Have astronomers demonstrated that dead stars can reignite ?

Astronomers using ESA’s Integral gamma-ray observatory have demonstrated beyond doubt that dead stars known as white dwarfs can reignite and explode as supernovae. The finding came after the unique signature of gamma rays from the radioactive elements created in one of these explosions was captured for the first time. (from esa.int ) 

The explosions in question are known as Type Ia supernovae, long suspected to be the result of a white dwarf star blowing up because of a disruptive interaction with a companion star. However, astronomers have lacked definitive evidence that a white dwarf was involved until now. The ‘smoking gun’ in this case was evidence for radioactive nuclei being created by fusion during the thermonuclear explosion of the white dwarf star.

Supernova_explosion_node_full_image_2“Integral has all the capabilities to detect the signature of this fusion, but we had to wait for more than ten years for a once-in-a-lifetime opportunity to catch a nearby supernova,” says Eugene Churazov, from the Space Research Institute (IKI) in Moscow, Russia and the Max Planck Institute for Astrophysics,in Garching, Germany.

Although Type Ia supernovae are expected to occur frequently across the Universe they are rare occurrences in any one galaxy, with typical rates of one every few hundred years.

Integral’s chance came on 21 January 2014, when students at the University College London’s teaching observatory at Mill Hill, UK detected a type Ia supernova, later named SN2014J, in the nearby galaxy M82.

According to the theory of such explosions, the carbon and oxygen found in a white dwarf should be fused into radioactive nickel during the explosion. This nickel should then quickly decay into radioactive cobalt, which would itself subsequently decay, on a somewhat longer timescale, into stable iron.

Because of its proximity – at a distance of about 11.5 million light-years from Earth, SN2014J is the closest of its type to be detected in decades – Integral stood a good chance of seeing the gamma rays produced by the decay. Within one week of the initial discovery, an observing plan to use Integral had been drawn-up and approved.

Using Integral to study the aftermath of the supernova explosion, scientists looked for the signature of cobalt decay – and they found it, in exactly the quantities that the models predicted.

“The consistency of the spectra, obtained by Integral 50 days after the explosion, with that expected from cobalt decay in the expanding debris of the white dwarf was excellent,” says Churazov, who is lead author of a paper describing this study and reported in the journal Nature.

With that confirmation in hand, other astronomers could begin to look into the details of the process. In particular, how the white dwarf is detonated in the first place.

White dwarfs are inert stars that contain up to 1.4 times the mass of the Sun squeezed into a volume about the same size as the Earth. Being inert, they can’t simply blow themselves up. Instead, astronomers believe that they leech matter from a companion star, which builds up on the surface until a critical total mass is reached. At that point, the pressure in the heart of the white dwarf triggers a catastrophic thermonuclear detonation.

Early Integral observations of SN2014J tell a somewhat different story, and have been the focus of a separate study, reported online in Science Express by Roland Diehl from the Max Planck Institute for Extraterrestrial Physics, Germany, and colleagues.

Diehl and his colleagues detected gamma rays from the decay of radioactive nickel just 15 days after the explosion. This was unexpected, because during the early phase of a Type Ia supernova, the explosion debris is thought to be so dense that the gamma rays from the nickel decay should be trapped inside.

“We were puzzled by this surprising signal, and some from the group even thought it must be wrong,” says Diehl. “We had long and ultimately very fruitful discussions about what might explain these data.”

A careful examination of the theory showed that the signal would have been hidden only if the explosion had begun in the heart of the white dwarf. Instead, Diehl and colleagues think that what they are seeing is evidence for a belt of gas from the companion star that must have built up around the equator of the white dwarf. This outer layer detonated, forming the observed nickel and then triggering the internal explosion that became the supernova.

“Regardless of the fine details of how these supernovae are triggered, Integral has proved beyond doubt that a white dwarf is involved in these stellar cataclysms,” says Erik Kuulkers, ESA’s Integral Project Scientist. “This clearly demonstrates that even after almost twelve years in operation, Integral is still playing a crucial role in unraveling some of the mysteries of the high-energy Universe.”

Mandela laid to rest in Qunu, ending a journey that transformed the south of Africa

With military pomp and traditional rituals, South Africa buried Nelson Mandela on Sunday, the end of an exceptional journey for the prisoner turned president who transformed the nation. (from cnn.com)

tata madiba

Mandela was laid to rest in his childhood village of Qunu.

Tribal leaders clad in animal skins joined dignitaries in dark suits at the grave site overlooking the rolling green hills.

As pallbearers walked toward the site after a funeral ceremony, helicopters whizzed past dangling the national flag. Cannons fired a 21-gun salute, its echoes ringing over the quiet village.

Mandela’s widow, Graca Machel, dabbed her eyes with a handkerchief as she watched the proceedings.

“Yours was truly a long walk to freedom. Now you have achieved the ultimate freedom in the bosom of God, your maker,” an officiator at the grave site said.

Military pallbearers gently removed the South African flag that draped the coffin and handed it to President Jacob Zuma, who gave it to Mandela’s family.

At the request of the family, the lowering of the casket was closed to the media.

Sony PS4 dev kit FCC filing shows off extra ports, 2.75GHz max clock frequency

Sony proudly showed off its PlayStation 4 hardware for the first time at E3, and now we’re getting a peek at what developers are working with this generation thanks to the FCC. (from engadget.com)


Sony PS4 dev kit FCC filing shows off extra ports, 275GHz max clock speed

The DUH-D1000AA prototype Development Kit for PS4 is listed in these documents, tested for its Bluetooth and 802.11 b/g/n WiFi radios. As one would expect, the diagrams show it eschews the sleek design of the consumer model for extra cooling, a shape made for rack mounts plus extra indicator lights and ports. Also of note is a “max clock frequency” listing of 2.75GHz, and although we don’t know how fast the game system will run by default, it’s interesting to hear what all that silicon may be capable of (as a commenter points out below, that may relate to the system’s 8GB of GDDR5 RAM) while maintaining a temperature between 5 and 35 degrees celsius. Hit the link below to check out the documents for yourself, after seeing this and the system’s controller become a part of the FCC’s database all we’re left waiting for is Mark Cerny’s baby.

Sony PS4 development kit FCC filing pops up with extra pot

Creating electricity with caged atoms

Clathrates are crystals consisting of tiny cages in which single atoms can be enclosed. These atoms significantly alter the material properties of the crystal. By trapping cerium atoms in a clathrate, scientists at the Vienna University of Technology have created a material which has extremely strong thermoelectric properties. It can be used to turn waste heat into electricity. (from phys.org)

A lot of energy is wasted when machines turn hot, unnecessarily heating up their environment. Some of this thermal energy could be harvested using thermoelectric materials; they create electric current when they are used to bridge hot and cold objects. At the Vienna University of Technology (TU Vienna), a new and considerably more efficient class of thermoelectric materials can now be produced. It is the material’s very special crystal structure that does the trick, in connection with an astonishing new physical effect; in countless tiny cages within the crystal, cerium atoms are enclosed. These trapped magnetic atoms are constantly rattling the bars of their cage, and this rattling seems to be responsible for the material’s exceptionally favourable properties.

“Clathrates” is the technical term for crystals, in which host atoms are enclosed in cage-like spaces. “These clathrates show remarkable thermal properties”, says Professor Silke Bühler-Paschen (TU Vienna). The exact behaviour of the material depends on the interaction between the trapped atoms and the cage surrounding them. “We came up with the idea to trap cerium atoms, because their magnetic properties promised particularly interesting kinds of interaction”, explains Bühler-Paschen.
For a long time, this task seemed impossible. All earlier attempts to incorporate magnetic atoms such as the rare-earth metal cerium into the clathrate structures failed. With the help of a sophisticated crystal growth technique in a mirror oven, Professor Andrey Prokofiev (TU Vienna) has now succeeded in creating clathrates made of barium, silicon and gold, encapsulating single cerium atoms.

The thermoelectric properties of the novel material have been tested. Thermoelectrics work when they connect something hot with something cold: “The thermal motion of the electrons in the material depends on the temperature”, explains Bühler-Paschen. “On the hot side, there is more thermal motion than on the cold side, so the electrons diffuse towards the colder region. Therefore, a voltage is created between the two sides of the thermoelectric material.”

Experiments show that the cerium atoms increase the material’s thermopower by 50%, so a much higher voltage can be obtained. Furthermore, the thermal conductivity of clathrates is very low. This is also important, because otherwise the temperatures on either side would equilibrate, and no voltage would remain.

“The reason for these remarkably good material properties seem to lie in a special kind of electron-electron correlation – the so-called Kondo effect”, Silke Bühler-Paschen believes. The electrons of the cerium atom are quantum mechanically linked to the atoms of the crystal. Actually, the Kondo effect is known from low temperature physics, close to absolute zero temperature. But surprisingly, these quantum mechanical correlations also play an important role in the novel clathrate materials, even at a temperature of hundreds of degrees Celcius.

“The rattling of the trapped cerium atoms becomes stronger as the temperature increases”, says Bühler-Paschen. “This rattling stabilizes the Kondo effect at high temperatures. We are observing the world’s hottest Kondo effect.”

The research team at TU Vienna will now try to achieve this effect also with different kinds of clathrates. In order to make the material commercially more attractive, the expensive gold could possibly be substituted by other metals, such as copper. Instead of cerium, a cheaper mixture of several rare-earth elements could be used. There are high hopes that such designer clathrates can be technologically applied in the future, to turn industrial waste heat into valuable electrical energy.

First Flight of Japanese ‘Artificial Intelligence’ Rocket

More than five decades of rocketry from Japan’s Kagoshima Prefecture will continue with the maiden voyage of the new Epsilon vehicle to insert an ultraviolet observatory into low-Earth orbit to observe Venus, Mars, and Jupiter. The 700-pound Spectroscopic Planet Observatory for Recognition of Interaction of Atmosphere (SPRINT-A) will utilize an extreme ultraviolet spectrometer and guiding camera and will spend about a year in orbit. Yet as exciting as this scientific payload may be, the Epsilon itself carries much promise for the Japan Aerospace Exploration Agency (JAXA). The rocket’s project manager has described it as a vehicle which will literally “open up the future.” (from americaspace.com)

The 78-foot-tall Epsilon vehicle marries one Solid Rocket Booster (SRB) from the H-IIA rocket as its first stage with upper-stage hardware from the 2006-retired M-V rocket. As a launcher, it is reportedly capable of transporting up to 2,600 pounds of payload into low-Earth orbit. Originally scheduled to fly on 22 August from the Uchinoura Space Center in Kagoshima, its launch date was postponed as JAXA required additional time to resolve a problem surrounding an incorrect line routing in the signal relay equipment used to check Epsilon’s critical functions.

Yet it is the cost savings—estimated to be about 30 percent better than the M-V—which JAXA is particularly keen to stress. The launch is estimated to cost in the range of 5.3 billion yen ($53 million), significantly lower than the 7 billion yen ($70 million) fee for an M-V, and such savings have been made partially through the streamlining of launch procedures. It is anticipated that subsequent Epsilon launches may bring costs still lower, into the 3.0-3.8 billion yen ($30-38 million) bracket.

Japan has been flying solid-fueled “pencil” rockets since the mid-1950s, and Epsilon stands firmly upon the shoulders of previous titans and utilizes new, cutting-edge technology. “We aim to greatly simplify the launch system by using artificial intelligence,” said Project Manager Yasuhiro Morita, quoted in a JAXA interview. Morita is a professor in the Department of Space Systems and Astronautics with the Institute of Space and Astronautical Science (ISAS), a subdivision of JAXA. “Today, a typical scenario is hundreds of people assembling at the launch center and working for several months in preparation for a launch. On the day of the launch, dozens of people are in the control room, monitoring every aspect. The Epsilon launch vehicle will drastically change this picture.” By running autonomous health and other checks, supported by artificial intelligence, it is hoped that control personnel with ultimately be able to run the whole show from a pair of laptop computers.

“Rockets use technology from many generations ago,” explained Morita, “so they are like a showcase of deficiencies. There has long been a notion that new technology should be tested over an extended period of time before being used in actual launch vehicles. Consequently, the latest artificial intelligence applications have not yet been employed in rockets. The Epsilon launch vehicle will be the first rocket with artificial intelligence that will perform checks and monitor its own operation autonomously.”

Moving forward from desktop and laptop computers, it is Morita’s hope that by 2017 the Epsilon will be in a position to “monitor and judge its own flight safety autonomously, so that we can remove the radar and antenna used to track and send commands to the rocket.” By assigning further artificial intelligence assets to the vehicle—including the capability to act as its own Range Safety Officer and destroy itself in the event of off-nominal events—the Epsilon will eliminate the need for expensive, ground-based hardware and further simplify launch and tracking facilities.

As the maiden flight of the Epsilon, the mission has attracted a great deal of publicity, both in Japan and around the world. In April-May 2013, it was the subject of a New Launch Vehicle Message Posting Campaign. Some 5,812 messages—the vast majority in Japanese and a few hundred in other languages—were received as part of an effort to share individuals’ “expectations, hopes, dreams, or feelings toward our new launch vehicle.” JAXA then processed these messages into strings of small letters on the Epsilon itself, in order to “make people feel more familiar with space, gaining more understanding of and support for space programs.” According to JAXA, this was a key goal of the Epsilon project.

Testing and processing of the new rocket has gone relatively smoothly, with its upper stage motor static-fired in September 2011 to evaluate the performance of insulation material, followed by last October’s extension test of the second stage motor nozzle. More recently, in April 2013, it was reported that a full-scale model of Epsilon had been transferred from the maintenance tower to the launch pad to demonstrate rollout and other pre-launch protocols.

Liftoff will begin with the ignition of the first-stage’s Nissan-built solid motor, producing an estimated 505,000 pounds of thrust. This will burn for about two minutes, after which the second stage—a modified version of the M-V’s M-34 upper stage, also solid-fueled, with an extendible nozzle—will pick up the thrust for 104 seconds to execute the next stage of the rocket’s climb to orbit. The third stage, based upon the KM-V2b upper stage from the M-V, will then fire for approximately 91 seconds, after which a hydrazine-fed small liquid propulsion system will provide the final boost. According to JAXA’s Epsilon press kit, this final stage will perform two burns and SPRINT-A will be separated from the vehicle about 61 minutes after launch.

The satellite is expected to operate for about a year in an orbit of 590-715 miles, inclined 31 degrees to the equator, from which it will observe the magnetospheric environments of Venus, Mars, and Jupiter. “Capturing the extreme ultraviolet rays emitted from a planet and its periphery, which cannot be observed from the ground, allows us to collect information on the atmosphere that flows into space and the magnetosphere covering the planet,” noted JAXA in its SPRINT-A mission brochure. “This enables us to analyze the composition of the atmosphere and the behavior of the magnetosphere. Our primary theme is each planet’s magnetosphere, the region where the magnetic field of a planet has influence.” Jupiter’s magnetic field is 10,000 times stronger than that of Earth and rotates on its axis at a high rate of around 10 hours per cycle, whereas those of Venus and Mars are far weaker. SPRINT-A will focus on the interactions between planetary magnetospheres and the solar wind.

Guardian says Britain forced it to destroy Snowden material

 

 

The editor of The Guardian Rusbridger leaves Downing Street in London

WASHINGTON/RIO DE JANEIRO (Reuters) – The Guardian, a major outlet for revelations based on leaks from former U.S. intelligence contractor Edward Snowden, says the British government threatened legal action against the newspaper unless it either destroyed the classified documents or handed them back to British authorities.(from news.yahoo.com)

In an article posted on the British newspaper’s website on Monday, Guardian editor Alan Rusbridger said that a month ago, after the newspaper had published several stories based on Snowden’s material, a British official advised him: “You’ve had your fun. Now we want the stuff back.”

Rusbridger’s disclosure follows Sunday’s detainment at London’s Heathrow Airport under British anti-terrorism laws of David Miranda, domestic partner of U.S. journalist and Guardian writer Glenn Greenwald.

Miranda, a Brazilian citizen in transit from Berlin to Brazil, said he was released without charge after nine hours of questioning but minus his laptop, cellphone and memory sticks.

Greenwald, who met face to face in Hong Kong with Snowden and has written or co-authored many of the newspaper’s stories about U.S. surveillance of global communications, vowed on Monday to publish more documents and said Britain will “regret” detaining his partner.

Rusbridger said that after further talks with the British government, two “security experts” from Government Communications Headquarters, the British equivalent of the ultra-secretive U.S. National Security Agency, visited the Guardian’s London offices.

In the building’s basement, Rusbridger wrote, government officials watched as computers which contained material provided by Snowden were physically pulverized. “We can call off the black helicopters,” Rusbridger says one of the officials joked.

A source familiar with the event said Guardian employees destroyed the computers as government security experts looked on.

Rusbridger, in his article, said he told British officials that due to the nature of “international collaborations” among journalists, it would remain possible for media organizations to “take advantage of the most permissive legal environments.” Henceforth, he said, the Guardian “did not have to do our reporting from London.”

A source familiar with the matter said that this meant British authorities were on notice that the Guardian was likely to continue to report on the Snowden revelations from outside British government jurisdiction.

‘HAD YOUR DEBATE’

Rusbridger said that in meetings with British officials, before the computers were destroyed, he told them the Guardian could not do its journalistic duty if it gave in to the government’s requests.

In response, he wrote, a government official told him that the newspaper had already achieved the aim of sparking a debate on government surveillance. “You’ve had your debate. There’s no need to write any more,” the unnamed official was quoted as saying.

The Guardian’s decision to publicize the government threat – and the newspaper’s assertion that it can continue reporting on the Snowden revelations from outside of Britain – appears to be the latest step in an escalating battle between the news media and governments over reporting of secret surveillance programs.

One U.S. security official told Reuters that one of the main purposes of the British government’s detention and questioning of Miranda was to send a message to recipients of Snowden’s materials, including the Guardian, that the British government was serious about trying to shut down the leaks.

White House spokesman Josh Earnest told reporters on Monday that while the United States did not ask British authorities to detain Miranda, British officials had given the United States a “heads up” about the British government’s plan to question him.

Greenwald, asked by a reporter if the detention of his partner would deter him from future reporting, said the opposite would happen.

“I will be far more aggressive in my reporting from now. I am going to publish many more documents. I am going to publish things on England, too. I have many documents on England’s spy system,” Greenwald, speaking in Portuguese, told reporters at Rio de Janeiro’s airport where he met Miranda upon his return to Brazil.

During Miranda’s trip to Berlin, which the Guardian said it had paid for, he visited with Laura Poitras, an independent film-maker who was the first journalist to interact with Snowden. Poitras co-authored stories based on Snowden’s material for the Washington Post and the German magazine Der Spiegel.

Greenwald told the New York Times that Miranda went to Berlin to deliver materials downloaded by Snowden to Poitras and to acquire from Poitras a different set of materials for delivery to Greenwald, who lives with Miranda near Rio de Janeiro.

Greenwald told the Forbes website that “everything” Miranda had “was heavily encrypted.” Greenwald did not immediately respond to an email from Reuters requesting comment.

While British authorities confirmed that Miranda had been detained under an anti-terrorism law, they did not further explain their actions. Brazil’s government complained about Miranda’s detention in a statement on Sunday that said the use of the British anti-terrorism law was unjustified.