Watching the death of a rare giant star

A University of Arizona-led team of astronomers has created a detailed, three-dimensional image of a dying hypergiant star. The team, led by UArizona researchers Ambesh Singh and Lucy Ziurys, traced the distribution, directions and velocities of a variety of molecules surrounding a red hypergiant star known as VY Canis Majoris.

Their findings, which they presented on June 13 at the 240th Meeting of the American Astronomical Society in Pasadena, California, offer insights, at an unprecedented scale, into the processes that accompany the death of giant stars. The work was done with collaborators Robert Humphreys from the University of Minnesota and Anita Richards from the University of Manchester in the United Kingdom.

Extreme supergiant stars known as hypergiants are very rare, with only a few known to exist in the Milky Way. Examples include Betelgeuse, the second brightest star in the constellation Orion, and NML Cygni, also known as V1489 Cygni, in the constellation Cygnus. Unlike stars with lower masses -- which are more likely to puff up once they enter the red giant phase but generally retain a spherical shape -- hypergiants tend to experience substantial, sporadic mass loss events that form complex, highly irregular structures composed of arcs, clumps and knots.

Located about 3,009 light-years from Earth, VY Canis Majoris -- or VY CMa, for short -- is a pulsating variable star in the slightly southern constellation of Canis Major. Spanning anywhere from 10,000 to 15,000 astronomical units (with 1 AU being the average distance between Earth and the sun) VY CMa is possibly the most massive star in the Milky Way, according to Ziurys.

"Think of it as Betelgeuse on steroids," said Ziurys, a Regents Professor with joint appointments in UArizona Department of Chemistry and Biochemistry and Steward Observatory, both part of the College of Science. "It is much larger, much more massive and undergoes violent mass eruptions every 200 years or so."

The team chose to study VY CMa because it is one of the best examples of these types of stars.

"We are particularly interested in what hypergiant stars do at end of their lives," said Singh, a fourth-year doctoral student in Ziurys' lab. "People used to think these massive stars simply evolve into supernovae explosions, but we are no longer sure about that."

"If that were the case, we should see many more supernovae explosions across the sky," Ziurys added. "We now think they might quietly collapse into black holes, but we don't know which ones end their lives like that, or why that happens and how."

Previous imaging of VY CMa with NASA's Hubble Space Telescope and spectroscopy showed the presence of distinct arcs and other clumps and knots, many extending thousands of AU from the central star. To uncover more details of the processes by which hypergiant stars end their lives, the team set out to trace certain molecules around the hypergiant and map them to preexisting images of the dust, taken by the Hubble Space Telescope.

"Nobody has been able to make a complete image of this star," Ziurys said, explaining that her team set out to understand the mechanisms by which the star sheds mass, which appear to be different from those of smaller stars entering their red giant phase at the end of their lives.

"You don't see this nice, symmetrical mass loss, but rather convection cells that blow through the star's photosphere like giant bullets and eject mass in different directions," Ziurys said. "These are analogous to the coronal arcs seen in the sun, but a billion times larger."

The team used the Atacama Large Millimeter Array, or ALMA, in Chile to trace a variety of molecules in material ejected from the stellar surface. While some observations are still in progress, preliminary maps of sulfur oxide, sulfur dioxide, silicon oxide, phosphorus oxide and sodium chloride were obtained. From these data, the group constructed an image of the global molecular outflow structure of VY CMa on scales that encompassed all ejected material from the star.

"The molecules trace the arcs in the envelope, which tells us molecules and dust are well-mixed," Singh said. "The nice thing about emissions of molecules at radio wavelengths is that they provide us with velocity information, as opposed to the dust emission, which is static."

By moving ALMA's 48 radio dishes into different configurations, the researchers were able to obtain information about the directions and velocities of the molecules and map them across the different regions of the hypergiant's envelope in considerable detail, even correlating them to different mass ejection events over time.

Processing the data required some heavy lifting in terms of computing power, Singh said.

"So far, we have processed almost a terabyte from ALMA, and we still receive data that we have to go through to get the best resolution possible," he said. "Just calibrating and cleaning the data requires up to 20,000 iterations, which takes a day or two for each molecule."

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100,000-year-old polar bear genome reveals ancient hybridization with brown bears

An analysis of ancient DNA from a 100,000-year-old polar bear has revealed that extensive hybridization between polar bears and brown bears occurred during the last warm interglacial period in the Pleistocene, leaving a surprising amount of polar bear ancestry in the genomes of all living brown bears.

The study, led by scientists at the University of California, Santa Cruz, was published June 16 in Nature Ecology & Evolution. The researchers obtained ancient DNA from the skull of a juvenile polar bear that was found in 2009 on the coast of the Beaufort Sea in Arctic Alaska. Scientists nicknamed the bear 'Bruno,' although DNA analysis later showed it to be a female.

"The availability of Bruno's paleogenome has made it possible to detect an ancient admixture event that impacted all living brown bears," said first author Ming-Shan Wang, a postdoctoral scientist in the UCSC Paleogenomics Lab.

Corresponding author Beth Shapiro, professor of ecology and evolutionary biology at UC Santa Cruz and an investigator at the Howard Hughes Medical Institute, said the team's genomic analyses show that Bruno belonged to a polar bear population that was ancestral to living polar bears. At some point, probably after around 125,000 years ago, she said, the polar bear lineage leading to Bruno and the brown bear lineage leading to all living brown bears crossed paths and hybridized.

As a result of this ancient admixture, polar bear ancestry accounts for as much as 10% of the genomes of brown bears living today. "We never would have seen this without Bruno's genome, because all living brown bears have that admixture as part of their genomes," Shapiro said.

Although polar bears and brown bears are distinct species with striking differences in appearance, behavior, and habitats, they are closely related and can readily hybridize when their ranges overlap. Reports of hybrids have increased in recent years as the climate warms and disappearing sea ice forces polar bears onto Arctic coastal areas, while brown bears expand their range northward.

Previous studies of ancient DNA have shown that admixture has occurred in certain populations of brown bears at least four different times between around 15,000 and 25,000 years ago. In all cases, the direction of gene flow was from polar bears into brown bears.

"The admixed individuals, if they survive, do so as brown bears, perhaps because they have difficulty hunting successfully on the sea ice if they are not completely white," Shapiro explained. "Polar bears have always been a small population with not much genetic diversity."

The new study did find some evidence of possible gene flow from brown bears into Bruno's lineage, but the absence of admixture in polar bears today supports the idea that brown bear ancestry reduces a bear's fitness for life as a polar bear. After diverging from brown bears about 500,000 years ago, polar bears evolved into highly specialized hunters of marine mammals on the Arctic sea ice. Brown bears, in contrast, are generalists ranging widely across North America, Europe, and Asia.

Bruno lived during a time of changing climate after the peak of a warm interglacial period when temperatures and sea levels were considerably higher than they are now. Similar conditions can be expected in the future as a result of rapid climate change driven by the burning of fossil fuels and other human activities. As Arctic sea ice declines, many polar bear populations are already struggling to survive.

"If the rapid, unnatural, and severe human-caused warming of the Arctic we are documenting today continues unabated, it is uncertain whether polar bears will have a sea ice habitat to return to and survive genetically," said coauthor Ian Stirling, a polar bear biologist and research scientist with Environment and Climate Change Canada.

According to Shapiro, "We shouldn't be surprised to see admixture happening again today as the climate changes and these species are overlapping and encountering each other again in the wild. Climate change allows gene flow to occur between what we think of as different species."

Climatic shifts that have brought polar bears and brown bears together in the past include glacial periods when sea ice was more extensive, allowing polar bears to mix with brown bears in southeast Alaska, the Kuril Islands, and even Ireland. The brown bears in these locations (now extinct in Ireland) acquired additional polar bear genes on top of the ancient admixture revealed by Bruno's genome.

As for what brown bears might have gained from their polar bear ancestry, scientists can only speculate. "It's possible that brown bears got something cool from polar bears, but we can't say for sure at this point," Shapiro said.

Finding Bruno's skull was serendipitous. Coauthors Pamela Groves, Daniel Mann and Michael Kunz from the University of Alaska Fairbanks were walking the Beaufort Sea coastline in 2009 surveying for recent coastal erosion when they stumbled upon the skull resting just above the high tide line.

"We weren't even looking for bones, as typically we find ancient bones a hundred miles inland where they have been stored in permafrost along sleepy rivers," said Groves. Since polar bears spend most of their lives at sea, finding any polar bear remains is extremely unusual. Bruno is the only ancient polar bear skull ever recorded and the only ancient polar bear bone known from North America.

"Understanding how past changes in climate drove interactions between organisms is critical to predicting how current changes will create new admixtures, increase disease transmission, or impact natural resources or society," said Leslie Rissler, program director at the U.S. National Science Foundation, which funded the research.

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Martian meteorite upsets planet formation theory

A new study of an old meteorite contradicts current thinking about how rocky planets like the Earth and Mars acquire volatile elements such as hydrogen, carbon, oxygen, nitrogen and noble gases as they form. The work is published June 16 in Science.

A basic assumption about planet formation is that planets first collect these volatiles from the nebula around a young star, said Sandrine Péron, a postdoctoral scholar working with Professor Sujoy Mukhopadhyay in the Department of Earth and Planetary Sciences, University of California, Davis.

Because the planet is a ball of molten rock at this point, these elements initially dissolve into the magma ocean and then degass back into the atmosphere. Later on, chondritic meteorites crashing into the young planet deliver more volatile materials.

So scientists expect that the volatile elements in the interior of the planet should reflect the composition of the solar nebula, or a mixture of solar and meteoritic volatiles, while the volatiles in the atmosphere would come mostly from meteorites. These two sources -- solar vs. chondritic -- can be distinguished by the ratios of isotopes of noble gases, in particular krypton.

Mars is of special interest because it formed relatively quickly -- solidifying in about 4 million years after the birth of the Solar System, while the Earth took 50 to 100 million years to form.

"We can reconstruct the history of volatile delivery in the first few million years of the Solar System," Péron said.

Meteorite from Mars' interior

Some meteorites that fall to Earth come from Mars. Most come from surface rocks that have been exposed to Mars' atmosphere. The Chassigny meteorite, which fell to Earth in north-eastern France in 1815, is rare and unusual because it is thought to represent the interior of the planet.

By making extremely careful measurements of minute quantities of krypton isotopes in samples of the meteorite using a new method set up at the UC Davis Noble Gas Laboratory, the researchers could deduce the origin of elements in the rock.

"Because of their low abundance, krypton isotopes are challenging to measure," Péron said.

Surprisingly, the krypton isotopes in the meteorite correspond to those from chondritic meteorites, not the solar nebula. That means that meteorites were delivering volatile elements to the forming planet much earlier than previously thought, and in the presence of the nebula, reversing conventional thinking.

"The Martian interior composition for krypton is nearly purely chondritic, but the atmosphere is solar," Péron said. "It's very distinct."

The results show that Mars' atmosphere cannot have formed purely by outgassing from the mantle, as that would have given it a chondritic composition. The planet must have acquired atmosphere from the solar nebula, after the magma ocean cooled, to prevent substantial mixing between interior chondritic gases and atmospheric solar gases.

The new results suggest that Mars' growth was completed before the solar nebula was dissipated by radiation from the Sun. But the irradiation should also have blown off the nebular atmosphere on Mars, suggesting that atmospheric krypton must have somehow been preserved, possibly trapped underground or in polar ice caps.

"However, that would require Mars to have been cold in the immediate aftermath of its accretion," Mukhopadhyay said. "While our study clearly points to the chondritic gases in the Martian interior, it also raises some interesting questions about the origin and composition of Mars' early atmosphere."

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Origins of the Black Death identified

The Black Death, the biggest pandemic of our history, was caused by the bacterium Yersinia pestis and lasted in Europe between the years 1346 and 1353. Despite the pandemic's immense demographic and societal impacts, its origins have long been elusive. Now, a multidisciplinary team of scientists, including researchers from the Max Planck Institute for Evolutionary Anthropology in Leipzig, the University of Tübingen, in Germany, and the University of Stirling, in the United Kingdom, have obtained and studied ancient Y. pestis genomes that trace the pandemic's origins to Central Asia.

In 1347, plague first entered the Mediterranean via trade ships transporting goods from the territories of the Golden Horde in the Black Sea. The disease then disseminated across Europe, the Middle East and northern Africa claiming up to 60 percent of the population in a large-scale outbreak known as the Black Death. This first wave further extended into a 500-year-long pandemic, the so-called Second Plague Pandemic, which lasted until the early 19th century.

The origins of the Second Plague Pandemic have long been debated. One of the most popular theories has supported its source in East Asia, specifically in China. To the contrary, the only so-far available archaeological findings come from Central Asia, close to Lake Issyk Kul, in what is now Kyrgyzstan. These findings show that an epidemic devastated a local trading community in the years 1338 and 1339. Specifically, excavations that took place almost 140 years ago revealed tombstones indicating that individuals died in those years of an unknown epidemic or "pestilence." Since their first discovery, the tombstones inscribed in Syriac language, have been a cornerstone of controversy among scholars regarding their relevance to the Black Death of Europe.

In this study, an international team of researchers analysed ancient DNA from human remains as well as historical and archaeological data from two sites that were found to contain "pestilence" inscriptions. The team's first results were very encouraging, as DNA from the plague bacterium, Yersinia pestis, was identified in individuals with the year 1338 inscribed on their tombstones. "We could finally show that the epidemic mentioned on the tombstones was indeed caused by plague," says Phil Slavin, one of the senior authors of the study and historian at the University of Sterling, UK.

Researchers found the Black Death's source strain

But could this have been the origin of the Black Death? Researchers have previously associated the Black Death's initiation with a massive diversification of plague strains, a so-called Big Bang event of plague diversity. But the exact date of this event could not be precisely estimated, and was thought to have happened sometime between the 10th and 14th centuries. The team now pieced together complete ancient plague genomes from the sites in Kyrgyzstan and investigated how they might relate with this Big Bang event. "We found that the ancient strains from Kyrgyzstan are positioned exactly at the node of this massive diversification event. In other words, we found the Black Death's source strain and we even know its exact date [meaning the year 1338]," says Maria Spyrou, lead author and researcher at the University of Tübingen.

But where did this strain come from? Did it evolve locally or did it spread in this region from elsewhere? Plague is not a disease of humans; the bacterium survives within wild rodent populations across the world, in so-called plague reservoirs. Hence, the ancient Central Asian strain that caused the 1338-1339 epidemic around Lake Issyk Kul must have come from one such reservoir. "We found that modern strains most closely related to the ancient strain are today found in plague reservoirs around the Tian Shan mountains, so very close to where the ancient strain was found. This points to an origin of Black Death's ancestor in Central Asia," explains Johannes Krause, senior author of the study and director at the Max Planck Institute for Evolutionary Anthropology.

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Once seen as fleeting, a new solar tech proves its lasting power

Princeton Engineering researchers have developed the first perovskite solar cell with a commercially viable lifetime, marking a major milestone for an emerging class of renewable energy technology. The team projects their device can perform above industry standards for around 30 years, far more than the 20 years used as a threshold for viability for solar cells.

The device is not only highly durable, it also meets common efficiency standards. It is the first of its kind to rival the performance of silicon-based cells, which have dominated the market since their introduction in 1954.

Perovskites are semiconductors with a special crystal structure that makes them well suited for solar cell technology. They can be manufactured at room temperature, using much less energy than silicon, making them cheaper and more sustainable to produce. And whereas silicon is stiff and opaque, perovskites can be made flexible and transparent, extending solar power well beyond the iconic panels that populate hillsides and rooftops across America.

But unlike silicon, perovskites are notoriously fragile. Early perovskite solar cells (PSC), created between 2009 and 2012, lasted only minutes. The projected lifetime of the new device represents a five-fold increase over the previous record, set by a lower efficiency PSC in 2017. (That device operated under continuous illumination at room temperature for one year. The new device would operate for five years under similar lab conditions.)

The Princeton team, led by Lynn Loo, the Theodora D. '78 and William H. Walton III '74 Professor in Engineering, revealed their new device and their new method for testing such devices in a paper published June 16 in Science.

Loo said the record-setting design has highlighted the durable potential of PSCs, especially as a way to push solar cell technology beyond the limits of silicon. But she also pointed past the headline result to her team's new accelerated aging technique as the work's deeper significance.

"We might have the record today," she said, "but someone else is going to come along with a better record tomorrow. The really exciting thing is that we now have a way to test these devices and know how they will perform in the long term."

Due to perovskites' well-known frailty, long-term testing hasn't been much of a concern until now. But as the devices get better and last longer, testing one design against another will become crucial in rolling out durable, consumer-friendly technologies.

"This paper is likely going to be a prototype for anyone looking to analyze performance at the intersection of efficiency and stability," said Joseph Berry, a senior fellow at the National Renewable Energy Laboratory who specializes in the physics of solar cells and who was not involved in this study. "By producing a prototype to study stability, and showing what can be extrapolated [through accelerated testing], it's doing the work everyone wants to see before we start field testing at scale. It allows you to project in a way that's really impressive."

While efficiency has accelerated at a remarkable pace over the past decade, Berry said, the stability of these devices has improved more slowly. For them to become widespread and rolled out by industry, testing will need to become more sophisticated. That's where Loo's accelerated aging process comes in.

"These kinds of tests are going to be increasingly important," Loo said. "You can make the most efficient solar cells, but it won't matter if they aren't stable."

How they got here

Early in 2020, Loo's team was working on various device architectures that would maintain relatively strong efficiency -- converting enough sunlight to electric power to make them valuable -- and survive the onslaught of heat, light and humidity that bombard a solar cell during its lifetime.

Xiaoming Zhao, a postdoctoral researcher in Loo's lab, had been working on a number of designs with colleagues. The efforts layered different materials in order to optimize light absorption while protecting the most fragile areas from exposure. They developed an ultra-thin capping layer between two crucial components: the absorbing perovskite layer and a charge-carrying layer made from cupric salt and other substances. The goal was to keep the perovskite semiconductor from burning out in a matter of weeks or months, the norm at that time.

It's hard to comprehend how thin this capping layer is. Scientists use the term 2D to describe it, meaning two dimensions, as in something that has no thickness at all. In reality, it's merely a few atoms thick -- more than a million times smaller than the smallest thing a human eye can see. While the idea of a 2D capping layer isn't new, it is still considered a promising, emerging technique. Scientists at NREL have shown that 2D layers can greatly improve long-haul performance, but no one had developed a device that pushed perovskites anywhere close to the commercial threshold of a 20-year lifetime.

Zhao and his colleagues went through scores of permutations of these designs, shifting minute details in the geometry, varying the number of layers, and trying out dozens of material combinations. Each design went into the light box, where they could irradiate the sensitive devices in relentless bright light and measure their drop in performance over time.

In the fall of that year, as the first wave of the pandemic subsided and researchers to returned to their labs to tend to their experiments in carefully coordinated shifts, Zhao noticed something odd in the data. One set of the devices still seemed to be operating near its peak efficiency.

"There was basically zero drop after nearly half a year," he said.

That's when he realized he needed a way to stress test his device faster than his real-time experiment allowed.

"The lifetime we want is about 30 years, but you can't take 30 years to test your device," Zhao said. "So we need some way to predict this lifetime within a reasonable timeframe. That's why this accelerated aging is very important."

The new testing method speeds up the aging process by illuminating the device while blasting it with heat. This process speeds up what would happen naturally over years of regular exposure. The researchers chose four aging temperatures and measured results across these four different data streams, from the baseline temperature of a typical summer day to an extreme of 230 degrees Fahrenheit, higher than the boiling point of water.

They then extrapolated from the combined data and forecast the device's performance at room temperature over tens of thousands of hours of continuous illumination. The results showed a device that would perform above 80 percent of its peak efficiency under continuous illumination for at least five years at an average temperature of 95 degrees Fahrenheit. Using standard conversion metrics, Loo said that's the lab equivalent of 30 years of outdoor operation in an area like Princeton, NJ.

Berry of NREL concurred. "It's very credible," he said. "Some people are still going to want to see it play out. But this is much more credible science than a lot of other attempts at forecasting."

The Michael Jordan of solar cells

Perovskite solar cells were pioneered in 2006, with the first published devices following in 2009. Some of the earliest devices lasted only seconds. Others minutes. In the 2010s the device lifetimes grew to days and weeks and finally months. Then in 2017, a group from Switzerland published a groundbreaking paper on a PSC that lasted for one full year of continuous illumination.

Meanwhile, the efficiency of these devices has skyrocketed over the same period. While the first PSC showed a power-conversion efficiency of less than 4 percent, researchers boosted that metric nearly tenfold in as many years. It was the fastest improvement scientists had seen in any class of renewable-energy technology to date.

So why the push for perovskites? Berry said a combination of recent advances make them uniquely desirable: newly high efficiencies, an extraordinary "tunability" that allows scientists to make highly specific applications, the ability to manufacture them locally with low energy inputs, and now a credible forecast of extended life coupled with a sophisticated aging process to test a wide array of designs.

Loo said it's not that PSCs will replace silicon devices so much that the new technology will complement the old, making solar panels even cheaper, more efficient and more durable than they are now, and expanding solar energy into untold new areas of modern life. For example, her group recently demonstrated a completely transparent perovskite film (having different chemistry) that can turn windows into energy producing devices without changing their appearance. Other groups have found ways to print photovoltaic inks using perovskites, allowing formfactors scientists are only now dreaming up.

But the main advantage in the long run, according to both Berry and Loo: Perovskites can be manufactured at room temperature, whereas silicon is forged at around 3000 degrees Fahrenheit. That energy has to come from somewhere, and at the moment that means burning a lot of fossil fuels.

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The benefits of exercise in a pill? Science is closer to that goal

Researchers at Baylor College of Medicine, Stanford School of Medicine and collaborating institutions report today in the journal Nature that they have identified a molecule in the blood that is produced during exercise and can effectively reduce food intake and obesity in mice. The findings improve our understanding of the physiological processes that underlie the interplay between exercise and hunger.

"Regular exercise has been proven to help weight loss, regulate appetite and improve the metabolic profile, especially for people who are overweight and obese," said co-corresponding author Dr. Yong Xu, professor of pediatrics- nutrition and molecular and cellular biology at Baylor. "If we can understand the mechanism by which exercise triggers these benefits, then we are closer to helping many people improve their health."

"We wanted to understand how exercise works at the molecular level to be able to capture some of its benefits," said co-corresponding author Jonathan Long, MD, assistant professor of pathology at Stanford Medicine and an Institute Scholar of Stanford ChEM-H (Chemistry, Engineering & Medicine for Human Health). "For example, older or frail people who cannot exercise enough, may one day benefit from taking a medication that can help slow down osteoporosis, heart disease or other conditions."

Xu, Long and their colleagues conducted comprehensive analyses of blood plasma compounds from mice following intense treadmill running. The most significantly induced molecule was a modified amino acid called Lac-Phe. It is synthesized from lactate (a byproduct of strenuous exercise that is responsible for the burning sensation in muscles) and phenylalanine (an amino acid that is one of the building blocks of proteins).

In mice with diet-induced obesity (fed a high-fat diet), a high dose of Lac-Phe suppressed food intake by about 50% compared to control mice over a period of 12 hours without affecting their movement or energy expenditure. When administered to the mice for 10 days, Lac-Phe reduced cumulative food intake and body weight (owing to loss of body fat) and improved glucose tolerance.

The researchers also identified an enzyme called CNDP2 that is involved in the production of Lac-Phe and showed that mice lacking this enzyme did not lose as much weight on an exercise regime as a control group on the same exercise plan.

Interestingly, the team also found robust elevations in plasma Lac-Phe levels following physical activity in racehorses and humans. Data from a human exercise cohort showed that sprint exercise induced the most dramatic increase in plasma Lac-Phe, followed by resistance training and then endurance training. "This suggests that Lac-Phe is an ancient and conserved system that regulates feeding and is associated with physical activity in many animal species," Long said.

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To find a planet, look for the signatures of planet formation

Finding forming planets is a tough but important job for astronomers: Only three planets have ever been discovered caught in the process of forming, and the most recent of these was found just weeks ago.

Evan Rich, a postdoctoral researcher at the University of Michigan, suggests that instead of looking for individual planets forming, astronomers might have better luck looking for the likely environments in which they form.

In doing just that, Rich and a team of astronomers have found that systems with stars less than three solar masses are more likely to have large rings composed of tiny dust grains, about a micron in size -- potential indications of planet formation -- than larger stars and may have discovered a new planet around a very young star.

Rich will present his findings, collected in the first summary paper produced from a survey called Gemini-Large Imaging with GPI Herbig/T-tauri Survey, or Gemini-LIGHTS, at the American Astronomical Society's annual meeting this month. His study has also been accepted for publication in the Astronomical Journal.

"It turns out that finding these planets in particular is very, very difficult," Rich said. "So we're taking the strategy of actually looking at the material itself rather than for the planet.

"What is the environment of planet formation? What are the dynamics? How do these differentiate between a very low mass star compared to a very high mass star? Does the temperature of the star have an effect on the disk? One of the ultimate goals is to question how all these parameters affect planet formation."

Rich and his research team used the Gemini South Telescope in Chile to look at stars more massive than the sun to to study how planet formation here might be different. Specifically, the team used the Gemini Planet Imager to view the objects in infrared light, or light slightly redder than our eyes can see. The astronomers also looked at these stars in polarized light in order to look for dim material such as dust next to the stars themselves.

"The material we're looking at is sometimes a million times dimmer than the star itself, and using these processes allows us to see that dim material around very bright stars," Rich said. "What's happening is the light from the star is scattering off the dust, like when light from the sun reflects off the surface of a pond."

What you see reflected off the surface of a pond is unpolarized light, which means its lightwaves are vibrating in all directions. Polarizing the light aligns its vibrations into a single plane. Similarly, when light from stars scatters off dust grains orbiting the stars, the astronomers can distinguish between the unpolarized light of the star and the unpolarized light from the dust, and can allow them to observe the dust grains in this protoplanetary disk.

"In some ways, this is like using polarized sunglasses but instead of using the glasses to suppress the scattered light, we use it to enhance it," said co-author John Monnier, U-M professor of astronomy.

The astronomers imaged 44 targets and detected some form of dust around 80% of them. The team released a gallery showing a range of different morphologies that tell the researchers about the dynamics happening within the disk itself.

"It's truly incredible that we're at a point right now in astronomy where not only are we able to get images of planet-forming disks around young stars, but we can populate entire galleries to sort and study, reconstructing planetary origin stories," said Alicia Aarnio, assistant professor of physics and astronomy at the University of North Carolina-Greensboro, who led the target selection.

"The theory is that when planets form, they make almost perfect tree rings going out from the sun," Rich said. "We think that if you see rings and gaps in the dust disk, there could be planets."

The team has found so far that only systems with stars less than three solar masses have these rings. Stars above solar masses don't seem to have the same rings, and since these rings are a potential signature of planet formation, this could be a good indicator of where and how planets are forming.

The researchers also saw a pattern in the stars without dust.

"It was surprising to see that the presence of even a small companion to a host star, like a brown dwarf, dramatically reduced signs of ongoing planet formation," Monnier.

This finding reinforces the idea that close binary stars seem to make planets less often than single stars, a result first proposed to explain data from the Kepler Space Telescope.

The team found a host of objects orbiting the stars, including three brown dwarfs and one planetary-mass companion candidate just outside a planet-forming disk system, called V1295 Aql. This object appears to be about 13 times the mass of Jupiter, which puts it right on the edge between what's considered a planet or what's considered a brown dwarf star. If future observations confirm its orbit, it would be one of only a few known exoplanets around massive stars.

"The dust rings, gaps and spiral arms seen by Gemini are telling us how and when planets form in real-time. With more accurate simulations and new telescopes like the James Webb Space Telescope and the Extremely Large Telescope, we are zeroing in on the key ingredients to understand how our solar system came to be," said Jaehan Bae, a planet formation theorist and former postdoctoral fellow and Ph.D. student at U-M, who is now an assistant professor of astronomy at the University of Florida.

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Near-sun comet roasted to death

Astronomers using a fleet of world leading telescopes on the ground and in space have captured images of a periodic rocky near-Sun comet breaking apart. This is the first time such a comet has been caught in the act of disintegrating and could help explain the scarcity of such periodic near-Sun comets.

The Solar System is a dangerous place. In textbooks we see figures of celestial bodies orbiting around the Sun in orderly orbits. But that's because if an object's orbit doesn't fit this pattern, gravitational effects from other objects destabilize the orbit. One common fate for such ejected bodies is to become comets in near-Sun orbits where they will eventually plunge into the Sun. Because these comets pass so close to the Sun, they are difficult to spot and study. Most have been discovered by accident in solar telescope observations. But even taking this difficulty into account, there are far fewer near-Sun comets than expected, indicating that something is destroying them before they get a chance to make their fatal final dive into the Sun.

To better understand these comets, a group of astronomers from Macau, the US, Germany, Taiwan, and Canada observed an elusive near-Sun comet called 323P/SOHO with multiple telescopes including the Subaru Telescope, the Canada France Hawaii Telescope (CFHT), the Gemini North telescope, Lowell's Discovery Telescope, and the Hubble Space Telescope. The orbit of 323P/SOHO was poorly constrained, so the group didn't know exactly where to look for it, but the wide field of view of the Subaru Telescope allowed them to "cast a wide net" and find the comet as it approached the Sun. This was the first time 323P/SOHO was captured by a ground-based telescope. With this data, the researchers were able to better constrain the orbit, they knew where to point the other telescopes and were waiting when 323P/SOHO started to move away from the Sun again.

To their surprise the researchers found that 323P/SOHO had changed remarkably during its close passage by the Sun. In the Subaru Telescope data, 323P/SOHO was just a dot, but in follow-up data it had a long comet tail of ejected dust. The researchers believe that the intense radiation from the Sun caused parts of the comet to break off due to thermal fracturing, similar to how ice cubes crack when you pour a hot drink over them. This mass loss mechanism could help explain what happens to near-Sun comets and why there are so few of them left.

But the team's results raised more questions than they answered. They found that 323P/SOHO rotates rapidly, taking just more than half an hour per revolution, and that its color is unlike anything else in the Solar System. Observations of other near-Sun comets are needed to see if they also share these traits.

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Preadolescents exposed to high levels of air pollution in their first years of life display changes in brain connectivity

Higher exposure to air pollution is associated with higher functional brain connectivity among several brain regions in preadolescents, while exposure to traffic noise was not, according to a study led by ISGlobal, an institution supported by "la Caixa" Foundation. The findings also identify the first years of life as the most sensitive period of exposure to air pollution.

Traffic-related air pollution and noise are affecting an increasing number of people worldwide. "We already know that children are particularly vulnerable to the effect of these exposures, because of their immature metabolism and developing brain," says ISGlobal researcher and senior author Mónica Guxens. In fact, several studies by Guxens and others have found an association between exposure to traffic-related air pollution during early childhood and alterations in the brain structure.

In this study, the research team used magnetic resonance imaging (MRI) to explore whether higher exposure to air pollution or noise could also be associated with possible alterations in brain connectivity (i.e. the way in which different brain regions interact). "The use of MRI has opened up new possibilities in epidemiological research for investigating the structure and the functioning of the brain," says Guxens.

The researchers used data of 2,197 children from the Generation R Study, born between April 2002 and Jan 2006 and living in Rotterdam, the Netherlands. Using land use models, they estimated levels of nitrogen oxides (NOx and NO2) and particulate matter (PM) at the participants' homes at different time periods: during pregnancy, from birth to 3 years, from 3 to 6 years, and from 6 years of age to the age at which the MRI scan was performed. Noise levels due to traffic road were estimated using existing noise maps. Between 9 and 12 years of age, the participants were invited to undergo an MRI scan in the resting state (i.e. with no external stimuli).

The findings show that higher exposures to NO2 and PM2.5 absorbance (an indicator of black carbon particles) from birth to 3 years, and to NOx from 3 to 6 years of age were associated with higher functional brain connectivity among several brain regions in the preadolescents. The associations were identified in brain areas predominantly involved in two networks that have strongly opposing functions: the task negative (or "default-mode") network tends to be activated in resting conditions and the task positive network tends to be activated during tasks that demand attention. "We still have to understand the consequences of this increased activity of both networks in resting conditions, but for now we can say that the brain connectivity in children exposed to higher levels of air pollution is different from what we would expect," says Laura Pérez-Crespo, first author of the study.

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Lager beer, whether it contains alcohol or not, could help men's gut microbes

Like wine, beer can have health benefits when consumed in moderation. Non-alcoholic beers have become wildly popular recently, but are these drinks also healthful? In a pilot study, researchers in ACS' Journal of Agricultural and Food Chemistry report that compared to their pre-trial microbiome, men who drank either one alcoholic or non-alcoholic lager daily had a more diverse set of gut microbes, which can reduce the risk for some diseases.

Trillions of microorganisms line human gastrointestinal tracts, directly impacting their host's well-being. Studies have shown that when more types of bacteria are present, people tend to have a lower chance of developing chronic diseases, such as heart disease and diabetes. And beer contains compounds, such as polyphenols, as well as microorganisms from its fermentation, that could impact the variety of microbes in the human gut. A previously published "cross-over" study showed that when both men and women consumed non-alcoholic lager beer for 30 days, their gut microbiome diversity increased. Many of those same people were also in a second group that drank an alcoholic version of the beer, and it didn't have the same effect. Few other clinical trials have tested this issue, so Ana Faria and colleagues wanted to see if they would find similar results with men in a different type of study -- a parallel, randomized trial design -- with two separate groups of participants.

In this double-blind study, 19 healthy men were randomly divided into two groups who drank 11 fluid ounces of either alcoholic or non-alcoholic lager with dinner for 4 weeks. The researchers found that the participants' weight, body mass index and serum markers for heart health and metabolism didn't change during the study. But at the end of the 4-week period, both groups had greater bacterial diversity in their gut microbiome and higher levels of fecal alkaline phosphatase, indicating an improvement in intestinal health. The researchers suggest that these results could differ from those of the prior study because of the different designs of the trials, and because the participants were living in different communities. But based on this pilot study, the researchers say that consuming one bottle of beer, regardless of its alcohol content, may be beneficial to the gut microbiome and intestinal health of men. However, they add that because the safest level of alcohol consumption is none, non-alcoholic beer may be the more healthful choice.

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A large predator from the Pyrenees

A fossilized lower jaw has led an international team of palaeontologists, headed by Bastien Mennecart from the Natural History Museum Basel, to discover a new species of predator that once lived in Europe. These large predators belong to a group of carnivores colloquially known as "bear dogs." They could weigh around 320 kilograms, appeared 36 million years ago before becoming extinct around 7.5 million years ago.

Palaeontologist Bastien Mennecart and his research group precisely described the fossilized lower jaw of a carnivore and discovered that it must be a specimen from a new species. The jawbone comes from 12.8 to 12 million-year-old marine deposits that were examined in the small community of Sallespisse in the Pyrénées-Atlantiques department of south western France.

The teeth of time

The jawbone was striking because of its teeth. Unlike the familiar amphicyonidae specimens, this animal has a unique fourth lower premolar. This tooth is particularly important for determining species and genera. Correspondingly, the lower jaw examined probably represents a new genus. It is called Tartarocyon. This name comes from Tartaro, a large, powerful, one-eyed giant from Basque mythology. The legend of Tartaro is also known in Béarn, the region where the lower jaw was found. Floréal Solé, a specialist in carnivorous mammals, Jean-François Lesport and Antoine Heitz from the Natural History Museum Basel chose the name of the new genus.

Dog-like predator

The fossilized lower jaw can be classified as belonging to predators that resembled a cross between a bear and a large dog, known as "bear dogs." Their scientific name is "Amphicyonidae." They belong to a group of carnivores such as dogs, cats, bears, seals and badgers. These predators were a widespread part of the European fauna of the Miocene (23 to 5.3 million years ago). They were very species-rich and diverse, weighing between 9 kg and 320 kg. Tarataroyon is estimated at 200 kg. The last European Amphicyonidae disappeared during the late Miocene 7.5 million years ago.

Key contemporary witnesses

Discoveries of fossilized terrestrial vertebrates that lived on the northern edge of the Pyrenees 13 to 11 million years ago are very rare. The discovery and description of the lower jaw is even more significant. That is because it offers the opportunity to explore the development of European "bear dogs" against the background of known environmental events at this time.

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No signs (yet) of life on Venus

The unusual behaviour of sulphur in Venus' atmosphere cannot be explained by an 'aerial' form of extra-terrestrial life, according to a new study.

Researchers from the University of Cambridge used a combination of biochemistry and atmospheric chemistry to test the 'life in the clouds' hypothesis, which astronomers have speculated about for decades, and found that life cannot explain the composition of the Venusian atmosphere.

Any life form in sufficient abundance is expected to leave chemical fingerprints on a planet's atmosphere as it consumes food and expels waste. However, the Cambridge researchers found no evidence of these fingerprints on Venus.

Even if Venus is devoid of life, the researchers say their results, reported in the journal Nature Communications, could be useful for studying the atmospheres of similar planets throughout the galaxy, and the eventual detection of life outside our Solar System.

"We've spent the past two years trying to explain the weird sulphur chemistry we see in the clouds of Venus," said co-author Dr Paul Rimmer from Cambridge's Department of Earth Sciences. "Life is pretty good at weird chemistry, so we've been studying whether there's a way to make life a potential explanation for what we see."

The researchers used a combination of atmospheric and biochemical models to study the chemical reactions that are expected to occur, given the known sources of chemical energy in Venus's atmosphere.

"We looked at the sulphur-based 'food' available in the Venusian atmosphere -- it's not anything you or I would want to eat, but it is the main available energy source," said Sean Jordan from Cambridge's Institute of Astronomy, the paper's first author. "If that food is being consumed by life, we should see evidence of that through specific chemicals being lost and gained in the atmosphere."

The models looked at a particular feature of the Venusian atmosphere -- the abundance of sulphur dioxide (SO2). On Earth, most SO2 in the atmosphere comes from volcanic emissions. On Venus, there are high levels of SO2 lower in the clouds, but it somehow gets 'sucked out' of the atmosphere at higher altitudes.

"If life is present, it must be affecting the atmospheric chemistry," said co-author Dr Oliver Shorttle from Cambridge's Department of Earth Sciences and Institute of Astronomy. "Could life be the reason that SO2 levels on Venus get reduced so much?"

The models, developed by Jordan, include a list of metabolic reactions that the life forms would carry out in order to get their 'food', and the waste by-products. The researchers ran the model to see if the reduction in SO2 levels could be explained by these metabolic reactions.

They found that the metabolic reactions can result in a drop in SO2 levels, but only by producing other molecules in very large amounts that aren't seen. The results set a hard limit on how much life could exist on Venus without blowing apart our understanding of how chemical reactions work in planetary atmospheres.

"If life was responsible for the SO2 levels we see on Venus, it would also break everything we know about Venus's atmospheric chemistry," said Jordan. "We wanted life to be a potential explanation, but when we ran the models, it isn't a viable solution. But if life isn't responsible for what we see on Venus, it's still a problem to be solved -- there's lots of strange chemistry to follow up on."

Although there's no evidence of sulphur-eating life hiding in the clouds of Venus, the researchers say their method of analysing atmospheric signatures will be valuable when JWST, the successor to the Hubble Telescope, begins returning images of other planetary systems later this year. Some of the sulphur molecules in the current study are easy to see with JWST, so learning more about the chemical behaviour of our next-door neighbour could help scientists figure out similar planets across the galaxy.

"To understand why some planets are alive, we need to understand why other planets are dead," said Shorttle. "If life somehow managed to sneak into the Venusian clouds, it would totally change how we search for chemical signs of life on other planets."

"Even if 'our' Venus is dead, it's possible that Venus-like planets in other systems could host life," said Rimmer, who is also affiliated with Cambridge's Cavendish Laboratory. "We can take what we've learned here and apply it to exoplanetary systems -- this is just the beginning."

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Pioneering study shows climate played crucial role in changing location of ancient coral reefs

The study, published in Nature Communications, demonstrates how changes in temperature and plate tectonics, where the positions of Earth's continents were in very different positions than today, have determined the distribution of corals through the ages.

Although climate has often been regarded as the main driver of the location of coral reefs, this had yet to be proven due to limited fossil records. Now, for the first time, a team of international scientists used habitat modelling and reconstructions of past climates to predict the distribution of suitable environments for coral reefs over the last 250 million years.

The researchers, from the University of Vigo, in Spain, the University of Bristol and University College London in the UK, then checked their predictions using fossil evidence of warm-water coral reefs. They showed that corals in the past, from 250 to about 35 million years ago, existed much further from the equator than today, due to warmer climatic conditions, and a more even distribution of shallow ocean floor.

"Our work demonstrates that warm-water coral reefs track tropical-to-subtropical climatic conditions over geological timescales. In warmer intervals, coral reefs expanded poleward. However, in colder intervals, they became constrained to tropical and subtropical latitudes," said first author Dr Lewis Jones, a computational palaeobiologist research fellow at the University of Vigo.

Suitable coral habitats became restricted to the tropical regions from about 35 million years ago, driven by global cooling and increases in shallow oceans resulting from tectonic changes of the Indo-Australian Archipelago which is recognised as a marine biodiversity hotspot.

Although this suggests warm temperatures permitted long-term poleward expansions of corals in the past, the researchers say coral reef ecosystems are unlikely to match the rapid rate of human-induced climate change.

"Current anthropogenic climate change will result in the poleward expansion of suitable habitat for coral reefs. In fact, we are already witnessing the expansion of some tropical reef corals. However, whether coral reef ecosystems -- and all the biodiversity they support -- can keep pace with the current rapid rate of anthropogenic climate change is another question," Jones said.

"Limiting global warming is fundamental to saving coral reefs, as well as the biodiversity they house. Yet, perhaps even more important is reducing the rate of global warming."

Warm-water coral reefs, also known as 'rainforests of the sea', support the greatest biodiversity of marine organisms on Earth. In today's oceans, these biologically rich ecosystems, including reef fishes, are limited to the tropics and subtropics, where temperatures of the ocean surface typically do not fall below 18ºC. A substantial proportion of this modern biodiversity is found in the Indo-Australian Archipelago. However, in the geological past, coral reef ecosystems also existed outside of the tropics and subtropics, with their fossil remains found much further from the equator.

Co-author Dr Alex Farnsworth, Senior Research Associate in meteorology and climate modelling from the University of Bristol Cabot Institute for the Environment, said: "Climate has changed significantly throughout geological time, however understanding how it has impacted coral reef ecosystems has been difficult due to a lack of quantifiable data which has significant gaps.

"Using this new combined data-model approach we can start to better understand reef ecosystems evolution and behaviour."

Previous work has failed to find a strong relationship between temperature and the distribution of coral reefs because the fossil record is incomplete and biased. For example, not all the remains of organisms or ecosystems that existed in the past are recorded in the fossil record, and it has been shown the single most important factor explaining the sampled distribution of ancient reefs is Gross Domestic Product, with the majority of known fossil reef data stemming from wealthy countries, purely because these are the regions where we have looked hardest.

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Earliest record of wildfires provide insights to Earth's past vegetation and oxygen levels

While wildfires over recent years have raged across much of the western United States and pose significant hazards to wildlife and local populations, wildfires have been a long-standing part of Earth's systems without the influence of humans for hundreds of millions of years.

"Wildfire has been an integral component in earth-system processes for a long time and its role in those processes has almost certainly been underemphasized," said Ian Glasspool, lead author of a study published yesterday in Geology that describes the earliest record of wildfire found yet to date.

In the study, Glasspool and co-author Robert Gastaldo document 430-million-year-old charcoal produced by wildfires found in samples from Wales and Poland. Their discovery pushes back the earliest record of wildfire by an additional 10 million years.

Glasspool explained that wildfire has three essential ingredients: a source of fuel, a source of ignition (which comes in the form of lightning strikes), and sufficient atmospheric oxygen.

"It looks now as though our evidence of fire coincides closely with our evidence of the earliest land plant macrofossils. So as soon as there's fuel, at least in the form of plant macrofossils, there is wildfire pretty much instantly," said Glasspool.

However, the types of plants that existed 430 million years ago during the Silurian period would have looked starkly different from the plants we see and are familiar with today. Instead of grasses, trees, and flowers, flat-lying plants barely even an inch tall would have covered much of the landscape, with the occasional waist-height or knee-height plant. In contrast to much of the diminutive plant cover, the ancient fungus Prototaxites would have stood nearly 30 feet (9 meters) tall, towering over the landscape. These Silurian plants would have been strongly dependent on water for their reproduction and likely would not have been found in seasonally dry areas.

"The Silurian landscape had to have enough vegetation across it to have wildfires propagated and to leave a record of that wildfire," said Gastaldo. "At points in time that we're sampling windows of, there was enough biomass around to be able to provide us with a record of wildfire that we can identify and use to pinpoint the vegetation and process in time."

In addition to a sufficient source of fuel, which Silurian plant life was able to provide, the other crucial factor in producing early wildfires is atmospheric oxygen levels. At the present day, oxygen makes up approximately 21% of the gasses in the planet's atmosphere. Atmospheric oxygen levels have changed greatly over Earth's history, with essentially zero oxygen in Earth's atmosphere for the first part of the planet's history.

As the research study describes, modern burn experiments indicate that wildfires are unlikely to occur below levels of 16% atmospheric oxygen.

"If you drop below that level you might initiate a fire but it's not going to propagate," said Glasspool. "So when you look at the probability of finding charcoal in the record, you're really only going to find charcoal if that fire was able to propagate, and you can put a minimum threshold value on atmospheric oxygen when you find charcoal."

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Cats' strange reactions to catnip make it a better insect repellent

Anyone who has seen a cat experience catnip knows that it makes them go a bit wild -- they rub in it, roll on it, chew it, and lick it aggressively. It is widely accepted that this plant, and its Asian counterpart, silvervine, have intoxicative properties, but this might not be the only reason that cats rub on and chew the plants so enthusiastically. Researchers in Japan have found that when cats damage catnip, much higher amounts of strong insect repellents are released, indicating that the cats' behavior protects them from pests. This study appears in the journal iScience on June 14.

Cats' reaction to catnip and silvervine is so ubiquitous that lead author Masao Miyazaki, an animal behavior researcher at Iwate University, had to know what was going on. "Even in the famous musical Cats there are scenes where you see a cat intoxicate another cat using catnip powder," he says. Miyazaki began his career in veterinary medicine and developed an interest in how chemicals, such as pheromones, drive companion animals' instinctual behaviors.

Catnip and silvervine leaves contain the compounds nepetalactol and nepetalactone, iridoids that protect the plants from pests. To see how cats' behavior was affecting the chemicals released by the plants, Miyazaki worked with chemists at Nagoya University. "We found that physical damage of silvervine by cats promoted the immediate emission of total iridoids, which was 10-fold higher than from intact leaves," says Miyazaki.

Not only were more iridoids released, but their composition changed in ways that seemed to encourage the cats. "Nepetalactol accounts for over 90% of total iridoids in intact leaves, but this drops to about 45% in damaged leaves as other iridoids greatly increase," says Miyazaki. "The altered iridoid mixture corresponding to damaged leaves promoted a much more prolonged response in cats."

In previous work, Miyazaki and his team showed that these compounds effectively repel Aedes albopictus mosquitoes. Now the team has shown that when cats damage the plants by rubbing, rolling, licking, and chewing, the repellent properties are even more effective. The diversification of iridoids in damaged silver vine leaves makes it more repellent to mosquitoes at low concentration.

To test if the felines were reacting to these compounds specifically, the cats were given dishes with pure nepetalactone and nepetalactol. "Cats show the same response to iridoid cocktails and natural plants except for chewing," says Miyazaki. They lick the chemicals on the plastic dish and rub against and roll over on the dish."

"When iridoid cocktails were applied on the bottom of dishes that were then covered by a punctured plastic cover, cats still exhibited licking and chewing even though they couldn't contact the chemicals directly," says Miyazaki. "This means that licking and chewing is an instinctive behavior elicited by olfactory stimulation of iridoids."

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Simulations reveal hydrodynamics of planetary engulfment by expanding star

When our sun exhausts the hydrogen fuel in its core some 5 billion years from now, it will expand to become a red giant, engulfing the inner planets. The dynamics and possible outcomes of planetary engulfment are poorly understood, but it is thought to be a relatively common fate for planetary systems.

A new study using hydrodynamical simulations reveals the forces acting on a planet when it is swallowed by an expanding star. The results show that the interactions of a substellar body (a planet or brown dwarf) with the hot gas in the outer envelope of a sun-like star can lead to a range of outcomes depending on the size of the engulfed object and the stage of the star's evolution.

Lead author Ricardo Yarza at the University of California, Santa Cruz, will present the new findings on June 13, 2022, at the 240th meeting of the American Astronomical Society (AAS) in Pasadena.

"Evolved stars can be hundreds or even thousands of times larger than their planets, and this disparity of scales makes it difficult to perform simulations that accurately model the physical processes occurring at each scale," said Yarza, a graduate student in astronomy and astrophysics at UCSC. "Instead, we simulate a small section of the star centered on the planet to understand the flow around the planet and measure the drag forces acting on it."

The results may help explain recent observations of planets and brown dwarfs closely orbiting stellar remnants such as white dwarfs and subdwarfs. Previous studies have suggested that these systems may be the end result of a planetary engulfment process that involves shrinking of the engulfed body's orbit and ejection of the outer layers of the star.

"As the planet travels inside the star, drag forces transfer energy from the planet to the star, and the stellar envelope can become unbound if the transferred energy exceeds its binding energy," Yarza explained.

According to the calculations by Yarza and his colleagues, no substellar bodies smaller than about 100 times the mass of Jupiter can eject the envelope of a sun-like star before it has expanded to about 10 times the radius of the sun. At later stages of stellar evolution and expansion, however, the stellar envelope could be ejected by an object as small as ten times the mass of Jupiter, which would shrink its orbit by several orders of magnitude in the process.

The study also found that planetary engulfment can increase the luminosity of a sun-like star by several orders of magnitude for up to several thousand years, depending on the mass of the engulfed object and the evolutionary stage of the star.

The framework provided by this study can be incorporated into future work to explore the effect of engulfment on the structure of the star. "Our work can inform simulations of planetary engulfment at the scale of the star by providing an accurate reference picture of the physics at the scale of the planet," Yarza said.

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Bioarchaeological evidence of very early Islamic burials in the Levant

A new study combining archaeological, historical and bioarchaeological data provides new insights into the early Islamic period in modern-day Syria. The research team was planning to focus on a much older time period but came across what they believe to be remains of early Muslims in the Syrian countryside.

The Middle East is well known as a region with a rich and fascinating history embracing a wide range of ethnicities, cultures and religious practices. While a great part of this diverse and dynamic history is known through historical records, the impressive material culture and archaeological sites in the region, until recently important bioarcheological data was more difficult to retrieve due to the poor preservation of organic materials in harsh environments. New technologies that are more capable of analysing degraded material, however, have changed this and stories from prehistoric to historic times have emerged, enriching our knowledge of this region at the crossroads between three continents. Now, a multinational and interdisciplinary team is presenting new bioarchaeological insights into the early Islamic period in modern-day Syria.

During 2009 and 2010, excavations at the Neolithic site of Tell Qarassa in modern-day Syria encountered a number of burials. These excavations were coordinated by a Spanish-French team integrating Syrian students in all archaeological campaigns, thereby contributing to their training in archaeology. The research was conducted with permission from and in constant coordination with the General Directorate of Antiquities and Museums (DGAM) of the Syrian Arab Republic. Shortly after these excavations, the Syrian civil war began, which continues to this day.

"With the goal of studying the first farming groups in the region, we subjected the remains of 14 humans to ancient DNA analysis," says archaeogeneticist Cristina Valdiosera of the University of Burgos, Spain, who coordinated the study. "Only two individuals from upper layers of the site contained sufficient amounts of endogenous DNA and these came from graves that we assumed belonged to a later prehistoric period. After radiocarbon dating it became clear we had something unexpected and special."

The graves dated to the Umayyad Era in the late 7th and early 8th centuries (the second caliphate). In light of these surprisingly recent dates, a reassessment of the burial style showed that it would be consistent with early Muslim burial practices. It would have been impossible to pinpoint this cultural identity without the radiocarbon dates as there were no previously known Muslim settlements or burial sites in the area and the archaeological site itself was only known as a prehistoric site.

"The genomic results were also surprising as the two individuals seemed genetically different from most ancient or modern-day Levantines. The most similar -- though not identical -- modern-day groups were Bedouins and Saudis, suggesting a possible connection to the Arabian Peninsula," says evolutionary biologist Megha Srigyan, who conducted the data analysis during her Master's studies at Uppsala University, Sweden.

"Most of our evidence is indirect but the different types of data, taken together, point to this man and woman belonging to transient groups far from home, suggesting the presence of early Muslims in the Syrian countryside," says population geneticist Torsten Günther at Uppsala University, who co-coordinated the study.

The analysis of one man and one woman provided evidence of new cultural/religious practices arriving in the Levant.

"It is extraordinary that by studying just two individuals, we were able to uncover a small but remarkable piece of the colossal puzzle that makes up the history of the Levant," says Cristina Valdiosera.

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Pre-historic Wallacea: A melting pot of human genetic ancestries

The Wallacean islands have always been separated from Asia and Oceania by deep-sea waters. Yet, these tropical islands were a corridor for modern humans migrating into the Pleistocene Australia-New Guinea landmass (Sahul) and have been home to modern human groups for at least 47 thousand years. The archaeological record attests a major cultural transition across Wallacea that started around 3,500 years ago and is associated with the expansion of Austronesian-speaking farmers, who intermixed with local hunter-gatherer groups. However, previous genetic studies of modern-day inhabitants have yielded conflicting dates for this intermixing, ranging from 1,100 to nearly 5,000 years ago.

To shed light on the details of this expansion and the resulting human interactions, an international team of researchers analyzed DNA from 16 ancient individuals from different islands in Wallacea, greatly increasing the amount of ancient genomic data representing this region. "We found striking differences between regions in Wallacea and surprisingly, the ancestry of ancient individuals from the southern islands cannot be simply explained by admixture between Austronesian- and Papuan-related groups," says Sandra Oliveira, one of the study's lead authors.

Early ancestry contribution from Mainland Southeast Asia

The team identified an additional ancestry contribution from Mainland Southeast Asia, closest to present-day Austroasiatic speakers, and proposed that admixture occurred first between the Mainland Southeast Asian and Papuan-related ancestry and that gene flow from Austronesian-related groups occurred only later. "That Mainland Southeast Asian component is a great mystery to me. I suspect that we might be looking at small groups, perhaps of early farmers, who travelled a long way, left no archaeological or linguistic traces along the way, but who increased their population sizes after arrival," says Peter Bellwood, an author of the study who has conducted archaeological work in Island Southeast Asia for decades.

While the identity of the people who spread this ancestry is still unclear, the discovery of the Mainland Southeast Asian ancestry and its possible antiquity in the southern Wallacean islands has major implications for the understanding of the Neolithic dispersals into Island Southeast Asia. "This finding is very important for the archaeologists in the region," adds Toetik Koesbardiati, an Indonesian anthropologist involved in the study. He adds, "We will certainly intensify our efforts to study this migration with other lines of evidence."

Multiple admixture events throughout Wallacea

This work also revealed a closer relationship between the Austronesian-related ancestry of ancient individuals from northern Wallacea and the Pacific, compared to those from southern Wallacea -- a pattern matched by linguistic evidence. Additionally, it shed light on the timing of the Asian-Papuan genetic admixture. "Previous studies based on present-day populations have reported widely different estimates, some of which preceeded the archaeological evidence for the Austronesian expansion, while others were much more recent. Since we now have ancient individuals from different time periods we can directly show that admixture occurred in multiple pulses or continuously since at least 3,000 years ago throughout Wallacea," explains Mark Stoneking, a senior author of the study. He adds, "Future studies on older genomes might extend this date even further."

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Rubbery camouflage skin exhibits smart and stretchy behaviors

The skin of cephalopods, such as octopuses, squids and cuttlefish, is stretchy and smart, contributing to these creatures' ability to sense and respond to their surroundings. A Penn State-led collaboration has harnessed these properties to create an artificial skin that mimics both the elasticity and the neurologic functions of cephalopod skin, with potential applications for neurorobotics, skin prosthetics, artificial organs and more.  

Led by Cunjiang Yu, Dorothy Quiggle Career Development Associate Professor of Engineering Science and Mechanics and Biomedical Engineering, the team published its findings on June 1 in the Proceedings of the National Academy of Sciences. 

Cephalopod skin is a soft organ that can endure complex deformations, such as expanding, contracting, bending and twisting. It also possesses cognitive sense-and-respond functions that enable the skin to sense light, react and camouflage its wearer. While artificial skins with either these physical or these cognitive capabilities have existed previously, according to Yu, until now none has simultaneously exhibited both qualities -- the combination needed for advanced, artificially intelligent bioelectronic skin devices.  

"Although several artificial camouflage skin devices have been recently developed, they lack critical noncentralized neuromorphic processing and cognition capabilities, and materials with such capabilities lack robust mechanical properties," Yu said. "Our recently developed soft synaptic devices have achieved brain-inspired computing and artificial nervous systems that are sensitive to touch and light that retain these neuromorphic functions when biaxially stretched."  

To simultaneously achieve both smartness and stretchability, the researchers constructed synaptic transistors entirely from elastomeric materials. These rubbery semiconductors operate in a similar fashion to neural connections, exchanging critical messages for system-wide needs, impervious to physical changes in the system's structure. The key to creating a soft skin device with both cognitive and stretching capabilities, according to Yu, was using elastomeric rubbery materials for every component. This approach resulted in a device that can successfully exhibit and maintain neurological synaptic behaviors, such as image sensing and memorization, even when stretched, twisted and poked 30% beyond a natural resting state.  

"With the recent surge of smart skin devices, implementing neuromorphic functions into these devices opens the door for a future direction toward more powerful biomimetics," Yu said. "This methodology for implementing cognitive functions into smart skin devices could be extrapolated into many other areas, including neuromorphic computing wearables, artificial organs, soft neurorobotics and skin prosthetics for next-generation intelligent systems."

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Scientists release first analysis of rocks plucked from speeding asteroid

After a six-year journey, a plucky spacecraft called Hayabusa2 zinged back into Earth's atmosphere in late 2020 and landed deep in the Australian outback. When researchers from the Japanese space agency JAXA opened it, they found its precious payload sealed and intact: a handful of dirt that Hayabusa2 managed to scoop off the surface of a speeding asteroid.

Scientists have now begun to announce the first results from the analysis of this extraordinary sample. What they found suggests that this asteroid is a piece of the same stuff that coalesced into our sun four-and-a-half billion years ago.

"We previously only had a handful of these rocks to study, and all of them were meteorites that fell to Earth and were stored in museums for decades to centuries, which changed their compositions," said geochemist Nicolas Dauphas, one of the three University of Chicago researchers who worked with a Japan-led international team of scientists to analyze the fragments. "Having pristine samples from outer space is simply incredible. They are witnesses from parts of the solar system that we have not otherwise explored."

'It's spectacular'

In 2018, Hayabusa2 landed atop a moving asteroid named Ryugu and collected particles from above and below its surface. After spending a year and a half orbiting the asteroid, it returned to Earth with a sealed capsule containing about five grams of dust and rock. Scientists around the world have been eagerly anticipating the unique sample -- one that could help redefine our understanding of how planets evolve and how our solar system formed.

Scientists are particularly excited because these particles would never have reached Earth without the protective barrier of a spacecraft.

"Usually, all we get to study of asteroids is the pieces that are big enough to make it to the ground as meteorites," said UChicago geochemist Andrew M. Davis, another member of the analysis team. "If you took this handful and dropped it in the atmosphere, it would burn up. You would lose it, and a lot of evidence about the history of this asteroid would go with it.

"We really haven't had a sample like this before. It's spectacular."

Davis, Dauphas and UChicago colleague Reika Yokochi are all part of a team assembled to help Japanese researchers analyze the samples. Each part of the capsule's contents is being rigorously studied. Yokochi is part of a team that is analyzing the gases that were trapped in the capsule or in the dirt. Dauphas and Davis are part of a team that is studying the chemical and isotopic compositions grains to reveal their history.

The first compilation of these results, reported in Science on June 9, reveal the makeup of Ryugu.

The rock is similar to a class of meteorites known as "Ivuna-type carbonaceous chondrites." These rocks have a similar chemical composition to what we measure from the sun and are thought to date back to the very beginnings of the solar system approximately four-and-a-half billion years ago -- before the formation of the sun, the moon and Earth. [should Moon be capitalized to distinguish it from other moons?]

Back then, all that existed was a gigantic, rotating cloud of gas. Scientists think that most of that gas was pulled into the center and formed the star we know as the sun. As the remnants of that gas expanded into a disk and cooled, it transformed into rocks, which still float around the solar system today; it appears Ryugu may be one of them.

Scientists said the fragments show signs of having been soaked in water at some point. "One must picture an aggregate of ice and dust floating in space, that turned into a giant mudball when ice was melted by nuclear energy from the decay of radioactive elements that were present in the asteroid when it formed," said Dauphas. But surprisingly, today the rock itself appears to be relatively dry.

Using radioisotope dating, they estimated that Ryugu was altered by water circulation only about five million years after the solar system formed.

These findings are particularly interesting to researchers because they hint at similar formation conditions between comets and some asteroids such as Ryugu.

"By examining these samples, we can constrain the temperatures and conditions that must have been occurring in their lifetimes, and try to understand what happened," Yokochi explained.

She compared the process to trying to figure out how a soup was made, but with only the final result rather than the recipe: "We can take the soup and separate the ingredients, and try to tell from their conditions how much it was heated and in what order."

The scientists noted that a percentage of the find will be set aside so that we can analyze them in the future with more advanced technology -- much as we did with lunar samples from Apollo.

"After we got moon samples from Apollo 50 years ago, our ideas about how the moon formed completely changed," Davis said. "We're still learning new things from them, because our instruments and technology have advanced.

"The same will be true for these samples. This is a gift that keeps on giving."

This mission is the first of several international missions that will bring back samples from another asteroid named Bennu, as well as unexplored areas on our moon, Mars, and Mars' moon Phobos. This should all be taking place in the next 10 to 20 years.

Read more at Science Daily

Scientists craft living human skin for robots

From action heroes to villainous assassins, biohybrid robots made of both living and artificial materials have been at the center of many sci-fi fantasies, inspiring today's robotic innovations. It's still a long way until human-like robots walk among us in our daily lives, but scientists from Japan are bringing us one step closer by crafting living human skin on robots. The method developed, presented June 9 in the journal Matter, not only gave a robotic finger skin-like texture, but also water-repellent and self-healing functions.

"The finger looks slightly 'sweaty' straight out of the culture medium," says first author Shoji Takeuchi, a professor at the University of Tokyo, Japan. "Since the finger is driven by an electric motor, it is also interesting to hear the clicking sounds of the motor in harmony with a finger that looks just like a real one."

Looking "real" like a human is one of the top priorities for humanoid robots that are often tasked to interact with humans in healthcare and service industries. A human-like appearance can improve communication efficiency and evoke likability. While current silicone skin made for robots can mimic human appearance, it falls short when it comes to delicate textures like wrinkles and lacks skin-specific functions. Attempts at fabricating living skin sheets to cover robots have also had limited success, since it's challenging to conform them to dynamic objects with uneven surfaces.

"With that method, you have to have the hands of a skilled artisan who can cut and tailor the skin sheets," says Takeuchi. "To efficiently cover surfaces with skin cells, we established a tissue molding method to directly mold skin tissue around the robot, which resulted in a seamless skin coverage on a robotic finger."

To craft the skin, the team first submerged the robotic finger in a cylinder filled with a solution of collagen and human dermal fibroblasts, the two main components that make up the skin's connective tissues. Takeuchi says the study's success lies within the natural shrinking tendency of this collagen and fibroblast mixture, which shrank and tightly conformed to the finger. Like paint primers, this layer provided a uniform foundation for the next coat of cells -- human epidermal keratinocytes -- to stick to. These cells make up 90% of the outermost layer of skin, giving the robot a skin-like texture and moisture-retaining barrier properties.

The crafted skin had enough strength and elasticity to bear the dynamic movements as the robotic finger curled and stretched. The outermost layer was thick enough to be lifted with tweezers and repelled water, which provides various advantages in performing specific tasks like handling electrostatically charged tiny polystyrene foam, a material often used in packaging. When wounded, the crafted skin could even self-heal like humans' with the help of a collagen bandage, which gradually morphed into the skin and withstood repeated joint movements.

"We are surprised by how well the skin tissue conforms to the robot's surface," says Takeuchi. "But this work is just the first step toward creating robots covered with living skin." The developed skin is much weaker than natural skin and can't survive long without constant nutrient supply and waste removal. Next, Takeuchi and his team plan to address those issues and incorporate more sophisticated functional structures within the skin, such as sensory neurons, hair follicles, nails, and sweat glands.

Read more at Science Daily