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28th October 2015

From science fiction to reality – a sonic tractor beam

UK researchers have invented a sonic tractor beam that can move small objects up to 40cm.


sonic tractor beam 2015 technology
Asier Marzo, PHD student and lead author, levitating a polystyrene ball with soundwaves.


Tractor beams are mysterious rays that can grab and lift objects. The concept was created by science-fiction writers, but has since come to fascinate scientists and engineers. A team of researchers at the Universities of Sussex and Bristol, in collaboration with tech firm Ultrahaptics, have demonstrated a working tractor beam that uses high-amplitude soundwaves to generate an "acoustic hologram" able to pick up and move small objects.

This technique, published yesterday in Nature Communications, could be developed for a wide range of applications. For example, a sonic production line could transport delicate objects and assemble them, without any physical contact. Or a miniature version could grip and transport drug capsules or microsurgical instruments through living tissue.

Sriram Subramanian, Professor of Informatics at the University of Sussex and co-founder of Ultrahaptics, explained: "In our device we manipulate objects in mid-air and seemingly defy gravity. We can individually control dozens of loudspeakers to tell us an optimal solution to generate an acoustic hologram that can manipulate multiple objects in real-time without contact."




The researchers used an array of 64 miniature loudspeakers, driven at 40Khz, to create high-pitched and high-intensity sound waves to levitate a spherical bead (4mm in diameter) made of expanded polystyrene. The whole system consumes 9 Watts of power. The tractor beam works by surrounding the object with high-intensity sound, creating a force field that keeps the objects in place. By controlling the output of the loudspeakers with extreme precision, an object can be either held in place, moved or rotated.

Asier Marzo, PhD student and the lead author, said: "It was an incredible experience the first time we saw the object held in place by the tractor beam. All my hard work has paid off. It's brilliant."

Bruce Drinkwater, Professor of Ultrasonics in the University of Bristol's Department of Mechanical Engineering, added: "We all know that soundwaves can have a physical effect. But here we have managed to control the sound to a degree never previously achieved."

The team have shown that three different shapes of acoustic force fields work as tractor beams. The first is an acoustic force field that resembles a pair of fingers or tweezers; the second is an acoustic vortex, with objects becoming trapped at the core; the third is best described as a high-intensity cage that surrounds objects and holds them in place from all directions.

Previous work on acoustic studies had to surround the object with loudspeakers, which limits the extent of movement and restricts many applications. Last year, the University of Dundee presented the concept of a tractor beam, but no objects were held in the ray.

The team is now designing different variations of this system: a much bigger version with a different working principle that aims to levitate a soccer ball from a distance of 10 metres; and a smaller version, targeted at manipulating tiny particles inside the human body.


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24th September 2015

New world record for quantum teleportation distance

Researchers at the National Institute of Standards and Technology (NIST) have "teleported" or transferred quantum information carried in light particles over 100 kilometres (km) of optical fibre, four times farther than the previous record.


quantum teleportation world record distance 2015


Researchers at NIST have “teleported” or transferred quantum information carried in light particles over 100 km (62 miles) of optical fibre – four times farther than the previous record. The experiment confirmed that quantum communication is feasible over long distances in fibre. Other research groups have teleported quantum information over longer distances in free space, but the ability to do so over conventional fibre-optic lines offers more flexibility for network design.

Not to be confused with Star Trek's fictional "beaming up" of people, quantum teleportation involves the transfer, or remote reconstruction, of information encoded in quantum states of matter or light. Teleportation is useful in both quantum communications and quantum computing, which offer prospects for novel capabilities such as unbreakable encryption. The basic method for quantum teleportation was first proposed more than 20 years ago and has been performed by a number of research groups, including one at NIST using atoms in 2004.

The new record, described in Optica, involved transferring quantum information contained in one photon – its specific time slot in a sequence – to another photon transmitted over 102 km of spooled fibre in a laboratory in Colorado. The achievement was made possible by advanced single-photon detectors designed and made at NIST.


quantum teleportation world record distance 2015


"Only about 1 percent of photons make it all the way through 100 km of fibre," says NIST's Marty Stevens. "We never could have done this experiment without these new detectors, which can measure this incredibly weak signal."

Until now, so much quantum data was lost in fibre that transmission rates and distances were low. This new teleportation technique could be used to make devices called quantum repeaters that could resend data periodically, in order to extend network reach, perhaps enough to eventually build a "quantum internet." Previously, researchers thought quantum repeaters might need to rely on atoms or other matter, instead of light – a difficult engineering challenge that would also slow down transmission.

Various quantum states can be used to carry information; the NIST experiment used quantum states that indicate when in a sequence of time slots a single photon arrives. This method is novel, in that four of NIST's photon detectors were positioned to filter out specific quantum states. The detectors rely on superconducting nanowires made of molybdenum silicide. They can record over 80 percent of arriving photons, revealing whether they are in the same or different time slots, each just 1 nanosecond long. The experiments were performed at wavelengths commonly used in telecommunications. Below is an infographic with more details.


quantum teleportation world record distance 2015


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29th August 2015

Breakthrough in fusion energy

U.S. physicists have achieved a breakthrough in fusion power by containing superheated hydrogen plasma for five milliseconds, far longer than any other effort before.

California-based Tri Alpha Energy reportedly held gas in a steady state at 10,000,000°C – only stopping when they ran out of fuel. Particle physicist and adviser to the secretive company, Burton Richter of Stanford University, comments: "They've succeeded finally in achieving a lifetime limited only by the power available to the system."

"Until you learn to control and tame [the hot gas], it's never going to work. In that regard, it's a big deal. They seem to have found a way to tame it," says Jaeyoung Park, head of rival fusion startup Energy/Matter Conversion Corporation in San Diego. "The next question is how well can you confine [heat in the gas]. I give them the benefit of the doubt. I want to watch them for the next 2 or 3 years."

Tri Alpha Energy's reactor is based on field-reversed configuration (FRC). This was first observed in the laboratory in the late 1950s. For decades, research on FRC was limited to plasma lasting for a maximum of only 0.3 milliseconds. In recent experiments, Tri Alpha Energy achieved a huge increase of up to two milliseconds. During their latest attempts, reported this week in the journal Science, angled beams at higher energies of 10 megawatts maintained stability for even longer – five milliseconds without decaying.

The company's goal is to scale their technique up to longer times and higher temperatures (3 billion degrees Celsius), such that atomic nuclei will collide with enough force to fuse and release energy. Tri Alpha Energy intends to dismantle their current machine and build a more powerful version in 2016. Houyang Guo, Chief Experimental Strategist, during a recent physics seminar at the University of Wisconsin–Madison, revealed that confinement times of 100 milliseconds to one second might be possible in the near future. Ultimately, fusion reactors could supply humanity with a practically limitless supply of clean energy.




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20th July 2015

New massless particle is observed for the first time

Scientists report the discovery of the Weyl fermion after an 85-year search. This massless quasiparticle could lead to future electronics that are faster and with less waste heat.


weyl fermion massless particle 2015 science


An international team led by Princeton University scientists has discovered an elusive massless particle, first theorised 85 years ago. This particle is known as the Weyl fermion, and could give rise to faster and more efficient electronics, because of its unusual ability to behave as both matter and antimatter inside a crystal. Weyl fermions, if applied to next-generation electronics, could allow a nearly free and efficient flow of electricity in electronics – and thus greater power – especially for computers. The researchers report their discovery in the journal Science.

Proposed by the mathematician and physicist Hermann Weyl in 1929, Weyl fermions have been long sought by scientists, because they are regarded as possible building blocks of other subatomic particles, and are even more basic than electrons. Their basic nature means that Weyl fermions could provide a much more stable and efficient transport of particles than electrons, the main particle behind modern electronics. Unlike electrons, Weyl fermions are massless and possess a high degree of mobility.

"The physics of the Weyl fermion are so strange – there could be many things that arise from this particle that we're just not capable of imagining now," explained Professor M. Zahid Hasan, who led the team.

The researchers' find differs from other particle discoveries, in that the Weyl fermion can be reproduced and potentially applied. Particles such as the Higgs boson are typically detected in the fleeting aftermath of collisions. The Weyl fermion, however, was captured inside a specially designed synthetic metallic crystal called tantalum arsenide.


weyl fermion massless particle 2015 science
Professor M. Zahid Hasan


The Weyl fermion has two characteristics that could improve future electronics, possibly helping to continue the exponential growth in computer power, while also proving useful in developing efficient quantum computing. Firstly, they behave like a composite of monopole- and antimonopole-like particles inside a crystal. This means that Weyl particles that have opposite, magnetic-like charges, can nonetheless move independently of each other with a high degree of mobility. Secondly, Weyl fermions can be used to create massless electrons that move very quickly with no backscattering. In electronics, backscattering hinders efficiency and generates heat. While normal electrons are lost when they collide with an obstruction, Weyl electrons simply move through and around roadblocks.

"It's like they have their own GPS and steer themselves without scattering," said Hasan. "They will move and move only in one direction since they are either right-handed or left-handed and never come to an end because they just tunnel through. These are very fast electrons that behave like unidirectional light beams and can be used for new types of quantum computing."

Hasan and his group researched and simulated dozens of crystal structures before finding the one suitable for holding Weyl fermions. Once fashioned, the crystals were loaded into a scanning tunnelling spectromicroscope (pictured above) and cooled to near absolute zero. Crystals passing the spectromicroscope test were taken to the Lawrence Berkeley National Laboratory in California, for testing with high-energy photon beams. Once fired through the crystal, the beams' shape, size and direction indicated the presence of the long-elusive Weyl fermion.

The hunt for the Weyl fermion began in the earliest days of quantum theory, when physicists first realised that their equations implied the existence of antimatter counterparts to electrons and other commonly known particles.

"People figured that although Weyl's theory was not applicable to relativity or neutrinos, it is the most basic form of fermion and had all other kinds of weird and beautiful properties that could be useful," said Hasan.

"After more than 80 years, we found that this fermion was already there, waiting. It is the most basic building block of all electrons," he said. "It is exciting that we could finally make it come out following Weyl's 1929 theoretical recipe."


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15th July 2015

Large Hadron Collider discovers new particle

After a 50 year hunt, scientists have reported strong evidence of a new particle – the pentaquark.


large hadron collider pentaquark 2015 science


The LHCb experiment at CERN's Large Hadron Collider (LHC) has reported the discovery of a class of particles known as pentaquarks. The team has submitted a paper reporting these findings to the journal Physical Review Letters.

"The pentaquark is not just any new particle," said LHCb spokesperson Guy Wilkinson. "It represents a way to aggregate quarks – namely the fundamental constituents of ordinary protons and neutrons in a pattern that has never been observed before in over 50 years of experimental searches. Studying its properties may allow us to understand better how ordinary matter, the protons and neutrons from which we're all made, is constituted."

Our understanding of the structure of matter was revolutionised in 1964 when American physicist, Murray Gell-Mann, proposed that a category of particles known as baryons, which includes protons and neutrons, are comprised of three fractionally charged objects called quarks, and that another category, mesons, are formed of quark-antiquark pairs. Gell-Mann was awarded the Nobel Prize in physics for this work in 1969. This quark model also allows the existence of other quark groups, such as pentaquarks – composed of four quarks and an antiquark. Until now, however, no conclusive evidence for pentaquarks had been seen.

"Benefitting from the large data set provided by the LHC, and the excellent precision of our detector, we have examined all possibilities for these signals, and conclude that they can only be explained by pentaquark states", says LHCb physicist Tomasz Skwarnicki of Syracuse University. "More precisely the states must be formed of two up quarks, one down quark, one charm quark and one anti-charm quark."


2015 pentaquark data


LHCb researchers looked for pentaquark states by examining the decay of a baryon known as Λb (Lambda b) into three other particles, a J/ψ- (J-psi), a proton and a charged kaon. Earlier experiments that have searched for pentaquarks have proved inconclusive. Where the LHCb experiment differs is that it has been able to look for pentaquarks from many perspectives, with all pointing to the same conclusion. It's as if the previous searches were looking for silhouettes in the dark, whereas LHCb conducted the search with the lights on, and from all angles. The next step in the analysis will be to study how the quarks are bound together within the pentaquarks.

"The quarks could be tightly bound," said LHCb physicist Liming Zhang of Tsinghua University, "or they could be loosely bound in a sort of meson-baryon molecule, in which the meson and baryon feel a residual strong force similar to the one binding protons and neutrons to form nuclei."

More studies will be needed to distinguish between these possibilities, and to see what else pentaquarks can teach us. The new data that LHCb will collect in LHC run 2 will allow progress to be made on these questions.


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3rd June 2015

The Large Hadron Collider is reactivated

The Large Hadron Collider has been reactivated after a two-year pause, during which upgrades and repairs were taking place. The machine is now able to experiment with higher energies, increasing from 8 to 13 trillion electron volts (TeV).


large hadron collider 2015 technology


Today, CERN's Large Hadron Collider (LHC) started delivering physics data for the first time in 27 months. After a two year shutdown and several months recommissioning, the LHC is now providing collisions to all of its experiments at the unprecedented energy of 13 TeV (6.5 Tev per beam), a more than 50% increase from the collision energy of its first run. This marks the start of season 2 at the LHC, opening the way to new discoveries. The LHC will now run round the clock for the next three years.

"With the LHC back in the collision-production mode, we celebrate the end of two months of beam commissioning," said Frédérick Bordry, CERN Director of Accelerators and Technology. "It is a great accomplishment and a rewarding moment for all of the teams involved in the work performed during the long shutdown of the LHC, in the powering tests and in the beam commissioning process. All these people have dedicated so much of their time to making this happen."

Today at 10.40am local time, the LHC operators declared "stable beams", a signal for the LHC experiments that they can start taking data. Beams are made of "trains" of proton bunches, moving at almost the speed of light around the 27 km ring of the LHC. These so-called bunch trains circulate in opposite directions, guided by powerful superconducting magnets. Today the LHC was filled with 6 bunches each containing around 100 billion protons. This rate will be progressively increased as the run goes on to 2,800 bunches per beam, allowing the LHC to produce up to 1 billion collisions per second.

During the first run of the LHC, the ATLAS and CMS experiments announced the discovery of the so-called Higgs boson, which was the last piece of the puzzle known as the Standard Model, a theory that describes the fundamental particles from which everything visible in the universe is made, along with interactions at work between them.


standard model


"The first 3-year run of the LHC, which culminated with a major discovery in July 2012, was only the start of our journey. It is time for new physics!" said CERN Director General Rolf Heuer. "We have seen the first data beginning to flow. Let's see what they will reveal to us about how our universe works."

With run 2 starting today, physicists have the ambition to further explore the Standard Model and even to find evidence of new physics phenomena beyond its boundaries, which could explain remaining mysteries such as dark matter, believed to make up about a quarter of the universe, or nature's apparent preference for matter over antimatter, without which we would not exist.

Over the two-year shutdown, the four large experiments – ALICE, ATLAS, CMS and LHCb – also went through an important programme of maintenance and improvements in preparation for the new energy frontier.


lhc diagram


"The collisions we are seeing today indicate that the work we have done in the past two years to prepare and improve our detector has been successful and marks the beginning of a new era of exploration of the secrets of nature," said CMS spokesperson Tiziano Camporesi. "We can hardly express our excitement within the collaboration: this is especially true for the youngest colleagues."

"The successful restart of physics data-taking, with all systems in great shape to collect, process and analyse the new data quickly, is a testament to the commitment and immense hard work of very many people from across ATLAS during the long shutdown," said Dave Charlton, spokesperson for ATLAS. "We are now starting to delve into the new data to see what nature has in store for us at these new unexplored energies."

"All within the collaboration are tremendously excited that the new run has now begun," said LHCb spokesperson Guy Wilkinson. "It will allow us to follow up on puzzles from our run-1 studies, and to probe with higher sensitivity the difference in behaviour between matter and antimatter."

"Proton-proton collisions will provide essential reference data for the run with heavy-ion beams foreseen for the end of the year, in which the LHC will provide both higher energy and luminosity as compared to run 1," said ALICE spokesperson Paolo Giubellino. "In addition, we plan to extend the exploration of the intriguing signals that have emerged from Run 1."

There are plans for even larger experiments in the decades ahead. China is planning a 52 km (32.5 mi) particle accelerator – twice the circumference of the LHC – with construction beginning in 2019 and the first tests in 2028. Meanwhile, a successor to the LHC known as the Very Large Hadron Collider (VLHC) with 50 TeV per beam is planned for 2035.


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20th May 2015

A breakthrough in large-scale graphene fabrication

One of the barriers to using graphene at a commercial scale could be overcome using a new method demonstrated by researchers at the Department of Energy's Oak Ridge National Laboratory (ORNL).


graphene future timeline technology


Graphene – a material stronger and stiffer than carbon fibre – has enormous commercial potential, but has been impractical to employ on a large scale, with researchers limited to using only small flakes of it. Now, using chemical vapour deposition, a team at the ORNL has fabricated polymer composites that contain 2-inch-by-2-inch sheets of the one-atom thick, hexagonally arranged carbon atoms.

The findings, reported in the journal Applied Materials & Interfaces, could help usher in a new era of flexible electronics and change the way this reinforcing material is viewed and ultimately used.

"Before our work, superb mechanical properties of graphene were shown at a micro scale," said Ivan Vlassiouk, who led the research. "We have extended this to a larger scale, which considerably extends the potential applications and market for graphene."

While most approaches for polymer nanocomposition construction employ tiny flakes of graphene or other carbon nanomaterials that are difficult to disperse in the polymer, the team used larger sheets of graphene. This eliminates the flake dispersion and agglomeration problems, allowing the material to better conduct electricity with less actual graphene in the polymer.


graphene future timeline technology


"In our case, we were able to use chemical vapour deposition to make a nanocomposite laminate that is electrically conductive – with graphene loading that is fifty times less compared to current state-of-the-art samples," said Vlassiouk. This is a key to making the material competitive on the market.

If Vlassiouk and his team can reduce the cost and demonstrate scalability, researchers envision graphene being used in aerospace (structural monitoring, flame-retardants, anti-icing, conductive), the automotive sector (catalysts, wear-resistant coatings), structural applications (self-cleaning coatings, temperature control materials), electronics (displays, printed electronics, thermal management), energy (photovoltaics, filtration, energy storage) and manufacturing (catalysts, barrier coatings, filtration).


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24th March 2015

Huge lava tubes could house cities on Moon

Old lava tubes big enough to house entire cities could be structurally stable on the moon, according to a theoretical study presented at the Lunar and Planetary Science Conference.


lava tubes cities on moon


Lava tubes big enough to house cities could be structurally stable on the moon, according to a theoretical study presented at the Lunar and Planetary Science Conference. These volcanic features could be an important target for human space exploration in the future, because they could provide shelter from cosmic radiation, meteorite impacts and temperature extremes.

Lava tubes are tunnels formed from the lava flow of volcanic eruptions. The edges of the lava cool as it flows to form a pipe-like crust around the flowing river of lava. When the eruption ends and the lava flow stops, the pipe drains leave behind a hollow tunnel, said Jay Melosh, a Purdue University distinguished professor of earth, atmospheric and planetary sciences who is involved in the research.

"There has been some discussion of whether lava tubes might exist on the moon," he said. "Some evidence, like the sinuous rilles observed on the surface, suggest that if lunar lava tubes exist they might be really big."

Sinuous rilles are large channels visible on the lunar surface thought to be formed by lava flows. The sinuous rilles range in size up to 10 km wide, and the Purdue team explored whether lava tubes of the same scale could exist.

David Blair, a graduate student in Purdue's Department of Earth, Atmospheric and Planetary Sciences, led the study that examined whether empty lava tubes more than 1 km wide could remain structurally stable on the moon.

"We found that if lunar lava tubes existed with a strong arched shape like those on Earth, they would be stable at sizes up to 5,000 metres, or several miles wide, on the moon," Blair said. "This wouldn't be possible on Earth, but gravity is much lower on the moon and lunar rock doesn't have to withstand the same weathering and erosion. In theory, huge lava tubes – big enough to easily house a city – could be structurally sound on the moon."

Blair worked with Antonio Bobet, a Purdue professor of civil engineering, and applied known information about lunar rock and the moon's environment to civil engineering technology used to design tunnels on Earth. The team found that a lava tube's stability depended on the width, roof thickness and the stress state of the cooled lava, and the team modelled a range of these variables. The researchers also modelled lava tubes with walls created by lava placed in one thick layer and with lava placed in many thin layers, Blair said.

Only one other study, published in 1969, has attempted to model lunar lava tubes, he said.


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18th March 2015

Revolutionary 3-D printing method is 100 times faster

A new 3-D printer uses light and oxygen to synthesise materials from a pool of liquid, up to 100 times faster and with far more accuracy than previous methods.




A new 3-D printing technology has been developed by Silicon Valley startup, Carbon3D Inc., enabling objects to rise from a liquid media continuously – rather than being built layer-upon-layer as they have been for the past 25 years. This method represents a fundamentally new approach to 3-D printing. Due to appear as the cover article in the 20th March print issue of Science, it allows ready-to-use products to be made up to 100 times faster than previous methods and creates previously unachievable geometries. This opens opportunities for innovation across a range of major industries.

The method – known as Continuous Liquid Interface Production (CLIP) – manipulates light and oxygen to fuse objects in liquid media, creating the first 3D printing process that uses "tunable photochemistry", instead of the traditional layer-by-layer approach that has defined the technology for decades. This works by projecting beams of light through an oxygen-permeable window into a liquid resin. Working in tandem, light and oxygen control the solidification of the resin, creating objects with feature sizes below 20 microns, about the width of a skin cell.

"By rethinking the whole approach to 3-D printing – and the chemistry and physics behind the process – we have developed a new technology that can create parts radically faster than traditional technologies by essentially 'growing' them in a pool of liquid," said Joseph DeSimone, the CEO of Carbon3D, who revealed the technology at a TED talk on 16th March.


clip diagram


CLIP enables a very wide range of materials to be used to make 3D parts with novel properties – including elastomers, silicones, nylon-like materials, ceramics and biodegradable materials. In the future, it might even be possible to create living matter, such as artificial meat, or replacement organs for transplantation into human bodies.

Conventionally made 3-D printed parts are notorious for having mechanical properties that vary depending on the direction the parts were printed because of the layer-by-layer approach. Much more like injection-moulded parts, CLIP produces consistent and predictable mechanical properties – smooth on the outside and solid on the inside.


CLIP vs traditional 3d printing


“In addition to using new materials, CLIP can allow us to make stronger objects with unique geometries that other techniques cannot achieve, such as cardiac stents personally tailored to meet the needs of a specific patient,” said DeSimone. “Since CLIP facilitates 3-D polymeric object fabrication in a matter of minutes instead of hours or days, it would not be impossible within coming years to enable personalised coronary stents, dental implants or prosthetics to be 3-D printed on-demand in a medical setting.”

Through a sponsored research agreement between Carbon3D and the University of North Carolina at Chapel Hill, the team is currently pursuing further advances to the technology, including new materials that are compatible with it. Carbon3D has partnered with Sequoia Capital and several other firms to raise $40 million for commercialising the process.


3d printing speed times


“If 3D printing hopes to break out of the prototyping niche it has been trapped in for decades, we need to find a disruptive technology that attacks the problem from a fresh perspective and addresses 3D printing’s fundamental weaknesses,” said Jim Goetz, Carbon3D board member and Sequoia partner. “When we met Joe and saw what his team had invented, it was immediately clear to us that 3D printing would never be the same.”

“We had studied the additive manufacturing ecosystem comprehensively and had concluded that the promise far exceeded the current reality in the marketplace,” said Adam Grosser, Carbon3D board member and Managing Director at Silver Lake Kraftwerk. “When we witnessed the CLIP process, we believed we had found a company that had invented a solution to speed, quality, and material selection. We are proud to work alongside Carbon3D to create a new category of 3D manufacturing.”


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11th January 2015

Neutron star hidden by warp in space-time

Astronomers have observed and measured a neutron star slipping out of view because of the warp in space-time its orbit creates. The star is expected to reappear in about 160 years.


  neutron star warp in space time
Illustration of one orbit of pulsar J1906 (on the right, with radio beams) around its companion (centred). In the space-time curvature caused by the companion (blue), the pulsar rotation axis slants throughout the orbit. For illustration the effect is exaggerated 1 million times here.
Videos and image credit: Joeri van Leeuwen / ASTRON / University of British Columbia (CC BY-SA 4.0)


In an interstellar race against time, astronomers have measured the space-time warp in the gravity of a binary star system and determined the mass of a neutron star – just before it vanished from view.

The team, including University of British Columbia astronomer Ingrid Stairs, measured the masses of both stars in a binary pulsar system called J1906, which lies in a globular cluster known as Terzan 5, about 25,000 light years away. The pulsar spins and emits a lighthouse-like beam of radio waves every 144 milliseconds and orbits its companion star in under four hours.

"By precisely tracking the motion of the pulsar, we were able to measure the gravitational interaction between the two highly compact stars with extreme precision," says Stairs, a professor of physics and astronomy. "These two stars each weigh more than the Sun, but are still over 100 times closer together than the Earth is to the Sun. The resulting extreme gravity causes many remarkable effects."

According to general relativity, neutron stars wobble like a spinning top as they move through the gravitational well of a massive, nearby companion star. Orbit after orbit, the pulsar travels through a space-time that is curved, which impacts the star's spin axis.






"Through the effects of the immense mutual gravitational pull, the spin axis of the pulsar has now wobbled so much that the beams no longer hit Earth," explains Joeri van Leeuwen, an astrophysicist at the Netherlands Institute for Radio Astronomy, and University of Amsterdam, who led the study.

"The pulsar is now all but invisible to even the largest telescopes on Earth. This is the first time such a young pulsar has disappeared through precession. Fortunately this cosmic spinning top is expected to wobble back into view, but it might take as long as 160 years."

Only a handful of double neutron stars have had their mass calculated, with J1906 being the youngest. The results were published on Thursday in the Astrophysical Journal and presented at the American Astronomical Society meeting.


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