The sleepy sun turns out to be a factory of extremely energetic light.

Scientists have discovered that the sun puts out more of this light, called high-energy gamma rays, overall than predicted. But what’s really weird is that the rays with the highest energies appear when the star is supposed to be at its most sluggish, researchers report in an upcoming study in Physical Review Letters. The research is the first to examine these gamma rays over most of the solar cycle, a roughly 11-year period of waxing and waning solar activity.
That newfound oddity is probably connected to the activity of the sun’s magnetic fields, the researchers say, and could lead to new insights about the mysterious environment.

“The almost certain thing that’s going on here is the magnetic fields are much more powerful, much more variable, and much more weirdly shaped than we expect,” says astrophysicist John Beacom of the Ohio State University in Columbus.
The sun’s high-energy gamma rays aren’t produced directly by the star. Instead, the light is triggered by cosmic rays — protons that zip through space with some of the highest energies known in nature
— that smack into solar protons and produce high-energy gamma rays in the process ( SN: 10/14/27, p. 7 ) .
All of those gamma rays would get lost inside the sun, if not for magnetic fields. Magnetic fields are known to take charged particles like cosmic rays and spin them around like a house in a tornado. Theorists have predicted that cosmic rays whose paths have been scrambled by the tangled mass of magnetic fields at the solar surface should send high-energy gamma rays shooting back out of the sun, where astronomers can see them.

Beacom and colleagues, led by astrophysicist Tim Linden of Ohio State, sifted through data from NASA’s Fermi Gamma-ray Space Telescope from August 2008 to November 2017. The observations spanned a period of low solar activity in 2008 and 2009, a period of higher activity in 2013 and a decline in activity to the minimum of the next cycle, which started in 2018 (SN: 11/2/13, p. 22). The team tracked the number of solar gamma rays emitted per second, as well as their energies and where on the sun they came from.

There were more high-energy gamma rays, above 50 billion electron volts, or GeV, than anyone predicted, the team reports. Weirder still, rays with energies above 100 GeV appeared only during the solar minimum, when the sun’s activity level was low. One photon emitted during the solar minimum had an energy as high as 467.7 GeV.

Strangest of all, the sun seems to emit gamma rays from different parts of its surface at different times in its cycle. Because cosmic rays that hit the sun come in from all directions, you would expect the entire sun to light up in gamma rays uniformly. But Beacom’s team found that during the solar minimum, gamma rays came mainly from near the equator, and during the solar maximum, when the sun’s activity level was high, they clustered near the poles.

“All of these things are way more weird than anyone had predicted,” Beacom says. “And that means the magnetic fields must be way more weird than anyone had thought.”
Beacom and colleagues tried to connect the excess gamma rays to other solar behaviors that change with magnetic activity, like solar flares or sunspots (SN: 9/30/17, p. 6). “So far nothing has really held up to any sort of scrutiny,” says astrophysicist Annika Peter, also at Ohio State.

High-energy gamma rays may offer a new way to probe the magnetic fields in the uppermost layer of the solar surface, called the photosphere. “You can’t see [the fields] with a telescope,” Beacom says. “But these [cosmic rays] are journeying there, and the gamma rays they send back are messengers of the terrible conditions there.”

More observations are coming soon. NASA’s Parker Solar Probe, which launched on August 12, will take the first direct measurements of the magnetic field in the sun’s outer atmosphere, or corona (SN: 7/21/18, p. 12). And as the sun enters the next solar minimum, the highest-energy gamma rays are starting to return. In February, Fermi caught its first gamma ray with an energy above 100 GeV since 2009.

“There really is something strange afoot,” says solar physicist Craig DeForest of the Southwest Research Institute, who is based in Boulder, Colo., and was not involved in the work. “When there’s some new discovery, scientists don’t shout ‘Eureka!’ They go, ‘Hm, that’s funny. That can’t be right.’ This is a classic case of that.”

A new material that converts light into heat could be laminated onto airplanes, wind turbines, rooftops and offshore oil platforms to help combat ice buildup.

This deicer, called a photothermal trap, has three layers: a top coating of a ceramic-metal mix that turns incoming light into thermal energy, a middle layer of aluminum that spreads this heat across the entire sheet — warming up even areas not bathed in light — and a foam insulation base. The photothermal trap, described online August 31 in Science Advances, can be powered by sunshine or LEDs.

Engineer Susmita Dash of the Indian Institute of Science in Bengaluru and colleagues laid a 6.3-centimeter-wide sheet of the deicing material out in the sun on a day averaging about –3.5° Celsius, alongside a sheet of aluminum. Within four minutes, the photothermal trap heated to about 30° C, while the aluminum warmed to only about 6° C. After five minutes, snow on the surface of the photothermal trap had mostly melted off, but snow remained caked on the aluminum.

Deicing surfaces typically involves energy-intensive heating systems or environmentally unfriendly chemical sprays. By harnessing light to melt ice away, the new photothermal trap may provide a more sustainable means of keeping surfaces ice-free. “This is a new direction for anti-icing,” says Kevin Golovin, a materials scientist and engineer at the University of British Columbia in Kelowna not involved in the work.

New images of gas churning inside an ancient starburst galaxy help explain why this galactic firecracker underwent such frenzied star formation.

Using the Atacama Large Millimeter/submillimeter Array, or ALMA, researchers have taken the most detailed views of the disk of star-forming gas that permeated the galaxy COSMOS-AzTEC-1, which dates back to when the universe was less than 2 billion years old. The telescope observations, reported online August 29 in Nature, reveal an enormous reservoir of molecular gas that was highly susceptible to collapsing and forging new stars.
COSMOS-AzTEC-1 and its starburst contemporaries have long puzzled astronomers, because these galaxies cranked out new stars about 1,000 times as fast as the Milky Way does. According to standard theories of cosmology, galaxies shouldn’t have grown up fast enough to be such prolific star-formers so soon after the Big Bang.

Inside a normal galaxy, the outward pressure of radiation from stars helps counteract the inward pull of gas’s gravity, which pumps the brakes on star formation. But in COSMOS-AzTEC-1, the gas’s gravity was so intense that it overpowered the feeble radiation pressure from stars, leading to runaway star formation. The new ALMA pictures unveil two especially large clouds of collapsing gas in the disk, which were major hubs of star formation.
“It’s like a giant fuel depot that built up right after the Big Bang … and we’re catching it right in the process of the whole thing lighting up,” says study coauthor Min Yun, an astronomer at the University of Massachusetts Amherst.

Yun and colleagues still don’t know how COSMOS-AzTEC-1 stocked up such a massive supply of star-forming material. But future observations of the galaxy and its ilk using ALMA or the James Webb Space Telescope, set to launch in 2021, may help clarify the origins of these ancient cosmic monsters (SN Online: 6/11/14).

Obesity can affect brainpower, and a study in mice may help explain how.

In the brains of obese mice, rogue immune cells chomp nerve cell connections that are important for learning and memory, scientists report September 10 in the Journal of Neuroscience. Drugs that stop this synapse destruction may ultimately prove useful for protecting the brain against the immune cell assault.

Like people, mice that eat lots of fat quickly pack on pounds. After 12 weeks of a high-fat diet, mice weighed almost 40 percent more than mice fed standard chow. These obese mice showed signs of diminished brainpower, neuroscientist Elizabeth Gould of Princeton University and colleagues found. Obese mice were worse at escaping mazes and remembering an object’s location than mice of a normal weight.
On nerve cells, microscopic knobs called dendritic spines receive signals. Compared with normal-sized mice, obese mice had fewer dendritic spines in several parts of the mice’s hippocampi, brain structures important for learning and memory.

The dendritic spine destruction comes from immune cells called microglia, the results suggest. In obese mice, higher numbers of active microglia lurked among these sparser nerve cell connections compared with mice of normal weights. When the researchers interfered with microglia in obese mice, dendritic spines were protected and the mice’s performance on thinking tests improved.

Figuring out ways to stop microglia’s damage might one day prove to protect against obesity-related brain trouble, a concern relevant to the estimated 650 million obese adults worldwide. Obese people are also at a higher risk of dementias such as Alzheimer’s, and some researchers suspect microglia may be a culprit in those brain diseases more generally.

I’m relatively new to Oregon, but one of the ways I know I’m starting to settle in is my ability to recognize marijuana shops. Some are easy. But others, with names like The Agrestic and Mr. Nice Guy, are a little trickier to identify for someone who hasn’t spent much time in a state that has legalized marijuana.

A growing number of states have legalized both medical and recreational marijuana. At the same time, women who are pregnant or breastfeeding are using the drug in increasing numbers. A 2017 JAMA study described both survey results and urine tests of nearly 280,000 pregnant women in Northern California, where medical marijuana was legalized in 1996. The study showed that in 2009, about 4 percent of the women tested used marijuana. In 2016, about 7 percent of women did. Those California numbers may be even higher now, since recreational marijuana became legal there this year.
Some of those numbers may be due in part to women using marijuana to treat their morning sickness, a more recent study by some of the same researchers suggests. Their report, published August 20 in JAMA Internal Medicine, found that pregnant women with severe nausea and vomiting were 3.8 times more likely to use marijuana than pregnant women without morning sickness.

So some pregnant women are definitely using the drug, and exposing their fetuses to it, too. Ingredients in marijuana are known to make their way to fetuses by crossing the placenta during pregnancy (and by entering breast milk after the baby is born). But what actually happens when those marijuana compounds arrive?

That’s the question the American Academy of Pediatrics grapples with in a clinical report published in the August issue of Pediatrics. In an effort to provide guidance to caregivers and women, the AAP sums up the existing scientific literature on how marijuana affects mothers and babies.

While it seems like a bad idea to expose developing babies to marijuana, the science to back up that intuition is frustratingly slim. Some studies have turned up negative outcomes for babies, such as lower birth weight and a greater likelihood of needing the neonatal intensive care unit. And marijuana use during pregnancy has been tied to a greater risk of anemia in mothers. But other studies found no such effects.
This subject — and any topic that involves drugs and babies — is hard to study. Ethical reasons prevent scientists from assigning some pregnant women to use marijuana and others to abstain. Such randomization is a key feature of a solid study, and one that’s just not available in this case. That leaves scientists to study women who are already using marijuana while pregnant, and those women may have other characteristics that make a direct comparison difficult. That makes it harder to say whether it was marijuana, or something else, that is linked to a particular outcome.

Still, despite what the AAP calls “limited research,” there may be enough hints, from observational studies of women already using marijuana and from animal studies, to make pregnant women pause before using marijuana. Add to those red flags the fact that today’s marijuana is a lot more potent than it used to be, meaning that more of the active compound THC could reach the developing baby. And toxins such as pesticides might come along for the ride, perhaps causing other kinds of trouble.

These questions are more pressing as marijuana becomes easier to get legally, and as more pregnant women use it. Hopefully this shift will prompt scientists to figure out better ways to study the drug’s effects — or lack thereof.

NOORDWIJK, THE NETHERLANDS — Life might arise in the darkest of places: the moon of a planet wandering the galaxy without a star.

The gravitational tug-of-war between a moon and its planet can keep certain satellites toasty enough for liquid water to exist there — a condition widely considered crucial for life. Now computer simulations suggest that, given the right orbit and atmosphere, some moons orbiting rogue planets can stay warm for over a billion years, astrophysicist Giulia Roccetti reported March 23 at the PLANET-ESLAB 2023 Symposium. She and her colleagues also report their findings March 20 in the International Journal of Astrobiology.
“There might be many places in the universe where habitable conditions can be present,” says Roccetti, of the European Southern Observatory in Garching, Germany. But life presumably also needs long-term stability. “What we are looking for is places where these habitable conditions can be sustained for hundreds of millions, or billions, of years.”

Habitability and stability don’t necessarily need to come from a nearby sun. Astronomers have spotted about 100 starless planets, some possibly formed from gas and dust clouds the way stars form, others probably ejected from their home solar systems (SN: 7/24/17). Computer simulations suggest that there may be as many of these free-floating planets as there are stars in the galaxy.

Such orphaned planets might also have moons — and in 2021, researchers calculated that these moons need not be cold and barren places.

Unless a moon’s orbit is a perfect circle, the gravitational pull of its planet continually deforms it. Resulting friction inside the moon generates heat. In our own solar system, this process plays out on moons such as Saturn’s Enceladus and Jupiter’s Europa (SN: 11/6/17; SN: 8/6/20). A sufficiently thick, heat-trapping atmosphere, likely one dominated by carbon dioxide, might then keep the surface warm enough for water to remain liquid. That water could come from chemical reactions with the carbon dioxide and hydrogen in the atmosphere, initiated by the impact of high-speed charged particles from space.

But such a moon won’t stay warm forever. The same gravitational forces that heat it up also mold its orbit into a circle. Gradually, the ebb and flow of gravity felt by the moon deforms it less and less, and the supply of frictional heat dwindles.

In the new study, Roccetti and her colleagues ran 8,000 computer simulations of a sunlike star with three Jupiter-sized planets. These simulations showed that planets that are ejected from their solar system will often sail off into space with their moons in tow.

The team then ran simulations of those moons, assumed to be the size of Earth, whizzing around their planets along the orbit they ended up with during the ejection. The goal was to see if gravitational heating occurred and if it lasted long enough for life to potentially originate there. Earth may have become habitable within a few hundred million years, although the earliest evidence of living organisms here date to about 1 billion years after the planet formed (SN: 1/26/18).
Because an atmosphere is crucial to heat retention, the team did their calculations with three alternatives. For moons with an atmosphere the same pressure as Earth’s, the period of potential habitability lasted at most about 50 million years, the team found. But it can last nearly 300 million years if the atmospheric pressure is 10 times that of Earth, and for about 1.6 billion years at pressures 10 times greater still. That amount of pressure may sound extreme, but it’s close to conditions on the similarly sized Venus.

Warmth and water might not be enough to let living organisms appear, though. Moons of free-floating planets “will not be the most favorable places for life to arise,” says astrophysicist Alex Teachey, of the Academia Sinica Institute of Astronomy & Astrophysics in Taipei, Taiwan.

“I think stars, due to their incredible power output and their longevity, are going to be far better sources of energy for life,” says Teachey, who studies the moons of exoplanets. “A big open question … is whether you can even start life in a place like Europa or Enceladus, even if the conditions are right to sustain life, because you don’t have, for example, solar radiation that can help along the process of mutation for evolution.”

But Roccetti — although not an astrobiologist herself — thinks moons of orphan planets have a few important advantages. They will have some, but not too much, water, which many astrobiologists think is a better starting point for life than, say, an ocean world. And not having a star nearby means there are no solar flares, which in many cases will destroy the atmosphere of an otherwise promising planet.

“There are many environments in our universe which are very different from what we have here on Earth,” she says, “and it is important to investigate all of them.”

Slow-motion large land snails made for easy catching and good eating as early as 170,000 years ago.

Until now, the oldest evidence of Homo sapiens eating land snails dated to roughly 49,000 years ago in Africa and 36,000 years ago in Europe. But tens of thousands of years earlier, people at a southern African rock-shelter roasted these slimy, chewy — and nutritious — creepers that can grow as big as an adult’s hand, researchers report in the April 15 Quaternary Science Reviews.
Analyses of shell fragments excavated at South Africa’s Border Cave indicate that hunter-gatherers who periodically occupied the site heated large African land snails on embers and then presumably ate them, say chemist Marine Wojcieszak and colleagues. Wojcieszak, of the Royal Institute for Cultural Heritage in Brussels, studies chemical properties of archaeological sites and artifacts.

The supersized delicacy became especially popular between about 160,000 and 70,000 years ago, the researchers say. Numbers of unearthed snail shell pieces were substantially larger in sediment layers dating to that time period.

New discoveries at Border Cave challenge an influential idea that human groups did not make land snails and other small game a big part of their diet until the last Ice Age waned around 15,000 to 10,000 years ago, Wojcieszak says.

Long before that, hunter-gatherer groups in southern Africa roamed the countryside collecting large land snails to bring back to Border Cave for themselves and to share with others, the team contends. Some of the group members who stayed behind on snail-gathering forays may have had limited mobility due to age or injury, the researchers suspect.

“The easy-to-eat, fatty protein of snails would have been an important food for the elderly and small children, who are less able to chew hard foods,” Wojcieszak says. “Food sharing [at Border Cave] shows that cooperative social behavior was in place from the dawn of our species.”

Border Cave’s ancient snail scarfers also push back the human consumption of mollusks by several thousand years, says archaeologist Antonieta Jerardino of the University of South Africa in Pretoria. Previous excavations at a cave on South Africa’s southern tip found evidence of humans eating mussels, limpets and other marine mollusks as early as around 164,000 years ago (SN: 7/29/11).

Given the nutritional value of large land snails, an earlier argument that it was eating fish and shellfish that energized human brain evolution may have been overstated, says Jerardino, who did not participate in the new study.
It’s not surprising that ancient H. sapiens recognized the nutritional value of land snails and occasionally cooked and ate them by 170,000 years ago, says Teresa Steele, an archaeologist at the University of California, Davis who was not part of the work. But intensive consumption of these snails starting around 160,000 years ago is unexpected and raises questions about whether climate and habitat changes may have reduced the availability of other foods, Steele says.

Researchers have already found evidence that ancient people at Border Cave cooked starchy plant stems, ate an array of fruits and hunted small and large animals. The oldest known grass bedding, from around 200,000 years ago, has also been unearthed at Border Cave (SN: 8/13/20).

Several excavations have been conducted at the site since 1934. Three archaeologists on the new study — Lucinda Backwell and Lyn Wadley of Wits University in Johannesburg and Francesco d’Errico of the University of Bordeaux in France — directed the latest Border Cave dig, which ran from 2015 through 2019.

Discoveries by that team inspired the new investigation. Excavations uncovered shell fragments of large land snails, many discolored from possible burning, in all but the oldest sediment layers containing remnants of campfires and other H. sapiens activity. The oldest layers date to at least 227,000 years ago.

Chemical and microscopic characteristics of 27 snail shell fragments from various sediment layers were compared with shell fragments of modern large African snails that were heated in a metal furnace. Experimental temperatures ranged from 200° to 550° Celsius. Heating times lasted from five minutes to 36 hours.

All but a few ancient shell pieces displayed signs of extended heat exposure consistent with having once been attached to snails that were cooked on hot embers. Heating clues on shell surfaces included microscopic cracks and a dull finish.

Only lower parts of large land snail shells would have rested against embers during cooking, possibly explaining the mix of burned and unburned shell fragments unearthed at Border Cave, the researchers say.

The battle over the heft of a hard-to-detect particle is heating up. What’s at stake? Only the leading theory describing all known matter in the universe.

A recalculation of the mass of an elementary particle, the W boson, has increased the tension between measurements from competing particle collider experiments. The ultimate outcome could bolster the standard model of particle physics, which describes the fundamental forces and quantum bits that make up everything we see in the cosmos. Or it could reveal signs of the standard model’s breakdown, depending on which lab’s answer prevails.
A reanalysis of old data from the Large Hadron Collider’s ATLAS experiment yields a W boson mass of about 80,360 million electron volts, or MeV. Researchers with the experiment, at CERN in Geneva, reported the measurement March 23 at the Rencontres de Moriond conference in La Thuile, Italy. The revised value is closely aligned with predictions from the standard model.

It also boasts reduced uncertainty from the researchers’ previous analysis of the data, which they reported in 2018, increasing their confidence that they got the mass right.

But the updated mass is at odds with that of another group. In 2022, scientists from the Collider Detector at Fermilab, or CDF, experiment shocked the physics community with a measurement of 80,434 MeV — about 100 MeV heavier than expected (SN: 4/7/22). If the CDF report is correct, it implies that something is off with the standard model that has persevered in the face of every experimental challenge thrown at it over the last 50 years.

The W boson is responsible for the weak force, one of three fundamental forces in the standard model (SN: 2/5/83). And “it’s the only mass of a particle in the standard model that can be calculated,” says theoretical physicist Sven Heinemeyer of the Karlsruhe Institute of Technology in Germany. That is, the standard model theory yields a specific mass for the W boson, whereas the masses of other particles such as electrons and quarks are inputs and can be — as far as the theory is concerned — any value. Finding a W boson mass that’s different from standard model predictions would show the current theory is wrong.

The ATLAS reanalysis offers a stronger counterpoint to the CDF claim than the earlier ATLAS analysis of the same data. “The new analysis is an important confirmation of our previous result,” says Andreas Hoecker, a physicist at CERN.

The latest ATLAS value widens the chasm that separates CDF’s mass measurement from the herd of other studies. But it shouldn’t be seen as erasing CDF’s standard model challenge, says Duke University physicist Ashutosh Kotwal, a member of the CDF collaboration.

“The perspective on the CDF [announcement of a heavy W boson in 2022] does not change because of the ATLAS reanalysis,” Kotwal says. Because the reanalysis is based on data that ATLAS already released in 2017, he says, “the fact that ATLAS obtains a similar value as before is to be expected.”
Heinemeyer, who is not affiliated with ATLAS or CDF, sees a shift in the W boson mass landscape, but no sign of a resolution of the discrepancy.

“Having one new measurement is not enough,” Heinemeyer says. “If more and more measurements were to come out now from ATLAS and [other experiments], and they would all be in the same ballpark, at some point the community would decide CDF did something wrong.”

The next word on the W boson mass will probably come with pending studies from ATLAS and other experiments at CERN. The CDF experiment shut down in 2011, so it will not contribute further to the debate.

In the meantime, researchers hope to scrutinize each other’s analyses to search for clues that might help explain discrepancies in W boson mass measurements. “The CDF April 2022 paper provides a number of cross-checks of the CDF methodology and is transparent,” Kotwal says. “I look forward to detailed discussions of the ATLAS methodology.”

In the end, the conflict might reveal a new crack in the standard model. Or it could turn out to be another example of one of the most successful theories in history standing strong.

A 13-sided shape known as “the hat” has mathematicians tipping their caps.

It’s the first true example of an “einstein,” a single shape that forms a special tiling of a plane: Like bathroom floor tile, it can cover an entire surface with no gaps or overlaps but only with a pattern that never repeats.

“Everybody is astonished and is delighted, both,” says mathematician Marjorie Senechal of Smith College in Northampton, Mass., who was not involved with the discovery. Mathematicians had been searching for such a shape for half a century. “It wasn’t even clear that such a thing could exist,” Senechal says.

Although the name “einstein” conjures up the iconic physicist, it comes from the German ein Stein, meaning “one stone,” referring to the single tile. The einstein sits in a weird purgatory between order and disorder. Though the tiles fit neatly together and can cover an infinite plane, they are aperiodic, meaning they can’t form a pattern that repeats.

With a periodic pattern, it’s possible to shift the tiles over and have them match up perfectly with their previous arrangement. An infinite checkerboard, for example, looks just the same if you slide the rows over by two. While it’s possible to arrange other single tiles in patterns that are not periodic, the hat is special because there’s no way it can create a periodic pattern.
Identified by David Smith, a nonprofessional mathematician who describes himself as an “imaginative tinkerer of shapes,” and reported in a paper posted online March 20 at arXiv.org, the hat is a polykite — a bunch of smaller kite shapes stuck together. That’s a type of shape that hadn’t been studied closely in the search for einsteins, says Chaim Goodman-Strauss of the National Museum of Mathematics in New York City, one of a group of trained mathematicians and computer scientists Smith teamed up with to study the hat.

It’s a surprisingly simple polygon. Before this work, if you’d asked what an einstein would look like, Goodman-Strauss says, “I would’ve drawn some crazy, squiggly, nasty thing.”

Mathematicians previously knew of nonrepeating tilings that involved multiple tiles of different shapes. In the 1970s, mathematician Roger Penrose discovered that just two different shapes formed a tiling that isn’t periodic (SN: 3/1/07). From there, “It was natural to wonder, could there be a single tile that does this?” says mathematician Casey Mann of the University of Washington Bothell, who was not involved with the research. That one has finally been found, “it’s huge.”
Other shapes have come close. Taylor-Socolar tiles are aperiodic, but they are a jumble of multiple disconnected pieces — not what most people think of as a single tile. “This is the first solution without asterisks,” says mathematician Michaël Rao of CNRS and École Normale Supérieure de Lyon in France.

Smith and colleagues proved that the tile was an einstein in two ways. One came from noticing that the hats arrange themselves into larger clusters, called metatiles. Those metatiles then arrange into even larger supertiles, and so on indefinitely, in a type of hierarchical structure that is common for tilings that aren’t periodic. This approach revealed that the hat tiling could fill an entire infinite plane, and that its pattern would not repeat.

The second proof relied on the fact that the hat is part of a continuum of shapes: By gradually changing the relative lengths of the sides of the hat, the mathematicians were able to form a family of tiles that can take on the same nonrepeating pattern. By considering the relative sizes and shapes of the tiles at the extremes of that family — one shaped like a chevron and the other reminiscent of a comet — the team was able to show that the hat couldn’t be arranged in a periodic pattern.
While the paper has yet to be peer-reviewed, the experts interviewed for this article agree that the result seems likely to hold up to detailed scrutiny.

Nonrepeating patterns can have real-world connections. Materials scientist Dan Shechtman won the 2011 Nobel Prize in chemistry for his discovery of quasicrystals, materials with atoms arranged in an orderly structure that never repeats, often described as analogs to Penrose’s tilings (SN: 10/5/11). The new aperiodic tile could spark further investigations in materials science, Senechal says.

Similar tilings have inspired artists, and the hat appears to be no exception. Already the tiling has been rendered artistically as smiling turtles and a jumble of shirts and hats. Presumably it’s only a matter of time before someone puts hat tiles on a hat.

The new aperiodic monotile discovered by Dave Smith, Joseph Myers, Craig Kaplan, and Chaim Goodman-Strauss, rendered as shirts and hats. The hat tiles are mirrored relative to the shirt tiles. pic.twitter.com/BwuLUPVT5a

— Robert Fathauer (@RobFathauerArt) March 21, 2023
And the hat isn’t the end. Researchers should continue the hunt for additional einsteins, says computer scientist Craig Kaplan of the University of Waterloo in Canada, a coauthor of the study. “Now that we’ve unlocked the door, hopefully other new shapes will come along.”

The ghost catfish transforms from glassy to glam when white light passes through its mostly transparent body. Now, scientists know why.

The fish’s iridescence comes from light bending as it travels through microscopic striped structures in the animal’s muscles, researchers report March 13 in the Proceedings of the National Academy of Sciences.

Many fishes with iridescent flair have tiny crystals in their skin or scales that reflect light (SN: 4/6/21). But the ghost catfish (Kryptopterus vitreolus) and other transparent aquatic species, like eel larvae and icefishes, lack such structures to explain their luster.

The ghost catfish’s see-through body caught the eye of physicist Qibin Zhao when he was in an aquarium store. The roughly 5-centimeter-long freshwater fish is a popular ornamental species. “I was standing in front of the tank and staring at the fish,” says Zhao, of Shanghai Jiao Tong University. “And then I saw the iridescence.”

To investigate the fish’s colorful properties, Zhao and colleagues first examined the fish under different lighting conditions. The researchers determined its iridescence arose from light passing through the fish rather than reflecting off it. By using a white light laser to illuminate the animal’s muscles and skin separately, the team found that the muscles generated the multicolored sheen.
The researchers then characterized the muscles’ properties by analyzing how X-rays scatter when traveling through the tissue and by looking at it with an electron microscope. The team identified sarcomeres — regularly spaced, banded structures, each roughly 2 micrometers long, that run along the length of muscle fibers — as the source of the iridescence.

The sarcomeres’ repeating bands, comprised of proteins that overlap by varying amounts, bend white light in a way that separates and enhances its different wavelengths. The collective diffraction of light produces an array of colors. When the fish contracts and relaxes its muscles to swim, the sarcomeres slightly change in length, causing a shifting rainbow effect.
The purpose of the ghost catfish’s iridescence is a little unclear, says Heok Hee Ng, an independent ichthyologist in Singapore who was not involved in the new study. Ghost catfish live in murky water and seldom rely on sight, he says. But the iridescence might help them visually coordinate movements when traveling in schools, or it could help them blend in with shimmering water to hide from land predators, like some birds, he adds.

Regardless of function, Ng is excited to see scientists exploring the ghost catfish’s unusual characteristics.

“Fishes actually have quite a number of these interesting structures that serve them in many ways,” he says. “And a lot of these structures are very poorly studied.”