A plasma cocoon lets growing stars keep their X-rays to themselves. Laboratory experiments that mimic maturing stars show that streams of plasma splash off a star’s surface, forming a varnish that keeps certain kinds of radiation inside.
That coating could explain a puzzling mismatch between X-ray and ultraviolet observations of growing stars, report physicist Julien Fuchs of École Polytechnique in Paris and colleagues November 1 in Science Advances.
Physicists think stars that are less than 10 million years old grow up by drawing matter onto their surfaces from an orbiting disk of dust and gas. Magnetic fields shape the incoming matter into columns of hot, charged plasma. The same disk will eventually form planets (SN Online: 11/6/14), so knowing how quickly stars gobble up the disk can help tell what kinds of planets can grow. When disk matter hits a stellar surface, the matter heats to about 1,700° Celsius and should emit a lot of light in ultraviolet and X-ray wavelengths. Measuring that light can help scientists infer how fast the star is growing. But previous observations found that such stars emit between four and 100 times fewer X-rays than they should.
One theory why is that something about how a star eats absorbs the X-rays. So Fuchs and his colleagues re-created the feeding process in a lab. First, the team zapped a piece of PVC representing the edge of the disk with a laser to create plasma, similar to the columns that feed stars. In space, a star’s gravity draws the plasma onto its surface at speeds of about 500 kilometers per second. The star’s strong magnetic field guides the charged plasma into organized columns millions of kilometers long. There’s not enough room or gravity in the lab to reproduce that exactly, but the plasma physics is the same on smaller scales, Fuchs says. His team applied magnetic fields up to 100,000 times stronger than Earth’s to the plasma to shape it into columns and accelerate it to the same speed it would have in space. The researchers placed a target made of Teflon representing the star’s surface just 11.7 millimeters away from the PVC, a distance equivalent to about 10 million kilometers in space.
When the plasma hits the Teflon surface, the plasma begins to ooze sideways. But the magnetic field that holds the plasma in a column stops the plasma’s spreading. Plasma and magnetic field push against each other until the buildup of pressure between them forces the plasma to curve away from the surface and back up the column, coating incoming plasma with outgoing plasma.
“This cocoon is building up,” Fuchs says. It absorbs enough X-rays to explain the surprisingly wimpy X-ray emission of growing stars, the experiment found. The team also compared the experiment setup with computer simulations of feeding stars to show that the lab configuration was a good representation of real stars.
The comparison with computer simulations makes the experiment more reliable, says experimental physicist Gianluca Gregori of the University of Oxford. “There is this reality check,” he says. “In the astrophysical community, there’s a tendency to think that there are observations, and there are simulations. But what this paper tells is that there are other ways you can understand what happens in the universe.”
WASHINGTON, D.C. — Helper cells in the brain just got tagged with a new job — forming traumatic memories.
When rats experience trauma, cells in the hippocampus — an area important for learning — produce signals for inflammation, helping to create a potent memory. But most of those signals aren’t coming from the nerve cells, researchers reported November 15 at the Society for Neuroscience meeting.
Instead, more than 90 percent of a key inflammation protein comes from astrocytes. This role in memory formation adds to the repertoire of these starburst-shaped cells, once believed to be responsible for only providing food and support to more important brain cells (SN Online: 8/4/15). The work could provide new insight into how the brain creates negative memories that contribute to post-traumatic stress disorder, said Meghan Jones, a neuroscientist at the University of North Carolina at Chapel Hill.
Jones and her colleagues gave rats a short series of foot shocks painful enough to “make you curse,” she said. A week after that harrowing experience, rats confronted with a milder shock remained jumpy. In some rats, Jones and her colleagues inhibited astrocyte activity during the original trauma, which prevented the cells from releasing the inflammation protein. Those rats kept their cool in the face of the milder shock.
These preliminary results show that neurons get a lot of help in creating painful memories. Studies like these are “changing how we think about the circuitry that’s involved in depression and post-traumatic stress disorder,” says neuroscientist Georgia Hodes of Virginia Tech in Blacksburg. “Everyone’s been focused on what neurons are doing. [This is] showing an important effect of cells we thought of as only being supportive.”
Sperm from stressed-out dads can carry that stress from one generation to another. “But one question that really hasn’t been addressed is, ‘How do dad’s experiences actually change his germ cell?’” Jennifer Chan, a neuroendocrinologist at the University of Pennsylvania, said November 13 in Washington, D.C., at the annual meeting of the Society for Neuroscience.
Now, from a study in mice, Chan and her colleagues have some answers, and even hints at ways to stop this stress inheritance. The researchers focused on the part of the male reproductive tract called the caput epididymis, a place where sperm cells mature. Getting rid of a stress-hormone sensor there called the glucocorticoid receptor stopped the transmission of stress, the researchers found. When faced with an alarming predator odor, offspring of chronically stressed mice dads overproduce the stress hormone corticosterone. But mice dads that lacked this receptor in the epididymis had offspring with normal hormonal responses.
Earlier work has shown that epididymis cells release small packets filled with RNA that can fuse to sperm and change their genetic payload. Experiments on cells in dishes revealed that chronic exposure to corticosterone changed the RNA in these vesicles. The results offer an explanation of how stress can change sperm: By activating the glucocorticoid receptor, stress tweaks the RNA in epididymis vesicles. Then, those vesicles deliver their altered contents to sperm, passing stress to the next generation.
Similar vesicles are present in human seminal fluid, even after ejaculation. Chan and colleagues are testing whether humans carry similar signs of stress in these RNA-loaded vesicles by studying college students’ semen samples. Exam schedules will be used as a stress indicator, she said.
The most distant quasar yet spotted sends its light from the universe’s toddler years. The quasar, called J1342+0928, existed when the universe was only 690 million years old, right when the first stars and galaxies were forming.
Quasars are bright disks of gas and dust swirling around supermassive black holes. The black hole that powers J1342+0928 has a mass equivalent to 800 million suns, and it’s gobbling gas and dust so fast that its disk glows as bright as 40 trillion suns, Eduardo Bañados of the Carnegie Institution for Science in Pasadena, Calif., and his colleagues report December 6 in Nature. “The newly discovered quasar gives us a unique photo of the universe when it was 5 percent [of] its present age,” Bañados says. “If the universe was a 50-year-old person, we would be seeing a photo of that person when she/he was 2 1/2 years old.”
This quasar is only slightly smaller than the previous distance record-holder, which weighs as much as 2 billion suns and whose light is 12.9 billion years old, emitted when the universe was just 770 million years old (SN: 7/30/11, p. 12). Scientists still aren’t sure how supermassive black holes like these grew so big so early.
“They either have to grow faster than we thought, or they started as a bigger baby,” says study coauthor Xiaohui Fan of the Steward Observatory in Tucson.
The temperature of the gas surrounding the newfound quasar places it squarely in the epoch of reionization (SN: 4/1/17, p. 13), when the first stars stripped electrons from atoms of gas that filled interstellar space. That switched the universe’s gas from mostly cold and neutral to hot and ionized. When this particular black hole formed, the universe was about half hot and half cold, Fan says. “We’re very close to the epoch when the first-generation galaxies are appearing,” Fan says.
NEW ORLEANS — The New Horizons team may get more than it bargained for with its next target. Currently known as 2014 MU69, the object might, in fact, be two rocks orbiting each other — and those rocks may themselves host a small moon.
MU69 orbits the sun in the Kuiper Belt, a region more than 6.5 billion kilometers from Earth. That distance makes it difficult to get pictures of the object directly. But last summer, scientists positioned telescopes around the globe to catch sight of MU69’s shadow as it passed in front of a distant background star (SN Online: 7/20/17), a cosmic coincidence known as an occultation. Analyzing that flickering starlight raised the idea that MU69 might have two lobes, like a peanut, or might even be a pair of distinct objects. Whatever its shape, MU69 is not spherical and may not be alone, team members reported in a news conference on December 12 at the fall meeting of the American Geophysical Union.
Another stellar flicker sighting raised the prospect of a moon. On July 10, NASA’s airborne Stratospheric Observatory for Infrared Astronomy observed MU69 pass in front of a different star (SN: 3/19/16, p. 4). SOFIA saw what looked like a new, shorter dip in the star’s light. Comparing that data with orbit calculations from the European Space Agency’s Gaia spacecraft suggested that the blip could be another object around MU69.
A double object with a smaller moon could explain why MU69 sometimes shifts its position from where scientists expect it to be during occultations, said New Horizons team member Marc Buie of the Southwest Research Institute in Boulder, Colo.
The true shape will soon be revealed. The New Horizons spacecraft set its sights on the small space rock after flying past Pluto in 2015, and will fly past MU69 on January 1, 2019.
Our solar system is no longer the sole record-holder for most known planets circling a star.
An artificial intelligence algorithm sifted through data from the planet-hunting Kepler space telescope and discovered a previously overlooked planet orbiting Kepler 90 — making it the first star besides the sun known to host eight planets. This finding, announced in a NASA teleconference December 14, shows that the kinds of clever computer codes used to translate text and recognize voices can also help discover strange new worlds. The discovery, also reported in a paper accepted to the Astronomical Journal, can also help astronomers better understand the planetary population of our galaxy. “Finding systems like this that have lots of planets is a really neat way to test theories of planet formation and evolution,” says Jeff Coughlin, an astronomer at the SETI Institute in Mountain View, Calif., and NASA’s Ames Research Center in Moffett Field, Calif.
Kepler 90 is a sunlike star about 2,500 light-years from Earth in the constellation Draco. The latest addition to Kepler 90’s planetary family is a rocky planet about 30 percent larger than Earth called Kepler 90i. It, too, is the third planet from its sun — but with an estimated surface temperature higher than 400° Celsius, it’s probably not habitable.
Story continues below graphic The seven previously known planets in this system range from small, rocky worlds like Kepler 90i to gas giants, which are all packed closer to their star than Earth is to the sun. “It’s very possible that Kepler 90 has even more planets,” study coauthor Andrew Vanderburg, an astronomer at the University of Texas at Austin, said in the teleconference. “There’s a lot of unexplored real estate in the Kepler 90 system.” Astronomers have identified over 2,300 new planets in Kepler data by searching for tiny dips in a star’s brightness when a planet passes in front of it. Kepler has collected too much data for anyone to go through it all by hand, so humans or computer programs typically only verify the most promising signals of the bunch. That means that worlds that produce weaker light dips — like Kepler 90i — can get passed over. Vanderburg and Christopher Shallue, a software engineer at Google in Mountain View, Calif., designed a computer code called a neural network, which mimics the way the human brain processes information, to seek out such overlooked exoplanets. Researchers previously automated Kepler data analysis by hard-coding programs with rules about how to detect bona fide exoplanet signals, Coughlin explains. Here, Vanderburg and Shallue provided their code with more than 10,000 Kepler signals that had been labeled by human scientists as either exoplanet or non-exoplanet signals. By studying these examples, the neural network learned on its own what the light signal of an exoplanet looked like, and could then pick out the signatures of exoplanets in previously unseen signals.
The fully trained neural network examined 670 star systems known to host multiple planets to see whether previous searches had missed anything. It spotted Kepler 90i, as well as a sixth, Earth-sized planet around the star Kepler 80. This feat marks the first time a neural network program has successfully identified new exoplanets in Kepler data, Jessie Dotson, an astrophysicist at NASA’s Ames Research Center said at the teleconference.
Vanderburg and Shallue now plan to apply their neural network to Kepler’s full cache of data on more than 150,000 stars, to see what other unrecognized exoplanets it might turn up.
Coughlin is also excited about the prospect of using artificial intelligence to assess data from future exoplanet search missions, like NASA’s TESS satellite set to launch next year. “The hits are going to keep on coming,” regarding potential exoplanet signals, he says. Having self-taught computer programs help humans slog through the data could significantly speed up the rate of scientific discovery.
Globs of an inflammation protein beckon an Alzheimer’s protein and cause it to accumulate in the brain, a study in mice finds. The results, described in the Dec. 21/28 Nature, add new details to the relationship between brain inflammation and Alzheimer’s disease.
Researchers suspect that this inflammatory cycle is an early step in the disease, which raises the prospect of being able to prevent the buildup of amyloid-beta, the sticky protein found in brains of people with Alzheimer’s disease. “It is a provocative paper,” says immunologist Marco Colonna of Washington University School of Medicine in St. Louis. Finding an inflammatory protein that can prompt A-beta to clump around it is “a big deal,” he says.
Researchers led by Michael Heneka of the University of Bonn in Germany started by studying specks made of a protein called ASC that’s produced as part of the inflammatory response. (A-beta itself is known to kick-start this inflammatory process.) Despite being called specks, these are large globs of protein that are created by and then ejected from brain immune cells called microglia when inflammation sets in. A-beta then accumulates around these ejected ASC specks in the space between cells, Haneke and colleagues now propose. A-beta can directly latch on to ASC specks, experiments in lab dishes revealed. The two proteins were also caught in close contact in brain tissue taken from people with Alzheimer’s disease. Researchers didn’t see any ASC specks mingling with A-beta in the brains of people without the disease. Mice engineered to produce lots of A-beta had telltale signs of its accumulation in their brains at 8 and 12 months of age, roughly comparable to middle age in people. But in mice that also lacked the ability to produce ASC specks, this A-beta brain load was much lighter, and these mice performed better on a memory test. Similar reductions in A-beta loads came when researchers used an antibody to prevent A-beta from sticking to ASC specks, results that suggest the specks are needed for A-beta to clump up.
The details show “a quite new and specific mechanism” that’s worth exploring for potential treatments, says Richard Ransohoff, a neuroinflammation biologist at Third Rock Ventures, a venture capital firm in Boston.
To be effective as a treatment, an antibody like the one in the study that kept A-beta from sticking to ASC would need to be able to enter the brain and persist at high levels — a big challenge, Ransohoff says. Still, the results are promising, he says. “I like the data. I like the line of experimentation.”
Many questions remain. The results are mainly from mice, and it’s not clear whether ASC specks and A-beta have similar interactions in human brains. Nor is it obvious how to stop the A-beta from accumulating around the specks without affecting the immune system more generally.
What’s more, the role of the microglia immune cells that release ASC specks is complex, Colonna says. In some cases, microglia serve as brain protectors by surrounding and sequestering sticky A-beta plaques in the brain (SN: 11/30/13, p. 22). But the current results suggest that by releasing ASC specks, the same cells can also make A-beta accumulation worse. The dueling roles of the cells — protective in some cases and potentially harmful in others — make it challenging to figure out how to tweak their behavior therapeutically, Colonna says.
Our Top 10 stories of 2017 cover the science that was earthshaking, field-advancing or otherwise important. But choosing our favorite stories requires some different metrics.
Here are some of our staff’s favorites from 2017, selected for their intrigue, their power, their element of surprise — or because they were just really, really fun.
Stories that moved us “The eclipse the eclipse the eclipse omg the eclipse.”
Astronomy writer Lisa Grossman didn’t hesitate in her e-mail reply when I asked for everyone’s personal favorites of the year. For the Great American Eclipse, Lisa wrote a 10-part preview of questions scientists would pursue during totality. She then traveled to Wyoming for the eclipse itself, reporting from a Baptist summer camp–turned-observatory. The whole experience was surprisingly emotional, Lisa says, and one that has stuck with her. “I keep looking at the sun now and thinking about how all that beautiful gossamer structure is there, all the time, and we just can’t see it. And how lucky we are that the moon is just the size and distance it is, so that we can experience this.” The Cassini spacecraft’s journey to Saturn also struck an emotional chord with the SN staff. “Cassini crashing into Saturn wins the award for ‘2017 science event that made me cry the most,’” says staff writer Laurel Hamers. After traveling 4.9 billion miles over nearly 20 years, the spacecraft dove into Saturn’s atmosphere and vaporized. “It was a very human drama about a machine,” says audience engagement editor Mike Denison. “It was the sort of science story even a layman like me can get very invested in.”
At its core, Cassini’s mission was basic exploration — the same drive that made the moon landing so captivating. “It’s amazing that there is still so much of our solar system we haven’t explored directly, and the goodies from that mission and the final dive will be reported for years to come,” writes acting editor in chief Beth Quill. “Plus, I love the narrative potential of a spacecraft that sacrifices itself.”
Physics writer Emily Conover’s personal favorite was also our No. 1 story, the detection of two neutron stars colliding — a finding that she had predicted. “I’m patting myself on the back a little bit for that,” she says.
“It was a lot of fun to think about how we’ve detected something completely new and confirmed that some of the tangible stuff around us, like the gold in my wedding ring, came from collisions like that,” she adds. “It’s one of those stories that if you think about it hard enough, it makes you feel like a very small part in a giant, wonderful, fascinating universe.”
Stories that surprised us We spend our days devouring science, combing scientific journals, interviewing scientists, attending meetings and reading science news in other publications. You’d think very little would surprise us. Not true. Maria Temming’s story on the discovery of a mysterious void in the Great Pyramid of Giza was one of our most-read stories of the year . By placing detectors throughout the pyramid to measure subatomic particles called muons, researchers discovered a previously unknown cavity inside the pyramid. “The topic was this beautiful juxtaposition of modern, cutting-edge technology — as in the muon detectors — with the ancient technology of pyramid construction,” says Maria, SN ’s technology writer. “It’s also kind of hilarious to think that the Great Mysterious Thing in this story is not the high-energy particles from outer space — that’s the thing we’ve got a handle on!” Science News for Students managing editor and Wild Things blogger Sarah Zielinski has a keen eye for amazing animal stories, so her pick for a favorite story surprised me: It was our May story and infographic on how an asteroid impact would kill you. “You assume that you know what an asteroid impact would do,” Sarah says, “but it turns out that your assumptions are completely wrong.”
Senior writer Tina Hesman Saey has been covering molecular and developmental biology for more than a decade, but was surprised when a new study overturned the idea that female is the default sex in developing mammals, and that only male tissues have to be actively built. A study she reported on this year found that male structures must be demolished to set off female development. “I was amazed that no one knew a basic of developmental biology: that development of female reproductive organs is an active process,” Tina says. A story about circulation in sea spiders takes the surprise prize for biology writer Susan Milius. “I had never written a story about them, so they were on my taxonomic bucket list,” she says. It turns out that oxygen-rich blood circulates up and down the animal’s legs as contractions move bits of food through the digestive tract in the legs. “It’s circulation by gut lump!” Susan says. “This still blows me away.” The story of how the house mouse came to live with people was a favorite for Science News for Students writer and Scicurious blogger Bethany Brookshire. “It was something I’d never thought of before and it was interesting to find how just how much we were affecting the species around us, even the littlest ones!”
Graphic designer Tracee Tibbitts highlighted two more, well, animalistic animal stories: One about a coconut crab attacking a bird, and one about gulls eating hookworms from seals’ feces — directly from the source. “We see a lot of cute animal stories online that give us warm fuzzies or a ‘they’re just like us!’ reaction,” Tracee says. “But both of these stories remind us that — NOPE. Animals are still wild and out there fighting each other for food and resources and survival.”
Stories that intrigued, for better or worse The gene-editing technology CRISPR/Cas9 caught Beth’s attention this year, “though I would say that last year and would say it again next year,” she says. “It is especially interesting to me to watch a technology from its infancy and understand the twists and turns it takes, all the ways it’s used and the ethical implications that arise.”
CRISPR made our Top 10 list this year as Tina had predicted in 2016. “I was right that CRISPR would still be a thing,” Tina says.
But Susan hadn’t expected CRISPR to creep into her beat as well. “What I missed by light-years was how fast CRISPR would cease to be just Tina’s business and become a matter that someone writing about conservation, ecology and real outdoor evolution has to watch,” Susan says. In an in-depth story on ticks, Susan described preliminary work to engineer mice using CRISPR gene editing to curb the spread of the Lyme disease parasite. “It might happen in six or seven years, and at the current speed, gene editing for wild, free-roaming organisms may, for better or worse — or both — be a real thing,” Susan says. “I certainly see the need for caution, but wow, are the possibilities changing fast.”
Stories scientists tell Part of the fun of many of the stories we cover is talking to the researchers who do the work. “I had so much fun interviewing scientists for [the neutron star collision] story,” Emily says. “Some of the members of LIGO were practically losing their minds about how amazing the detection was. It was so easy to get caught up in the excitement.” Tina got a chance to talk to planetary scientists and astrochemists — not her usual crowd — for a news story on a molecule on Saturn’s moon Titan that could be a key building block for any strange life-forms that might exist in the moon’s frigid methane lakes. In 2016, Tina had written a feature story on what alien life might look like , and in it described computer simulations of a molecule that could form bubblelike structures that resemble cell membranes. The new work showed that the molecule actually does exist on Titan. “It was a thrill to see that one prediction about truly alien life might come true,” Tina says. Laurel enjoyed talking to scientists trying to create better surgical adhesives inspired by slugs, worms and other critters. “People who study weird slime-making animals give the best interviews,” she says.
Associate editor Cassie Martin had a challenging time getting in touch with a scientist for a piece on the cholera epidemic in Yemen. “Finding a scientist and health worker in the war-torn country without actually traveling there took a lot of time and determination,” Cassie says. Once she did, though, she learned more than she expected. “I learned so much about what was happening not only with the epidemic, but about how war affects the scientific enterprise.”
For a video story on the anniversary of the detection of supernova 1987A, web producer Helen Thompson talked to Ian Shelton, who discovered the stellar explosion. The video told the story of the night of the discovery and reviewed all the insights the explosion has given to astronomy. The video also featured Shelton’s voice — and his likeness, in Claymation form. “I got to do a video that combined Claymation and glitter, which are my two favorite things,” Helen says.
Story continues below video The story of the moment You know when someone asks you what your favorite TV show is, and the show that springs to mind is the one you’re binge-watching right now? That often happens with our favorite science stories. Behavioral sciences writer Bruce Bower is putting the finishing touches on a feature story, due out early next year, on fantasy and reality in children’s play. Today, it’s his favorite. “It brings together psychology, anthropology/ethnography and archaeology, an interdisciplinary service that journalists can provide because scientists rarely do,” Bruce says.
For biomedical writer Aimee Cunningham, it’s all of the stories. “The majority of the stories I’ve written this year have met my criteria for why I do this work: to talk to interesting people, learn cool science and share what I find out.”
And that’s what we love about the work that we do. Here’s to 2018 and all the moving, surprising, intriguing, fascinating stories it will bring.
Immune reactions against proteins commonly used as molecular scissors might make CRISPR/Cas9 gene editing ineffective in people, a new study suggests.
About 79 percent of 34 blood donors tested had antibodies against the Cas9 protein from Staphylococcus aureus bacteria, Stanford University researchers report January 5 at bioRxiv.org. About 65 percent of donors had antibodies against the Cas9 protein from Streptococcus pyogenes.
Nearly half of 13 blood donors also had T cells that seek and destroy cells that make S. aureus Cas9 protein. The researchers did not detect any T cells that attack S. pyogenes Cas9, but the methods used to detect the cells may not be sensitive enough to find them, says study coauthor Kenneth Weinberg. Cas9 is the DNA-cutting enzyme that enables researchers to make precise edits in genes. Antibodies and T cells against the protein could cause the immune system to attack cells carrying it, making gene therapy ineffective.
The immune reactions may be a technical glitch that researchers will need to work around, but probably aren’t a safety concern as long as cells are edited in lab dishes rather than in the body, says Weinberg, a stem cell biologist and immunologist.
“We think we need to address this now … as we move toward clinical trials,” he says, but “this is probably going to turn out to be more of a hiccup than a brick wall.”
A new version of the periodic table showcases the predicted properties of 2-D metals, an obscure class of synthetic materials.
Arrayed in 1-atom-thick sheets, most of these 2-D metals have yet to be seen in the real world. So Janne Nevalaita and Pekka Koskinen, physicists at the University of Jyväskylä in Finland, simulated 2-D materials of 45 metallic elements, ranging from lithium to bismuth. For each sheet, the researchers measured the average chemical bond length, bond strength and the material’s compressibility, how difficult it is to squeeze the atoms closer together. The team then charted those features in the new periodic table. The new work, described in the Jan. 15 Physical Review B, could help researchers identify which 2-D metals are most promising for various applications, like spurring chemical reactions or sensing gases.
These metals are similar to previously studied 2-D materials, such as the supermaterial graphene (SN: 10/3/15, p. 7) and its cousin diamondene (SN: 9/2/17, p. 12). But whereas those materials were made up of covalent bonds — in which pairs of atoms share electrons — these 2-D metals are composed of metallic bonds, where electrons flow more freely among atoms. “It’s a whole new type of family of nanostructures,” Koskinen says. “Sky’s the limit, for what the applications could be.”
Like other superflat materials, some potential 2-D metals might exhibit exotic quantum qualities, such as 2-D magnetism or superconductivity, the ability to transmit electricity without resistance. Such properties may make those materials useful for quantum computing, says Joshua Robinson, a materials scientist at Penn State not involved in the work.
Nevalaita and Koskinen created three periodic tables that chart the properties of 2-D metals with atoms in triangular, square or honeycomb configurations. Using their trio of tables, the researchers discovered that the properties of 2-D metals were related to those of their 3-D counterparts. For instance, atoms of any given metal arranged in a triangular lattice typically had about 70 percent the bond strength of atoms in the 3-D version of that metal. Square and honeycomb lattices generally showed about 66 percent and 54 percent the bond strength of 3-D metals, respectively. The periodic tables revealed similar relationships between 2-D and 3-D metals in bond length and compressibility. These findings could allow researchers to get a quick profile of a 2-D metal that has never been created in the lab or in a computer simulation, just based on the well-known characteristics of its 3-D analog.
Nevalaita and Koskinen also compared the stability of 2-D metals whose atoms were arranged in the three different configurations. The researchers found that many 2-D metals were stable in triangular and honeycomb patterns, but not in squares. Future computer simulations could examine the electric and magnetic properties of these materials, Koskinen says. Knowing the stability and property profiles of 2-D metals could inform which materials scientists fabricate in the lab.
“This is the tip of the iceberg in the area of 2-D metals,” says Mauricio Terrones, a chemical physicist at Penn State not involved in the work.
