There’s no sorrier sight than a puking preschooler. That’s the conclusion I recently reached around 2 a.m. as my poor 4-year-old heaved into the dim abyss. Luckily, her bout with the stomach flu was brief, and she was feeling better by the next day.
Stomach flu, also known as gastroenteritis, is a common affliction caused by bacteria or viruses that inflame the gut. Though mercifully short, the misery this brings is complete, for both the sufferer and the person charged with scrubbing chunks out of sheets, carpet and a stuffed toy cupcake. So when presented with something that could potentially cut short the puking, any parent would jump at the chance. That’s the promise of probiotics, “good” bacteria (typically in pill form) that some people think might help restore the irritated gut and get kids feeling better faster. But according to two big studies (here and here) of puking kids and probiotics, parents should save their money for something else.
For both studies, scientists studied kids ages 3 months to 4 years who came to an emergency department with acute gastroenteritis. In addition to receiving regular care, these kids took either a probiotic or placebo for five days. Then the researchers tallied up the kids’ symptoms to see if those who got the live bugs fared better than those who received a placebo. Long story short, the scientists found absolutely no differences.
The trials used different bacteria as probiotics. One used Lactobacillus rhamnosus, sold as products such as Culturelle, and the other used that bacteria plus Lactobacillus helveticus, a combination sold as Lacidofil. Neither of the formulations cut puking or other symptoms short. The kids had about the same duration of diarrhea (about two days) and missed the same amount of daycare (two days on average).
As far as studies go, these results, both published November 22 in the New England Journal of Medicine, are pretty clear: Probiotics didn’t help puking kids feel better faster. Of course, it’s possible that certain types of probiotics are good for other things, as an editorial in the same issue of the NEJM points out. Scientists have been studying whether probiotics can curb colic in babies, with some hints that helpful bacteria may reduce crying in breastfed babies (though the jury is still out). Other bacteria might also help newborns at risk of developing dangerous infections, as a recent study on babies in rural India suggests.
But when it comes to gastroenteritis in kids, probiotics’ benefits don’t seem to be there. If you’re desperate and willing to throw money at the problem, go ahead and buy your poor puking kid some probiotics. There’s no evidence they hurt, and it might make you feel like you’re doing something. Still, you’re probably better off spending your money on juice and popsicles.
Data from NASA’s now-defunct Cassini spacecraft show that five odd-shaped moons embedded in Saturn’s rings are different colors, and that the hues come from the rings themselves, researchers report. That observation could help scientists figure out how the moons were born.
“The ring moons and the rings themselves are kind of one and the same,” says planetary scientist Bonnie Buratti of NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “For as long as the moons have existed, they’ve been accreting particles from the rings.” Saturn has more than 60 moons, but those nearest to the planet interact closely with its main band of rings. Between December 2016 and April 2017, Cassini passed close to five of these ring-dwelling moons: ravioli-shaped Pan and Atlas (SN Online: 3/10/17), ring-sculpting Daphnis and Pandora (SN: 9/2/17, p. 16) and potato-shaped Epimetheus. The flybys brought Cassini between two and 10 times closer to the moons than it had ever been, before the spacecraft deliberately crashed into Saturn in September 2017 (SN Online: 9/15/17).
Examining those close-ups, Buratti and her colleagues noticed that the moons’ colors vary depending on the objects’ distances from Saturn. And the moon hues are similar to the colors of the rings that the objects are closest to, the team reports online March 28 in Science. Close-in Pan was the reddest moon, while the farthest-out Epimetheus was the bluest. The researchers think the red material comes from Saturn’s dense main rings, and mostly consists of organics and iron (SN Online: 10/4/18). The blue material is probably water ice from Saturn’s more distant E ring, which is created by plumes erupting from the larger, icy moon Enceladus. The team thinks that the rings are continually depositing material onto the moons. “It’s an ongoing process,” Buratti says. She notes that “skirts” of material at Atlas and Pan’s equators are probably made of accreted ring debris, too.
The overall similarity between the moons and rings led the researchers to conclude that these small moons are leftover shards of a destructive event that created the rings in the first place. But it’s unknown whether that event was a collision between long-gone, larger moons, the shredding of one moon by Saturn’s gravity, or some other occurrence (SN: 1/20/18, p. 7).
Saturn, its rings and its moons are “very dynamic,” says planetary scientist Matija Ćuk of the SETI Institute in Mountain View, Calif. The idea that the rings are still shedding material onto the moons today “sounds perfectly reasonable.” He isn’t sure the moons formed at the same time as the rings, though. It’s possible “they formed from the rings since that catastrophic event,” he says.
Just a few powerful storms in Antarctica can have an outsized effect on how much snow parts of the southernmost continent get. Those ephemeral storms, preserved in ice cores, might give a skewed view of how quickly the continent’s ice sheet has grown or shrunk over time.
Relatively rare extreme precipitation events are responsible for more than 40 percent of the total annual snowfall across most of the continent — and in some places, as much as 60 percent, researchers report March 22 in Geophysical Research Letters. Climatologist John Turner of the British Antarctic Survey in Cambridge and his colleagues used regional climate simulations to estimate daily precipitation across the continent from 1979 to 2016. Then, the team zoomed in on 10 locations — representing different climates from the dry interior desert to the often snowy coasts and the open ocean — to determine regional differences in snowfall.
While snowfall amounts vary greatly by location, extreme events packed the biggest wallop along Antarctica’s coasts, especially on the floating ice shelves, the researchers found. For instance, the Amery ice shelf in East Antarctica gets roughly half of its annual precipitation — which typically totals about half a meter of snow — in just 10 days, on average. In 1994, the ice shelf got 44 percent of its entire annual precipitation on a single day in September.
Ice cores aren’t just a window into the past; they are also used to predict the continent’s future in a warming world. So characterizing these coastal regions is crucial for understanding Antarctica’s ice sheet — and its potential future contribution to sea level rise. Editor’s note: This story was updated April 5, 2019, to correct that the results were reported March 22 (not March 25).
Editor’s note: On April 10, the Event Horizon Telescope collaboration released a picture of the supermassive black hole at the center of galaxy M87. Read the full story here.
We’re about to see the first close-up of a black hole.
The Event Horizon Telescope, a network of eight radio observatories spanning the globe, has set its sights on a pair of behemoths: Sagittarius A*, the supermassive black hole at the Milky Way’s center, and an even more massive black hole 53.5 million light-years away in galaxy M87 (SN Online: 4/5/17). In April 2017, the observatories teamed up to observe the black holes’ event horizons, the boundary beyond which gravity is so extreme that even light can’t escape (SN: 5/31/14, p. 16). After almost two years of rendering the data, scientists are gearing up to release the first images in April.
Here’s what scientists hope those images can tell us.
What does a black hole really look like? Black holes live up to their names: The great gravitational beasts emit no light in any part of the electromagnetic spectrum, so they themselves don’t look like much.
But astronomers know the objects are there because of a black hole’s entourage. As a black hole’s gravity pulls in gas and dust, matter settles into an orbiting disk, with atoms jostling one another at extreme speeds. All that activity heats the matter white-hot, so it emits X-rays and other high-energy radiation. The most voraciously feeding black holes in the universe have disks that outshine all the stars in their galaxies (SN Online: 3/16/18). The EHT’s image of the Milky Way’s Sagittarius A, also called SgrA, is expected to capture the black hole’s shadow on its accompanying disk of bright material. Computer simulations and the laws of gravitational physics give astronomers a pretty good idea of what to expect. Because of the intense gravity near a black hole, the disk’s light will be warped around the event horizon in a ring, so even the material behind the black hole will be visible. And the image will probably look asymmetrical: Gravity will bend light from the inner part of the disk toward Earth more strongly than the outer part, making one side appear brighter in a lopsided ring.
Does general relativity hold up close to a black hole? The exact shape of the ring may help break one of the most frustrating stalemates in theoretical physics.
The twin pillars of physics are Einstein’s theory of general relativity, which governs massive and gravitationally rich things like black holes, and quantum mechanics, which governs the weird world of subatomic particles. Each works precisely in its own domain. But they can’t work together.
“General relativity as it is and quantum mechanics as it is are incompatible with each other,” says physicist Lia Medeiros of the University of Arizona in Tucson. “Rock, hard place. Something has to give.” If general relativity buckles at a black hole’s boundary, it may point the way forward for theorists.
Since black holes are the most extreme gravitational environments in the universe, they’re the best environment to crash test theories of gravity. It’s like throwing theories at a wall and seeing whether — or how — they break. If general relativity does hold up, scientists expect that the black hole will have a particular shadow and thus ring shape; if Einstein’s theory of gravity breaks down, a different shadow.
Medeiros and her colleagues ran computer simulations of 12,000 different black hole shadows that could differ from Einstein’s predictions. “If it’s anything different, [alternative theories of gravity] just got a Christmas present,” says Medeiros, who presented the simulation results in January in Seattle at the American Astronomical Society meeting. Even slight deviations from general relativity could create different enough shadows for EHT to probe, allowing astronomers to quantify how different what they see is from what they expect. Do stellar corpses called pulsars surround the Milky Way’s black hole? Another way to test general relativity around black holes is to watch how stars careen around them. As light flees the extreme gravity in a black hole’s vicinity, its waves get stretched out, making the light appear redder. This process, called gravitational redshift, is predicted by general relativity and was observed near SgrA* last year (SN: 8/18/18, p. 12). So far, so good for Einstein.
An even better way to do the same test would be with a pulsar, a rapidly spinning stellar corpse that sweeps the sky with a beam of radiation in a regular cadence that makes it appear to pulse (SN: 3/17/18, p. 4). Gravitational redshift would mess up the pulsars’ metronomic pacing, potentially giving a far more precise test of general relativity.
“The dream for most people who are trying to do SgrA* science, in general, is to try to find a pulsar or pulsars orbiting” the black hole, says astronomer Scott Ransom of the National Radio Astronomy Observatory in Charlottesville, Va. “There are a lot of quite interesting and quite deep tests of [general relativity] that pulsars can provide, that EHT [alone] won’t.”
Despite careful searches, no pulsars have been found near enough to SgrA* yet, partly because gas and dust in the galactic center scatters their beams and makes them difficult to spot. But EHT is taking the best look yet at that center in radio wavelengths, so Ransom and colleagues hope it might be able to spot some.
“It’s a fishing expedition, and the chances of catching a whopper are really small,” Ransom says. “But if we do, it’s totally worth it.” How do some black holes make jets? Some black holes are ravenous gluttons, pulling in massive amounts of gas and dust, while others are picky eaters. No one knows why. SgrA* seems to be one of the fussy ones, with a surprisingly dim accretion disk despite its 4 million solar mass heft. EHT’s other target, the black hole in galaxy M87, is a voracious eater, weighing in at between about 3.5 billion and 7.22 billion solar masses. And it doesn’t just amass a bright accretion disk. It also launches a bright, fast jet of charged subatomic particles that stretches for about 5,000 light-years.
“It’s a little bit counterintuitive to think a black hole spills out something,” says astrophysicist Thomas Krichbaum of the Max Planck Institute for Radio Astronomy in Bonn, Germany. “Usually people think it only swallows something.”
Many other black holes produce jets that are longer and wider than entire galaxies and can extend billions of light-years from the black hole. “The natural question arises: What is so powerful to launch these jets to such large distances?” Krichbaum says. “Now with the EHT, we can for the first time trace what is happening.”
EHT’s measurements of M87’s black hole will help estimate the strength of its magnetic field, which astronomers think is related to the jet-launching mechanism. And measurements of the jet’s properties when it’s close to the black hole will help determine where the jet originates — in the innermost part of the accretion disk, farther out in the disk or from the black hole itself. Those observations might also reveal whether the jet is launched by something about the black hole itself or by the fast-flowing material in the accretion disk.
Since jets can carry material out of the galactic center and into the regions between galaxies, they can influence how galaxies grow and evolve, and even where stars and planets form (SN: 7/21/18, p. 16).
“It is important to understanding the evolution of galaxies, from the early formation of black holes to the formation of stars and later to the formation of life,” Krichbaum says. “This is a big, big story. We are just contributing with our studies of black hole jets a little bit to the bigger puzzle.”
Editor’s note: This story was updated April 1, 2019, to correct the mass of M87’s black hole; the entire galaxy’s mass is 2.4 trillion solar masses, but the black hole itself weighs in at several billion solar masses. In addition, the black hole simulation is an example of one that uphold’s Einstein’s theory of general relativity, not one that deviates from it.
As the morning sun peeked through the trees, Rodger Kram readied himself for the coming marathon. But not the kind he used to run.
Kram, a physiologist at the University of Colorado Boulder, stood next to undergrad James Wilson at the end of a rural dirt road. Each donned a strap of nylon webbing onto his head. Attached to the bottom of their straps — called tumplines — a log rested horizontally across the duo’s lower backs. The pair was about to embark on a 25-kilometer trek to replicate how the ancient people of Chaco Canyon may have transported timber around 1,000 years ago (SN: 5/17/17). By the end of the day, their successful journey suggested that it would have taken just a few days for three people with tumplines to carry a full-size timber to Chaco, Kram, Wilson and colleagues reported on February 22 in the Journal of Archaeological Science: Reports.
Located in the northwest corner of New Mexico, Chaco Canyon is home to grand structures built between A.D. 850 and 1200. Multistoried stone buildings called great houses had roofs with timber beams about 5 meters long and 22 centimeters in diameter. The site contained at least 200,000 timbers of this size. But the wood came from forests more than 75 kilometers away (SN: 9/26/01). Load-pulling animals and wheels weren’t there at the time, and the timbers don’t appear to have been dragged. Scientists are puzzled by how the ancient people, ancestors of modern-day Diné and Pueblo peoples, moved the large timbers.
A 1986 study suggested that each log used as a beam had a mass of 275 kilograms. But Kram suspected this number couldn’t be correct.
In 2016, he cut a section of a tree outside of his house — ponderosa pine, the same species used in Chaco — and weighed it on his bathroom scale. He then extrapolated that a 5-meter-long timber would be closer to 90 kilograms. This revelation led to a 2022 study recalculating the masses of the Chaco Canyon timbers as between 85 and 140 kilograms.
“As soon as we figured out that the weight was reasonable, I wanted to carry them,” Kram says.
He and Wilson proposed that tumplines could have been used to transport the timbers. These head straps have been found on every inhabited continent and are thought to have been used since at least around 2,000 years ago. They are still widely used to carry heavy loads, such as by professional porters in Nepal. A tumpline is placed on the crown of the head — to be in line with the cervical spine — with the attached cargo resting on the small of the back. While there is no evidence that the people of Chaco used tumplines to haul timbers, there is proof that they used them to transport other items, like water vessels.
To see if tumpline timber transportation was humanly possible, Kram and Wilson trained for three months during the summer of 2020, gradually increasing their load weight and walk duration. Strangers who passed by couldn’t hide their confusion.
On the final day, the pair walked 25 kilometers while carrying a ponderosa pine that had been air-dried, which is how the people of Chaco may have prepared timbers. The 60-kilogram log was 2.5 meters long and 24 centimeters in diameter. The entire trek took almost 10 hours, and the weight of the full timber only slightly slowed the duo’s pace.
“I felt happy at the end that it was proved feasible, and that the 132-pound log we shared was off our necks,” says Wilson, now a medical student at the University of Colorado School of Medicine in Aurora. But “I never really doubted that we could do it.”
We live in a sea of neutrinos. Every second, trillions of them pass through our bodies. They come from the sun, nuclear reactors, collisions of cosmic rays hitting Earth’s atmosphere, even the Big Bang. Among fundamental particles, only photons are more numerous. Yet because neutrinos barely interact with matter, they are notoriously difficult to detect.
The existence of the neutrino was first proposed in the 1930s and then verified in the 1950s (SN: 2/13/54). Decades later, much about the neutrino — named in part because it has no electric charge — remains a mystery, including how many varieties of neutrinos exist, how much mass they have, where that mass comes from and whether they have any magnetic properties. These mysteries are at the heart of Ghost Particle by physicist Alan Chodos and science journalist James Riordon. The book is an informative, easy-to-follow introduction to the perplexing particle. Chodos and Riordon guide readers through how the neutrino was discovered, what we know — and don’t know — about it, and the ongoing and future experiments that (fingers crossed) will provide the answers.
It’s not just neutrino physicists who await those answers. Neutrinos, Riordon says, “are incredibly important both for understanding the universe and our existence in it.” Unmasking the neutrino could be key to unlocking the nature of dark matter, for instance. Or it could clear up the universe’s matter conundrum: The Big Bang should have produced equal amounts of matter and antimatter, the oppositely charged counterparts of electrons, protons and so on. When matter and antimatter come into contact, they annihilate each other. So in theory, the universe today should be empty — yet it’s not (SN: 9/22/22). It’s filled with matter and, for some reason, very little antimatter.
Science News spoke with Riordon, a frequent contributor to the magazine, about these puzzles and how neutrinos could act as a tool to observe the cosmos or even see into our own planet. The following conversation has been edited for length and clarity.
SN: In the first chapter, you list eight unanswered questions about neutrinos. Which is the most pressing to answer?
Riordon: Whether they’re their own antiparticles is probably one of the grandest. The proposal that neutrinos are their own antiparticles is an elegant solution to all sorts of problems, including the existence of this residue of matter we live in. Another one is figuring out how neutrinos fit in the standard model [of particle physics]. It’s one of the most successful theories there is, but it can’t explain the fact that neutrinos have mass. SN: Why is now a good time to write a book about neutrinos?
Riordon: All of these questions about neutrinos are sort of coming to a head right now — the hints that neutrinos may be their own antiparticles, the issues of neutrinos not quite fitting the standard model, whether there are sterile neutrinos [a hypothetical neutrino that is a candidate for dark matter]. In the next few years, a decade or so, there will be a lot of experiments that will [help answer these questions,] and the resolution either way will be exciting.
SN: Neutrinos could also be used to help scientists observe a range of phenomena. What are some of the most interesting questions neutrinos could help with?
Riordon: There are some observations that simply have to be done with neutrinos, that there are no other technological alternatives for. There’s a problem with using light-based telescopes to look back in history. We have this really amazing James Webb Space Telescope that can see really far back in history. But at some point, when you go far enough back, the universe is basically opaque to light; you can’t see into it. Once we narrow down how to detect and how to measure the cosmic neutrino background [neutrinos that formed less than a second after the Big Bang], it will be a way to look back at the very beginning. Other than with gravitational waves, you can’t see back that far with anything else. So it’ll give us sort of a telescope back to the beginning of the universe.
The other thing is, when a supernova happens, all kinds of really cool stuff happens inside, and you can see it with neutrinos because neutrinos come out immediately in a burst. We call it the “cosmic neutrino bomb,” but you can track the supernova as it’s going along. With light, it takes a while for it to get out [of the stellar explosion]. We’re due for a [nearby] supernova. We haven’t had one since 1987. It was the last visible supernova in the sky and was a boon for research. Now that we have neutrino detectors around the world, this next one is going to be even better [for research], even more exciting.
And if we develop better instrumentation, we could use neutrinos to understand what’s going on in the center of the Earth. There’s no other way that you could probe the center of the Earth. We use seismic waves, but the resolution is really low. So we could resolve a lot of questions about what the planet is made of with neutrinos.
SN: Do you have a favorite “character” in the story of neutrinos?
Riordon: I’m certainly very fond of my grandfather Clyde Cowan [he and Frederick Reines were the first physicists to detect neutrinos]. But Reines is a riveting character. He was poetic. He was a singer. He really was this creative force. I mentioned [in the book] that they put this “SNEWS” sign on their detector for “supernova early warning system,” which sort of echoed the ballistic missile early warning systems at the time [during the Cold War]. That’s so ripe.
When you’re stressed and anxious, you might feel your heart race. Is your heart racing because you’re afraid? Or does your speeding heart itself contribute to your anxiety? Both could be true, a new study in mice suggests.
By artificially increasing the heart rates of mice, scientists were able to increase anxiety-like behaviors — ones that the team then calmed by turning off a particular part of the brain. The study, published in the March 9 Nature, shows that in high-risk contexts, a racing heart could go to your head and increase anxiety. The findings could offer a new angle for studying and, potentially, treating anxiety disorders. The idea that body sensations might contribute to emotions in the brain goes back at least to one of the founders of psychology, William James, says Karl Deisseroth, a neuroscientist at Stanford University. In James’ 1890 book The Principles of Psychology, he put forward the idea that emotion follows what the body experiences. “We feel sorry because we cry, angry because we strike, afraid because we tremble,” James wrote.
The brain certainly can sense internal body signals, a phenomenon called interoception. But whether those sensations — like a racing heart — can contribute to emotion is difficult to prove, says Anna Beyeler, a neuroscientist at the French National Institute of Health and Medical Research in Bordeaux. She studies brain circuitry related to emotion and wrote a commentary on the new study but was not involved in the research. “I’m sure a lot of people have thought of doing these experiments, but no one really had the tools,” she says.
Deisseroth has spent his career developing those tools. He is one of the scientists who developed optogenetics — a technique that uses viruses to modify the genes of specific cells to respond to bursts of light (SN: 6/18/21; SN: 1/15/10). Scientists can use the flip of a light switch to activate or suppress the activity of those cells. In the new study, Deisseroth and his colleagues used a light attached to a tiny vest over a mouse’s genetically engineered heart to change the animal’s heart rate. When the light was off, a mouse’s heart pumped at about 600 beats per minute. But when the team turned on a light that flashed at 900 beats per minutes, the mouse’s heartbeat followed suit. “It’s a nice reasonable acceleration, [one a mouse] would encounter in a time of stress or fear,” Deisseroth explains.
When the mice felt their hearts racing, they showed anxiety-like behavior. In risky scenarios — like open areas where a little mouse might be someone’s lunch — the rodents slunk along the walls and lurked in darker corners. When pressing a lever for water that could sometimes be coupled with a mild shock, mice with normal heart rates still pressed without hesitation. But mice with racing hearts decided they’d rather go thirsty.
“Everybody was expecting that, but it’s the first time that it has been clearly demonstrated,” Beyeler says. The researchers also scanned the animals’ brains to find areas that might be processing the increased heart rate. One of the biggest signals, Deisseroth says, came from the posterior insula (SN: 4/25/16). “The insula was interesting because it’s highly connected with interoceptive circuitry,” he explains. “When we saw that signal, [our] interest was definitely piqued.”
Using more optogenetics, the team reduced activity in the posterior insula, which decreased the mice’s anxiety-like behaviors. The animals’ hearts still raced, but they behaved more normally, spending some time in open areas of mazes and pressing levers for water without fear. A lot of people are very excited about the work, says Wen Chen, the branch chief of basic medicine research for complementary and integrative health at the National Center for Complementary and Integrative Health in Bethesda, Md. “No matter what kind of meetings I go into, in the last two days, everybody brought up this paper,” says Chen, who wasn’t involved in the research.
The next step, Deisseroth says, is to look at other parts of the body that might affect anxiety. “We can feel it in our gut sometimes, or we can feel it in our neck or shoulders,” he says. Using optogenetics to tense a mouse’s muscles, or give them tummy butterflies, might reveal other pathways that produce fearful or anxiety-like behaviors.
Understanding the link between heart and head could eventually factor into how doctors treat panic and anxiety, Beyeler says. But the path between the lab and the clinic, she notes, is much more convoluted than that of the heart to the head.
In the classic fairy tale, Hansel and Gretel dropped bread crumbs while walking through a treacherous forest so they wouldn’t lose their way. Rovers may one day use a similar trick to traverse other planets without losing their data.
Typically, if a rover permanently loses communication during a mission, all the information that it has gathered is lost. To avoid this, researchers suggest using a multi-rover system in which a smaller rover piggybacks on a larger “mother rover.” The smaller rover would then venture into any especially uncertain territory, such as a cave or lava tubes, deploying sensors the size of an AirPods case like bread crumbs as it goes. The sensors could then communicate with each other via a wireless network and funnel any collected data back to the mother rover, theoretical physicist Wolfgang Fink and colleagues propose February 11 in Advances in Space Research. As proof of concept, the team built prototype sensors that communicate via Wi-Fi.
It’s not that the smaller rover would be following the “bread crumbs” back the way it came. Instead, “we use [the sensors] for the data to find its way communication-wise out of the cave to the mother rover,” says Fink, of the University of Arizona in Tucson.
The technology could also be useful here on Earth, especially after a natural disaster such as an earthquake. A rover could be sent with the deployable sensors into rubble where it’s too dangerous for people to perform search-and-rescue missions (SN: 12/3/14).
The bread crumb–like communication network could allow researchers to “cater to the essence of scientific exploration,” Fink says, by allowing rovers to overcome some of the constraints posed by tricky terrain. “To get to the real exciting science, you most of the time have to go to exotic places, hard-to-get-to places.”
For the first time, astronomers have caught a glimpse of shock waves rippling along strands of the cosmic web — the enormous tangle of galaxies, gas and dark matter that fills the observable universe.
Combining hundreds of thousands of radio telescope images revealed the faint glow cast as shock waves send charged particles flying through the magnetic fields that run along the cosmic web. Spotting these shock waves could give astronomers a better look at these large-scale magnetic fields, whose properties and origins are largely mysterious, researchers report in the Feb. 17 Science Advances. Finally, astronomers “can confirm what so far has only been predicted by simulations — that these shock waves exist,” says astrophysicist Marcus Brüggen of the University of Hamburg in Germany, who was not involved in the new study.
At its grandest scale, our universe looks something like Swiss cheese. Galaxies aren’t distributed evenly through space but rather are clumped together in enormous clusters connected by ropy filaments of dilute gas, galaxies and dark matter and separated by not-quite-empty voids (SN: 10/3/19).
Tugged by gravity, galaxy clusters merge, filaments collide, and gas from the voids falls onto filaments and clusters. In simulations of the cosmic web, all that action consistently sets off enormous shock waves in and along filaments.
Filaments make up most of the cosmic web but are much harder to spot than galaxies (SN: 1/20/14). While scientists have observed shock waves around galaxy clusters before, shocks in filaments “have never been really seen,” says astronomer Reinout van Weeren of Leiden University in the Netherlands, who was not involved in the study. “But they should be basically all around the cosmic web.”
Shock waves around filaments would accelerate charged particles through the magnetic fields that suffuse the cosmic web (SN: 6/6/19). When that happens, the particles emit light at wavelengths that radio telescopes can detect — though the signals are very weak. A single shock wave in a filament “would look like nothing, it’d look like noise,” says radio astronomer Tessa Vernstrom of the International Centre for Radio Astronomy Research in Crawley, Australia.
Instead of looking for individual shock waves, Vernstrom and her colleagues combined radio images of more than 600,000 pairs of galaxy clusters close enough to be connected by filaments to create a single “stacked” image. This amplified weak signals and revealed that, on average, there is a faint radio glow from the filaments between clusters.
“When you can dig below the noise and still actually get a result — to me, that’s personally exciting,” Vernstrom says.
The faint signal is highly polarized, meaning that the radio waves are mostly aligned with one another. Highly polarized light is unusual in the cosmos, but it is expected from radio light cast by shock waves, van Weeren says. “So that’s really, I think, very good evidence for the fact that the shocks are likely indeed present.” The discovery goes beyond confirming the predictions of cosmic web simulations. The polarized radio emissions also offer a rare peek at the magnetic fields that permeate the cosmic web, if only indirectly.
“These shocks,” Brüggen says, “are really able to show that there are large-scale magnetic fields that form [something] like a sheath around these filaments.”
He, van Weeren and Vernstrom all note that it’s still an open question how cosmic magnetic fields arose in the first place. The role these fields play in shaping the cosmic web is equally mysterious.
“It’s one of the four fundamental forces of nature, right? Magnetism,” Vernstrom says. “But at least on these large scales, we don’t really know how important it is.”
An uncomfortable truth is that there is another influenza pandemic in humankind’s future. Whether it will be a relative of the lethal avian flu strain currently wreaking havoc in bird populations around the globe is anyone’s guess.
Because the virus, called H5N1, can be deadly to birds, mammals and people, researchers closely monitor reports of new cases. Worryingly, a new variant of H5N1 that emerged in 2020 has not only spread farther than ever before among birds, but has also spilled over into other animals, raising the specter of a human outbreak (SN: 12/12/22).
The variant was linked to a seal die-off in Maine last summer. In October, there was an H5N1 outbreak on a mink farm in Spain, researchers reported in January in Eurosurveillance. (It’s unclear how the mink were exposed, but the animals were fed poultry by-products.) Sea lions off the coast of Peru and wild bears, foxes and skunks, which prey upon or scavenge birds, in the United States and Europe have also tested positive for the virus.
Globally, hundreds of millions of domestic poultry have been culled or died from the new variant. It’s also likely that millions of wild birds have died, though few governmental agencies are counting, says Michelle Wille a viral ecologist at the University of Sydney who studies avian influenza. “This virus is catastrophic for bird populations.”
A handful of human cases have also been reported, though there’s no evidence that the virus is spreading among people. Of seven cases, six people recovered and one person from China died. In February, health officials in China reported an eighth case in a woman whose current condition is unknown.
What’s more, four of the reported human cases — including a U.S. case from Colorado and two workers linked to the Spanish mink farm — were in people who didn’t have any respiratory symptoms. That leaves open the possibility that those people were not truly infected. Instead, tests may have picked up viral contamination, say in the nose, that the people breathed in while handling infected birds.
The impossibility of predicting which avian influenza viruses might make the jump to people and spark an outbreak is in part related to knowledge gaps. These bird pathogens don’t typically easily infect or circulate among mammals including humans. And scientists don’t have a full grasp on how these viruses might need to change for human transmission to occur.
For now, it’s encouraging that so few people have gotten infected amid such a large outbreak among birds and other animals, says Marie Culhane, a food animal veterinarian at the University of Minnesota in St. Paul. Still, experts around the globe are diligently watching for any signs the virus may be evolving to spread more easily between people.
The good news is that flu drugs and vaccines that work against the virus already exist, Wille says. Compared with where the world was when the coronavirus behind the COVID-19 pandemic came on the scene, “we are already ahead of the game.”
How the virus would need to change to spread among people is a big unknown This new iteration of bird flu is what’s called a highly pathogenic avian influenza, one that is particularly lethal for both domestic and wild birds. Aquatic birds such as ducks naturally carry avian flus with no or minor signs of infection. But when influenza viruses shuffle between poultry and waterfowl, variants with changes that make them lethal to birds can emerge and spread.
Avian viruses can be severe or even deadly for people. Since 2003, there have been 873 human cases of H5N1 infections reported to the World Health Organization. A little less than half of those people died. In February, an 11-year-old girl in Cambodia died after she developed severe pneumonia from an avian flu virus, the country’s first reported infection since 2014. Her father was also infected with the virus — a different variant than the one behind the widespread outbreak in birds —though he has not developed symptoms. It’s unknown how the two people were exposed.
Some of what scientists know about H5N1’s pandemic potential comes from controversial research on ferrets done more than a decade ago (SN: 6/21/13). Experiments showed that some changes to proteins that help the virus break into cells and make more copies of itself could help the virus travel through the air to infect ferrets, a common laboratory stand-in for humans in influenza research.
While researchers know these mutations are important in lab settings, it’s still unclear how crucial those changes are in the real world, says Jonathan Runstadler, a disease ecologist and virologist at Tufts University’s Cummings School of Veterinary Medicine in North Grafton, Mass. Viruses change constantly, but not all genetic tweaks work together. A change may help one version of the virus transmit better, while also hurting another variant and making it less likely to spread.
“We’re not sure how critical or how big a difference or how much to worry about those mutations when they happen in the wild,” Runstadler says. “Or when they happen five years down the road when there are other changes in the virus’s genetic background that are impacting those [original] mutations.”
That doesn’t stop researchers from trying to pinpoint specific changes. Runstadler and his team look for viruses in nature that have jumped into new animals and work backward to figure out which mutations were crucial. And virologist Louise Moncla says her lab is trying to develop ways to scan entire genetic blueprints of viruses from past outbreaks to look for signatures of a virus that can jump between different animal species.
“There’s a ton that we don’t know about avian influenza viruses and host switching,” says Moncla, of the University of Pennsylvania.
Genetic analyses of H5N1 circulating on the mink farm in Spain, for instance, revealed a change known to help the virus infect mice and mammalian cells grown in the lab. Such a change could make it easier for the virus to spread among mammals, including people. There could have been mink-to-mink transmission on the farm, the researchers concluded, but it remains unclear how much of a role that specific mutation played in the outbreak.
It’s a numbers game for when influenza viruses with the ability to transmit among mammals might make the jump from birds, Runstadler says. “The more chances you give the virus to spill over and adapt, the higher the risk will be that one of those adaptations will be effective [at helping the virus spread among other animals] or take root and be a real problem.”
The ongoing outbreak is still a big problem for birds Irrespective of our inability to forecast human’s future with H5N1, it’s clear that many species of birds — and some other animals that eat them — are dying now. And more species of birds are dying in this outbreak than previous ones, Culhane and Wille say.
“We have seen huge outbreaks in raptors and seabirds, which were never really affected before,” Wille says. It’s possible that genetic changes have helped the virus to spread more efficiently among birds than previous versions of H5N1, but that’s unknown. “There are a number of studies underway to try and figure it out,” Wille says. Historically, these deadly avian flus have not been a persistent problem in the Americas, Moncla says. Sporadic outbreaks of H5N1 variants are typically limited to places such as parts of Asia, where the virus has circulated in birds since its emergence in the late 1990s, and northern Africa.
North America’s last big avian flu outbreak was in 2015, when experts detected more than 200 cases of a different bird flu virus in commercial and backyard poultry across the United States. The poultry industry culled more than 45 million birds to stop that virus’s spread, Culhane says. “But it didn’t go away from the rest of the world.”
The latest version of H5N1 arrived on North American shores from Europe in late 2021, first popping up in Canada in Newfoundland and Labrador. From there, it spread south into the United States, where so far tens of millions of domestic poultry have been culled to prevent transmission on farms where the virus has been detected. By December 2022, the virus had made it to South America. In Peru, tens of thousands of pelicans and more than 700 sea lions have died since mid-January.
It’s important to understand exactly how nonbird animals are getting exposed, Culhane says. Highly pathogenic avian influenzas infect every organ of a bird’s body. So, a fox chowing down on an infected bird is exposing its own mouth, nose and stomach to a lot of virus as it eats its meal.
For now, experts are keeping an eye on infected animals to raise the alarm early if H5N1 starts transmitting among mammals.
“I do think that the mink outbreak, and then the sea lion outbreak, is a wake-up call,” Moncla says. “We should be doing our very best to implement all the science we can to try and understand what’s happening with these viruses so that if the situation does change, we are better prepared.”
