gas, compressing, heating and pushing it out of the way. Much of this gas is the raw material from which stars are made, so the outflows significantly affect star formation in the galaxies that host them.

The astronomers used the Hubble Space Telescope's Wide Field Camera 3 (WFC3) to study the central regions of Centaurus A, catalogued as NGC 5128, a bright galaxy 13 million light years away in the direction of the southern constellation of Centaurus.

In visible light, a prominent belt of dust can be seen running across the galaxy and when observed at X-ray and radio wavelengths it has jets extending for up to a million light years from a central black hole.

With WFC3, the scientists took a close look at the 'inner filament', a region located close to the outflow that is a source of ultraviolet and X-ray emission, as well as being bright in visible light. Using the Hubble images, the team were then able to map out the star formation history of the filament with unprecedented accuracy.

They found that the tip of the filament closest to the outflow contains young stars, the ages of which are similar to the time since the outflow 'switched on' but that there are no young stars further up the filament. This is exactly what is expected from an outflow overrunning a cloud of gas sitting in its path.

The densest central parts of the cloud are compressed and collapse to form stars, while the gas on the outskirts is swept away from the tip of the filament, like a pile of autumn leaves in the wind.

Dr Shabala comments: "This enhancement of star formation by outflows would have been even more important in a younger universe, where dense clumps of gas were much more common. Our study highlights the need to consider the role of 'positive' feedback from outflows in our current paradigm of galaxy formation. It adds an exciting new piece to a great puzzle - that of understanding how galaxies came to be the way they are today."

]]> Thu, 09 FEB 2012 08:59:27 AEST Boulder CO (SPX) Feb 06, 2012 - Physicists at JILA have created the first "frequency comb" in the extreme ultraviolet band of the spectrum, high-energy light less than 100 nanometers (nm) in wavelength. Laser-generated frequency combs are the most accurate method available for precisely measuring frequencies, or colors, of light.

In reaching the new band of the spectrum, the JILA experiments demonstrated for the first time a very fine mini-comb-like structure within each subunit, or harmonic, of the larger comb, drastically sharpening the measurement tool.

The new comb, described in the Feb. 2 issue of the journal Nature,* confirms and expands on the JILA group's 2005 claim of the ability to generate extreme ultraviolet (EUV) frequencies for making precise measurements in that part of the electromagnetic spectrum.

The new tool can aid in the development of "nuclear clocks" based on ticks in the nuclei of atoms, and measurements of previously unexplored behavior in atoms and molecules.

JILA is a joint venture of the National Institute of Standards and Technology (NIST) and the University of Colorado Boulder.

"Nobody doubted that the EUV frequency comb was there, it's just that nobody had seen it with real experimental proof," says NIST/JILA Fellow Jun Ye, the group leader. "The new work provides the first experimental proof, and also really shows that one can now do science with it."

Frequency combs are created with ultrafast pulsed lasers and produce a span of very fine, evenly spaced "teeth," each a specific frequency, which can be used like a ruler to measure light.

Frequency combs are best known for measuring visible and near-infrared light at wavelengths of about 400 to 1500 nm (frequencies of about 750 to 200 terahertz, or trillions of cycles per second), enabling development of next-generation atomic clocks.

In the past few years researchers at JILA, NIST and many other laboratories have pushed comb boundaries toward other regions of the electromagnetic spectrum.

To create the world's first extreme ultraviolet (EUV) frequency comb, JILA scientists used a high-power laser to generate infrared light pulses that bounce back and forth and overlap in an optical cavity 154 million times per second(a frequency of 154 megahertz, or MHz).

When xenon gas is injected into the cavity, the laser field drives an electron temporarily out of each atom of gas. When the electron snaps back into the atom, it generates a train of light pulses with a duration of several hundred attoseconds each (1 attosecond is 0.000 000 000 000 000 001 seconds). The process generates "harmonics"-strong signals at regular fractions of the original infrared wavelength.

As a result of the high repetition frequency of the laser (154 MHz), for the first time ever, each harmonic has its own set of "teeth" marking individual frequencies, a mini frequency comb within the big comb.

The EUV comb is the first system for high-accuracy laser spectroscopy-the use of light to probe matter and make measurements traceable to international standards-at wavelengths below 200 nm, a frequency of more than 1 petahertz (quadrillion cycles per second).

The EUV comb is the culmination of several technical advances, including improved high-power ytterbium fiber lasers, an optical cavity formed by five mirrors in which light pulses overlap perfectly and build on each other in a stable way, and better understanding of the plasma (a mix of electrons and electrically charged atoms, or ions) required to generate EUV light inside the cavity. Researchers finally achieved an ideal balance of high power and stability in the cavity.

Applications for the new comb include the development of nuclear clocks, based on changes in energy levels of an atom's nucleus instead of the electronic structure as in today's atomic clocks. The nucleus is well isolated from external interference and thus might make an extremely stable clock.

Other applications include studies of plasmas such as those in outer space; and searches for any changes in the fundamental "constants" of nature, values crucial to many scientific calculations. Ye hopes to continue extending combs toward shorter wavelengths to create an X-ray frequency comb.

This research is a result of a five-year collaboration between JILA and IMRA America Inc., of Ann Arbor, Mich., which designed and built the high-power precision ytterbium fiber laser specifically for this project. The research was funded in part by the Defense Advanced Research Projects Agency, the Air Force Office of Scientific Research, NIST and the National Science Foundation.

]]> Thu, 09 FEB 2012 08:59:27 AEST Los Angeles CA (SPX) Jan 31, 2012 - UCLA researchers have explained the puzzling disappearing act of energetic electrons in Earth's outer radiation belt, using data collected from a fleet of orbiting spacecraft.

In a paper published Jan. 29 in the advance online edition of the journal Nature Physics, the team shows that the missing electrons are swept away from the planet by a tide of solar wind particles during periods of heightened solar activity.

"This is an important milestone in understanding Earth's space environment," said lead study author Drew Turner, an assistant researcher in the UCLA Department of Earth and Space Sciences and a member of UCLA's Institute for Geophysics and Planetary Physics (IGPP). "We are one step closer towards understanding and predicting space weather phenomena."

During powerful solar events such as coronal mass ejections, parts of the magnetized outer layers of sun's atmosphere crash onto Earth's magnetic field, triggering geomagnetic storms capable of damaging the electronics of orbiting spacecraft. These cosmic squalls have a peculiar effect on Earth's outer radiation belt, a doughnut-shaped region of space filled with electrons so energetic that they move at nearly the speed of light.

"During the onset of a geomagnetic storm, nearly all the electrons trapped within the radiation belt vanish, only to come back with a vengeance a few hours later," said Vassilis Angelopoulos, a UCLA professor of Earth and space sciences and IGPP researcher.

The missing electrons surprised scientists when the trend was first measured in the 1960s by instruments onboard the earliest spacecraft sent into orbit, said study co-author Yuri Shprits, a research geophysicist with the IGPP and the departments of Earth and space sciences, and atmospheric and oceanic sciences.

"It's a puzzling effect," he said. "Oceans on Earth do not suddenly lose most of their water, yet radiation belts filled with electrons can be rapidly depopulated."

Even stranger, the electrons go missing during the peak of a geomagnetic storm, a time when one might expect the radiation belt to be filled with energetic particles because of the extreme bombardment by the solar wind.

Where do the electrons go? This question has remained unresolved since the early 1960s. Some believed the electrons were lost to Earth's atmosphere, while others hypothesized that the electrons were not permanently lost at all but merely temporarily drained of energy so that they appeared absent.

"Our study in 2006 suggested that electrons may be, in fact, lost to the interplanetary medium and decelerated by moving outwards," Shprits said. "However, until recently, there was no definitive proof for this theory."

To resolve the mystery, Turner and his team used data from three networks of orbiting spacecraft positioned at different distances from Earth to catch the escaping electrons in the act.

The data show that while a small amount of the missing energetic electrons did fall into the atmosphere, the vast majority were pushed away from the planet, stripped away from the radiation belt by the onslaught of solar wind particles during the heightened solar activity that generated the magnetic storm itself.

A greater understanding of Earth's radiation belts is vital for protecting the satellites we rely on for global positioning, communications and weather monitoring, Turner said.

Earth's outer radiation belt is a harsh radiation environment for spacecraft and astronauts; the high-energy electrons can penetrate a spacecraft's shielding and wreak havoc on its delicate electronics. Geomagnetic storms triggered when the oncoming particles smash into Earth's magnetosphere can cause partial or total spacecraft failure.

"While most satellites are designed with some level of radiation protection in mind, spacecraft engineers must rely on approximations and statistics because they lack the data needed to model and predict the behavior of high-energy electrons in the outer radiation belt," Turner said.

During the 2003 "Halloween Storm," more than 30 satellites reported malfunctions, and one was a total loss, said Angelopoulos, a co-author of the current research. As the solar maximum approaches in 2013, marking the sun's peak activity over a roughly 11-year cycle, geomagnetic storms may occur as often as several times per month.

"High-energy electrons can cut down the lifetime of a spacecraft significantly," Turner said. "Satellites that spend a prolonged period within the active radiation belt might stop functioning years early."

While a mechanized spacecraft might include multiple redundant circuits to reduce the risk of total failure during a solar event, human explorers in orbit do not have the same luxury. High-energy electrons can punch through astronauts' spacesuits and pose serious health risks, Turner said.

"As a society, we've become incredibly dependent on space-based technology," he said. "Understanding this population of energetic electrons and their extreme variations will help create more accurate models to predict the effect of geomagnetic storms on the radiation belts."

Key observational data used in this study was collected by a network of NASA spacecraft known as THEMIS (Time History of Events and Macroscale Interactions during Substorms); Angelopoulos is the principal investigator of the THEMIS mission. Additional information was obtained from two groups of weather satellites called POES (Polar Operational Environmental Satellite) and GOES (Geostationary Operational Environmental Satellite).

A new collaboration between UCLA and Russia's Moscow State University promises to paint an even clearer picture of these vanishing electrons. Slated for launch in the spring of 2012, the Lomonosov spacecraft will fly in low Earth orbit to measure highly energetic particles with unprecedented accuracy, said Shprits, the principal investigator of the project. Several key instruments for the mission are being developed and assembled at UCLA.

Earth's radiation belts were discovered in 1958 by Explorer I, the first U.S. satellite that traveled to space.

"What we are studying was the first discovery of the space age," Shprits said. "People realized that launches of spacecraft didn't only make the news, they could also make scientific discoveries that were completely unexpected."

This project received federal funding from NASA and the National Science Foundation. Other co-authors include Michael Hartinger, a UCLA graduate student in Earth and space sciences.

]]> Thu, 09 FEB 2012 08:59:27 AEST Houston TX (SPX) Jan 31, 2012 - Rice University physicists have gone to extremes to prove that Isaac Newton's classical laws of motion can apply in the atomic world: They've built an accurate model of part of the solar system inside a single atom of potassium.

In a new paper published this week in Physical Review Letters, Rice's team and collaborators at the Oak Ridge National Laboratory and the Vienna University of Technology showed they could cause an electron in an atom to orbit the nucleus in precisely the same way that Jupiter's Trojan asteroids orbit the sun.

The findings uphold a prediction made in 1920 by famed Danish physicist Niels Bohr about the relationship between the then-new science of quantum mechanics and Newton's tried-and-true laws of motion.

"Bohr predicted that quantum mechanical descriptions of the physical world would, for systems of sufficient size, match the classical descriptions provided by Newtonian mechanics," said lead researcher Barry Dunning, Rice's Sam and Helen Worden Professor of Physics and chair of the Department of Physics and Astronomy.

"Bohr also described the conditions under which this correspondence could be observed. In particular, he said it should be seen in atoms with very high principal quantum numbers, which are exactly what we study in our laboratory."

Bohr was a pioneer of quantum physics. His 1913 atomic model, which is still widely invoked today, postulated a small nucleus surrounded by electrons moving in well-defined orbits and shells.

The word "quantum" in quantum mechanics derives from the fact that these orbits can have only certain well-defined energies. Jumps between these orbits lead to absorption or emission of specific amounts of energy termed quanta. As an electron gains energy, its quantum number increases, and it jumps to higher orbits that circle ever farther from the nucleus.

In the new experiments, Rice graduate students Brendan Wyker and Shuzhen Ye began by using an ultraviolet laser to create a Rydberg atom. Rydberg atoms contain a highly excited electron with a very large quantum number. In the Rice experiments, potassium atoms with quantum numbers between 300 and 600 were studied.

"In such excited states, the potassium atoms become hundreds of thousands of times larger than normal and approach the size of a period at the end of a sentence," Dunning said. "Thus, they are good candidates to test Bohr's prediction."

He said comparing the classical and quantum descriptions of the electron orbits is complicated, in part because electrons exist as both particles and waves. To "locate" an electron, physicists calculate the likelihood of finding the electron at different locations at a given time.

These predictions are combined to create a "wave function" that describes all the places where the electron might be found. Normally, an electron's wave function looks like a diffuse cloud that surrounds the atomic nucleus, because the electron might be found on any side of the nucleus at a given time.

Dunning and co-workers previously used a tailored sequence of electric field pulses to collapse the wave function of an electron in a Rydberg atom; this limited where it might be found to a localized, comma-shaped area called a "wave packet." This localized wave packet orbited the nucleus of the atom much like a planet orbits the sun. But the effect lasted only for a brief period.

"We wanted to see if we could develop a way to use radio frequency waves to capture this localized electron and make it orbit the nucleus indefinitely without spreading out," Ye said.

They succeeded by applying a radio frequency field that rotated around the nucleus itself. This field ensnared the localized electron and forced it to rotate in lockstep around the nucleus.

A further electric field pulse was used to measure the final result by taking a snapshot of the wave packet and destroying the delicate Rydberg atom in the process.

After the experiment had been run tens of thousands of times, all the snapshots were combined to show that Bohr's prediction was correct: The classical and quantum descriptions of the orbiting electron wave packets matched. In fact, the classical description of the wave packet trapped by the rotating field parallels the classical physics that explains the behavior of Jupiter's Trojan asteroids.

Jupiter's 4,000-plus Trojan asteroids - so called because each is named for a hero of the Trojan wars - have the same orbit as Jupiter and are contained in comma-shaped clouds that look remarkably similar to the localized wave packets created in the Rice experiments. And just as the wave packet in the atom is trapped by the combined electric field from the nucleus and the rotating wave, the Trojans are trapped by the combined gravitational field of the sun and orbiting Jupiter.

The researchers are now working on their next experiment: They're attempting to localize two electrons and have them orbit the nucleus like two planets in different orbits.

"The level of control that we're able to achieve in these atoms would have been unthinkable just a few years ago and has potential applications in, for example, quantum computing and in controlling chemical reactions using ultrafast lasers," Dunning said.

The research was funded by the National Science Foundation, the Robert A. Welch Foundation, the Austrian Science Fund and the Department of Energy. Paper co-authors include S. Yoshida of the Vienna University of Technology; C.O. Reinhold of Oak Ridge National Laboratory and the University of Tennessee; and J. Burgdorfer of Vienna University of Technology and the University of Tennessee.

A copy of the PRL paper is available here.

]]> Thu, 09 FEB 2012 08:59:27 AEST Heidelberg, Germany (SPX) Jan 30, 2012 - Scientists have found that micron-size particles which are trapped at fluid interfaces exhibit a collective dynamic that is subject to seemingly unrelated governing laws. These laws show a smooth transitioning from long-ranged cosmological-style gravitational attraction down to short-range attractive and repulsive forces.

The study by Johannes Bleibel from the Max Planck Institute for Intelligent Systems in Stuttgart, Germany, and his colleagues has just been published in the journal EPJ E . The authors used so-called colloidal particles that are larger than molecules but too small to be observed with the naked eye.

These particles are adsorbed at the interface between two fluids and assembled into a monolayer. This constitutes a 2D model in which particles that are larger than a micron deform the interface through their own weight and generate an effective long-range attraction which looks like gravitation in 2D.

Thus, the particles assemble in clusters. To model long-range forces between particles, the researchers used numerical simulations based on random movement of particles, known as Brownian dynamics.

Here, they took advantage of the formal analogy between so-called capillary attraction - the long-ranged interaction through interface deformation - and gravitational attraction.

They used a particle-mesh method as employed in simulations of what are known as self-gravitating fluids, corresponding to the collapse of a system under its own gravity, traditionally used in cosmological studies.

The authors also found that this long-range interaction no longer matters beyond a certain length determined by the properties of both the particles and the interface, and short-range forces come into play.

This means that for systems exceeding this length, particles first tend to self-assemble into several clusters which eventually merge into a single, large cluster.

The study of monolayer aggregates of micron-size colloids is used as a template for nanoparticles deposited onto substrates in nanotechnology applications.

Reference1. Bleibel J, Dominguez A, Oettel M, Dietrich S (2011). Collective dynamics of colloids at fluid interfaces, European Physical Journal E (EPJ E) 34:125, DOI: 10.1140/epje/i2011-11125-2.

]]> Thu, 09 FEB 2012 08:59:27 AEST Riverside CA (SPX) Jan 30, 2012 - Does antimatter behave differently in gravity than matter? Physicists at the University of California, Riverside have set out to determine the answer. Should they find it, it could explain why the universe seems to have no antimatter and why it is expanding at an ever increasing rate.

In the lab, the researchers took the first step towards measuring the free fall of "positronium" - a bound state between a positron and an electron. The positron is the antimatter version of the electron. It has identical mass to the electron, but a positive charge. If a positron and electron encounter each other, they annihilate to produce two gamma rays.

Physicists David Cassidy and Allen Mills first separated the positron from the electron in positronium so that this unstable system would resist annihilation long enough for the physicists to measure the effect of gravity on it.

"Using lasers we excited positronium to what is called a Rydberg state, which renders the atom very weakly bound, with the electron and positron being far away from each other," said Cassidy, an assistant project scientist in the Department of Physics and Astronomy, who works in Mills's lab. "This stops them from destroying each other for a while, which means you can do experiments with them."

Rydberg atoms are highly excited atoms. They are interesting to physicists because many of the atoms' properties become exaggerated.

In the case of positronium, Cassidy and Mills, a professor of physics and astronomy, were interested in achieving a long lifetime for the atom in their experiment. At the Rydberg level, positronium's lifetime increases by a factor of 10 to 100.

"But that's not enough for what we're trying to do," Cassidy said. "In the near future we will use a technique that imparts a high angular momentum to Rydberg atoms," Cassidy said. "This makes it more difficult for the atoms to decay, and they might live for up to 10 milliseconds - an increase by a factor of 10,000 - and offer themselves up for closer study."

Cassidy and Mills already have made Rydberg positronium in large numbers in the lab. Next, they will excite them further to achieve lifetimes of a few milliseconds. They will then make a beam of these super-excited atoms to study its deflection due to gravity.

"We will look at the deflection of the beam as a function of flight time to see if gravity is bending it," Cassidy explained.

"If we find that antimatter and matter don't behave in the same way, it would be very shocking to the physics world. Currently there is an assumption that matter and antimatter are exactly the same - other than a few properties like charge.

This assumption leads to the expectation that they should both have been created in equal amounts in the Big Bang. But we do not see much antimatter in the universe, so physicists are searching for differences between matter and antimatter to explain this."

Study results appear in the Jan. 27 issue of Physical Review Letters. Cassidy and Mills expect to attempt the next step in their gravity experiments this summer. They were joined in the research by Harry Tom, a professor of physics and astronomy, and Tomu H. Hisakado, a graduate student in Mills's lab.

]]> Thu, 09 FEB 2012 08:59:27 AEST Pasadena CA (JPL) Jan 27, 2012 - NASA's Nuclear Spectroscopic Telescope Array, or NuSTAR, shipped to Vandenberg Air Force Base, Calif., on Tuesday, to be mated to its Pegasus launch vehicle. The observatory will detect X-rays from objects ranging from our sun to giant black holes billions of light-years away. It is scheduled to launch March 14 from an aircraft operating out of Kwajalein Atoll in the Marshall Islands.

"The NuSTAR mission is unique because it will be the first NASA mission to focus X-rays in the high-energy range, creating the most detailed images ever taken in this slice of the electromagnetic spectrum," said Fiona Harrison, the mission's principal investigator at the California Institute of Technology in Pasadena, Calif.

The observatory shipped from Orbital Sciences Corporation in Dulles, Va., where the spacecraft and science instrument were integrated. It is scheduled to arrive at Vandenberg on Jan. 27, where it will be mated to the Pegasus, also built by Orbital, on Feb. 17.

The mission will be launched from the L-1011 "Stargazer" aircraft, which will take off near the equator from Kwajalein Atoll in the Pacific. NuSTAR and its Pegasus will fly from Vandenberg to Kwajalein attached to the underside of the L-1011, and are scheduled to arrive on March 7.

On launch day, after the airplane arrives at the planned drop site over the ocean, the Pegaus will drop from the L-1011 and carry NuSTAR to an orbit around Earth.

"NuSTAR is an engineering achievement, incorporating state-of-the-art high-energy X-ray mirrors and detectors that will enable years of astronomical discovery," said Yunjin Kim, the mission's project manager at NASA's Jet Propulsion Laboratory in Pasadena.

NuSTAR's advanced telescope consists of two sets of 133 concentric shells of mirrors, which were shaped from flexible glass similar to that found in laptop screens. Because X-rays require large focusing distances, or focal lengths, the telescope has a lengthy 33-foot (10-meter) mast, which will unfold a week after launch.

These and other advances in technology will enable NuSTAR to explore the cosmic world of high-energy X-rays with much improved sensitivity and resolution over previous missions. During its two-year primary mission, NuSTAR will map the celestial sky in X-rays, surveying black holes, mapping supernova remnants, and studying particle jets travelling away from black holes near the speed of light.

NuSTAR also will probe the sun, looking for microflares theorized to be on the surface that could explain how the sun's million-degree corona, or atmosphere, is heated. It will even test a theory of dark matter, the mysterious substance making up about one-quarter of our universe, by searching the sun for evidence of a hypothesized dark matter particle.

"NuSTAR will provide an unprecedented capability to discover and study some of the most exotic objects in the universe, from the corpses of exploded stars in the Milky Way to supermassive black holes residing in the hearts of distant galaxies," said Lou Kaluzienski, NuSTAR program scientist at NASA Headquarters in Washington.

NuSTAR is a small-explorer mission managed by JPL for NASA's Science Mission Directorate. The spacecraft was built by Orbital Sciences Corporation. Its instrument was built by a consortium including Caltech, JPL, Columbia University, New York, N.Y., NASA's Goddard Space Flight Center in Greenbelt, Md., the Danish Technical University in Denmark, the University of California, Berkeley, and ATK-Goleta. NuSTAR will be operated by U.C. Berkeley, with the Italian Space Agency providing its equatorial ground station located at Malindi, Kenya. NASA's Explorer Program is managed by Goddard. JPL is managed by Caltech for NASA.

]]> Thu, 09 FEB 2012 08:59:27 AEST Washington DC (SPX) Jan 23, 2012 - On June 30, 2012, a "leap second" will be added to the world's clocks at 23 hours, 59 minutes, 59 seconds Coordinated Universal Time (UTC). This corresponds to 7:59:59 p.m. Eastern Daylight Time, when the extra second will be inserted at the U.S. Naval Observatory's Master Clock Facility in Washington, DC.

Historically, time was based on the mean rotation of the Earth relative to celestial bodies, and the second was defined in this reference frame.

However, the invention of atomic clocks defined a much more precise "atomic" timescale and a second that is independent of Earth's rotation. In 1970, an international agreement established two timescales: one based on the rotation of the Earth, known as UT1, and one based on atomic time, Coordinated Universal Time, or UTC.

The International Earth Rotation and Reference Systems Service (IERS) is the organization which monitors the difference in the two time scales and calls for leap seconds to be inserted in or removed from UTC when necessary to keep them within 0.9 second of each other.

In order to create UTC, a secondary timescale, TAI, is first generated; it consists of UTC without leap seconds. When the system was instituted in 1972, the difference between TAI and UT1 was determined to be 10 seconds.

Since 1972, 24 additional leap seconds have been added at intervals varying from six months to seven years, with the most recent being inserted on December 31, 2008. After the insertion of the leap second in June, the cumulative difference between UTC and TAI will be 35 seconds.

Confusion sometimes arises over the misconception that the occasional insertion of leap seconds every few years indicates that the Earth should stop rotating within a few millennia.

This is because some mistake leap seconds to be a measure of the rate at which the Earth is slowing. The one-second increments are, however, indications of the accumulated difference in time between the two systems.

The decision as to when to make a leap second is determined by the IERS, for which the USNO serves as the Rapid Service/Prediction Center.

Measurements show that the Earth currently runs slow, compared to atomic time, at about one millisecond per day. These data are generated by the USNO using the technique of Very Long Baseline Interferometry (VLBI).

VLBI measures the rotation of the Earth by observing the apparent positions of distant objects near the edge of the observable universe. These observations show that after roughly 1,000 days, the difference between Earth rotation time and atomic time would be about one second.

Instead of allowing this to happen a leap second is inserted to bring the two times closer together. We can easily change the time of an atomic clock, but it is not possible to alter the Earth's rotational speed to match the atomic clocks.

]]> Thu, 09 FEB 2012 08:59:27 AEST Washington DC (SPX) Jan 19, 2012 - The High Frequency Instrument aboard the Planck space telescope has completed its survey of the remnant light from the Big Bang explosion that created our universe. The sensor ran out of coolant on Jan. 14, as expected, ending its ability to detect this faint energy.

"The High Frequency Instrument has reached the end of its observing life, but the Low Frequency Instrument will continue observing for another year, and analysis of data from both instruments is still in the early phase," said Charles Lawrence, the U.S. Planck project scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif.

"The scientific payoff from the High Frequency Instrument's brilliantly successful operation is still to come."

NASA plays an important role in the Planck mission, which is led by the European Space Agency. In addition to helping with the analysis of the data, NASA contributed several key components to the mission itself.

JPL built the state-of-the-art detectors that allowed the High Frequency Instrument to detect icy temperatures down to nearly absolute zero, the coldest temperature theoretically attainable.

Less than half a million years after the universe was created 13.7 billion years ago, the initial fireball cooled to temperatures of about 4,000 degrees Celsius (about 7,200 degrees Fahrenheit), releasing bright, visible light. As the universe has expanded, it has cooled dramatically, and its early light has faded and shifted to microwave wavelengths.

By studying patterns imprinted in that light today, scientists hope to understand the Big Bang and the very early universe, as it appeared long before galaxies and stars first formed.

Planck has been measuring these patterns by surveying the whole sky with its High Frequency Instrument and its Low Frequency Instrument. Combined, they give Planck unparalleled wavelength coverage and the ability to resolve faint details.

Launched in May 2009, the minimum requirement for success was for the spacecraft to complete two whole surveys of the sky. In the end, Planck worked perfectly in completing not two, but five whole-sky surveys with both instruments.

The Low Frequency Instrument will continue surveying the sky for a large part of 2012, providing data to improve the quality of the final results. The first results on the Big Bang and very early universe will not come for another year.

]]> Thu, 09 FEB 2012 08:59:27 AEST Geneva, Switzerland (UPI) Jan 19, 2012 - A decision whether to keep a system of adding so-called leap seconds to the global time system is being considered at a meeting in Switzerland, scientists say.

More than 100 nations are represented at the Radiocommunications Assembly in Geneva to consider the future of world timekeeping, CNN reported Thursday.

The current Co-ordinated Universal Time or UTC is based on extremely accurate atomic clocks, but they are so precise they do not match the rotation of the Earth, which constantly varies due to the action of the tides and changes within the Earth's core.

To compensate, the so-called "leap seconds" have to be added or subtracted periodically to synchronize UTC to the Earth's rotation.

Many countries, including the United States and most European nations, have argued for doing away with leap seconds as being too cumbersome.

They say precise timing systems, such as those utilized by global positioning satellites, can be disrupted by the inclusion of leap seconds.

"There are many applications today that depend on precise time keeping," Peter Whibberley, a research scientist at Britain's National Physical Laboratory, said.

While leap seconds may be cumbersome, Whibberly said, some form of correction is necessary.

Without some method of adjustment, the precise time measured by atomic clocks and time according to the Earth's rotation will start to deviate more and more.

"Without a correction, eventually our clocks would show the middle of the day occurring at night," he said. "We have to have some means of making a correction but at the moment no one knows how that's going to be done."

]]> Thu, 09 FEB 2012 08:59:27 AEST Subscribe to our daily selection of space, military, environment and energy newsletters responseText http://visitor.constantcontact.com/manage/optin/ea?v=0016gbbKsaiGSpQFojVO8ZoHw%3D%3D