[neilep (OP)]

Scientists elucidate the origin of the darkest galaxies in the universe

Ghostly galaxies composed almost entirely of dark matter speckle the universe. Unlike normal galaxies, these extreme systems contain very few stars and are almost devoid of gas. Most of the luminous matter, so common in most galaxies, has been stripped away, leaving behind a dark matter shadow. These intriguing galaxies-known as dwarf spheroidals-are so faint that, although researchers believe they exist throughout the universe, only those relatively close to Earth have ever been observed. And until recently, no scientific model proposed to unravel their origin could simultaneously explain their exceptional dark matter content and their penchant for existing only in close proximity to much larger galaxies.

Now, Stelios Kazantzidis, a researcher at Stanford University's Kavli Institute for Particle Astrophysics and Cosmology (KIPAC), in collaboration with Lucio Mayer of the Swiss Federal Institute of Technology in Zurich and the University of Zurich, Chiara Mastropietro of the University of Munich in Germany and James Wadsley of McMaster University in Canada, has developed an elegant explanation for how galaxies come to be dominated by dark matter. Kazantzidis, who completed part of the study as a fellow at the University of Chicago's Kavli Institute for Cosmological Physics, reports his findings in the Feb. 15 issue of Nature.

"These results are so exciting because they are based on a combination of physical effects that has never before been postulated," said Kazantzidis. "This is one step toward a more complete understanding of the formation of structure in the universe, which is one of the fundamental goals of astrophysics."

Using supercomputers to create novel simulations of galaxy formation, Kazantzidis and his collaborators found that a dark matter-dominated galaxy begins life as a normal system. But when it approaches a much more massive galaxy, it simultaneously encounters three environmental effects-"ram pressure," "tidal shocking" and the cosmic ultraviolet background-that transform it into a mere dark-matter shadow of its former self.

About 10 billion years ago, when the gas-rich progenitors of dark matter-dominated galaxies originally fell into the Milky Way, the universe was hot with a radiation called the cosmic ultraviolet background. As a small satellite galaxy traveled along its elliptical path around a more massive galaxy, called the host, this radiation made the gas within the smaller galaxy hotter. This state allowed ram pressure-a sort of "wind resistance" a galaxy feels as it speeds along its path-to strip away the gas within the satellite galaxy.

Simultaneously, as the satellite galaxy moved closer to the massive system, it encountered the overwhelming gravitational force of the much larger mass. This force wrenched luminous stars from the small galaxy. Over billions of years of evolution, the satellite passed by the massive galaxy several times as it traversed its orbital path. Each time its stars shook and the satellite lost some of them as a result of a mechanism called tidal shocking. These effects conspired to eventually strip away nearly all the luminous matter-gas and stars-and left behind only a dark-matter shadow of the original galaxy.

The dark matter, on the other hand, was nongaseous and therefore unaffected by the ram pressure force or the cosmic ultraviolet background, the scientists posit. It did experience tidal shocking, but this force alone was not strong enough to pull away a substantial amount of dark matter.

The numerical simulations conducted by Kazantzidis and his collaborators constitute the most extensive calculations ever performed on this topic, consuming up to two months of supercomputing time each at the University of Zurich, the Pittsburgh Supercomputing Center and elsewhere.

"Computer models of galaxy formation in the last decade or so have focused on modeling the properties of dark matter rather than those of the more familiar baryonic [luminous] matter," said co-author Mayer. "Instead, our work suggests that we cannot understand the origin of galaxies without modeling the detailed physics of baryonic matter, even in a dark matter-dominated universe."

The scientists say this new understanding of the origin of the darkest galaxies in the universe may soon lead to fundamental insights into the nature of dark matter.

"Elucidating the nature of dark matter is one of the grandest challenges of modern cosmology," said Kazantzidis. "In the next several years, numerous experiments will attempt to detect dark matter using dwarf spheroidal galaxies as targets." Kazantzidis' work will benefit these studies by offering a better explanation of the origin of ghostly galaxies.

Mystery of the missing satellites

Additionally, the work may help to explain a long-standing discrepancy between theory and observation. The leading modern cosmological model, Lambda Cold Dark Matter ((CDM), predicts that many more small galaxies surround massive galaxies like the Milky Way and Andromeda than are currently observed. This mismatch, which is often referred to as the "missing satellites problem," has been traditionally regarded as one of the toughest challenges to the (CDM paradigm. Kazantzidis' work suggests that the process by which small galaxies are stripped of their luminous matter is common, and implies that the "missing" galaxies could exist in the form of dark matter-dominated satellites.

"These galaxies could just be too dark to detect," he said. "But their possible existence will substantially alleviate the missing satellites problem with profound implications for the predictive power of the (CDM theory." Coincidentally, in the last few months, one of the most advanced observational programs ever undertaken, the Sloan Digital Sky Survey, has revealed in the vicinity of the Milky Way a number of what appear to be ultra-faint satellite galaxies. If this finding is confirmed by follow-up observations and analysis, these newly discovered systems would be explained by Kazantzidis' calculations and would contribute to solving the long-standing missing satellites problem, he says.

SOURCE: EUREKAALERT.ORG

[ROBERT]

Chimpanzees 'hunt using spears' 

Chimpanzees in Senegal have been observed making and using wooden spears to hunt other primates, according to a study in the journal Current Biology.
Researchers documented 22 cases of chimps fashioning tools to jab at smaller primates sheltering in cavities of hollow branches or tree trunks.

The report's authors, Jill Pruetz and Paco Bertolani, said the finding could have implications for human evolution. Chimps had not been previously observed hunting other animals with tools.

Pruetz and Bertolani made the discovery at their research site in Fongoli, Senegal, between March 2005 and July 2006.

 

http://news.bbc.co.uk/2/hi/science/nature/6387611.stm

I hope no-one tells Charlton Heston, he may shoot "the filthy apes".   []
http://www.vpc.org/nrainfo/heston.html

[neilep (OP)]

Study reveals leaks in Antarctic 'plumbing system'
NASA NEWS RELEASE
Posted: February 24, 2007

WASHINGTON - Scientists using NASA satellites have discovered an extensive network of waterways beneath a fast-moving Antarctic ice stream that provide clues as to how "leaks" in the system impact sea level and the world's largest ice sheet. Antarctica holds about 90 percent of the world's ice and 70 percent of the world's reservoir of fresh water.

With data from NASA satellites, a team of scientists led by research geophysicist Helen Fricker of the Scripps Institution of Oceanography, La Jolla, Calif., detected for the first time the subtle rise and fall of the surface of fast-moving ice streams as the lakes and channels nearly a half-mile of solid ice below filled and emptied. Results were presented at the annual meeting of the American Association for the Advancement of Science (AAAS) in San Francisco. The study was published in the Feb. 16 issue of Science magazine.

"This exciting discovery of large lakes exchanging water under the ice sheet surface has radically altered our view of what is happening at the base of the ice sheet and how ice moves in that environment," said co-author Robert Bindschadler, chief scientist of the Laboratory for Hydrospheric and Biospheric Sciences at NASA's Goddard Space Flight Center, Greenbelt, Md.

"NASA's state-of-the-art satellite instruments are so sensitive we are able to capture an unprecedented three-dimensional look at the system beneath the thick ice sheet and measure from space changes of a mere 3 feet in its surface elevation. That is like seeing an elevation change in the thickness of a paperback book from an airplane flying at 35,000 feet."

The surface of the ice sheet appears stable to the naked eye, but because the base of an ice stream is warmer, water melts from the basal ice to flow, filling the system's "pipes" and lubricating flow of the overlying ice. This web of waterways acts as a vehicle for water to move and change its influence on the ice movement.

Moving back and forth through the system's "pipes" from one lake to another, the water stimulates the speed of the ice stream's flow a few feet per day, contributing to conditions that cause the ice sheet to either grow or decay. Movement in this system can influence sea level and ice melt worldwide.

"There's an urgency to learning more about ice sheets when you note that sea level rises and falls in direct response to changes in that ice," Fricker said. "With this in mind, NASA's ICESat, Aqua and other satellites are providing a vital public service."

In recent years, scientists have discovered more than 145 subglacial lakes, a smaller number of which composes this "plumbing system" in the Antarctic. Bindschadler and Fricker; Ted Scambos of the National Snow and Ice Data Center in Boulder, Colo.; and Laurence Padman of Earth and Space Research in Corvallis, Ore.; observed water discharging from these under-ice lakes into the ocean in coastal areas. Their research has delivered new insight into how much and how frequently these waterways "leak" water and how many connect to the ocean.

The study included observations of a subglacial lake the size of Lake Ontario buried under an active area of west Antarctica that feeds into the Ross Ice Shelf. The research team combined images from the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument aboard NASA's Aqua satellite and data from the Geoscience Laser Altimeter System (GLAS) on NASA's Ice Cloud and Land Elevation Satellite (ICESat) to unveil a multi-dimensional view of changes in the elevation of the icy surface above the lake and surrounding areas during a three-year period. Those changes suggest the lake drained and that its water relocated elsewhere.

MODIS continuously takes measurements of broad-sweeping surface areas at three levels of detail, revealing the outline of under-ice lakes. ICESat's GLAS instrument uses laser altimetry technology to measure even the smallest of elevation changes in the landscape of an ice sheet. Together, data from both have been used to create a multi-year series of calibrated surface reflectance images, resulting in a new technique called satellite image differencing that emphasizes where surface slopes have changed.

Souce: spaceflightnow.com

[neilep (OP)]

 
Detection of a colliding-wind beyond the Milky Way
EUROPEAN SPACE AGENCY NEWS RELEASE
Posted: February 25, 2007

Imagine two stars with winds so powerful that they eject an Earth's worth of material roughly once every month. Next, imagine those two winds colliding head-on. Such titanic collisions produce multimillion-degree gas, which radiates brilliantly in X-rays. Astronomers have conclusively identified the X-rays from about two-dozen of these systems in our Milky Way. But they have never seen one outside our galaxy - until now.

Thanks to the European Space Agency's XMM-Newton X-ray observatory, with help from NASA's Chandra X-ray Observatory, an international team led by Dr Yael Naze of the Universite de Liege in Belgium has found such a system in a nearby galaxy. This galaxy, the Small Magellanic Cloud, orbits the Milky Way and is located about 170 000 light-years from Earth.   

The binary system, known as HD 5980, contains two extremely massive stars, 'weighing' about 50 and 30 times the mass of the Sun. Each star radiates more than a million times as much light as the Sun, meaning they put out more light in one minute than our host star generates in an entire year.

The sheer photon pressure of this incredible outpouring of light blows off gas from each star in a supersonic 'wind'. These winds are so powerful that they carry away roughly an Earth mass each month, a rate 10 thousand million times greater than the solar wind, and at a speed 5 times faster than the solar wind itself.

HD 5980's two stars are separated by only about 90 million kilometres, roughly half Earth's average distance from the Sun. "These stars are so close to each other that if they were in our solar system they could fit inside the orbit of Venus," says Naze. As a result, the winds smash into each other with tremendous force, heating the gas and generating enormous numbers of X-rays.

"The system emits about 10 times more energy in X-rays alone than the Sun radiates over the entire spectrum," says team member Dr Michael F. Corcoran, a scientist with the Universities Space Research Association at NASA's Goddard Space Flight Center in Greenbelt, Maryland.

Using data from Chandra, the same team first reported HD 5980's highly energetic X-ray emission in 2002. But its origin was uncertain. Data taken from 2000 to 2005 with XMM-Newton shows that it is indeed produced by a wind collision.

The stars orbit each other every 20 days in a plane that is edge-on to Earth's line of sight, so the stars periodically eclipse each other. The wind collision is thus seen from different angles and through different amounts of material. XMM-Newton saw the X-ray emission rise and fall in a repeatable, predictable pattern.

"Similar X-ray variability from massive binaries inside the Milky Way have been detected, but this is the first indisputable evidence for the phenomenon outside our galaxy," says Naze. "This discovery highlights the great capabilities of modern X-ray observatories."

XMM-Newton has the largest mirrors of any X-ray observatory ever flown, and the sheer size of these mirrors allowed astronomers to monitor this distant system. HD 5980 itself is surrounded by hot interstellar material that creates a diffuse X-ray glow that makes the object difficult to study. "The Chandra data allowed us to pinpoint HD 5980 and resolve the system from the diffuse emission," says Corcoran.

HD 5980 is one of the Small Magellanic Cloud's brightest stars. Situated on the periphery of the star cluster NGC 346, the two stars are nearing the end of their lives and will eventually explode as supernovae. The more massive star, HD 5980A, is passing through a Luminous Blue Variable (LBV) phase - a short-lived, erratic stage that only the most massive stars go through. The most well-known LBV in our galaxy, Eta Carinae, produced a giant outburst that was recorded by astronomers in the 1840s. HD 5980A experienced a smaller-scale outburst that was seen in 1993-94. Its companion, HD 5980B, is an evolved Wolf-Rayet star that has already ejected much of its original envelope.

"It's interesting to be able to study an extragalactic colliding-wind binary like HD 5980 as if it were in our own galaxy", says Corcoran. "Colliding winds provide an important handle on how massive stars shed material. Being able to study them in external galaxies means we can study the effects of different compositions and environments on how these massive stars evolve. From the XMM-Newton data, we can study the delicate balance between the two winds, and determine the changing strength of the winds."

spaceflightnow.com
 

[neilep (OP)]

New coating is virtual black hole for reflections

Nonreflecting material may help solar cells catch more of the sun's rays.

Researchers have created an anti-reflective coating that allows light to travel through it, but lets almost none bounce off its surface. At least 10 times more effective than the coating on sunglasses or computer monitors, the material, which is made of silica nanorods, may be used to channel light into solar cells or allow more photons to surge through the surface of a light-emitting diode (LED).

Publishing in the March 1, 2007, Nature Photonics, lead author Jong Kyu Kim and a team from Rensselaer Polytechnic Institute in Troy, N.Y., reveal how they crafted the coating, which reflects almost as little light as do molecules of air.

Guided by National Science Foundation-supported electrical engineer Fred Schubert, the researchers developed a process based on an already common method for depositing layers of silica, the building block of quartz, onto computer chips and other surfaces.

The method grows ranks of nanoscale rods that lie at the same angle. That degree of the angle is determined by temperature. Under a microscope, the films look like tiny slices of shag carpet.

By laying down multiple layers, each at a different angle, the researchers created thin films that are uniquely capable of controlling light. With the right layers in the right configuration, the researchers believe they can even create a film that will reflect no light at all.

One critical application for the material is in the development of next-generation solar cells. By preventing reflections, the coating would allow more light, and more wavelengths of light, to transmit through the protective finish on a solar cell surface and into the cell itself. Engineers may be able to use such a technique to boost the amount of energy a cell can collect, bypassing current efficiency limits.

Another application would involve coating LEDs to eliminate reflections that cut down the amount of light the LED can emit. The researchers hope the efficiency gains could allow the light sources to compete more effectively with fluorescent and incandescent bulbs. So, they will next focus their attention on solid state lighting.


Source: eurekalert.org

[paul.fr]

Green light for Australian ban on old-style bulb


Agencies in Canberra and Sydney
Wednesday February 21, 2007
The Guardian

 
Photograph: Guardian
 
Australia is to ban incandescent lightbulbs in an effort to curb greenhouse gas emissions, with the government saying yesterday they would be phased out within three years.
The environment minister, Malcolm Turnbull, said yellow incandescent bulbs, which have been virtually unchanged for 125 years, would be replaced by more efficient compact fluorescent bulbs by 2009. "By that stage you simply won't be able to buy incandescent lightbulbs, because they won't meet the energy standard," he said in a radio interview.

[neilep (OP)]

Paleontologists discover new mammal from Mesozoic Era

Animals shows intermediate ear structure in evolution of modern mammals

An international team of American and Chinese paleontologists has discovered a new species of mammal that lived 125 million years ago during the Mesozoic Era, in what is now the Hebei Province in China.

The new mammal, documented in the March 15 issue of the journal Nature, provides first-hand evidence of early evolution of the mammalian middle ear--one of the most important features for all modern mammals. The discovery was funded by the National Science Foundation (NSF).

"This early mammalian ear from China is a rosetta-stone type of discovery which reinforces the idea that development of complex body parts can be explained by evolution, using exquisitely preserved fossils," said H. Richard Lane, program director in NSF's Division of Earth Sciences, which co-funded the discovery with NSF's Division of Environmental Biology and its Assembling the Tree of Life (AToL) program.

Named Yanoconodon allini after the Yan Mountains in Hebei, the fossil was unearthed in the fossil-rich beds of the Yixian Formation and is the first Mesozoic mammal recovered from Hebei. The fossil site is about 300 kilometers outside of Beijing.

The researchers discovered that the skull of Yanoconodon revealed a middle ear structure that is an intermediate step between those of modern mammals and those of near relatives of mammals, also known as mammaliaforms.

"This new fossil offers a rare insight in the evolutionary origin of the mammalian ear structure," said Zhe-Xi Luo, a paleontologist at the Carnegie Museum of Natural History (CMNH) in Pittsburgh, Pa. "Evolution of the ear is important for understanding the origins of key mammalian adaptations."

Mammals have highly sensitive hearing, far better than the hearing capacity of all other vertebrates, scientists have found. Consequently, paleontologists and evolutionary biologists have been searching for more than a century for clues to the evolutionary origins of mammal ear structure.

Mammalian hearing adaptation is made possible by a sophisticated middle ear of three tiny bones, known as the hammer (malleus), the anvil (incus) and the stirrup (stapes), plus a bony ring for the eardrum (tympanic membrane).

The mammal middle ear bones evolved from the bones of the jaw hinge in their reptilian relatives. However, paleontologists long have attempted to understand the evolutionary pathway via which these precursor jaw bones became separated from the jaw and moved into the middle ear of modern mammals.

"Now we have a definitive piece of evidence, in a beautifully preserved fossil split on two rock slabs," said Luo. "Yanoconodon clearly shows an intermediate condition in the evolutionary process of how modern mammals acquired their middle ear structure."

Yanoconodon is about 5 inches (or 15 cm) long and estimated to weigh about 30 grams. Its teeth are notable for the three cusps in a straight line on molars (thus known as a triconodont) for feeding on insects and worms. It has a long body, short and sprawling limbs and claws that were ideal for either digging or living on the ground.

In addition to its unique ear structure, Yanoconodon also has a surprisingly high number of 26 thoracic ("chest") and lumbar ("waist") vertebrae, unlike most living and extinct terrestrial mammals that commonly have 19 or 20 thoracic and lumbar vertebrae. The extra vertebrae give Yanoconodon a more elongated body form, in contrast to its relatively shorter and very primitive limb and foot structures. The new mammal also has lumbar ribs, a rare feature among modern mammals.

"The discoveries of exquisitely preserved Mesozoic mammals from China have built the evidence such that biologists and paleontologists are able to make sense of how developmental mechanisms have impacted the morphological evolution of the earliest mammals," said Luo.


SOURCE: EUREKALERT

[neilep (OP)]

Keeping the body in sync -- the stability of cellular clocks

A study in Switzerland uses the tools of physics to show how our circadian clocks manage to keep accurate time in the noisy cellular environment.

In an article appearing March 13 in the journal Molecular Systems Biology, researchers from the Ecole Polytechnique Federale de Lausanne demonstrate that the stability of cellular oscillators depends on specific biochemical processes, reflecting recent association studies in families affected by advanced sleep phase syndrome.

Circadian rhythms are cyclical changes in physiology, gene expression, and behavior that run on a cycle of approximately one day, even in conditions of constant light or darkness. Peripheral organs in the body have their own cellular clocks that are reset on a daily basis by a central master clock in the brain. The operation of the cellular clocks is controlled by the coordinated action of a limited number of core clock genes. The oscillators work like this: the cell receives a signal from the master pacemaker in the hypothalamus, and then these clock genes respond by setting up concentration gradients that change in a periodic manner. The cell “interprets” these gradients and unleashes tissue-specific circadian responses. Some examples of output from these clocks are the daily rhythmic changes in body temperature, blood pressure, heart rate, concentrations of melatonin and glucocorticoids, urine production, acid secretion in the gastrointestinal tract, and changes in liver metabolism.

In the tiny volume of the cell, however, the chemical environment is constantly fluctuating. How is it possible for all these cell-autonomous clocks to sustain accurate 24-hour rhythms in such a noisy environment?

Using mouse fibroblast circadian bioluminescence recordings from the Schibler Lab at the University of Geneva, the researchers turned to dynamical systems theory and developed a mathematical model that identified the molecular parameters responsible for the stability of the cellular clocks. Stability is a measure of how fast the system reverts to its initial state after being perturbed.

“To my knowledge we are the first to discuss how the stability of the oscillator directly affects bioluminescence recordings,” explains Felix Naef, a systems biology professor at EPFL and the Swiss Institute for Experimental Cancer Research. “We found that the phosphorylation and transcription rates of a specific gene are key determinants of the stability of our internal body clocks.”

This result is consistent with recent research from the University of California, San Francisco involving families whose circadian clocks don’t tick quite right. These families’ clocks are shorter than 24 hours, and they also have mutations in oscillator-related genes. The current results shed light on how a genetically-linked phosphorylation event gone wrong could lead to inaccurate timing of our body clockworks.

SOURCE: EUREKALERT

[neilep (OP)]

Robotic telescope unravels mystery of cosmic blasts

Scientists have used the world's largest robotic telescope to make the earliest-ever measurement of the optical polarisation* of a Gamma Ray Burst (GRB) just 203 seconds after the start of the cosmic explosion. This finding, which provides new insight into GRB physics, is published in Science today (15th March 2007).

The scientists from Liverpool John Moores University and colleagues in the UK, Italy, France and Slovenia used the Liverpool Telescope on the island of La Palma and its novel new polarimeter, RINGO, to perform the measurement following detection of the burst by NASA's Swift satellite.

Gamma Ray Bursts are the most instantaneously powerful explosions in the Universe and are identified as brief, intense and completely unpredictable flashes of high energy gamma rays on the sky. They are thought to be produced by the death throes of a massive star and signal the birth of a new black hole or neutron star (magnetar) and ejection of an ultra-high speed jet of plasma. Until now, the composition of the ejected material has remained a mystery and, in particular the importance of magnetic fields has been hotly debated by GRB scientists.

The Liverpool measurement was obtained nearly 100 times faster than any previously published optical polarisation measurement for a GRB afterglow and answers some fundamental questions about the presence of magnetic fields.

Principal author of the Science paper and GRB team leader Dr Carole Mundell of the Astrophysics Research Institute, Liverpool John Moores University, said "Our new measurements, made shortly after the Gamma Ray Burst, show that the level of polarisation in the afterglow is very low. Combined with our knowledge of how the light from this explosion faded, this rules-out the presence of strong magnetic fields in the emitting material flowing out from the explosion - a key element of some theories of GRBs."

The so-called optical afterglow is thought to originate from light emitted when this ejected material impacts the gas surrounding the star. In the first few minutes after the initial burst of gamma rays, the optical light carries important clues to the origin of these catastrophic explosions; capturing this light at the earliest possible opportunity and measuring its properties is ideally suited to the capabilities of large robotic telescopes like the Liverpool Telescope.

Lord Martin Rees, Astronomer Royal and President of the Royal Society said "We are still flummoxed about the underlying 'trigger' for gamma ray bursts, and why they sometimes emit bright flashes of light. Theorists have a lot of tentative ideas, and these observations narrow down the range of options."

Professor Keith Mason, CEO of the Particle Physics and Astronomy Council (PPARC) and UK lead investigator on Swift’s Ultra Violet/Optical Telescope, said, "This result demonstrates well the effectiveness of Swift’s rapid response alert system, allowing robotic telescopes, such as the Liverpool Telescope, to follow up gamma ray bursts within seconds, furthering our knowledge with each detection."

SOURCE: EUREKALERT

[neilep (OP)]

A dead star seen snacking on shredded asteroid
SPITZER SCIENCE CENTER NEWS RELEASE


For the last two years, astronomers have suspected that a nearby white dwarf star called GD 362 was "snacking" on a shredded asteroid. Now, an analysis of chemical "crumbs" in the star's atmosphere conducted by NASA's Spitzer Space Telescope has confirmed this suspicion.

"This is a really fascinating system, that could offer clues to what our solar system may look like in approximately five billion years when our Sun becomes a white dwarf," said Dr. Michael Jura, of the University of California at Los Angeles (UCLA).

White dwarfs are essentially the glowing embers of stars that were once like our Sun. Sun-like stars spend most of their lives producing energy by fusing hydrogen atoms into "heavier" helium atoms. Our Sun is currently doing this.

Once the Sun-like star runs out of hydrogen, helium atoms will fuse to produce other heavier elements like carbon, which will eventually sink to the star's core. Meanwhile, the heat released during this helium fusion is so strong that the will star expand and vaporize all dust, rocks and planets that orbit nearby. At this stage, the star is called a "red giant." Ultimately, the red giant will shed its external layers, exposing a dense, hot core about the size of Earth, known as a "white dwarf."

Closely orbiting planets, asteroids, and dust are not expected to survive the red-giant phase of a Sun-like star's life, so astronomers were shocked to find so much dust around the white dwarf GD 362. According to Jura, GD 362 has been a white dwarf for approximately 900 million years -- so surrounding dust should have already been destroyed. He also notes that astronomers were surprised to find chemical elements heavier than hydrogen and helium in GD 362's atmosphere, because these elements should have already sunk to the star's core. When an abundance of heavy elements were first found in GD 362's atmosphere in 2004, scientists were not sure where they came from.

An explanation came in 2005, when two teams of astronomers independently found evidence for dust orbiting GD 362. Both groups argued that the elements in the atmosphere came from orbiting dust particles that rained onto star, and was vaporized by the white dwarf's intense heat. However, astronomers did not know where the dust came from.

Some astronomers predicted that the dust circled the star similar to the way rings of debris orbit Saturn. They believed that the ring of dust around GD 362 came from a large asteroid that had wandered too close to the star, and was shredded by the white dwarf's gravity. Meanwhile, others suspected that dust grains floated into the system from outer space and got pulled into GD 362's atmosphere.

According to Jura, new observations from Spitzer provide direct evidence for the first scenario. He notes that the silicates (sand-like dust grains) in asteroids are very different from the silicates randomly floating around the universe. Using Spitzer's infrared spectrograph instrument, Jura's team determined that the silicates in GD 362's atmosphere resembled the sand-like grains found in asteroids.

With Spitzer's Multiband Imaging Photometer (MIPS) instrument, Jura's team also noticed that the dust disk surrounding GD 362 was confined, meaning they saw an end to the dust disk.

"If this dust was floating in from the interstellar medium [or outer space] and falling onto the star, then we would see a trail of dust leading beyond this star system -- the dust disk shouldn't end. In the Spitzer observations, we see that the dust is confined to a region close to the star," said Jura.

Jura's paper on this topic was has been accepted by the Astronomical Journal. Other authors of this work include Dr. Jay Farihi, of the Gemini Observatory, Hawaii; and Drs. Ben Zuckerman and Eric Becklin, also of UCLA. Becklin led the Gemini North observations that first discovered dust in GD 362's atmosphere.

Source: spaceflightnow.com

[neilep (OP)]

Star burps, then explodes
UNIVERSITY OF CALIFORNIA-BERKELEY NEWS RELEASE

BERKELEY - Tens of millions of years ago, in a galaxy far, far away, a massive star suffered a nasty double whammy.

Signs of the first shock reached Earth on Oct. 20, 2004, when the star was observed letting loose an outburst so enormous and bright that Japanese amateur astronomer Koichi Itagaki initially mistook it for a supernova. The star survived for nearly two years, however, until on Oct. 11, 2006, professional and amateur astronomers witnessed it blowing itself to smithereens as Supernova (SN) 2006jc.

"We have never observed a stellar outburst and then later seen the star explode," said University of California, Berkeley, astronomer Ryan Foley. His group studied the 2006 event with ground-based telescopes, including the 10-meter (32.8-foot) W. M. Keck telescopes in Hawaii. Narrow helium spectral lines showed that the supernova's blast wave ran into a slow-moving shell of material, presumably the progenitor's outer layers that were ejected just two years earlier. If the spectral lines had been caused by the supernova's fast-moving blast wave, the lines would have been much broader.

Another group, led by Stefan Immler of NASA's Goddard Space Flight Center in Greenbelt, Md., monitored SN 2006jc with NASA's Swift satellite and the Chandra X-ray Observatory. By observing how the supernova brightened in X-rays, a result of the blast wave slamming into the outburst ejecta, they could measure the amount of gas blown off in the 2004 outburst: about 0.01 solar mass, the equivalent of about 10 Jupiters.

"The beautiful aspect of our SN 2006jc observations is that although they were obtained in different parts of the electromagnetic spectrum, in the optical and in X-rays, they lead to the same conclusions," said Immler.

"This event was a complete surprise," added Alex Filippenko, leader of the UC Berkeley/Keck supernova group and a member of NASA's Swift satellite team. "It opens up a fascinating new window on how some kinds of stars die."

All the observations suggest that the supernova's blast wave took only a few weeks to reach the shell of material ejected two years earlier, which did not have time to drift very far from the star. As the wave smashed into the ejecta, it heated the gas to millions of degrees, hot enough to emit copious X-rays. The Swift satellite saw the supernova continue to brighten in X-rays for 100 days, something that has never been seen before in a supernova. All supernovae previously observed in X-rays have started off bright and then quickly faded to invisibility.

"You don't need a lot of mass in the ejecta to produce a lot of X-rays," noted Immler. Swift's ability to monitor the supernova's X-ray rise and decline over six months was crucial to the mass determination by Immler's team. But he added that Chandra's sharp resolution enabled his group to resolve the supernova from a bright X-ray source that appears in the field of view of Swift's X-ray telescope.

"We could not have made this measurement without Chandra," said Immler, who will submit his team's paper next week to the Astrophysical Journal. "The synergy between Swift's fast response and its ability to observe a supernova every day for a long period, and Chandra's high spatial resolution, is leading to a lot of interesting results."

Foley and his colleagues, whose paper appears in the March 10 Astrophysical Journal Letters, propose that the star recently transitioned from a Luminous Blue Variable (LBV) star to a Wolf-Rayet star. An LBV is a massive star in a brief but unstable phase of stellar evolution. Similar to the 2004 eruption, LBVs are prone to blow off large amounts of mass in outbursts so extreme that they are frequently mistaken for supernovae, events dubbed "supernova impostors." Wolf-Rayet stars are hot, highly evolved stars that have shed their outer envelopes.

Most astronomers did not expect that a massive star would explode so soon after a major outburst, or that a Wolf-Rayet star would produce such a luminous eruption, so SN 2006jc represents a puzzle for theorists.

"It challenges some aspects of our current model of stellar evolution," said Foley. "We really don't know what caused this star to have such a large eruption so soon before it went supernova."

"SN 2006jc provides us with an important clue that LBV-style eruptions may be related to the deaths of massive stars, perhaps more closely than we used to think," added coauthor and UC Berkeley astronomer Nathan Smith. "The fact that we have no well-established theory for what actually causes these outbursts is the elephant in the living room that nobody is talking about."

SN 2006jc occurred in galaxy UGC 4904, located 77 million light years from Earth in the constellation Lynx. The supernova explosion, a peculiar variant of a Type Ib, was first sighted by Itagaki, American amateur astronomer Tim Puckett and Italian amateur astronomer Roberto Gorelli.

SOURCE:SPACEFLIGHTNOW.COM

[neilep (OP)]

Ancient T. rex and mastodon protein fragments discovered, sequenced
68-million-year-old T. rex proteins are oldest ever sequenced

Scientists have confirmed the existence of protein in soft tissue recovered from the fossil bones of a 68 million-year-old Tyrannosaurus rex (T. rex) and a half-million-year-old mastodon.

Their results may change the way people think about fossil preservation and present a new method for studying diseases in which identification of proteins is important, such as cancer.

When an animal dies, protein immediately begins to degrade and, in the case of fossils, is slowly replaced by mineral. This substitution process was thought to be complete by 1 million years. Researchers at North Carolina State University (NCSU) and Harvard Medical School now know otherwise.

The researchers' findings appear as companion papers in this week's issue of the journal Science.

"Not only was protein detectably present in these fossils, the preserved material was in good enough condition that it could be identified," said Paul Filmer, program director in the National Science Foundation (NSF) Division of Earth Sciences, which funded the research. "We now know much more about what conditions proteins can survive in. It turns out that some proteins can survive for very long time periods, far longer than anyone predicted."

Mary Schweitzer of NCSU and the North Carolina Museum of Natural Sciences discovered soft tissue in the leg bone of a T. rex and other fossils recovered from the Hell Creek sediment formation in Montana.

After her chemical and molecular analyses of the tissue indicated that original protein fragments might be preserved, she turned to colleagues John Asara and Lewis Cantley of Harvard Medical School, to see if they could confirm her suspicions by finding the amino acid used to make collagen, a fibrous protein found in bone.

Bone is a composite material, consisting of both protein and mineral. In modern bones, when minerals are removed, a collagen matrix--fibrous, resilient material that gives the bones structure and flexibility--is left behind. When Schweitzer demineralized the T. rex bone, she was surprised to find such a matrix, because current theories of fossilization held that no original organic material could survive that long.

"This information will help us learn more about evolutionary relationships, about how preservation happens, and about how molecules degrade over time, which could have important applications in medicine," Schweitzer said.

To see if the material had characteristics indicating the presence of collagen, which is plentiful, durable and has been recovered from other fossil materials, the scientists examined the resulting soft tissue with electron microscopy and atomic force microscopy. They then tested it against various antibodies that are known to react with collagen. Identifying collagen would indicate that it is original to T. rex--that the tissue contains remnants of the molecules produced by the dinosaur.

"This is the breakthrough that says it's possible to get sequences beyond 1 million years," said Cantley. "At 68 million years, it's still possible."

Asara and Cantley successfully sequenced portions of the dinosaur and mastodon proteins, identifying the amino acids and confirming that the material was collagen. When they compared the collagen sequences to a database that contains existing sequences from modern species, they found that the T. rex sequence had similarities to those of chickens, and that the mastodon was more closely related to mammals, including the African elephant.

The protein fragments in the T. rex fossil appear to most closely match amino acid sequences found in collagen of present-day chickens, lending support to the idea that birds and dinosaurs are evolutionarily related.

"Most people believe that birds evolved from dinosaurs, but that's based on the 'architecture' of the bones," Asara said. "This finding allows us the ability to say that they really are related because their sequences are related."

"Scientists had long assumed that the material in fossil bones would not be preserved after millions of years of burial," said Enriqueta Barrera, program director in NSF's Division of Earth Sciences. "This discovery has implications for the study of similarly well-preserved fossil material."

SOURCE: Eurekalert.org

[neilep (OP)]

3.2 Billion-Year-Old Surprise: Earth Had Strong Magnetic Field

Geophysicists at the University of Rochester announce in today's issue of Nature that the Earth's magnetic field was nearly as strong 3.2 billion years ago as it is today.

The findings, which are contrary to previous studies, suggest that even in its earliest stages the Earth was already well protected from the solar wind, which can strip away a planet's atmosphere and bathe its surface in lethal radiation.

"The intensity of the ancient magnetic field was very similar to today's intensity," says John Tarduno, professor of geophysics in the Department of Earth and Environmental Sciences at the University of Rochester. "These values suggest the field was surprisingly strong and robust. It's interesting because it could mean the Earth already had a solid iron inner core 3.2 billion years ago, which is at the very limit of what theoretical models of the Earth's formation could predict."

Geophysicists point to Mars as an example of a planet that likely lost its magnetosphere early in its history, letting the bombardment of radiation from the sun slowly erode its early atmosphere. Theories of Earth's field say it's generated by the convection of our liquid iron core, but scientists have always been curious to know when Earth's solid inner core formed because this process provides an important energy source to power the magnetic field. Scientists are also interested in when Earth's protective magnetic cocoon formed.

But uncovering the intensity of a field 3.2 billion years in the past has proven daunting, and until Tarduno's research, the only data scientists could tease from the rocks suggested the field was perhaps only a tenth as strong as today's.

Tarduno had previously shown that as far back as 2.5 billion years ago, the field was just as intense as it is today, but pushing back another 700 million years in time meant he had to find a way to overcome some special challenges.

The traditional approach to measuring the ancient Earth's magnetic field would not be good enough. The technique was developed more than four decades ago, and has changed little. With the old method, an igneous rock about an inch across is heated and cooled in a chamber that is shielded from magnetic interference. The magnetism is essentially drained from the particles in the rock and then it's refilled while scientists measure how much the particles can hold.

Tarduno, however, isolates choice, individual crystals from a rock, heats them with a laser, and measures their magnetic intensity with a super-sensitive detector called a SQUID—a Superconducting Quantum Interface Device normally used in computing chip design because it's extremely sensitive to the tiniest magnetic fields.

Certain rocks contain tiny crystals like feldspar and quartz—nano-meter sized magnetic inclusions that lock in a record of the Earth's magnetic field as they cool from molten magma to hard rock. Simply finding rocks of this age is difficult enough, but these rocks have also witnessed billions of years of geological activity that could have reheated them and possibly changed their initial magnetic record.

To reduce the chance of this contamination, Tarduno picked out the best preserved grains of feldspar and quartz out of 3.2 billion-year-old granite outcroppings in South Africa. Feldspar and quartz are good preservers of the paleomagnetic record because their minute magnetic inclusions essentially take a snapshot of the field as they cool from a molten state. Tarduno wanted to measure the smallest magnetic inclusions because larger magnetic crystals can lose their original magnetic signature at much lower temperatures, meaning they are more likely to suffer magnetic contamination from later warming geological events.

Once he isolated the ideal crystals, Tarduno employed a carbon dioxide laser to heat individual crystals much more quickly than older methods, further lessening the chance of contamination. With the University's ultra-sensitive SQUID he could measure how much magnetism these individual particles contained.

"The data suggest that the ancient magnetic field strength was at least 50 percent of the present-day field, which typically measures 40 to 60 microteslas," says Tarduno. "This means that a magnetosphere was definitely present, sheltering the Earth 3.2 billion years ago."

To further ensure his readings were accurate, Tarduno also checked the alignment of the magnetism in the particles, which record the polarity of the Earth's field at that time and location. By comparing the polarity to that of other samples of similar age and location, Tarduno could ensure that his measurements were not likely from later geological heating, but truly from 3.2 billion years ago.

Tarduno is now pushing back in time to 3.5 billion-year-old rocks to further investigate when the Earth's inner core first formed, giving new insights into early Earth processes that also may have had an effect on the atmosphere and the development of life on the planet.

Rory Cottrell, research scientist in Tarduno's laboratory, is co-author on the study. This research was funded by the National Science Foundation.

Source: University of Rochester News

[neilep (OP)]

XMM-Newton pinpoints intergalactic polluters
EUROPEAN SPACE AGENCY NEWS RELEASE
Posted: April 24, 2007

Warm gas escaping from the clutches of enormous black holes could be the key to a form of intergalactic 'pollution' that made life possible, according to new results from ESA's XMM-Newton space observatory.

Black holes are not quite the all-consuming monsters depicted in popular culture.

Until gas crosses the boundary of the black hole known as the Event Horizon, it can escape if heated sufficiently. For decades now, astronomers have watched warm gas from the mightiest black holes flowing away at speeds of 1000-2000 km/s and wondered just how much gas escapes this way. XMM-Newton has now made the most accurate measurements yet of the process.

The international team of astronomers, led by Yair Krongold, Instituto de Astronomia, Universidad Nacional Autonoma de Mexico, targeted a black hole two million times more massive than the Sun at the centre of the active galaxy NGC 4051.

Previous observations had only revealed the average properties of the escaping gas. XMM-Newton has the special ability to watch a single celestial object with several instruments at the same time. With this, the team collected more detailed information about variations in the gas' brightness and ionization state.

The team also saw that the gas was escaping from much closer to the black hole than previously thought. They could determine the fraction of gas that was escaping. "We calculate that between 2-5 percent of the accreting material is flowing back out," says team member Fabrizio Nicastro, Harvard-Smithsonian Centre for Astrophysics. This was less than some astronomers had expected.

The same heating process that allows the gas to escape also rips electrons from their atomic nuclei, leaving them ionised. The extent to which this has happened in an atom is known as its ionisation state. In particular, metals always have positive ionisation states.

The warm gas contains chemical elements heavier than Hydrogen and Helium. Astronomers term them 'metals' since they are elements in which electrons are ripped away and they have positive ionisation states - like metals. They include carbon, the essential element for life on Earth. These metals can only be made inside stars, yet they pollute vast tracts of space between galaxies. Astronomers have long wondered how they arrived in intergalactic space.

This new study provides a clue. More powerful active galaxies than NGC 4051, known as quasars, populate space. They are galaxies in which the central black hole is feeding voraciously. This would mean that quasars must have escaping gas that could carry metals all the way into intergalactic space.

If quasars are responsible for spraying metals into intergalactic space, the pollution would more likely be found in bubbles surrounding each quasar. So, different parts of the Universe would be enriched with metals at different speeds. This may explain why astronomers see differing quantities of metals depending upon the direction in which they look.

However, if the fraction of escaping gas is really as low as XMM-Newton shows in NGC 4051, astronomers need to find another source of intergalactic metals. This might be the more prevalent star-forming galaxies called Ultra Luminous Infra Red Galaxies.

"Based on this one measurement, quasars can contribute some but not all of the metals to the intergalactic medium," says Krongold.

To continue the investigation, the astronomers will have to use the same XMM-Newton technique on a more powerful active galaxy. Such observations will allow them to determine whether the fraction of gas escaping changes or stays the same. If the fraction goes up, they will have solved the puzzle. If it stays the same, the search will have to continue.

The above results have been taken from the study 'The Compact, Conical, Accretion-Disk Warm Absorber of the Seyfert 1 Galaxy NGC 4051 and its Implications for IGM-Galaxy Feedback Processes' by Yair Krongold et al. Published 20 April, in the Astrophysical Journal.

SOURCE: SPACEFLIGHTNOW.COM

[neilep (OP)]

Major Discovery: New Planet Could Harbor Water and Life
By Ker Than
Staff Writer
posted: 24 April 2007


An Earth-like planet spotted outside our solar system is the first found that could support liquid water and harbor life, scientists announced today.

Liquid water is a key ingredient for life as we know it. The newfound planet is located at the "Goldilocks" distance—not too close and not too far from its star to keep water on its surface from freezing or vaporizing away.

And while astronomers are not yet able to look for signs of biology on the planet, the discovery is a milestone in planet detection and the search for extraterrestrial life, one with the potential to profoundly change our outlook on the universe.

”The goal is to find life on a planet like the Earth around a star like the Sun. This is a step in that direction,” said study leader Stephane Udry of the Geneva Observatory in Switzerland. “Each time you go one step forward you are very happy.”

The new planet is about 50 percent bigger than Earth and about five times more massive. The new “super-Earth” is called Gliese 581 C, after its star, Gliese 581, a diminutive red dwarf star located 20.5 light-years away that is about one-third as massive as the Sun.

SOURCE: SPACE.COM

[neilep (OP)]

Japan's asteroid explorer begins voyage back to Earth
BY STEPHEN CLARK
SPACEFLIGHT NOW
Posted: April 25, 2007

A small Japanese asteroid probe riddled by a streak of bad luck began its slow limp home Wednesday, but officials still face a myriad of challenges to bring the craft back in 2010.

Controllers sent commands for the Hayabusa probe to start one of its four ion engines Wednesday, officially beginning its three-year journey to Earth.

The milestone came after months of tests to determine whether the 900-pound spacecraft was healthy enough to attempt the voyage. Hayabusa is running on a damaged battery and just one of its four ion engines is currently deemed ready for long-term operations, according to the Japanese Aerospace Exploration Agency, or JAXA.

Hayabusa also lost two of its three fast-spinning reaction wheels responsible for attitude control. After the failures, the craft was forced to exhaust all of its chemical propellant reserves.

Engineers devised a new attitude control scheme using excess xenon fuel used by Hayabusa's electric propulsion system. Officials estimate Hayabusa's tanks still hold more than 66 pounds of xenon, while only about 44 pounds are needed for the Earth-bound leg of its mission.

JAXA officials remain cautious about the chances of Hayabusa successfully reaching Earth.

"This is not an optimistic operation, but a very tough operation," said Junichiro Kawaguchi, Hayabusa project manager, in a February interview. "The spacecraft is not in a very healthy state."

The probe is still located in the vicinity of asteroid Itokawa, a small potato-shaped space rock that was the subject of three months of scientific scrutiny by Hayabusa in 2005. Ground teams believe the spacecraft is currently about 50 million miles from Earth.

Hayabusa will have to complete two more orbits around the Sun before reaching Earth in June 2010, when it is expected to separate its return capsule for a parachuted landing in southern Australia.

The reentry vehicle was designed to house small chunks of Itokawa retrieved as Hayabusa swooped down to the surface of the asteroid. A small pellet was to fire into the asteroid to force dust and rocks into the sample chamber, but reviews of data streaming back from the spacecraft later caused engineers to question whether the system worked as planned.

Officials will likely not know for sure if the capsule contains any samples until it lands.

The start of the return trip was postponed by a year after a fuel leak in December 2005 threw Hayabusa off course and cut off communications with the probe for six weeks.

On Tuesday, JAXA released a heap of catalogued raw science data from Hayabusa's mission. The data included more than 1,600 optical images, about 135,000 pieces of spectral data in the near-infrared and X-ray bands, and 1.7 million data points from a laser rangefinder.

Scientists also assembled a three-dimensional shape video of Itokawa, which is believed to have been formed by the collection of several smaller bodies linked together by loose material and weak gravity.

SOURCE: SPACEFLIGHTNOW.COM

[neilep (OP)]

Scientists discover vast intergalactic cloud of plasma
LOS ALAMOS NATIONAL LABORATORY NEWS RELEASE
Posted: April 30, 2007

LOS ALAMOS, New Mexico - Combining the world's largest radio telescope at Arecibo, Puerto Rico with a precision imaging, seven-antenna synthesis radio telescope at the Dominion Radio Astrophysical Observatory (DRAO), a team of researchers led by Los Alamos scientist Philipp Kronberg have discovered a new giant in the heavens, a giant in the form of a previously undetected cloud of intergalactic plasma that stretches more than 6 million light years across. The diffuse, magnetized intergalactic zone of high energy electrons may be evidence for galaxy-sized black holes as sources for the mysterious cosmic rays that continuously zip though the Universe. 

In research reported in the April issue of Astrophysical Journal, the team of researchers from Los Alamos, Arecibo, and DRAO in Penticton, British Columbia describe their discovery of a 2-3 megaparsec zone of diffuse, intergalactic plasma located beside the Coma cluster of galaxies. The combined use of the 305 meter Arecibo radio telescope to make a base scan of 50 square degrees of sky, and the DRAO, making 24 separate 12 hour observations over 24 days of the same sky area, resulted in an image comparable to that of a 1000 meter diameter radio telescope. After Arecibo mapped the larger cloud structure, DRAO data was used to enhance the resolution of the image. 

According to Kronberg, "One of the most exciting aspects of the discovery is the new questions it poses. For example, what kind of mechanism could create a cloud of such enormous dimensions that does not coincide with any single galaxy, or galaxy cluster? Is that same mechanism connected to the mysterious source of the ultra high energy cosmic rays that come from beyond our galaxy? And separately, could the newly discovered fluctuating radio glow be related to unwanted foregrounds of the Cosmic Microwave Background (CMB) radiation?" 

The synchrotron-radiating plasma cloud is spread across a vast region of space that may contain several black hole harboring radio galaxies. The cloud may be evidence that black holes in galaxies convert and transfer their enormous gravitational energy, by a yet unknown process, into magnetic fields and cosmic rays in the vast intergalactic regions of the Universe. 

Kronberg's work also provides the first preview of small (arc minute - level) features that could be associated with unwanted and confusing foregrounds to the CMB radiation. Because these same radiation frequencies are to be imaged by the PLANCK CMB Explorer, corrections to the observed CMB for foreground fluctuations (the so-called microwave "cirrus clouds") are vitally important to using CMB fluctuations as a probe of the early Universe. 

In addition to Kronberg, other members of the research team included, Roland Kothes from DRAO, and Christopher Salter and Phil Perillat from Arecibo and the National Astronomy and Ionosphere Center. The DRAO is operated by the Herzberg Institute of Astrophysics and the National Research Council of Canada. 

Los Alamos National Laboratory, a multidisciplinary research institution engaged in strategic science on behalf of national security, is operated by Los Alamos National Security, LLC, a team composed of Bechtel National, the University of California, BWX Technologies, and Washington Group International for the Department of Energy's National Nuclear Security Administration. 

Los Alamos enhances national security by ensuring the safety and reliability of the U.S. nuclear stockpile, developing technologies to reduce threats from weapons of mass destruction, and solving problems related to energy, environment, infrastructure, health, and global security concerns.

SOURCE:SPACEFLIGHTNOW.COM

[neilep (OP)]

Cosmologically speaking, diamonds may actually be forever
VANDERBILT UNIVERSITY NEWS RELEASE
Posted: April 30, 2007

NASHVILLE, Tenn. - If you've ever wondered about the ultimate fate of the universe, Lawrence Krauss and Robert Scherrer have some good news - sort of. 

In a paper published online on April 25 in the journal Physical Review D, the two physicists show that matter as we know it will remain as the universe expands at an ever-increasing clip. That is, the current status quo between matter and its alter ego, radiation, will continue as the newly discovered force of dark energy pushes the universe apart.

"Diamonds may actually be forever," quips Krauss, professor of physics and astronomy at Case Western Reserve University (CWRU) who is spending the year at Vanderbilt. "One of the only positive things that has arisen from the dark-energy dominated universe is that matter gets to beat radiation forever."

This viewpoint runs contrary to conventional wisdom among cosmologists. Today, there is more matter than radiation in the universe. But there were periods during the early universe that were dominated by radiation due to particle decays. The generally accepted view of the distant future has been that ordinary matter particles - protons and neutrons in particular - will gradually decay into radiation over trillions upon trillions of years, leaving a universe in which radiation once again dominates over matter; a universe lacking the material structures that are necessary for life.

It is only in the last decade that the existence of dark energy has been recognized. Before that Krauss and collaborators argued for its existence based on indirect evidence, but the first direct evidence came in 1998 when a major survey of exploding stars, called supernovae, revealed that the universe is apparently expanding at an increasing rate. Dark energy acts as a kind of anti-gravity that drives the expansion of the universe at large scales. Because it is associated with space itself, it is also called "vacuum energy." A number of follow-up observations have supported the conclusion that dark energy accounts for about 70 percent of all the energy in the universe.

"The discovery of dark energy has changed everything, but it has changed the view of the future more than the past. It is among the worst of all possible futures for life," says Krauss, who has spent the last few years exploring its implications. In an eternally expanding universe there is at least a chance that life could endure forever, but not in a universe dominated by vacuum energy, Krauss and CWRU collaborator Glenn Starkman have concluded. 

As the universe expands, the most distant objects recede at the highest velocity. The faster that objects recede, the more that the light coming from them is "red-shifted" to longer wavelengths. When their recessional velocity reaches light speed, they disappear because they are traveling away faster than the light that they emit. According to Krauss and Starkman, the process of disappearance has already begun: There are objects that were visible when the universe was half its present age that are invisible now. However, the process won't become really noticeable until the universe is about 100 billion years old. By ten trillion years, nothing but our local cluster of galaxies will be visible.

From the perspective of future civilizations, this process puts a finite limit on the amount of information and energy that will be available to maintain life. Assuming that consciousness is a physical phenomenon, this implies that life itself cannot be eternal, Krauss and Starkman argue. 

"Our current study doesn't change the process, but it does make it a little friendlier for matter and less friendly for radiation," says Scherrer, professor of physics at Vanderbilt. 

In their paper, Krauss and Scherrer analyzed all the ways that ordinary matter and dark matter could decay into radiation. (Dark matter is different from dark energy. It is an unknown form of matter that astronomers have only been able to detect by its gravitational effect on the ordinary matter in nearby galaxies. At this point, the physicists have no idea whether it is stable or will ultimately decay like ordinary matter.) Given known constraints on these various decay processes, the two show that none of them can produce radiation densities that exceed the density of the remaining matter. This is counter-intuitive because, when matter turns into energy, it does so according to Einstein's equation, E=mc2, and produces copious amounts of energy. 

"The surprising thing is that radiation disappears as fast as it is created in a universe with dark energy," says Krauss. 

The reason for radiation's vanishing act involves the expansion of space. Expanding space diminishes the density of radiant energy in two ways. The first is by increasing the separation between individual photons. The second is by reducing the amount of energy carried by individual photons. A photon's energy is contained entirely in its electromagnetic field. The shorter its wavelength and the higher its frequency, the more energy it contains. As space itself expands, the wavelengths of all the photons within it lengthen and their frequency drops. This means that the amount energy that individual photons contain also decreases. Taken together, these two effects dramatically reduce the energy density of radiation.

Protons and neutrons, by contrast, only suffer from the separation effect. Most of the energy that they carry is bound up in their mass and is not affected by spatial expansion. In an accelerating universe, that is enough of an advantage to maintain matter's dominance - forever. 

The research was funded by grants from the National Science Foundation and the U.S. Department of Energy. 

SOURCE:SPACEFLIGHTNOW.COM

[neilep (OP)]

Astronomers discover a super-massive planet
HARVARD-SMITHSONIAN CENTER FOR ASTROPHYSICS NEWS RELEASE
Posted: May 2, 2007

CAMBRIDGE, MA - Today, astronomers at the Harvard-Smithsonian Center for Astrophysics (CfA) announced that they have found the most massive known transiting extrasolar planet. The gas giant planet, called HAT-P-2b, contains more than eight times the mass of Jupiter, the biggest planet in our solar system. Its powerful gravity squashes it into a ball only slightly larger than Jupiter.

HAT-P-2b shows other unusual characteristics. It has an extremely oval orbit that brings it as close as 3.1 million miles from its star before swinging three times farther out, to a distance of 9.6 million miles. If Earth's orbit were as elliptical, we would loop from almost reaching Mercury out to almost reaching Mars. Because of its orbit, HAT-P-2b gets enormously heated up when it passes close to the star, then cools off as it loops out again. Although it has a very short orbital period of only 5.63 days, this is the longest period planet known that transits, or crosses in front of, its host star.

"This planet is so unusual that at first we thought it was a false alarm - something that appeared to be a planet but wasn't," said CfA astronomer Gaspar Bakos. "But we eliminated every other possibility, so we knew we had a really weird planet."

Bakos is lead author of a paper submitted to the Astrophysical Journal describing the discovery.

HAT-P-2b orbits an F-type star, which is almost twice as big and somewhat hotter than the Sun, located about 440 light-years away in the constellation Hercules. Once every 5 days and 15 hours, it crosses directly in front of the star as viewed from Earth-a sort of mini-eclipse. Such a transit offers astronomers a unique opportunity to measure a planet's physical size from the amount of dimming.

Brightness measurements during the transit show that HAT-P-2b is about 1.18 times the size of Jupiter. By measuring how the star wobbles as the planet's gravity tugs it, astronomers deduced that the planet contains about 8.2 times Jupiter's mass. A person who weighs 150 pounds on Earth would tip the scale at 2100 pounds, and experience 14 times Earth's gravity, by standing on the visible surface (cloud tops) of HAT-P-2b.

CfA astronomer and co-author Robert Noyes said, "All the other known transiting planets are like 'hot Jupiters.' HAT-P-2b is hot, but it's not a Jupiter. It's much denser than a Jupiter-like planet; in fact, it is as dense as Earth even though it's mostly made of hydrogen."

"This object is close to the boundary between a star and a planet," said Harvard co-author Dimitar Sasselov. "With 50 percent more mass, it could have begun nuclear fusion for a short time."

An intriguing feature of HAT-P-2b is its highly eccentric (e=0.5) orbit. Gravitational forces between star and planet tend to circularize the orbit of a close-in planet. There is no other planet known with such an eccentric, close-in orbit. In addition, all other known transiting planets have circular orbits.

The most likely explanation is the presence of a second, outer world whose gravity pulls on HAT-P-2b and perturbs its orbit. Although existing data cannot confirm a second planet, they cannot rule it out either.

HAT-P-2b orbits the star HD 147506. With visual magnitude 8.7, HD 147506 is the fourth brightest star known to harbor a transiting planet, making the star (but not the planet) visible in a small, 3-inch telescope.

HAT-P-2b was discovered using a network of small, automated telescopes known as HATNet, which was designed and built by Bakos. The HAT network consists of six telescopes, four at the Smithsonian Astrophysical Observatory's Whipple Observatory in Arizona and two at its Submillimeter Array facility in Hawaii. As part of an international campaign, the Wise HAT telescope, located in the Negev desert (Israel) also took part in the discovery. The HAT telescopes conduct robotic observations every clear night, each covering an area of the sky 300 times the size of the full moon with every exposure. About 26,000 individual observations were made to detect the periodic dips of intensity due to the transit.

[ukmicky]

Baby fish home in on mother's reef
It's a case of "reef, sweet reef" for baby tropical fish, say researchers who have found a way of tracking the movements of two generations of fish. Their study shows that baby fish are able to find their way home to the reef their mother lived on.

"We have suspected this for a long time," says Michael Berumen of the University of Arkansas in the US. "But it has spawned a big debate. We know fish are capable of returning to their home reef, but do they really? Until now, we didn't know the answer to that."

To see if this "self-recruitment" really does happen in the wild, Berumen and his colleagues in Australia and France travelled to Kimbe Island near Papua New Guinea. On the reef that surrounds the island (pictured, right), they collected 176 female clownfish and 123 female butterflyfish.

Clownfish spawn their eggs in a nest but the larvae can spend about 10 days floating around in open water before settling on a reef. Butterflyfish, like snappers, groupers and many other species targeted by the fisheries industry, are pelagic spawners – meaning they spray their eggs and sperm into open water. The juveniles do not settle on a reef until 38 days later.

Radioactive tag
The researchers injected both species with small amounts of a barium isotope. After travelling through the females' bloodstream, the radioactive tag ends up in their eggs and eventually in an ear bone in their offspring.

"It's a really neat technique that they've developed to actually tag fish through a whole reproductive season," says Stephen Simpson of Edinburgh University in the UK. "Particularly for a species of pelagic spawners whose eggs are much more difficult to find."

The scientists returned to the reef about one month after having released the tagged females and this time collected juveniles and counted how many carried the barium isotope. The team calculated that about 60% of the juveniles on the reef were the offspring of females from that reef.

"For pelagic spawners, this means the females spew their eggs into the water column and somehow the eggs hatch and the larvae find their way back to the reef, which they've never seen," says Simpson.

In the case of Butterflyfish, "there are 5 to 6 weeks during which they are potentially out at sea," says Berumen.

Smelly and noisy
How the fish find their way back to the reef is another question. According to Simpson, reef fish scientists have traditionally been divided between those who believe the dispersal of offspring is at the mercy of currents and those who believe it is driven by the behaviour of the offspring. He belongs to the second group and has shown that reef fish are capable of recognising the sound of their home reef. Other scientists have shown than fish can pick out their reef by its smell.

But where does this ability to sense the home reef come from? Simpson has a possible explanation: "You could imagine there is a suite of genes passed on to the embryos, who are therefore pre-programmed as to what they should do once their ears, eyes and nostrils develop".

The new research may not just be a curiosity. The knowledge of the area over which the reef fish travel could help design better marine reserves.

For example, the scientists say reserves that are too large may not enable fish from the protected areas to re-supply the surrounding areas, where fishing continues

http://environment.newscientist.com/article/dn11778-baby-fish-home-in-on-mothers-reef.html