BOSS quasars track the expanding universe: Most precise measurement yet

The Baryon Oscillation Spectroscopic Survey (BOSS), the largest component of the third Sloan Digital Sky Survey (SDSS-III), pioneered the use of quasars to map density variations in intergalactic gas at high redshifts, tracing the structure of the young universe. BOSS charts the history of the universe’s expansion in order to illuminate the nature of dark energy, and new measures of large-scale structure have yielded the most precise measurement of expansion since galaxies first formed.The latest quasar results combine two separate analytical techniques. A new kind of analysis, led by physicist Andreu Font-Ribera of the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) and his team, was published late last year. Analysis using a tested approach, but with far more data than before, has just been published by Timothe Delubac, of EPFL Switzerland and France’s Centre de Saclay, and his team. The two analyses together establish the expansion rate at 68 kilometers per second per million light years at redshift 2.34, with an unprecedented accuracy of 2.2 percent.”This means if we look back to the universe when it was less than a quarter of its present age, we’d see that a pair of galaxies separated by a million light years would be drifting apart at a velocity of 68 kilometers a second as the universe expands,” says Font-Ribera, a postdoctoral fellow in Berkeley Lab’s Physics Division. “The uncertainty is plus or minus only a kilometer and a half per second.” Font-Ribera presented the findings at the April 2014 meeting of the American Physical Society in Savannah, GA.BOSS employs both galaxies and distant quasars to measure baryon acoustic oscillations (BAO), a signature imprint in the way matter is distributed, resulting from conditions in the early universe. While also present in the distribution of invisible dark matter, the imprint is evident in the distribution of ordinary matter, including galaxies, quasars, and intergalactic hydrogen.”Three years ago BOSS used 14,000 quasars to demonstrate we could make the biggest 3D maps of the universe,” says Berkeley Lab’s David Schlegel, principal investigator of BOSS. “Two years ago, with 48,000 quasars, we first detected baryon acoustic oscillations in these maps. Now, with more than 150,000 quasars, we’ve made extremely precise measures of BAO.”The BAO imprint corresponds to an excess of about five percent in the clustering of matter at a separation known as the BAO scale. …

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The search for seeds of black holes

How do you grow a supermassive black hole that is a million to a billion times the mass of our sun? Astronomers do not know the answer, but a new study using data from NASA’s Wide-field Infrared Survey Explorer, or WISE, has turned up what might be the cosmic seeds from which a black hole will sprout. The results are helping scientists piece together the evolution of supermassive black holes — powerful objects that dominate the hearts of all galaxies.Growing a black hole is not as easy as planting a seed in soil and adding water. The massive objects are dense collections of matter that are literally bottomless pits; anything that falls in will never come out. They come in a range of sizes. The smallest, only a few times greater in mass than our sun, form from exploding stars. The biggest of these dark beasts, billions of times the mass of our sun, grow together with their host galaxies over time, deep in the interiors. But how this process works is an ongoing mystery.Researchers using WISE addressed this question by looking for black holes in smaller, “dwarf” galaxies. These galaxies have not undergone much change, so they are more pristine than their heavier counterparts. In some ways, they resemble the types of galaxies that might have existed when the universe was young, and thus they offer a glimpse into the nurseries of supermassive black holes.In this new study, using data of the entire sky taken by WISE in infrared light, up to hundreds of dwarf galaxies have been discovered in which buried black holes may be lurking. …

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Astronomers discover oldest star: Formed shortly after the Big Bang 13. 7 billion years ago

A team led by astronomers at The Australian National University has discovered the oldest known star in the Universe, which formed shortly after the Big Bang 13.7 billion years ago.The discovery has allowed astronomers for the first time to study the chemistry of the first stars, giving scientists a clearer idea of what the Universe was like in its infancy.”This is the first time that we’ve been able to unambiguously say that we’ve found the chemical fingerprint of a first star,” said lead researcher, Dr Stefan Keller of the ANU Research School of Astronomy and Astrophysics.”This is one of the first steps in understanding what those first stars were like. What this star has enabled us to do is record the fingerprint of those first stars.”The star was discovered using the ANU SkyMapper telescope at the Siding Spring Observatory, which is searching for ancient stars as it conducts a five-year project to produce the first digital map the southern sky.The ancient star is around 6,000 light years from Earth, which Dr Keller says is relatively close in astronomical terms. It is one of the 60 million stars photographed by SkyMapper in its first year.”The stars we are finding number one in a million,” says team member Professor Mike Bessell, who worked with Keller on the research.”Finding such needles in a haystack is possible thanks to the ANU SkyMapper telescope that is unique in its ability to find stars with low iron from their colour.”Dr Keller and Professor Bessell confirmed the discovery using the Magellan telescope in Chile.The composition of the newly discovered star shows it formed in the wake of a primordial star, which had a mass 60 times that of our Sun.”To make a star like our Sun, you take the basic ingredients of hydrogen and helium from the Big Bang and add an enormous amount of iron — the equivalent of about 1,000 times the Earth’s mass,” Dr Keller says.”To make this ancient star, you need no more than an Australia-sized asteroid of iron and lots of carbon. It’s a very different recipe that tells us a lot about the nature of the first stars and how they died.”Dr Keller says it was previously thought that primordial stars died in extremely violent explosions which polluted huge volumes of space with iron. But the ancient star shows signs of pollution with lighter elements such as carbon and magnesium, and no sign of pollution with iron.”This indicates the primordial star’s supernova explosion was of surprisingly low energy. Although sufficient to disintegrate the primordial star, almost all of the heavy elements such as iron, were consumed by a black hole that formed at the heart of the explosion,” he says.The result may resolve a long-standing discrepancy between observations and predictions of the Big Bang.The discovery was published in the latest edition of the journal Nature.Story Source:The above story is based on materials provided by The Australian National University. Note: Materials may be edited for content and length.

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Heavy metal in the early cosmos: Simulations shed light on formation and explosion of stars in earliest galaxies

Ab initio: “From the beginning.” It’s a term used in science to describe calculations that rely on established mathematical laws of nature, or “first principles,” without additional assumptions or special models. But when it comes to the phenomena that Milos Milosavljevic is interested in calculating, we’re talking really ab initio, as in from the beginning of time onward.Things were different in the early eons of the universe. The cosmos experienced rapid inflation; electrons and protons floated free from each other; the universe transitioned from complete darkness to light; and enormous stars formed and exploded to start a cascade of events leading to our present-day universe.Working with Chalence Safranek-Shrader and Volker Bromm at The University of Texas at Austin, Milosavljevic recently reported the results of several massive numerical simulations charting the forces of the universe in its first hundreds of millions of years using some of the world’s most powerful supercomputers, including the National Science Foundation-supported Stampede, Lonestar and Ranger (now retired) systems at the Texas Advanced Computing Center.The results, described in the Monthly Notices of the Royal Astronomical Society in January 2014, refine how the first galaxies formed, and in particular, how metals in the stellar nurseries influenced the characteristics of the stars in the first galaxies.”The universe formed at first with just hydrogen and helium,” Milosavljevic said. “But then the very first stars cooked metals and after those stars exploded, the metals were dispersed into ambient space.”Eventually the ejected metals fell back into the gravitational fields of the dark matter haloes, where they formed the second generation of stars. However, the first generation of metals ejected from supernovae did not mix in space uniformly.”It’s as if you have coffee and cream but you don’t stir it, and you don’t wait for a long enough time,” he explained. “You would drink some cream and coffee but not coffee with cream. There will be thin sheets of coffee and cream.”According to Milosavljevic, subtle effects like these governed the evolution of early galaxies. Some stars formed that were rich in metals, while others were metal-poor. Generally there was a spread in stellar chemical abundances because of the incomplete mixing.Another factor that influenced the evolution of galaxies was how the heavier elements emerged from the originating blast. Instead of the neat spherical blast wave that researchers presumed before, the ejection of metals from a supernova was most likely a messy process with blobs of shrapnel shooting in every direction.”Modeling these blobs properly is very important for understanding where metals ultimately go,” Milosavljevic said.Predicting future observationsIn astronomical terms, early in the universe translates to very far away. …

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One planet, two stars: New research shows how circumbinary planets form

Luke Skywalker’s home planet Tatooine would have formed far from its current location in the Star Wars universe, a new University of Bristol study into its real world counterparts, observed by the Kepler space telescope, suggests.Like the fictional Star Wars planet, Kepler-34(AB)b is a circumbinary planet, so-called because its orbit encompasses two stars. There are few environments more extreme than a binary star system in which planet formation can occur. Powerful gravitational perturbations from the two stars on the rocky building blocks of planets lead to destructive collisions that grind down the material. So, how can the presence of such planets be explained?In research published this week in Astrophysical Journal Letters, Dr Zoe Leinhardt and colleagues from Bristol’s School of Physics have completed computer simulations of the early stages of planet formation around the binary stars using a sophisticated model that calculates the effect of gravity and physical collisions on and between one million planetary building blocks.They found that the majority of these planets must have formed much further away from the central binary stars and then migrated to their current location.Dr Leinhardt said: “Our simulations show that the circumbinary disk is a hostile environment even for large, gravitationally strong objects. Taking into account data on collisions as well as the physical growth rate of planets, we found that Kepler 34(AB)b would have struggled to grow where we find it now.”Based on these conclusions for Kepler-34, it seems likely that all of the currently known circumbinary planets have also migrated significantly from their formation locations — with the possible exception of Kepler-47 (AB)c which is further away from the binary stars than any of the other circumbinary planets.Stefan Lines, lead author of the study, said: “Circumbinary planets have captured the imagination of many science-fiction writers and film-makers — our research shows just how remarkable such planets are. Understanding more about where they form will assist future exoplanet discovery missions in the hunt for earth-like planets in binary star systems.”Story Source:The above story is based on materials provided by University of Bristol. Note: Materials may be edited for content and length.

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Gravitational waves help us understand black-hole weight gain

Oct. 17, 2013 — Supermassive black holes: every large galaxy’s got one. But here’s a real conundrum: how did they grow so big?A paper in today’s issue of Science pits the front-running ideas about the growth of supermassive black holes against observational data — a limit on the strength of gravitational waves, obtained with CSIRO’s Parkes radio telescope in eastern Australia.”This is the first time we’ve been able to use information about gravitational waves to study another aspect of the Universe — the growth of massive black holes,” co-author Dr Ramesh Bhat from the Curtin University node of the International Centre for Radio Astronomy Research (ICRAR) said.”Black holes are almost impossible to observe directly, but armed with this powerful new tool we’re in for some exciting times in astronomy. One model for how black holes grow has already been discounted, and now we’re going to start looking at the others.”The study was jointly led by Dr Ryan Shannon, a Postdoctoral Fellow with CSIRO, and Mr Vikram Ravi, a PhD student co-supervised by the University of Melbourne and CSIRO.Einstein predicted gravitational waves — ripples in space-time, generated by massive bodies changing speed or direction, bodies like pairs of black holes orbiting each other.When galaxies merge, their central black holes are doomed to meet. They first waltz together then enter a desperate embrace and merge.”When the black holes get close to meeting they emit gravitational waves at just the frequency that we should be able to detect,” Dr Bhat said.Played out again and again across the Universe, such encounters create a background of gravitational waves, like the noise from a restless crowd.Astronomers have been searching for gravitational waves with the Parkes radio telescope and a set of 20 small, spinning stars called pulsars.Pulsars act as extremely precise clocks in space. The arrival time of their pulses on Earth are measured with exquisite precision, to within a tenth of a microsecond.When the waves roll through an area of space-time, they temporarily swell or shrink the distances between objects in that region, altering the arrival time of the pulses on Earth.The Parkes Pulsar Timing Array (PPTA), and an earlier collaboration between CSIRO and Swinburne University, together provide nearly 20 years worth of timing data. This isn’t long enough to detect gravitational waves outright, but the team say they’re now in the right ballpark.”The PPTA results are showing us how low the background rate of gravitational waves is,” said Dr Bhat.”The strength of the gravitational wave background depends on how often supermassive black holes spiral together and merge, how massive they are, and how far away they are. So if the background is low, that puts a limit on one or more of those factors.”Armed with the PPTA data, the researchers tested four models of black-hole growth. They effectively ruled out black holes gaining mass only through mergers, but the other three models are still a possibility.Dr Bhat also said the Curtin University-led Murchison Widefield Array (MWA) radio telescope will be used to support the PPTA project in the future.”The MWA’s large view of the sky can be exploited to observe many pulsars at once, adding valuable data to the PPTA project as well as collecting interesting information on pulsars and their properties,” Dr Bhat said.

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Hubble bubble may explain different measurements of expansion rate of the universe

Sep. 9, 2013 — The existence of the “Hubble Bubble” may explain, at least in part, the differing measurements for the expansion and therefore the age of the universe. That is the assumption of a team of physicists headed by Prof. Dr. Luca Amendola from the Institute for Theoretical Physics at Heidelberg University. In collaboration with colleagues from the Netherlands, the Heidelberg physicists developed a theoretical model that places the Milky Way inside of this type of cosmic bubble. The researchers believe the bubble can explain some of the deviations between previous measurements and the latest ones from the Planck satellite of the European Space Agency (ESA).The results of their research were published in the journal Physical Review Letters.The observable universe has been expanding since the Big Bang. It still is, causing galaxies in our Milky Way to recede. The actual speed of this expansion is known as the Hubble constant. Due to its importance in calculating basic properties of the universe, such as its age, modern cosmology is tasked with determining the value of the constant. …

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Researchers a step closer to finding cosmic ray origins

Aug. 30, 2013 — The origin of cosmic rays in the universe has confounded scientists for decades. But a study by researchers using data from the IceCube Neutrino Observatory at the South Pole reveals new information that may help unravel the longstanding mystery of exactly how and where these “rays” (they are actually high-energy particles) are produced.Cosmic rays can damage electronics on Earth, as well as human DNA, putting astronauts in space especially at risk.The research, which draws on data collected by IceTop, the IceCube Observatory’s surface array of detectors, is published online in Physical Review D, a leading journal in elementary particle physics.University of Delaware physicist Bakhtiyar Ruzybayev is the study’s corresponding author. UD scientists were the lead group for the construction of IceTop with support from the National Science Foundation and coordination by the project office at the University of Wisconsin, Madison.The more scientists learn about the energy spectrum and chemical composition of cosmic rays, the closer humanity will come to uncovering where these energetic particles originate.Cosmic rays are known to reach energies above 100 billion giga-electron volts (1011 GeV). The data reported in this latest paper cover the energy range from 1.6 times 106 GeV to 109 GeV.Researchers are particularly interested in identifying cosmic rays in this interval because the transition from cosmic rays produced in the Milky Way Galaxy to “extragalactic” cosmic rays, produced outside our galaxy, is expected to occur in this energy range.Exploding stars called supernovae are among the sources of cosmic rays here in the Milky Way, while distant objects such as collapsing massive stars and active galactic nuclei far from the Milky Way are believed to produce the highest energy particles in nature.As Ruzybayev points out, the cosmic-ray energy spectrum does not follow a simple power law between the “knee” around 4 PeV (peta-electron volts) and the “ankle” around 4 EeV (exa-electron volts), as previously thought, but exhibits features like hardening around 20 PeV and steepening around 130 PeV.”The spectrum steepens at the ‘knee,’ which is generally interpreted as the beginning of the end of the galactic population. Below the knee, cosmic rays are galactic in origin, while above that energy, particles from more distant regions in our universe become more and more likely,” Ruzybayev explained. “These measurements provide new constraints that must be satisfied by any models that try to explain the acceleration and propagation of cosmic rays.”IceTop consists of 81 stations in its final configuration, covering an area of one square kilometer on the South Pole surface above the detectors of IceCube, which are buried over a mile deep in the ice. The analysis presented in this article was performed using data taken from June 2010 to May 2011, when the array consisted of only 73 stations.The IceCube collaboration includes nearly 250 people from 39 research institutions in 11 countries, including the University of Delaware.

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How quickly can a bacterium grow? E. coli can replicate close to thermodynamic limits of efficiency

Aug. 27, 2013 — All living things must obey the laws of physics — including the second law of thermodynamics, which states that the universe’s disorder, or entropy, can only grow. Highly ordered cells and organisms appear to contradict this principle, but they actually do conform because they generate heat that increases the universe’s overall entropy.Still, questions remain: What is the theoretical threshold for how much heat a living cell must generate to fulfill its thermodynamic constraints? And how closely do cells approach that limit?In a recent paper in the Journal of Chemical Physics, MIT physicist Jeremy England mathematically modeled the replication of E. coli bacteria and found that the process is nearly as efficient as possible: E. coli produce at most only about six times more heat than they need to meet the constraints of the second law of thermodynamics.”Given what the bacterium is made of, and given how rapidly it grows, what would be the minimum amount of heat that it would have to exhaust into its surroundings? When you compare that with the amount of heat it’s actually exhausting, they’re roughly on the same scale,” says England, an assistant professor of physics. “It’s relatively close to the maximum efficiency.”England’s approach to modeling biological systems involves statistical mechanics, which calculates the probabilities of different arrangements of atoms or molecules. He focused on the biological process of cell division, through which one cell becomes two. During the 20-minute replication process, a bacterium consumes a great deal of food, rearranges many of its molecules — including DNA and proteins — and then splits into two cells.To calculate the minimum amount of heat a bacterium needs to generate during this process, England decided to investigate the thermodynamics of the reverse process — that is, two cells becoming one. …

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Ytterbium atomic clocks set record for stability

Aug. 22, 2013 — A pair of experimental atomic clocks based on ytterbium atoms at the National Institute of Standards and Technology (NIST) has set a new record for stability. The clocks act like 21st-century pendulums or metronomes that could swing back and forth with perfect timing for a period comparable to the age of the universe.NIST’s ultra-stable ytterbium lattice atomic clock. Ytterbium atoms are generated in an oven (large metal cylinder on the left) and sent to a vacuum chamber in the center of the photo to be manipulated and probed by lasers. Laser light is transported to the clock by five fibers (such as the yellow fiber in the lower center of the photo). Credit: Burrus/NIST View hi-resolution imageNIST physicists report in the Aug. 22 issue of Science Express that the ytterbium clocks’ tick is more stable than any other atomic clock. Stability can be thought of as how precisely the duration of each tick matches every other tick. The ytterbium clock ticks are stable to within less than two parts in 1 quintillion (1 followed by 18 zeros), roughly 10 times better than the previous best published results for other atomic clocks.This dramatic breakthrough has the potential for significant impacts not only on timekeeping, but also on a broad range of sensors measuring quantities that have tiny effects on the ticking rate of atomic clocks, including gravity, magnetic fields, and temperature. And it is a major step in the evolution of next-generation atomic clocks under development worldwide, including at NIST and at JILA, the joint research institute operated by NIST and the University of Colorado Boulder.”The stability of the ytterbium lattice clocks opens the door to a number of exciting practical applications of high-performance timekeeping,” NIST physicist and co-author Andrew Ludlow says.Each of NIST’s ytterbium clocks relies on about 10,000 rare-earth atoms cooled to 10 microkelvin (10 millionths of a degree above absolute zero) and trapped in an optical lattice — a series of pancake-shaped wells made of laser light. …

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Galaxies had ‘mature’ shapes 11. 5 billion years ago

Aug. 15, 2013 — Studying the evolution and anatomy of galaxies using the Hubble Space Telescope, an international team of astronomers led by doctoral candidate BoMee Lee and her advisor Mauro Giavalisco at the University of Massachusetts Amherst have established that mature-looking galaxies existed much earlier than previously known, when the universe was only about 2.5 billion years old, or 11.5 billion years ago.”Finding them this far back in time is a significant discovery,” says lead author Lee.The team used two cameras, Wide Field Camera 3 (WFC3), and Advanced Camera for Surveys (ACS), plus observations from the Hubble’s Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS), the largest project in the scope’s history with 902 assigned orbits of observing time, to explore the shapes and colors of distant galaxies over the last 80 percent of the Universe’s history. Results appear in the current online issue of The Astrophysical Journal.Lee points out that the huge CANDELS dataset allowed her team to analyze a larger number of these galaxies, a total 1,671, than ever before, consistently and in detail. “The significant resolution and sensitivity of WFC3 was a great resource for us to use in order to consistently study ancient galaxies in the early Universe,” says Lee.She and colleagues confirm for an earlier period than ever before that the shapes and colors of these extremely distant young galaxies fit the visual classification system introduced in 1926 by Edwin Hubble and known as the Hubble Sequence. It classifies galaxies into two main groups: Ellipticals and spirals, with lenticular galaxies as a transitional group. The system is based on their ability to form stars, which in turn determines their colors, shape and size.Why modern galaxies are divided into these two main types and what caused this difference is a key question of cosmology, says Giavalisco. “Another piece of the puzzle is that we still do not know why today ‘red and dead’ elliptical galaxies are old and unable to form stars, while spirals, like our own Milky Way, keep forming new stars. This is not just a classification scheme, it corresponds to a profound difference in the galaxies’ physical properties and how they were formed.”Lee adds, “This was a key question: When, and over what timescale did the Hubble Sequence form? To answer this, you need to peer at distant galaxies and compare them to their closer relatives, to see if they too can be described in the same way. The Hubble Sequence underpins a lot of what we know about how galaxies form and evolve. …

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Light slowed to a crawl in liquid crystal matrix

Aug. 13, 2013 — Light traveling in a vacuum is the Universe’s ultimate speed demon, racing along at approximately 300,000 kilometers per second. Now scientists have found an effective new way to put a speed bump in light’s path. Reported today in The Optical Society’s (OSA) open-access journal Optics Express, researchers from France and China embedded dye molecules in a liquid crystal matrix to throttle the group velocity of light back to less than one billionth of its top speed. The team says the ability to slow light in this manner may one day lead to new technologies in remote sensing and measurement science.The new approach to manipulating light, conducted by a group from France’s Université de Nice-Sophia Antipolis and China’s Xiamen University, uses little power, does not require an external electrical field, and operates at room temperature, making it more practical than many other slow light experiments. Putting the brakes on light can help scientists compare the characteristics of different light pulses more easily, which in turn can help them build highly sensitive instruments to measure extremely slow speeds and small movements, says Umberto Bortolozzo, one of the authors on the Optics Express paper. In a second paper, also published today and appearing in OSA’s journal Optics Letters, Bortolozzo and colleagues from the Université de Nice-Sophia Antipolis and the University of Rochester describe an instrument that uses slow light to measure speeds less than one trillionth of a meter per second.Scientists have known for a long time that a wave packet of light becomes more sluggish when it travels through matter, but the magnitude of this slow-down in typical materials such as glass or water is less than a factor of two. “The question is: can we do something to the matter in order to make light slow down much more considerably?” says Bortolozzo.The key to achieving a significant drop-off in speed is to take advantage of the fact that when light travels as a pulse it is really a collection of waves, each having a slightly different frequency, says Bortolozzo. However, all the waves in the pulse must travel together. Scientists can design materials to be like obstacles courses that “trip up” some of the waves more than others. …

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Cosmology in the lab using laser-cooled ions

Aug. 12, 2013 — Scientists would love to know which forces created our universe some 14 billion years ago. How could — due to a breaking of symmetry — matter, and thus stars and galaxies, be created from an originally symmetrical universe in which the same conditions prevailed everywhere shortly after the Big Bang. Now, the Big Bang is an experiment that cannot be repeated. But the principle of symmetry and its disturbance can definitely be investigated under controlled laboratory conditions.For this purpose, scientists from the Excellence Cluster QUEST at the Physikalisch-Technische Bundesanstalt (PTB) used laser-cooled ions in so-called “ion Coulomb crystals.” They were able to show for the first time how symmetry breaking can be generated in a controlled manner and how the occurrence of defects can then be observed. Realizing these so-called “topographical defects” within a well-controlled system opens up new possibilities when it comes to investigating quantum phase transitions and looking in detail into the non-equilibrium dynamics of complex systems. The results have been published in the current issue of the scientific journal Nature Communications.Within the scope of an international cooperation with colleagues from the Los Alamos National Lab (USA), from the University of Ulm (Germany) and from the Hebrew University (Israel), PTB researchers have now, for the first time, succeeded in demonstrating topological defects in an atomic-optical experiment in the laboratory. Topological defects are errors in the spatial structure which are caused by the breaking of the symmetry when particles of a system cannot communicate with each other. They form during a phase transition and present themselves as non-matching areas. For their activities, the scientists used the symmetry properties of ion Coulomb crystals which are comparable to those of the early universe.The experimental challenge for the researchers working with Tanja Mehlstäubler consisted in being able to control a complex multi-particle system and to induce an intentional change in the external conditions to obtain the symmetry breaking. …

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On the trail of dark energy: Physicists propose Higgs boson ‘portal’

Aug. 10, 2013 — One of the biggest mysteries in contemporary particle physics and cosmology is why dark energy, which is observed to dominate energy density of the universe, has a remarkably small (but not zero) value. This value is so small, it is perhaps 120 orders of magnitude less than would be expected based on fundamental physics.Resolving this problem, often called the cosmological constant problem, has so far eluded theorists.Now, two physicists — Lawrence Krauss of Arizona State University and James Dent of the University of Louisiana-Lafayette — suggest that the recently discovered Higgs boson could provide a possible “portal” to physics that could help explain some of the attributes of the enigmatic dark energy, and help resolve the cosmological constant problem.In their paper, “Higgs Seesaw Mechanism as a Source for Dark Energy,” Krauss and Dent explore how a possible small coupling between the Higgs particle, and possible new particles likely to be associated with what is conventionally called the Grand Unified Scale — a scale perhaps 16 orders of magnitude smaller than the size of a proton, at which the three known non-gravitational forces in nature might converge into a single theory — could result in the existence of another background field in nature in addition to the Higgs field, which would contribute an energy density to empty space of precisely the correct scale to correspond to the observed energy density.The paper was published online, Aug. 9, in Physical Review Letters.Current observations of the universe show it is expanding at an accelerated rate. But this acceleration cannot be accounted for on the basis of matter alone. Putting energy in empty space produces a repulsive gravitational force opposing the attractive force produced by matter, including the dark matter that is inferred to dominate the mass of essentially all galaxies, but which doesn’t interact directly with light and, therefore, can only be estimated by its gravitational influence.Because of this phenomenon and because of what is observed in the universe, it is thought that such ‘dark energy’ contributes up to 70 percent of the total energy density in the universe, while observable matter contributes only 2 to 5 percent, with the remaining 25 percent or so coming from dark matter.The source of this dark energy and the reason its magnitude matches the inferred magnitude of the energy in empty space is not currently understood, making it one of the leading outstanding problems in particle physics today.”Our paper makes progress in one aspect of this problem,” said Krauss, a Foundation Professor in ASU’s School of Earth and Space Exploration and Physics, and the director of the Origins Project at ASU. “Now that the Higgs boson has been discovered, it provides a possible ‘portal’ to physics at much higher energy scales through very small possible mixings and couplings to new scalar fields which may operate at these scales.””We demonstrate that the simplest small mixing, related to the ratios of the scale at which electroweak physics operates, and a possible Grand Unified Scale, produces a possible contribution to the vacuum energy today of precisely the correct order of magnitude to account for the observed dark energy,” Krauss explained. “Our paper demonstrates that a very small energy scale can at least be naturally generated within the context of a very simple extension of the standard model of particle physics.”While a possible advance in understanding the origin of dark energy, Krauss said the construct is only one step in the direction of understanding its mysteries.”The deeper problem of why the known physics of the standard model does not contribute a much larger energy to empty space is still not resolved,” he said.

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Largest magnetic fields in the universe

July 26, 2013 — Numerical simulations by AEI scientists show for the first time the occurrence of an instability in the interior of neutron stars that can lead to gigantic magnetic fields, possibly triggering one of the most dramatic explosions observed in the Universe.An ultra-dense (“hypermassive”) neutron star is formed when two neutron stars in a binary system finally merge. Its short life ends with the catastrophic collapse to a black hole, possibly powering a short gamma-ray burst, one of the brightest explosions observed in the universe. Short gamma-ray bursts as observed with satellites like XMM Newton, Fermi or Swift release within a second the same amount of energy as our Galaxy in one year. It has been speculated for a long time that enormous magnetic field strengths, possibly higher than what has been observed in any known astrophysical system, are a key ingredient in explaining such emission. Scientists at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute/AEI) have now succeeded in simulating a mechanism which could produce such strong magnetic fields prior to the collapse to a black hole.How can such ultra-high magnetic fields — stronger than ten or hundred million billion times Earth’s magnetic field — be generated from the much lower initial neutron star magnetic fields?This could be explained by a phenomenon that can be triggered in a differentially rotating plasma in the presence of magnetic fields: neighbouring plasma layers, which rotate at different speeds, “rub against each other,” eventually setting the plasma into turbulent motion. In this process called magnetorotational instability magnetic fields can be strongly amplified. This mechanism is known to play an important role in many astrophysical systems such as accretion disks and core-collapse supernovae. It had been speculated for a long time that magnetohydrodynamic instabilities in the interior of hypermassive neutron stars could bring about the necessary magnetic field amplification. The actual demonstration that this is possible has only now been achieved with the present numerical simulations.The scientists of the Gravitational Wave Modelling Group at the AEI simulated a hypermassive neutron star with an initially ordered (“poloidal”) magnetic field, whose structure is subsequently made more complex by the star’s rotation. Since the star is dynamically unstable, it eventually collapses to a black hole surrounded by a cloud of matter, until the latter is swallowed by the black hole.These simulations have unambiguously shown the presence of an exponentially rapid amplification mechanism in the stellar interior — the magnetorotational instability. …

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Earth’s gold came from colliding dead stars

July 17, 2013 — We value gold for many reasons: its beauty, its usefulness as jewelry, and its rarity. Gold is rare on Earth in part because it’s also rare in the universe. Unlike elements like carbon or iron, it cannot be created within a star. Instead, it must be born in a more cataclysmic event — like one that occurred last month known as a short gamma-ray burst (GRB). Observations of this GRB provide evidence that it resulted from the collision of two neutron stars — the dead cores of stars that previously exploded as supernovae. Moreover, a unique glow that persisted for days at the GRB location potentially signifies the creation of substantial amounts of heavy elements — including gold.”We estimate that the amount of gold produced and ejected during the merger of the two neutron stars may be as large as 10 moon masses — quite a lot of bling!” says lead author Edo Berger of the Harvard-Smithsonian Center for Astrophysics (CfA).A gamma-ray burst is a flash of high-energy light (gamma rays) from an extremely energetic explosion. Most are found in the distant universe. Berger and his colleagues studied GRB 130603B which, at a distance of 3.9 billion light-years from Earth, is one of the nearest bursts seen to date.Gamma-ray bursts come in two varieties — long and short — depending on how long the flash of gamma rays lasts. GRB 130603B, detected by NASA’s Swift satellite on June 3rd, lasted for less than two-tenths of a second.Although the gamma rays disappeared quickly, GRB 130603B also displayed a slowly fading glow dominated by infrared light. Its brightness and behavior didn’t match a typical “afterglow,” which is created when a high-speed jet of particles slams into the surrounding environment.Instead, the glow behaved like it came from exotic radioactive elements. …

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Space-time is not the same for everyone

July 9, 2013 — Before the Big Bang, space-time as we know it did not exist. So how was it born? The process of creating normal space-time from an earlier state dominated by quantum gravity has been studied for years by theorists at the Faculty of Physics, University of Warsaw. Recent analyses suggest a surprising conclusion: not all elementary particles are subject to the same space-time.Several billion years ago, in the era soon after the Big Bang, the Universe was so dense and so hot that elementary particles felt the existence of gravity strongly. For decades, physicists around the world have been attempting to discover the laws of quantum gravity describing this phase of the evolution of the Universe. Recently Professor Jerzy Lewandowski’s group at the Faculty of Physics, University of Warsaw (FUW) proposed its own model of the quantum Universe. Recent studies of its properties, discussed during the 20th International Conference on General Relativity and Gravitation (GR20), being held in Warsaw in conjunction with the 10th Edoardo Amaldi Conference on Gravitational Waves (Amaldi10), have surprised researchers. The analyses performed by Prof. Lewandowski and his PhD student Andrea Dapor show that different elementary particles “experience” the existence of different space-times.One of the attempts to describe quantum gravity is called loop quantum gravity (LQG). This theory assumes that space-time is structurally somewhat similar to a fabric: It consists of a large number of very small fibres entangled in loops. …

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Matter-antimatter asymmetry: Using the sun to illuminate a basic mystery of matter

July 8, 2013 — Antimatter has been detected in solar flares via microwave and magnetic-field data, according to a presentation by NJIT Research Professor of Physics Gregory D. Fleishman and two co-researchers at the 44th meeting of the American Astronomical Society’s Solar Physics Division. This research sheds light on the puzzling strong asymmetry between matter and antimatter by gathering data on a very large scale using the Sun as a laboratory.Share This:While antiparticles can be created and then detected with costly and complex particle-accelerator experiments, such particles are otherwise very difficult to study. However, Fleishman and the two co-researchers have reported the first remote detection of relativistic antiparticles — positrons — produced in nuclear interactions of accelerated ions in solar flares through the analysis of readily available microwave and magnetic-field data obtained from solar-dedicated facilities and spacecraft. That such particles are created in solar flares is not a surprise, but this is the first time their immediate effects have been detected.The results of this research have far-reaching implications for gaining valuable knowledge through remote detection of relativistic antiparticles at the Sun and, potentially, other astrophysical objects by means of radio-telescope observations. The ability to detect these antiparticles in an astrophysical source promises to enhance our understanding of the basic structure of matter and high-energy processes such as solar flares, which regularly have a widespread and disruptive terrestrial impact, but also offer a natural laboratory to address the most fundamental mysteries of the universe we live in.Electrons and their antiparticles, positrons, have the same physical behavior except that electrons have a negative charge while positrons, as their name implies, have a positive charge. This charge difference causes positrons to emit the opposite sense of circularly polarized radio emission, which Fleishman and his colleagues used to distinguish them. To do that required knowledge of the magnetic field direction in the solar flare, provided by NASA’s Solar and Heliospheric Observatory (SOHO), and radio images at two frequencies from Japan’s Nobeyama Radioheliograph. Fleishman and his colleagues found that the radio emission from the flare was polarized in the normal sense (due to more numerous electrons) at the lower frequency (lower energy) where the effect of positrons is expected to be small, but reversed to the opposite sense at the same location, although at the higher frequency (higher energy) where positrons can dominate.Share this story on Facebook, Twitter, and Google:Other social bookmarking and sharing tools:|Story Source: The above story is reprinted from materials provided by New Jersey Institute of Technology. Note: Materials may be edited for content and length. …

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Cloud behavior expands habitable zone of alien planets

July 1, 2013 — A new study that calculates the influence of cloud behavior on climate doubles the number of potentially habitable planets orbiting red dwarfs, the most common type of stars in the universe. This finding means that in the Milky Way galaxy alone, 60 billion planets may be orbiting red dwarf stars in the habitable zone.Researchers at the University of Chicago and Northwestern University based their study, which appears in Astrophysical Journal Letters, on rigorous computer simulations of cloud behavior on alien planets. This cloud behavior dramatically expanded the habitable zone of red dwarfs, which are much smaller and fainter than stars like the sun.Current data from NASA’s Kepler Mission, a space observatory searching for Earth-like planets orbiting other stars, suggest there is approximately one Earth-size planet in the habitable zone of each red dwarf. The UChicago-Northwestern study now doubles that number.”Most of the planets in the Milky Way orbit red dwarfs,” said Nicolas Cowan, a postdoctoral fellow at Northwestern’s Center for Interdisciplinary Exploration and Research in Astrophysics. “A thermostat that makes such planets more clement means we don’t have to look as far to find a habitable planet.”Cowan is one of three co-authors of the study, as are UChicago’s Dorian Abbot and Jun Yang. The trio also provide astronomers with a means of verifying their conclusions with the James Webb Space Telescope, scheduled for launch in 2018.The formula for calculating the habitable zone of alien planets — where they can orbit their star while still maintaining liquid water at their surface — has remained much the same for decades. But the formula largely neglects clouds, which exert a major climatic influence.”Clouds cause warming, and they cause cooling on Earth,” said Abbot, an assistant professor in geophysical sciences at UChicago. “They reflect sunlight to cool things off, and they absorb infrared radiation from the surface to make a greenhouse effect. That’s part of what keeps the planet warm enough to sustain life.”A planet orbiting a star like the sun would have to complete an orbit approximately once a year to be far enough away to maintain water on its surface. “If you’re orbiting around a low mass or dwarf star, you have to orbit about once a month, once every two months to receive the same amount of sunlight that we receive from the sun,” Cowan said.Tightly orbiting planetsPlanets in such a tight orbit would eventually become tidally locked with their sun. …

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Astronomers spy on galaxies in the raw

June 26, 2013 — A CSIRO radio telescope has detected the raw material for making the first stars in galaxies that formed when the Universe was just three billion years old — less than a quarter of its current age. This opens the way to studying how these early galaxies make their first stars.The telescope is CSIRO’s Australia Telescope Compact Array telescope near Narrabri, NSW. “It one of very few telescopes in the world that can do such difficult work, because it is both extremely sensitive and can receive radio waves of the right wavelengths,” says CSIRO astronomer Professor Ron Ekers.The raw material for making stars is cold molecular hydrogen gas, H2. It can’t be detected directly but its presence is revealed by a ‘tracer’ gas, carbon monoxide (CO), which emits radio waves.In one project, astronomer Dr Bjorn Emonts (CSIRO Astronomy and Space Science) and his colleagues used the Compact Array to study a massive, distant conglomerate of star-forming ‘clumps’ or ‘proto-galaxies’ that are in the process of coming together as a single massive galaxy. This structure, called the Spiderweb, lies more than ten thousand million light-years away [at a redshift of 2.16].CSIRO’s Compact Array radio telescope can detect star formation, helping to answer fundamental questions about how early galaxies started forming stars.Dr Emonts’ team found that the Spiderweb contains at least sixty thousand million [6 x 1010] times the mass of the Sun in molecular hydrogen gas, spread over a distance of almost a quarter of a million light-years. This must be the fuel for the star-formation that has been seen across the Spiderweb. “Indeed, it is enough to keep stars forming for at least another 40 million years,” says Emonts.In a second set of studies, Dr Manuel Aravena (European Southern Observatory) and colleagues measured CO, and therefore H2, in two very distant galaxies [at a redshift of 2.7].The faint radio waves from these galaxies were amplified by the gravitational fields of other galaxies — ones that lie between us and the distant galaxies. This process, called gravitational lensing, “acts like a magnifying lens and allows us to see even more distant objects than the Spiderweb,” says Dr Aravena.Dr Aravena’s team was able to measure the amount of H2 in both galaxies they studied. For one (called SPT-S 053816-5030.8), they could also use the radio emission to make an estimate of how rapidly the galaxy is forming stars — an estimate independent of the other ways astronomers measure this rate.The Compact Array’s ability to detect CO is due to an upgrade that has boosted its bandwidth — the amount of radio spectrum it can see at any one time — sixteen-fold [from 256 MHz to 4 GHz], and made it far more sensitive.”The Compact Array complements the new ALMA telescope in Chile, which looks for the higher-frequency transitions of CO,” says Ron Ekers.

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