After training a network of telescopes stretching from Hawaii to Antarctica to Spain at the heart of our galaxy for five nights running, astronomers said Wednesday they may have snapped the first-ever picture of a black hole.
It will take months to develop the image, but if scientists succeed the results may help peel back mysteries about what the universe is made of and how it came into being.
“Instead of building a telescope so big that it would probably collapse under its own weight, we combined eight observatories like the pieces of a giant mirror,” said Michael Bremer, an astronomer at the International Research Institute for Radio Astronomy (IRAM) and a project manager for the Event Horizon Telescope.
“This gave us a virtual telescope as big as Earth—about 10,000 kilometres (6,200 miles) is diameter,” he told AFP.
The bigger the telescope, the finer the resolution and level of detail.
The targeted supermassive black hole is hidden in plain sight, lurking in the centre of the Milky Way in a region called the Sagittarius constellation, some 26,000 light years from Earth.
Dubbed Sagittarius A* (Sgr A* for short), the gravity- and light-sucking monster weighs as much as four million Suns.
Theoretical astronomy tells us when a black hole absorbs matter—planets, debris, anything that comes too close—a brief flash of light is visible.
No going back
Black holes also have a boundary, called an event horizon.
The British astronomer Stephen Hawking has famously compared crossing this boundary to going over Niagra Falls in a canoe: if you are above the falls, it is still possible to escape if you paddle hard enough.
Once you tip over the edge, however, there’s no going back.
The Event Horizon Telescope radio-dish network is designed to detect the light cast-off when object disappear across that boundary.
“For the first time in our history, we have the technological capacity to observe black holes in detail,” said Bremer.
The virtual telescope trained on the middle of the Milky Way is powerful enough to spot a golf ball on the Moon, he said.
The 30-metre IRAM telescope, located in the Spanish Sierra Nevada mountains, is the only European observatory taking part in the international effort.
Other telescopes contributing to the project include the South Pole Telescope in Antarctica, the James Clerk Maxwell Telescope in Hawaii, and the Atacama Cosmology Telescope in the desert of northern Chile.
All the data—some 500 terabytes per station—will be collected and flown on jetliners to the MIT Haystack Observatory in Massachusetts, where it will be processed by supercomputers.
“The images will emerge as we combine all the data,” Bremer explained. “But we’re going to have to wait several months for the result.”
Material scientists have predicted and built two new magnetic materials, atom-by-atom, using high-throughput computational models. The success marks a new era for the large-scale design of new magnetic materials at unprecedented speed.
Although magnets abound in everyday life, they are actually rarities—only about five percent of known inorganic compounds show even a hint of magnetism. And of those, just a few dozen are useful in real-world applications because of variability in properties such as effective temperature range and magnetic permanence.
The relative scarcity of these materials can make them expensive or difficult to obtain, leading many to search for new options given how important magnets are in applications ranging from motors to magnetic resonance imaging (MRI) machines. The traditional process involves little more than trial and error, as researchers produce different molecular structures in hopes of finding one with magnetic properties. Many high-performance magnets, however, are singular oddities among physical and chemical trends that defy intuition.
In a new study, materials scientists from Duke University provide a shortcut in this process. They show the capability to predict magnetism in new materials through computer models that can screen hundreds of thousands of candidates in short order. And, to prove it works, they’ve created two magnetic materials that have never been seen before.
The results appear April 14, 2017, in Science Advances.
“Predicting magnets is a heck of a job and their discovery is very rare,” said Stefano Curtarolo, professor of mechanical engineering and materials science and director of the Center for Materials Genomics at Duke. “Even with our screening process, it took years of work to synthesize our predictions. We hope others will use this approach to create magnets for use in a wide range of applications.”
The group focused on a family of materials called Heusler alloys—materials made with atoms from three different elements arranged in one of three distinct structures. Considering all the possible combinations and arrangements available using 55 elements, the researchers had 236,115 potential prototypes to choose from.
To narrow the list down, the researchers built each prototype atom-by-atom in a computational model. By calculating how the atoms would likely interact and the energy each structure would require, the list dwindled to 35,602 potentially stable compounds.
From there, the researchers conducted a more stringent test of stability. Generally speaking, materials stabilize into the arrangement requiring the least amount of energy to maintain. By checking each compound against other atomic arrangements and throwing out those that would be beat out by their competition, the list shrank to 248.
Of those 248, only 22 materials showed a calculated magnetic moment. The final cut dropped any materials with competing alternative structures too close for comfort, leaving a final 14 candidates to bring from theoretical model into the real world.
But as most things in a laboratory turn out, synthesizing new materials is easier said than done.
“It can take years to realize a way to create a new material in a lab,” said Corey Oses, a doctoral student in Curtarolo’s laboratory and second author on the paper. “There can be all types of constraints or special conditions that are required for a material to stabilize. But choosing from 14 is a lot better than 200,000.”
For the synthesis, Curtarolo and Oses turned to Stefano Sanvito, professor of physics at Trinity College in Dublin, Ireland. After years of attempting to create four of the materials, Sanvito succeeded with two.
Both were, as predicted, magnetic.
The first newly minted magnetic material was made of cobalt, magnesium and titanium (Co2MnTi). By comparing the measured properties of similarly structured magnets, the researchers were able to predict the new magnet’s properties with a high degree of accuracy. Of particular note, they predicted the temperature at which the new material lost its magnetism to be 940 K (1232 degrees Fahrenheit). In testing, the actual “Curie temperature” turned out to be 938 K (1228 degrees Fahrenheit)—an exceptionally high number. This, along with its lack of rare earth elements, makes it potentially useful in many commercial applications.
“Many high-performance permanent magnets contain rare earth elements,” said Oses. “And rare earth materials can be expensive and difficult to acquire, particularly those that can only be found in Africa and China. The search for magnets free of rare-earth materials is critical, especially as the world seems to be shying away from globalization.”
The second material was a mixture of manganese, platinum and palladium (Mn2PtPd), which turned out to be an antiferromagnet, meaning that its electrons are evenly divided in their alignments. This leads the material to have no internal magnetic moment of its own, but makes its electrons responsive to external magnetic fields.
While this property doesn’t have many applications outside of magnetic field sensing, hard drives and Random Access Memory (RAM), these types of magnets are extremely difficult to predict. Nevertheless, the group’s calculations for its various properties remained spot on.
“It doesn’t really matter if either of these new magnets proves useful in the future,” said Curtarolo. “The ability to rapidly predict their existence is a major coup and will be invaluable to materials scientists moving forward.”
An asteroid as big as the Rock of Gibraltar will streak past Earth on April 19 at a safe but uncomfortably close distance, according to astronomers.
“Although there is no possibility for the asteroid to collide with our planet, this will be a very close approach for an asteroid this size,” NASA said in a statement.
Dubbed 2014-JO25 and roughly 650 metres (2,000 feet) across, the asteroid will come within 1.8 million kilometres (1.1 million miles) of Earth, less than five times the distance to the Moon.
It will pass closest to our planet after having looped around the Sun. 2014-J25’s will then continue on past Jupiter before heading back toward the centre of our Solar System.
Smaller asteroids whizz by Earth several times a week. But the last time one at least this size came as close was in 2004, when Toutatis—five kilometres (3.1 miles) across—passed within four lunar distances.
The next close encounter with a big rock will not happen before 2027, when the 800-metre (half-mile) wide asteroid 199-AN10 will fly by at just one lunar distance, about 380,000 km (236,000 miles).
The last time 2014-JO25 was in our immediate neighbourhood was 400 years ago, and it’s next brush with Earth won’t happen until sometime after 2600.
The April 19 flyby is an “outstanding opportunity” for astronomers and amateur stargazers, NASA said.
“Astronomers plan to observe it with telescopes around the world to learn as much about it as possible,” the US space agency said.
Besides its size and trajectory, scientists also know that its surface is twice as reflective as that of the Moon.
It should be visible with a small optical telescope for one or two nights before moving out of range.
2014-J25 was discovered in May 2014 by astronomers at the Catalina Sky Survey near Tucson, Arizona.
Also on April 19, a comet known as PanSTARRS will make its closest approach to Earth at a “very safe” distance of 175 million km (109 million miles), according to NASA.
The comet has brightened recently and should be visible in the dawn sky with binoculars or a small telescope.
Asteroids are composed of rocky and metallic material, whereas comets—generally smaller—are more typically made of ice, dust and rocky stuff.
Both were formed early in the history of the Solar System some 4.5 billion years ago.
Nearly a century after it was theorized, Harvard scientists have succeeded in creating the rarest – and potentially one of the most valuable – materials on the planet.
The material – atomic metallic hydrogen – was created by Thomas D. Cabot Professor of the Natural Sciences Isaac Silvera and post-doctoral fellow Ranga Dias. In addition to helping scientists answer fundamental questions about the nature of matter, the material is theorized to have a wide range of applications, including as a room-temperature superconductor. The creation of the rare material is described in a January 26 paper published in Science.
“This is the holy grail of high-pressure physics,” Silvera said. “It’s the first-ever sample of metallic hydrogen on Earth, so when you’re looking at it, you’re looking at something that’s never existed before.”
To create it, Silvera and Dias squeezed a tiny hydrogen sample at 495 gigapascal, or more than 71.7 million pounds-per-square inch – greater than the pressure at the center of the Earth. At those extreme pressures, Silvera explained, solid molecular hydrogen -which consists of molecules on the lattice sites of the solid – breaks down, and the tightly bound molecules dissociate to transforms into atomic hydrogen, which is a metal.
While the work offers an important new window into understanding the general properties of hydrogen, it also offers tantalizing hints at potentially revolutionary new materials.
“One prediction that’s very important is metallic hydrogen is predicted to be meta-stable,” Silvera said. “That means if you take the pressure off, it will stay metallic, similar to the way diamonds form from graphite under intense heat and pressure, but remains a diamond when that pressure and heat is removed.”
Understanding whether the material is stable is important, Silvera said, because predictions suggest metallic hydrogen could act as a superconductor at room temperatures.
“That would be revolutionary,” he said. “As much as 15 percent of energy is lost to dissipation during transmission, so if you could make wires from this material and use them in the electrical grid, it could change that story.”
Among the holy grails of physics, a room temperature superconductor, Dias said, could radically change our transportation system, making magnetic levitation of high-speed trains possible, as well as making electric cars more efficient and improving the performance of many electronic devices.
The material could also provide major improvements in energy production and storage – because superconductors have zero resistance energy could be stored by maintaining currents in superconducting coils, and then be used when needed.
Though it has the potential to transform life on Earth, metallic hydrogen could also play a key role in helping humans explore the far reaches of space, as the most powerful rocket propellant yet discovered.
“It takes a tremendous amount of energy to make metallic hydrogen,” Silvera explained. “And if you convert it back to molecular hydrogen, all that energy is released, so it would make it the most powerful rocket propellant known to man, and could revolutionize rocketry.”
The most powerful fuels in use today are characterized by a “specific impulse” – a measure, in seconds, of how fast a propellant is fired from the back of a rocket – of 450 seconds. The specific impulse for metallic hydrogen, by comparison, is theorized to be 1,700 seconds.
“That would easily allow you to explore the outer planets,” Silvera said. “We would be able to put rockets into orbit with only one stage, versus two, and could send up larger payloads, so it could be very important.”
To create the new material, Silvera and Dias turned to one of the hardest materials on Earth – diamond.
But rather than natural diamond, Silvera and Dias used two small pieces of carefully polished synthetic diamond which were then treated to make them even tougher and then mounted opposite each other in a device known as a diamond anvil cell.
“Diamonds are polished with diamond powder, and that can gouge out carbon from the surface,” Silvera said. “When we looked at the diamond using atomic force microscopy, we found defects, which could cause it to weaken and break.”
The solution, he said, was to use a reactive ion etching process to shave a tiny layer – just five microns thick, or about one-tenth of a human hair – from the diamond’s surface. The diamonds were then coated with a thin layer of alumina to prevent the hydrogen from diffusing into their crystal structure and embrittling them.
After more than four decades of work on metallic hydrogen, and nearly a century after it was first theorized, seeing the material for the first time, Silvera said, was thrilling.
“It was really exciting,” he said. “Ranga was running the experiment, and we thought we might get there, but when he called me and said, ‘The sample is shining,’ I went running down there, and it was metallic hydrogen.
“I immediately said we have to make the measurements to confirm it, so we rearranged the lab…and that’s what we did,” he said. “It’s a tremendous achievement, and even if it only exists in this diamond anvil cell at high pressure, it’s a very fundamental and transformative discovery.”
Optical fibers are the backbone of modern communications, shuttling information from A to B through thin glass filaments as pulses of light. They are used extensively in telecommunications, allowing information to travel at near the speed of light virtually without loss.
These days, biologists, physicists and other scientists regularly use optical fibers to pipe light around inside their labs. In one recent application, quantum research labs have been reshaping optical fibers, stretching them into tiny tapers (see Nanofibers and designer light traps). For these nanometer-scale tapers, or nanofibers, the injected light still makes its way from A to B, but some of it is forced to travel outside the fiber’s exterior surface. The exterior light, or evanescent field, can capture atoms and then carry information about that light-matter interaction to a detector.
Fine-tuning such evanescent light fields is tricky and requires tools for characterizing both the fiber and the light. To this end, researchers from JQI and the Army Research Laboratory (ARL) have developed a novel method to measure how light propagates through a nanofiber, allowing them to determine the nanofiber’s thickness to a precision less than the width of an atom. The technique, described in the January 20, 2017 issue of the journal Optica , is direct, fast and, unlike the standard imaging method, preserves the integrity of the fiber. As a result, the probe can be used in-situ with the nanofiber fabrication equipment, which will streamline implementation in quantum optics and quantum information experiments. Developing reliable and precise tools for this platform may enable nanofiber technology for sensing and metrology applications.
Light waves have a characteristic size called the wavelength. For visible light, the wavelength is roughly 100 times smaller than a human hair. Light can also have the appearance of different shapes, such a solid circle, ring, clover and more (see image below). Fibers restrict the way light waves can travel and twisting or bending a fiber will alter the light’s characteristics. Nanofibers are made by reshaping a normal fiber into an hourglass-like design, which further affects the guided light waves.
In this experiment, researchers inject a combination of light shapes into a nanofiber. The light passes down a thinning taper, squeezes through a narrow waist, and then exits out the other side of the taper. The changing fiber size distorts the light waves, and multiple patterns emerge from the interfering light shapes (See JQI News on Collecting lost light). This is analogous to musical notes, or sound waves, beating together to form a complex chord.
The researchers make direct measurements of the interference patterns (beats). To do this, they employ a second micron-sized fiber that acts as a non-invasive sensor. The nanofiber is on a moving stage and crosses the probe fiber at an oblique angle. At the touching point, a tiny fraction of nanofiber light evanescently enters the second fiber and travels to a detector. As they scan the probe along the length of the nanofiber, the probe detector collects information about the evolving patterns of nanofiber light. The researchers simultaneously monitor the light transmitting through the nanofiber to ensure that the probe process is harmless.
The team can achieve a high level of precision with this technique because they are not imaging the fiber with a camera, which would have a spatial resolution limited by the collected light’s wavelength. UMD graduate student Pablo Solano explains, “We are actually seeing the different light modes mix together and that sets the limits on determining the fiber waist—in this case sub-angstrom.” A standard tool known as scanning electron microscopy (SEM) can also measure fiber dimensions with nanoscale resolution. This, however, has a comparative disadvantage, says Eliot Fenton, a UMD undergraduate student working on the project, “With our new method, we can avoid using SEM, which destroys the fiber with imaging chemicals and heating.” Other techniques involve collecting randomly scattered light from the fiber, which is less direct and susceptible to errors. Solano summarizes how researchers can benefit from this new tool, “By directly and sensitively measuring the interference (beating) of light without destroying the fiber, we can know exactly the kind of electromagnetic field that we would apply to atoms.”
Astronomers have found a total of 76 new ultra-diffuse galaxies (UDGs) in the massive galaxy cluster designated Abell 2744 (also known as Pandora’s Cluster). The discovery updates the current census of galaxies in this cluster and could help better understand the nature of UDGs in general. The findings were presented in a paper published Dec. 30 on arXiv.org.
UDGs are extremely-low-density galaxies. The largest UDGs have sizes similar the Milky Way but have only about one percent as many stars as our home galaxy. The mystery of UDGs is still baffling scientists as they try explain why these faint but large galaxies are not ripped apart by the tidal field of their host clusters. Furthermore, it is not clear what fraction of UDGs are “failed” giant luminous galaxies, “inflated dwarfs,” or some other phenomenon.
Abell 2744 is a giant galaxy cluster located nearly 4 billion light years away in the Sculptor constellation. It is one of the most massive and most disturbed galaxy clusters known to date. Its intracluster light fraction is high and its stellar population consistent with the disruption of luminous galaxies, which makes it an excellent location to search for UDGs.
That is why a team of researchers led by Steven Janssens of the University of Toronto, Canada, has investigated Abell 2744 using data obtained with the Hubble Space Telescope (HST) Frontier Fields (FF) program. FF is known for producing the deepest images to date of galaxy clusters and gravitational lensing. The analysis of FF data allowed the astronomers to distinguish dozens of new UDGs in this giant galaxy cluster.
“We report the discovery of a large population of ultra-diffuse galaxies in the massive galaxy cluster Abell 2744 (z= 0.308) as observed by the Hubble Frontier Fields program,” the researchers wrote in the paper.
As a result, the team detected 76 new UDGs—41 in the cluster field and 35 in the parallel field. They also estimated the total number of UDGs that Abell 2744 contains. According to the paper, given the fact that the analyzed data from the observations samples only a small portion of the galaxy cluster, there should be approximately 2,100 ultra-diffuse galaxies in Abell 2744. The researchers noted that this is 10 times the number of UDGs that exist in a similar cluster known as Abell 1656 (or Coma Cluster).
“Abell 2744 hosts an estimated 2133±613 UDGs, 10 times the number in Coma,” the paper reads.
The research also allowed the scientists to estimate the number of ultra-compact dwarf (UCD) galaxies in Abell 2744. According to their calculations, there are about 385 UCDs in the galaxy cluster.
The researchers concluded that some UCDs in Abell 2744 may have once been nuclei or satellites of infalling UDGs, noting that the latter are ultimately destroyed by tidal forces.
“As UDGs fall in and dissolve (and, presumably, blend into the intra-cluster light), they leave behind a residue of unbound, but long-lived UCDs,” the team wrote.