Les trois satellites Swarm seront déployés à 530 kilomètres d'altitude pour l'un et à 460 kilomètres pour les deux autres

Les trois satellites européens de la constellation Swarm, fabriqués par l’industriel franco-allemand, Astrium, seront lancés cet été depuis la base russe de Plesetsk par une fusée Rockot. Une fois déployés sur leur orbite définitive, à 530 kilomètres d’altitude pour l’un et à 460 kilomètres pour les deux autres, ces trois sondes identiques, en forme de guitare électrique, mesureront le champ magnétique terrestre avec une précision inégalée de 1 milliardième de tesla.

Généré par la rotation du noyau de fer niché au cœur de notre belle planète, ce phénomène physique joue un rôle indispensable de bouclier en détournant le flux de particules (ions, électrons) éjectées par le soleil, responsable des aurores boréales visibles près des pôles. Mais les effets de ce vent solaire sont particulièrement délétères. Sans cette précieuse magnétosphère, toute vie, à commencer par la nôtre, serait impossible sur Terre. D’où l’importance de la mission Swarm, financée par l’Agence spatiale européenne, à hauteur de 220 millions d’euros, lancement compris, dans le cadre de son programme Earth Explorer.

Pendant quatre ans, durée théorique de la mission, les cinq instruments scientifiques présents à bord, en particulier le magnétomètre ASM fourni par le Centre national d’études spatiales (Cnes) et le laboratoire d’électronique (Leti) du CEA, mesureront les variations d’intensité de ce champ magnétique protecteur. Ce qui permettra, le cas échéant, de diffuser des bulletins d’alerte prévenant de l’arrivée de rayons nocifs à la surface de la Terre.

Swarm aidera également à mieux comprendre l’incidence du Soleil sur les cycles météorologiques et le climat, et à mieux prévoir les orages magnétiques susceptibles de perturber les communications terrestres, d’endommager des satellites ou de porter atteinte à la santé des astronautes présents à bord de la Station spatiale internationale (ISS). Les données fournies par Swarm contribueront enfin à améliorer la précision de la navigation pour le trafic aérien et mari­time.

Sur un plan plus fondamental, Swarm permettra d’étudier, depuis l’espace, la structure et les processus internes de notre planète, comme la composition du manteau ou le fonctionnement de la «dynamo terrestre» à l’origine du champ magnétique. «Cent cinquante ans après Jules Verne, nos trois satellites permettront aux scientifiques de réaliser un véritable Voyage au centre de la Terre », s’est félicité, Evert Dudok, le directeur de la division satellites d’Astrium, lors de la présentation de la mission, vendredi, à Munich.

Pour mener à bien toutes ces missions, il a fallu relever un énorme défi technique: «Les scientifiques veulent mesurer le champ magnétique de la Terre, pas celui des satellites», explique M. Dudok. Pour que ces derniers soient magnétiquement neutres, les ingénieurs de l’ESA et d’Astrium ont éliminé tous les matériaux susceptibles de s’aimanter, y compris les céramiques. «La structure est en fibre de carbone, l’antenne est déployable et les circuits électriques sont compensés», explique Yvon Menard, responsable du projet à l’ESA. Du grand art…..

En lire plus: lefigaro.fr

OPERA detector

by Edwin Cartlidge
It appears that the faster-than-light neutrino results, announced last September by the OPERA collaboration in Italy, was due to a mistake after all. A bad connection between a GPS unit and a computer may be to blame.

Physicists had detected neutrinos travelling from the CERN laboratory in Geneva to the Gran Sasso laboratory near L’Aquila that appeared to make the trip in about 60 nanoseconds less than light speed. Many other physicists suspected that the result was due to some kind of error, given that it seems at odds with Einstein’s special theory of relativity, which says nothing can travel faster than the speed of light. That theory has been vindicated by many experiments over the decades.

According to sources familiar with the experiment, the 60 nanoseconds discrepancy appears to come from a bad connection between a fiber optic cable that connects to the GPS receiver used to correct the timing of the neutrinos’ flight and an electronic card in a computer. After tightening the connection and then measuring the time it takes data to travel the length of the fiber, researchers found that the data arrive 60 nanoseconds earlier than assumed. Since this time is subtracted from the overall time of flight, it appears to explain the early arrival of the neutrinos. New data, however, will be needed to confirm this hypothesis.
Read more: news.sciencemag.org

(updated) Read also:

1. ‘Faster than light’ measurement blamed on loose cable

2. OPERA in Question

3. Opera Result Affected By Instrumental Error !

4. Faster-than-light neutrinos could be down to bad wiring

Extragalactic Space Balls

For the first time, NASA’s Spitzer Space Telescope has detected little spheres of carbon, called buckyballs, in a galaxy beyond our Milky Way galaxy. The space balls were detected in a dying star, called a planetary nebula, within the nearby galaxy, the Small Magellanic Cloud. What’s more, huge quantities were found — the equivalent in mass to 15 of our moons.

An infrared photo of the Small Magellanic Cloud taken by Spitzer is shown here in this artist’s illustration, with two callouts. The middle callout shows a magnified view of an example of a planetary nebula, and the right callout shows an even further magnified depiction of buckyballs, which consist of 60 carbon atoms arranged like soccer balls.

In July 2010, astronomers reported using Spitzer to find the first confirmed proof of buckyballs. Since then, Spitzer has detected the molecules again in our own galaxy — as well as in the Small Magellanic Cloud….
Read more: nasa.gov

Jiggling Soccer-Ball Molecules in Space

These data from NASA’s Spitzer Space Telescope show the signatures of buckyballs in space. Buckyballs, also called C60 or buckministerfullerenes, after architect Buckminister Fuller’s geodesic domes, are made of 60 carbon atoms structured like a black-and-white soccer ball. They were first discovered in a lab in 1985, but could not be definitively identified in space until now. Spitzer was able to find their spectral signatures — along with the signatures of their rugby-ball-like relatives, called C70 — by analyzing the infrared light from Tc 1, a planetary nebula consisting of material shed by a dying star.

Buckyballs jiggle, or vibrate, in a variety of ways — 174 ways to be exact. Four of these vibrational modes cause the molecules to either absorb or emit infrared light. All four modes were detected by Spitzer.

The space telescope first gathered light from the area around the dying star — specifically a region rich in carbon — then, with the help of its spectrograph instrument, spread the light into its various components, or wavelengths. Astronomers studied the data, a spectrum like the one shown here, to identify signatures, or fingerprints, of molecules. The four vibrational modes of buckyballs are indicated by the red arrows. Likewise, Spitzer identified four vibrational modes of C70, shown by the blue arrows….
Read more: nasa.gov2

Read more: arxiv.org/pdf

GJ 1214b orbits close to its host star, as this artist's impression shows

Astronomers have confirmed the existence of a new class of planet: a waterworld with a thick, steamy atmosphere.

The exoplanet GJ 1214b is a so-called “Super Earth” – bigger than our planet, but smaller than gas giants such as Jupiter.

Observations using the Hubble telescope now seem to confirm that a large fraction of its mass is water.

The planet’s high temperatures suggest exotic materials might exist there.

“GJ 1214b is like no planet we know of,” said lead author Zachory Berta, from the Harvard Smithsonian Center for Astrophysics.

The planet was discovered in 2009 by ground-based telescopes. It is about 2.7 times the Earth’s diameter, but weighs almost seven times as much. It orbits its red-dwarf star at a distance of just two million km, meaning temperatures on GJ 1214b probably reach above 200C.

In 2010, astronomers released measurements of its atmosphere. These suggested that GJ 1214b’s atmosphere was probably made up of water, but there was another possibility – that the planet was covered in a haze, of the type that envelopes Saturn’s moon Titan.

Hot ice

Mr Berta and his colleagues used the Hubble Space Telescope’s wide-field camera to study the planet as it crossed in front of its star – a transit. During these transits, the star’s light is filtered through the planet’s atmosphere, giving clues to the mixture of gases present.

The researchers said their results are more consistent with a dense atmosphere of water vapour, than one with a haze.

Calculations of the planet’s density also suggest that GJ 1214b has more water than Earth. This means the internal structure of this world would be very different to that of our own.

“The high temperatures and pressures would form exotic materials like ‘hot ice’ or ‘superfluid water’, substances that are completely alien to our everyday experience,” said Dr Berta.

The planet’s short distance from Earth makes it a likely candidate for follow-up observations with the James Webb Space Telescope, which may launch by the end of this decade.

The study has been accepted for publication by the Astrophysical Journal….

Read more: www.bbc.co.uk

Artist impression of binary system containing stellar-mass black hole IGR J17091. (NASA/CXC/M.Weiss)

Astronomers using NASA’s Chandra X-ray Observatory have clocked the fastest wind yet discovered blowing off a disk around a stellar-mass black hole. This result has important implications for understanding how this type of black hole behaves.

The record-breaking wind is moving about 20 million mph, or about 3 percent of the speed of light. This is nearly 10 times faster than had ever been seen from a stellar-mass black hole.

Stellar-mass black holes are born when extremely massive stars collapse. They typically weigh between five and 10 times the mass of the sun. The stellar-mass black hole powering this super wind is known as IGR J17091-3624, or IGR J17091 for short.

“This is like the cosmic equivalent of winds from a category five hurricane,” said Ashley King from the University of Michigan, lead author of the study published in the Feb. 20 issue of The Astrophysical Journal Letters. “We weren’t expecting to see such powerful winds from a black hole like this.”

The wind speed in IGR J17091 matches some of the fastest winds generated by supermassive black holes, objects millions or billions of times more massive.

“It’s a surprise this small black hole is able to muster the wind speeds we typically only see in the giant black holes,” said co-author Jon M. Miller, also from the University of Michigan. “In other words, this black hole is performing well above its weight class.”

Another unanticipated finding is that the wind, which comes from a disk of gas surrounding the black hole, may be carrying away more material than the black hole is capturing.

“Contrary to the popular perception of black holes pulling in all of the material that gets close, we estimate up to 95 percent of the matter in the disk around IGR J17091 is expelled by the wind,” King said.

Unlike winds from hurricanes on Earth, the wind from IGR J17091 is blowing in many different directions. This pattern also distinguishes it from a jet, where material flows in highly focused beams perpendicular to the disk, often at nearly the speed of light.

Simultaneous observations made with the National Radio Astronomy Observatory’s Expanded Very Large Array showed a radio jet from the black hole was not present when the ultra-fast wind was seen, although a radio jet is seen at other times. This agrees with observations of other stellar-mass black holes, providing further evidence the production of winds can stifle jets.

The high speed for the wind was estimated from a spectrum made by Chandra in 2011. Ions emit and absorb distinct features in spectra, which allow scientists to monitor them and their behavior. A Chandra spectrum of iron ions made two months earlier showed no evidence of the high-speed wind, meaning the wind likely turns on and off over time.

Astronomers believe that magnetic fields in the disks of black holes are responsible for producing both winds and jets. The geometry of the magnetic fields and rate at which material falls towards the black hole must influence whether jets or winds are produced.

IGR J17091 is a binary system in which a sun-like star orbits the black hole. It is found in the bulge of the Milky Way galaxy, about 28,000 light years away from Earth….
Read more: nasa.gov

OLD DNA A plant has been generated from the fruit of a little arctic flower, making it the oldest one by far that has been grown from ancient tissue (nytimes.com)

A plant that last flowered when woolly mammoths roamed the plains is back in bloom.

Biologists have resurrected a 30,000-year-old plant, cultivating it from fruit tissue recovered from frozen sediment in Siberia. The plant is by far the oldest to be brought back from the dead: the previous record holder was a sacred lotus, dating back about 1200 years.

The late David Gilichinsky from the Soil Cryology Laboratory in Moscow, Russia, and colleagues recovered the fruits of the ice age flowering plant (Silene stenophylla) from a fossilised squirrel burrow in frozen sediments near the Kolyma river in north-east Siberia. Radiocarbon dating of the fruit suggests the squirrel stashed it around 31,800 years ago, just before the ice rolled in.

By applying growth hormones to the fruit tissue, Gilichinsky and his colleagues managed to kick-start cell division and ultimately produce a viable flowering plant.

Modern day S. stenophylla looks similar to the resurrected plant, but has larger seeds and fewer buds. Modern plants also grow roots more rapidly. Studying these and other differences will reveal how the plant has evolved since the last ice age…….
Read more: newscientist.com and nytimes.com

A Hertzsprung-Russell diagram for stars of one solar mass in environments with varying asymmetric dark matter densities. At lower densities (blue and purple lines), the stars are brighter, while at higher densities (green and orange lines), the stars are cooler when compared to stars on the standard path that contain no dark matter. Image credit: Iocco, et al. ©2012 American Physical Society

Finding evidence for dark matter – the unknown substance that theoretically makes up 23% of the universe – has been one of the biggest challenges in modern cosmology. Several experiments are underway to detect dark matter candidates known as Weakly Interacting Massive Particles (WIMPs) as they travel through the Earth. And experiments at the Large Hadron Collider (LHC) are trying to produce WIMPs through proton beam collisions. Now in a new study, scientists have shown that feebly annihilating dark matter particles captured inside a star can provide an additional source of energy to the star, resulting in changes to its structure and appearance. Observing these stars could potentially offer scientists a tool to detect and analyze this kind of dark matter…….
Read more: physorg.com

This shows the largest of the newly detected graben found in highlands of the lunar farside. The broadest graben is about 500 meters (1,640 feet) wide and topography derived from Lunar Reconnaissance Orbiter Camera (LROC) Narrow Angle Camera (NAC) stereo images indicates they are almost 20 meters (almost 66 feet) deep. (Credit: NASA/Goddard/Arizona State University/Smithsonian Institution)

New images from NASA’s Lunar Reconnaissance Orbiter (LRO) spacecraft show the moon’s crust is being stretched, forming minute valleys in a few small areas on the lunar surface. Scientists propose this geologic activity occurred less than 50 million years ago, which is considered recent compared to the moon’s age of more than 4.5 billion years.

A team of researchers analyzing high-resolution images obtained by the Lunar Reconnaissance Orbiter Camera (LROC) show small, narrow trenches typically much longer than they are wide. This indicates the lunar crust is being pulled apart at these locations. These linear valleys, known as graben, form when the moon’s crust stretches, breaks and drops down along two bounding faults. A handful of these graben systems have been found across the lunar surface.

“We think the moon is in a general state of global contraction because of cooling of a still hot interior,” said Thomas Watters of the Center for Earth and Planetary Studies at the Smithsonian’s National Air and Space Museum in Washington, and lead author of a paper on this research appearing in the March issue of the journal Nature Geoscience. “The graben tell us forces acting to shrink the moon were overcome in places by forces acting to pull it apart. This means the contractional forces shrinking the moon cannot be large, or the small graben might never form.”

The weak contraction suggests that the moon, unlike the terrestrial planets, did not completely melt in the very early stages of its evolution. Rather, observations support an alternative view that only the moon’s exterior initially melted forming an ocean of molten rock.

In August 2010, the team used LROC images to identify physical signs of contraction on the lunar surface, in the form of lobe-shaped cliffs known as lobate scarps. The scarps are evidence the moon shrank globally in the geologically recent past and might still be shrinking today. The team saw these scarps widely distributed across the moon and concluded it was shrinking as the interior slowly cooled.

Based on the size of the scarps, it is estimated that the distance between the moon’s center and its surface shrank by approximately 300 feet. The graben were an unexpected discovery and the images provide contradictory evidence that the regions of the lunar crust are also being pulled apart.

“This pulling apart tells us the moon is still active,” said Richard Vondrak, LRO Project Scientist at NASA’s Goddard Space Flight Center in Greenbelt, Md. “LRO gives us a detailed look at that process.”

As the LRO mission progresses and coverage increases, scientists will have a better picture of how common these young graben are and what other types of tectonic features are nearby. The graben systems the team finds may help scientists refine the state of stress in the lunar crust.

“It was a big surprise when I spotted graben in the far side highlands,” said co-author Mark Robinson of the School of Earth and Space Exploration at Arizona State University, principal investigator of LROC. “I immediately targeted the area for high-resolution stereo images so we could create a three-dimensional view of the graben. It’s exciting when you discover something totally unexpected and only about half the lunar surface has been imaged in high resolution. There is much more of the moon to be explored.”

The research was funded by the LRO mission, currently under NASA’s Science Mission Directorate at NASA Headquarters in Washington. LRO is managed by NASA’s Goddard Space Flight Center in Greenbelt, Md.

Read more: spaceref.com - nasa.gov

http://youtu.be/h6_4bXkGAas

Nearly all the information astronomers have of the atmospheres of alien planets or exoplanets comes from worlds whose orbits happen to be precisely aligned from our vantage point. Once per orbit, these exoplanets go in front of (transit) their host stars from our point of view, and the light from these stars passes through the atmospheres of these planets on its way to Earth. The molecules in these alien atmospheres absorb some of this starlight, resulting in patterns known as spectra that allow scientists to identify what they are.

However, “we know of many other planets that do not transit their host stars, and we therefore know almost nothing about those atmospheres,” said astronomer Sloane Wiktorowicz at University of California, Santa Cruz. Indeed, “less than 10 percent of the known exoplanets have had their atmospheres detected. This is because planets are at least a thousand times fainter than their host stars.”

Instead of looking at starlight that has passed through alien atmospheres on its way to Earth, Wiktorowicz and his colleagues aim to look for light that has scattered off alien atmospheres. This strategy should work equally well for exoplanets in both transiting and non-transiting orbits, “which will open up many previously unstudied planets for exploration,” he explained.

Tripping the Light Fantastic

To understand how this strategy works, one can think of all light waves as electric fields rippling either up and down, left and right, or at any angle in between, a property known as polarization. When starlight gets scattered off a planet’s atmosphere, its polarization changes in a way that makes it distinct from both the direct light from a star and the light bouncing off the surface of a planet. Analyzing this polarization, a technique known as polarimetry, could yield details not only concerning the existence of an alien atmosphere, but also its composition and how it might be structured into different layers.

As a planet passes in front of its parent star, the brightness of the star decreases. Credit: Hans Deeg

“Polarimetry provides extra information over photometry — measuring planet brightness at different colors — because there is extra information encoded in the polarization of scattered light,” said astrophysicist Sara Seager at the Massachusetts Institute of Technology, who was the first to propose polarimetry studies for exoplanets. “This extra information can tell us whether or not clouds or hazes are present, and something about the properties of the clouds or hazes. It’s information that is difficult to get any other way.”

The canonical example are the clouds of Venus, Seager explained. “Very early in planetary atmosphere studies, people thought Venus could potentially have water clouds,” she said. Although photometry measurements of Venus could not uniquely identify the droplets in these clouds, polarimetry studies from ground-based measurements reported in the early 1970s discovered the Venusian clouds were sulfuric acid droplets, findings confirmed via spacecraft sent to the the planet.

With polarimetry, “we can tell if clouds are present on exoplanets and potentially what clouds are made of,” Seager said.

“It’s a completely new way to look at extrasolar planets, a completely novel technique for getting information,” said astronomer Greg Laughlin at the University of California, Santa Cruz, who did not take part in this research. “It’s very hard to get any information about what extrasolar planets are like — we can detect they exist, but anything that can tell you about their physical properties other than that is extraordinarily valuable. Also, it doesn’t require a billion-dollar build-up — we can do it with existing resources. I think Sloane’s on the ground floor of something that’s going to be a big deal.”

A major advantage of this strategy “is that we may be able to study the composition of exoplanet atmospheres with comparatively small, ground-based telescopes,” Wiktorowicz explained. This is crucial for future exoplanet research, given the difficulty in funding space-based observatories such as the James Webb Space Telescope.

One disadvantage of this method is that the farther the planet orbits from its star, the fainter it will be. This means only the closest-in planets can be studied with this technique, which means it won’t be of much help finding new exoplanets — existing planet-hunting strategies are already quite good at discovering worlds that are near their stars, Wiktorowicz said. Still, he noted this method is not meant to find new planets — “rather, it’s meant to study planets we already know about.”

POLISH2 See the Light

To see how starlight is polarized, Wiktorowicz and his colleagues developed a polarimeter based on bars of glass that vibrate tens of thousands of times per second. These “photoelastic modulators” will each very subtly alter a select polarization of light while leaving others unchanged. The latest version of his instrument, POLISH2, has two of these vibrating glass bars, which allows it to simultaneously detect all the key polarizations of light.

The search for exoplanet atmospheres using polarimetry has taken place for nearly two years with POLISH2, which is attached to the Lick Observatory’s 3-meter telescope.

“It’s amazing to think that we might be able to see light scattered from the surface of a planet tens of light years away,” Wiktorowicz said.

Bright yellow lines in the absorption-line spectrum are produced by the sodium content in the planet's atmosphere

Although POLISH2 should already be precise enough to detect exoplanets, “the issue is whether my system, and the stars themselves, are stable enough to allow such detections,” Wiktorowicz said. Many factors might affect what the instrument observes on a nightly basis. “Any changes to the telescope or the atmosphere or anything else might cause a change in measurements — the amount of dust that settles on a telescope mirror from one night to the next can actually affect what you see,” he explained.

To overcome this challenge, the researchers have to account for all the minute disturbances the polarimeter may experience nightly — to set the scale to zero, essentially. They do this by looking at nearby stars. The light from these stars tends to have almost no polarization, and thus helps calibrate every other measurement the instrument makes. In contrast, light from more distant stars has encountered more interstellar dust grains, which can reflect away some polarizations of light but not others, making the light from them that does reach Earth polarized.

Such calibration observations are very time-consuming — “about a third of every night is spent on them,” Wiktorowicz said.

To increase his chances of finding planets, “I’m currently working on improving my data-processing software, because squeezing out every last drop of information from 500 gigabytes of data per night can be difficult,” Wiktorowicz said. “Once this is done, I will re-analyze my old data, while gathering new data as well, and hopefully detect some planets.”

This strategy involves monitoring exoplanet systems at different times in that world’s orbit. “I’m spending most of my effort on two stars known to have one planet each,” Wiktorowicz said. “But I have recently added three more stars, and the list will increase with time.” In the end, “I hope to be able to study a few tens of exoplanets,” he added.
Bringing polarimetry to a 10-meter telescope would enable analysis of still more exoplanets. “A larger telescope should allow smaller, Neptune-sized planets to be detected, which are thought to be much different from larger, Jupiter-sized planets,” Wiktorowicz said. There has even been interest in bringing instruments similar to POLISH2 to the 30-meter telescopes that groups in Europe the United States and elsewhere are contemplating building. “Of course, we have to prove that it works on the smaller telescopes first,” he added.

Spectrum of planet around HR 8799. Credit: ESO/M. Janson

Seager , who did not participate on this work, noted, “research with exoplanets is pushed forward only when people like Sloane are brave enough and bold enough to push a technology most people don’t think is viable.”

Wiktorowicz and his colleagues detailed their findings Jan. 11 at the annual meeting of the American Astronomical Society in Austin, Texas.

Read more: astrobio.net

On Feb. 20, 1962, John Glenn rode the Friendship 7 capsule into space, the first time an American orbited the Earth. In this image, Glenn enters the capsule with assistance from technicians (space.com)

Fifty years ago, on February 20th, 1962 John Glenn became the first American astronaut to orbit the earth. This is a 1962 Universal Newsreel about his historic flight.

http://youtu.be/qY87RTXzA04

Read also: A Salute to John Glenn, 50 Years of American Manned Spaceflight

http://youtu.be/fdLAN18CSDE

The Vela Pulsar and its surrounding pulsar wind nebula

Pulsars, superdense neutron stars, are perhaps the most extraordinary physics laboratories in the Universe. Research on these extreme and exotic objects already has produced two Nobel Prizes. Pulsar researchers now are poised to learn otherwise-unavailable details of nuclear physics, to test General Relativity in conditions of extremely strong gravity, and to directly detect gravitational waves with a “telescope” nearly the size of our Galaxy.
Neutron stars are the remnants of massive stars that exploded as supernovae. They pack more than the mass of the Sun into a sphere no larger than a medium-sized city, making them the densest objects in the Universe, except for black holes, for which the concept of density is theoretically irrelevant. Pulsars are neutron stars that emit beams of radio waves outward from the poles of their magnetic fields. When their rotation spins a beam across the Earth, radio telescopes detect that as a “pulse” of radio waves.
By precisely measuring the timing of such pulses, astronomers can use pulsars for unique “experiments” at the frontiers of modern physics. Three scientists presented the results of such work, and the promise of future discoveries, at the American Association for the Advancement of Science meeting in Vancouver, British Columbia.
Pulsars are at the forefront of research on gravity. Albert Einstein published his theory of General Relativity in 1916, and his description of the nature of gravity has, so far, withstood numerous experimental tests. However, there are competing theories.
“Many of these alternate theories do just as good a job as General Relativity of predicting behavior within our Solar System. One area where they differ, though, is in the extremely dense environment of a neutron star,” said Ingrid Stairs, of the University of British Columbia.
In some of the alternate theories, gravity’s behavior should vary based on the internal structure of the neutron star.
“By carefully timing pulsar pulses, we can precisely measure the properties of the neutron stars. Several sets of observations have shown that pulsars’ motions are not dependent on their structure, so General Relativity is safe so far,” Stairs explained.
Recent research on pulsars in binary-star systems with other neutron stars, and, in one case, with another pulsar, offer the best tests yet of General Relativity in very strong gravity. The precision of such measurements is expected to get even better in the future, Stairs said.
Another prediction of General Relativity is that motions of masses in the Universe should cause disturbances of space-time in the form of gravitational waves. Such waves have yet to be directly detected, but study of pulsars in binary-star systems have given indirect evidence for their existence. That work won a Nobel Prize in 1993.
Now, astronomers are using pulsars throughout our Milky Way Galaxy as a giant scientific instrument to directly detect gravitational waves.
“Pulsars are such extremely precise timepieces that we can use them to detect gravitational waves in a frequency range to which no other experiment will be sensitive,” said Benjamin Stappers, of the University of Manchester in the UK.
By carefully timing the pulses from pulsars widely scattered within our Galaxy, the astronomers hope to measure slight variations caused by the passage of the gravitational waves. The scientists hope such Pulsar Timing Arrays can detect gravitational waves caused by the motions of supermassive pairs of black holes in the early Universe, cosmic strings, and possibly from other exotic events in the first few seconds after the Big Bang.
“At the moment, we can only place limits on the existence of the very low-frequency waves we’re seeking, but planned expansion and new telescopes will, we hope, result in a direct detection within the next decade,” Stappers said.
With densities as much as several times greater than that in atomic nuclei, pulsars are unique laboratories for nuclear physics. Details of the physics of such dense objects are unknown.
“By measuring the masses of neutron stars, we can put constraints on their internal physics,” said Scott Ransom of the National Radio Astronomy Observatory. “Just in the past three to four years, we’ve found several massive neutron stars that, because of their large masses, rule out some exotic proposals for what’s going on at the centers of neutron stars,” Ransom said.
The work is ongoing, and more measurements are needed. “Theorists are clever, so when we provide new data, they tweak their exotic models to fit what we’ve found,” Ransom said….
Read more: physorg.com

A voltage applied across the electrodes induces a current in the perpendicular electrodes, with the phosphorus atom making it all possible

In a remarkable feat of micro-engineering, UNSW physicists have created a working transistor consisting of a single atom placed precisely in a silicon crystal.

http://youtu.be/ue4z9lB5ZHg

Read more here

hubblesite.org

Read also: Peek into Isaac Newton’s theology papers

APOCALYPSE – Isaac Newton a prophétisé la fin du monde pour 2060

Une gravure de Sir Isaac Newton (AP Photo)

La controverse fait rage depuis des décennies : sir Isaac Newton, l’un des plus grands scientifiques de l’histoire, mort en 1727, était-il versé dans la théologie et le mysticisme ? Aux yeux de tous, Newton est celui qui a révolutionné la physique, les mathématiques et l’astronomie aux XVII^e et XVIII^e siècles, définissant notamment la loi de la gravité universelle et les trois lois du mouvement auxquelles il a donné son nom. Et pour beaucoup de nos contemporains, science et religion ne peuvent faire bon ménage.

“Contrairement à son image publique, la plupart des travaux de Newton n’étaient pas consacrés à la science mais davantage à la théologie, au mysticisme et à l’alchimie”, avance pourtant Haaretz. Le quotidien israélien en veut pour preuve les archives que vient de rendre publiques la Bibliothèque nationale d’Israël. Quelque sept mille cinq cents pages manuscrites d’archives, numérisées et mises en ligne en libre consultation dans le cadre du Projet Newton de l’université de Cambridge, qui dévoilent l’autre facette du grand scientifique britannique. Celle d’un influent théologien qui appliquait son approche scientifique à l’étude des textes sacrés, et notamment du mysticisme juif.

“De notre point de vue, il y a une contradiction entre les sciences naturelles et le rationalisme d’un côté, la théologie, le mysticisme et la foi de l’autre. Mais, dans son esprit, en tant que produit de son temps, comprendre les lois de la nature impliquait de comprendre comment le monde fonctionne”, explique Milka Levy-Rubin, commissaire de la collection de sciences humaines de la Bibliothèque nationale d’Israël.

AN -48 AVANT L’APOCALYPSE

Parmi les pages vieillies, une incroyable prédiction : la fin du monde aura lieu en 2060. Mais, quelle pomme a bien pu lui tomber sur la tête ? Cette conclusion, le physicien l’a tirée non pas au terme de savants calculs mathématiques, mais en lisant entre les lignes de la Bible et du Livre de Daniel de l’Ancien Testament. Newton est parti de la date symbolique du sacre de Charlemagne, en 800 ap. J.-C. Se référant au Livre de Daniel, qui selon lui prévoyait la fin du monde mille deux cent soixante ans plus tard, il a établi que la fin des temps serait 2060 (voir l’index des documents relatifs aux prophéties de Newton). Le décompte est lancé.

Les archives témoignent des heures passées par sir Isaac Newton dans les textes sacrés et les écrits mystiques. Tout aussi intéressantes sont les nombreuses tentatives qu’il a esquissées pour imaginer ce à quoi la fin des temps pourrait bien ressembler et les cartes qu’il a dessinées pour l’assister dans son calcul de l’apocalypse.

UNE SOMME THÉOLOGIQUE

Extrait d'un écrit manuscrit de sir Isaac Newton (capture d'écran)

Pour la commissaire des collections, l’importance des écrits théologiques du physicien britannique vont au-delà de l’édification intellectuelle qu’ils révèlent. C’est donc un véritable trésor qui s’est retrouvé sur les étagères de la Bibliothèque nationale par “un mélange de chance et de coïncidence”, rapporte Haaretz.

Cent cinquante ans après sa mort, les descendants de sir Isaac Newton ont transféré ses manuscrits à l’université de Cambridge, où le physicien avait étudié. L’université n’a retenu que ses écrits scientifiques et a rendu les autres manuscrits à ses descendants. En 1936, ces manuscrits ont été proposé aux enchères chez Sotheby’s, à Londres. Mais, au même moment, son concurrent Christie’s organisait une vente d’art impressionniste, bien plus attendue.

Une aubaine pour les deux seuls acheteurs : le célèbre économiste John Maynard Keynes et le collectionneur et orientaliste juif Abraham Shalom Yehuda, qui se sont partagé la collection. A Keynes, les manuscrits d’alchimie et à Yehuda, les écrits théologiques. A la mort du collectionneur, en 1969, ces précieux documents ont été donnés à la Bibliothèque nationale d’Israël.

lemonde.fr

The mosaic image captured by the Mars Express orbiter is colour-coded for elevation, showing the valleys and cliffs thought to have been carved out by ancient floods on the surface

The Tiu Vallis region on the surface is dotted with buttes, valleys and craters thought to have been carved out by energetic masses of liquid in the distant past

The flows of water have 'carved into' the Martian surface to a depth of 1,500 metres - impact craters also stand out from the landscape

The mosaic images were captured in 10 orbits of the Mars Express orbiter, and show an area 235 miles long

Read more: www.dailymail.co.uk

A view of one of the three events found by FINUDA: a schematic frontal view of the apparatus is shown, and the two blue lines represent the two 'pi' mesons moving along opposite bent trajectories in the magnetic field of the apparatus. Image credit: FINUDA collaboration

Physicists in Italy have discovered the first evidence of a rare nucleus that doesn’t exist in nature and lives for just 10-10 seconds before decaying. It’s a type of hypernucleus that, like all nuclei, contains an assortment of neutrons and protons. But unlike ordinary nuclei, hypernuclei also contain at least one hyperon, a particle that consists of three quarks, including at least one strange quark. Hypernuclei are thought to form the core of strange matter that may exist in distant parts of the universe, and could also allow physicists to probe the inside of the nucleus.

The particular hypernucleus investigated here, called “hydrogen six Lambda” (⁶_ΛH), was first predicted to exist in 1963. Now, in a study published in a recent issue of Physical Review Letters, physicists working in the FINUDA experiment at the Istituto Nazionale di Fisica Nucleare – Laboratori Nazionali di Frascati (INFN-LNF) in Frascati, Italy, have reported finding the first evidence for the particle. The FINUDA collaboration’s analysis of millions of events has turned up three events for the rare hypernucleus.

Strange properties

As its name suggests, ⁶_ΛH is a large type of hydrogen nucleus that consists of six particles: four neutrons, one proton, and one Lambda (Λ) hyperon. Since an ordinary hydrogen nucleus contains one proton and no neutrons, hydrogen nuclei that contain one or more neutrons are sometimes called “heavy hydrogen.” The most common types of heavy hydrogen are deuterium (which has one neutron) and tritium (which has two neutrons). Since ⁶_ΛH has four neutrons plus a L hyperon, physicists refer to it as “heavy hyperhydrogen.”

The L hyperon, which consists of one up, one down, and one strange quark, does an even more interesting thing to ⁶_ΛH: it increases its lifetime from 10^-22seconds (the lifetime of the hypernucleus core ⁵H without L) to 10^-10seconds. When scientists first discovered the L hyperon in 1947, they observed a similarly longer lifetime than predicted for this “strange” object. That observation led to the idea of the existence of the strange quark, with strangeness being the property that causes the quark to live so long.

Detection

Without the L hyperon, it would likely be impossible for physicists to directly observe a hydrogen nucleus with four neutrons, since such a heavy isotope is very difficult to produce and has a very short lifetime. Another hypernucleus, ⁴_ΛH, which has two neutrons instead of four, is more easily produced than ⁶_ΛH in similar experiments and has been detected many times. But detecting evidence of ⁶_ΛH is much more difficult. The 27 million collision events analyzed by the FINUDA collaboration represents about one full year of continuous data-taking from an experiment that spanned several years. Theoretically, the formation probability of ⁶_ΛH is at least 100 times smaller than that of ⁴_ΛH….
Read more: physorg.com

ALMA Prototype Radio Antennas

….. The Event Horizon Telescope (EHT)  is an international project aimed at taking the first picture of a black hole, specifically of Sagittarius A*, the site of the black hole that is believed to be lurking at the center of our Milky Way galaxy…..

….. Getting there will require a blend of new technology, old tricks, and the anointing of a brand-new radio telescope array that will come online over the next few years.
But Doeleman and the various collaborators building the EHT are now confident that what wasn’t even thinkable just a few years ago is now within reach, as technology has turned a time-tested astronomical technique into a tool that should give us our first glimpse of Einstein’s vision of gravity’s most violent manifestation.
That technique is very long baseline interferometry (VLBI), and it’s what allows the EHT team to build a telescope the size of Earth without actually building anything at all.
By feeding data from radio telescopes around the world into a supercomputer, they can create a telescope with an imaging area the size of the entire planet, allowing them to capture images in radio wavelengths at resolutions that should let them see straight to the heart of the Milky Way
Think of VLBI like this: You’re standing at the center of the galaxy, looking at Earth, which is way out at the Milky Way’s fringe.
Now, imagine Earth as a mirror, but only the places where there are radio telescope arrays on its surface are polished–the rest of this planet-sized mirror is blacked out.
These polished spots are the only places on the mirror that can collect data. This sparse mirror wouldn’t provide a very complete picture to someone peering through the other end.
But now imagine the Earth rotating. The polished portions of the lens–the parts collecting data–begin to slowly move across the blacked-out areas of the mirror, collecting data from different points on its surface as rotation and the seasonal tilt of the planet continue.
Eventually, the telescopes–and there are many scattered all over the globe–have collected data from positions all over this lens, just not all at the same time. Over months and years, this data is sufficient to stitch together a rather thorough view roughly equivalent to that captured by an Earth-sized telescope mirror.
That’s VLBI. By linking the data from many telescopes together, the EHT can generate a virtual telescope, with a data-gathering surface the size of the planet.
Their data is time-stamped by a hydrogen maser atomic clock, ensuring that given enough computing power, all the radio data can be neatly stitched together into a single picture. And given enough time, and as more radio telescopes come online, that picture grows clearer and clearer.
Up to a point, at least. VLBI has been employed by astronomers for decades, but an undertaking like the EHT wasn’t possible previously. The technology simply wasn’t there yet. It’s really not even there now, but it’s so close that Doeleman and his EHT colleagues can begin gathering data.
“We have the opportunity to make measurements that weren’t possible five years ago,” Doeleman says. “In the last five years, we’ve developed instrumentation to carry out VLBI at the highest frequencies where you get very good resolution.
We can also now swallow large swaths of bandwidth. Instead of a couple of hundred megahertz, we can now swallow many gigahertz.
You can think of that as being more energy, more photons from the black hole itself. That means our sensitivity goes way up. So it’s a combination of higher sensitivity and more telescopes around the Earth that’s letting us do what we couldn’t five years ago.
The technology is at a point now that it’s a matter of implementation rather than building new systems.”…..

Read more: popsci.com

Read also: Time crystals could behave almost like perpetual motion machines

If crystals exist in spatial dimensions, then they ought to exist in the dimension of time too, says Nobel prize-winning physicist

One of the most powerful ideas in modern physics is that the Universe is governed by symmetry. This is the idea that certain properties of a system do not change when it undergoes a transformation of some kind.

For example, if a system behaves the same way regardless of its orientation or movement in space, it must obey the law of conservation of momentum.

If a system produces the same result regardless of when it takes place, it must obey the law of conservation of energy.

We have the German mathematician, Emmy Noether, to thank for this powerful way of thinking. According to her famous theorem, every symmetry is equivalent to a conservation law. And the laws of physics are essentially the result of symmetry.

Equally powerful is the idea of symmetry breaking. When the universe displays less symmetry than the equations that describe it, physicists say the symmetry has been broken.

A well known example is the low energy solution associated with the precipitation of a solid from a solution—the formation of crystals, which have a spatial periodicity. In this case the spatial symmetry breaks down.

Spatial crystals are well studied and well understood. But they raise an interesting question: does the universe allow the formation of similar periodicities in time?

Today, Frank Wilczek at the Massachussettsi Institute of Technology and Al Shapere at the University of Kentucky, discuss this question and conclude that time symmetry seems just as breakable as spatial symmetry at low energies.

This process should lead to periodicities that they call time crystals. What’s more, time crystals ought to exist, probably under our very noses.

Let’s explore this idea in a bit more detail. First, what does it mean for a system to break time symmetry? Wilczek and Shapere think of it like this. They imagine a system in its lowest energy state that is completely described, independently of time.

Because it is in its lowest energy state,  this system ought to be frozen in space. Therefore, if the system moves, it must break time symmetry. This is equivalent tot he idea that the lowest energy state has a minimum value on a curve on space rather than at a single isolated point

That’s actually not so extraordinary. Wilczek points out that a superconductor can carry a current—the mass movement of electrons—even in its lowest energy state.

The rest is essentially mathematics. In the same way that the equations of physics allow the spontaneous formation of  spatial crystals, periodicities in space, so they must also allow the formation of periodicities in time or time crystals.

In particular, Wilczrek considers spontaneous symmetry breaking in a closed quantum mechanical system. This is where the mathematics become a little strange. Quantum mechanics forces physicists to think about imaginary values of time or iTime, as Wilczek calls it.

He shows that the same periodicities ought to arise in iTime and that this should manifest itself as periodic behaviour of various kinds of thermodynamic properties.

That has a number of important consequences. First up is the possibility that this process provides a mechanism for measuring time, since the periodic behaviour is like a pendulum. “The spontaneous formation of a time crystal represents the spontaneous emergence of a clock,” says Wilczek.

Another is the possibility that it may be possible to exploit time crystals to perform computations using zero energy. As Wilczek puts it, “it is interesting to speculate that a…quantum mechanical system whose states could be interpreted as a collection of qubits, could be engineered to traverse a programmed landscape of structured states in Hilbert space over time.”

Altogether this is a simple argument. But simplicity is often  deceptively powerful. Of course, there will be disputes over some of the issues this raises. One of them is that the motion that breaks time symmetry seems a little puzzling. Wilczek and Shapere acknowledge this: “Speaking broadly speaking, what we’re looking for looks perilously close to perpetual motion.”

That will need some defending. But if anyone has the pedigree to push these ideas forward, it’s Wilczek, who is a Nobel prize winning physicist.

We’ll look forward to the ensuing debate.

technologyreview.com

Refs:  arxiv.org/abs/1202.2539: Quantum Time Crystals

arxiv.org/abs/1202.2537 Classical Time Crystals