Two of the Milky Way's earliest building blocks identified

Astronomers have identified what could be two of the Milky Way's earliest building blocks: Named "Shakti" and "Shiva," these appear to be the remnants of two galaxies that merged between 12 and 13 billion years ago with an early version of the Milky Way, contributing to our home galaxy's initial growth. The new find is the astronomical equivalent of archeologists identifying traces of an initial settlement that grew into a large present-day city. It required combining data for nearly 6 million stars from ESA's Gaia mission with measurements from the SDSS survey. The results have been published in the Astrophysical Journal.

The early history of our home galaxy, the Milky Way, is one of joining smaller galaxies, which makes for fairly large building blocks. Now, Khyati Malhan and Hans-Walter Rix of the Max Planck Institute for Astronomy have succeeded in identifying what could be two of the earliest building blocks that can still be recognized as such today: proto-galactic fragments that merged with an early version of our Milky Way between 12 and 13 billion years ago, at the very beginning of the era of galaxy formation in the Universe. The components, which the astronomers have named Shakti and Shiva, were identified by combining data from ESA's astrometry satellite Gaia with data from the SDSS survey. For astronomers, the result is the equivalent of finding traces of an initial settlement that grew into a large present-day city.

Tracing the origins of stars that came from other galaxies

When galaxies collide and merge, several processes happen in parallel. Each galaxy carries along its own reservoir of hydrogen gas. Upon collision, those hydrogen gas clouds are destabilized, and numerous new stars are formed inside. Of course, the incoming galaxies also already have their own stars, and in a merger, stars from the galaxies will mingle. In the long run, such "accreted stars" will also account for some of the stellar population of the newly-formed combined galaxy. Once the merger is completed, it might seem hopeless to identify which stars came from which predecessor galaxy. But in fact, at least some ways of tracing back stellar ancestry exist.

Help comes from basic physics. When galaxies collide and their stellar populations mingle, most of the stars retain very basic properties, which are directly linked to the speed and direction of the galaxy in which they originated. Stars from the same pre-merger galaxy share similar values for both their energy and what physicists call angular momentum -- the momentum associated with orbital motion or rotation. For stars moving in a galaxy's gravitational field, both energy and angular momentum are conserved: they remain the same over time. Look for large groups of stars with similar, unusual values for energy and angular momentum -- and chances are, you might find a merger remnant.

Additional pointers can assist identification. Stars that formed more recently contain more heavier elements, what astronomers call "metals," than stars that formed a long time ago. The lower the metal content ("metallicity"), the earlier the star presumably formed. When trying to identify stars that already existed 13 billion years ago, one should look for stars with very low metal content ("metal-poor").

Virtual excavations in a large data set

Identifying the stars that joined our Milky Way as parts of another galaxy has only become possible comparatively recently. It requires large, high-quality data sets, and the analysis involves sifting the data in clever ways so as to identify the searched-for class of objects. This kind of data set has only been available for a few years. The ESA astrometry satellite Gaia provides an ideal data set for this kind of big-data galactic archeology. Launched in 2013, it has produced an increasingly accurate data set over the past decade, which by now includes positions, changes in position and distances for almost 1.5 billion stars within our galaxy.

Gaia data revolutionized studies of the dynamics of stars in our home galaxy, and has already led to the discovery of previously unknown substructures. This includes the so-called Gaia Enceladus/Sausage stream, a remnant of the most recent larger merger our home galaxy has undergone, between 8 and 11 billion years ago. It also includes two structures identified in 2022: the Pontus stream identified by Malhan and colleagues and the "poor old heart" of the Milky Way identified by Rix and colleagues. The latter is a population of stars that newly formed during the initial mergers that created the proto-Milky Way, and continue to reside in our galaxy's central region.

Traces of Shakti and Shiva

For their present search, Malhan and Rix used Gaia data combined with detailed stellar spectra from the Sloan Digital Sky Survey (DR17). The latter provide detailed information about the stars' chemical composition. Malhan says: "We observed that, for a certain range of metal-poor stars, stars were crowded around two specific combinations of energy and angular momentum."

In contrast with the "poor old heart," which was also visible in those plots, the two groups of like-minded stars had comparatively large angular momentum, consistent with groups of stars that had been part of separate galaxies which had merged with the Milky Way. Malhan has named these two structures Shakti and Shiva, the latter one of the principal deities of Hinduism and the former a female cosmic force often portrayed as Shiva's consort.

Their energy and angular momentum values, plus their overall low metallicity on par with that of the "poor old heart," makes Shakti and Shiva good candidates for some of the earliest ancestors of our Milky Way. Rix says: "Shakti and Shiva might be the first two additions to the 'poor old heart' of our Milky Way, initiating its growth towards a large galaxy."

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James Webb Space Telescope captures the end of planet formation

Scientists believe that planetary systems like our solar system contain more rocky objects than gas-rich ones. Around our sun, these include the inner planets -- Mercury, Venus, Earth and Mars -- the asteroid belt and the Kuiper belt objects such as Pluto.

Jupiter, Saturn, Uranus and Neptune, on the other hand, contain mostly gas. But scientists also have known for a long time that planet-forming disks start out with 100 times more mass in gas than solids, which leads to a pressing question: When and how does most of the gas leave a nascent planetary system?

A new study led by Naman Bajaj at the University of Arizona Lunar and Planetary Laboratory, published in the Astronomical Journal, provides answers. Using the James Webb Space Telescope, or JWST, the team obtained images from such a nascent planetary system -- also known as a circumstellar disk -- in the process of actively dispersing its gas into surrounding space.

"Knowing when the gas disperses is important as it gives us a better idea of how much time gaseous planets have to consume the gas from their surroundings," said Bajaj, a second-year doctoral student at UArizona's Lunar and Planetary Laboratory. "With unprecedented glimpses into these disks surrounding young stars, the birthplaces of planets, JWST helps us uncover how planets form."

During the very early stages of planetary system formation, planets coalesce in a spinning disk of gas and tiny dust around the young star, according to Bajaj. These particles clump together, building up into bigger and bigger chunks called planetesimals. Over time, these planetesimals collide and stick together, eventually forming planets. The type, size and location of planets that form depend on the amount of material available and how long it remains in the disk.

"So, in short, the outcome of planet formation depends on the evolution and dispersal of the disk," Bajaj said.

At the heart of this discovery is the observation of T Cha, a young star -- relative to the sun, which is about 4.6 billion years old -- enveloped by an eroding circumstellar disk notable for a vast dust gap, spanning approximately 30 astronomical units, or au, with one au being the average distance between the Earth and the sun.

Bajaj and his team were able, for the first time, to image the disk wind, as the gas is referred to when it slowly leaves the planet-forming disk. The astronomers took advantage of the telescope's sensitivity to light emitted by an atom when high-energy radiation -- for example, in starlight -- strips one or more electrons from its nucleus. This is known as ionization, and the light emitted in the process can be used as a sort of chemical "fingerprint" -- in the case of the T Cha system, tracing two noble gases, neon and argon. The observations also mark the first time a double ionization of argon has been detected in a planet-forming disk, the team writes in the paper.

"The neon signature in our images tells us that the disk wind is coming from an extended region away from the disk," Bajaj said. "These winds could be driven either by high-energy photons -- essentially the light streaming from the star -- or by the magnetic field that weaves through the planet-forming disk."

In an effort to differentiate between the two, the same group, this time led by Andrew Sellek, a postdoctoral researcher at Leiden University in the Netherlands, performed simulations of the dispersal driven by stellar photons, the intense light streaming from the young star. They compared these simulations to the actual observations and found dispersal by high-energy stellar photons can explain the observations, and hence cannot be excluded as a possibility. That study concluded that the amount of gas dispersing from the T Cha disk every year is equivalent to that of Earth's moon. These results will be published in a companion paper, currently under review with the Astronomical Journal.

While neon signatures had been detected in many other astronomical objects, they weren't known to originate in low-mass planet-forming disks until first discovered in 2007 with JWST's predecessor, NASA's Spitzer Space Telescope, by Ilaria Pascucci, a professor at LPL who soon identified them as a tracer of disk winds. Those early findings transformed research efforts focused on understanding gas dispersal from circumstellar disks. Pascucci is the principal investigator on the most recent observing project and a co-author on the publications reported here.

"Our discovery of spatially resolved neon emission -- and the first detection of double ionized argon -- using the James Webb Space Telescope could become the next step towards transforming our understanding of how gas clears out of a planet-forming disk," Pascucci said. "These insights will help us get a better idea of the history and impact on our own solar system."

In addition, the group has also discovered that the inner disk of T Cha is evolving on very short timescales of decades; they found that the spectrum observed by JWST differs from the earlier spectrum detected by Spitzer. According to Chengyan Xie, a second-year doctoral student at LPL who leads this in-progress work, this mismatch could be explained by a small, asymmetric disk inside of T Cha that has lost some of its mass in the short 17 years that have elapsed between the two observations.

"Along with the other studies, this also hints that the disk of T Cha is at the end of its evolution," Xie said. "We might be able to witness the dispersal of all the dust mass in T Cha's inner disk within our lifetime."

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Scientists uncover evidence that microplastics are contaminating archaeological remains

Researchers have for the first time discovered evidence of microplastic contamination in archaeological soil samples.

The team discovered tiny microplastic particles in deposits located more than seven metres deep, in samples dating back to the first or early second century and excavated in the late 1980s.

Preserving archaeology in situ has been the preferred approach to managing historical sites for a generation.

However, the research team say the findings could prompt a rethink, with the tiny particles potentially compromising the preserved remains.

Microplastics are small plastic particles, ranging from 1μm (one thousandth of a millimetre) to 5mm.

They come from a wide range of sources, from larger plastic pieces that have broken apart, or resin pellets used in plastic manufacturing which were frequently used in beauty products up until around 2020.

The study, published in the journal Science of the Total Environment, was carried out by the universities of York and Hull and supported by the educational charity York Archaeology.

Professor John Schofield from the University of York's Department of Archaeology, said: "This feels like an important moment, confirming what we should have expected: that what were previously thought to be pristine archaeological deposits, ripe for investigation, are in fact contaminated with plastics, and that this includes deposits sampled and stored in the late 1980s.

"We are familiar with plastics in the oceans and in rivers. But here we see our historic heritage incorporating toxic elements. To what extent this contamination compromises the evidential value of these deposits, and their national importance is what we'll try to find out next."

David Jennings, chief executive of York Archaeology, added: "We think of microplastics as a very modern phenomenon, as we have only really been hearing about them for the last 20 years, when Professor Richard Thompson revealed in 2004 that they have been prevalent in our seas since the 1960s with the post-war boom in plastic production,"

"This new study shows that the particles have infiltrated archaeological deposits, and like the oceans, this is likely to have been happening for a similar period, with particles found in soil samples taken and archived in 1988 at Wellington Row in York."

The study identified 16 different microplastic polymer types across both contemporary and archived samples.

"Where this becomes a concern for archaeology is how microplastics may compromise the scientific value of archaeological deposits. Our best-preserved remains -- for example, the Viking finds at Coppergate -- were in a consistent anaerobic waterlogged environment for over 1000 years, which preserved organic materials incredibly well. The presence of microplastics can and will change the chemistry of the soil, potentially introducing elements which will cause the organic remains to decay. If that is the case, preserving archaeology in situ may no longer be appropriate," added David Jennings.

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Researchers propose a new way to identify when babies become conscious

Academics are proposing a new and improved way to help researchers discover when consciousness emerges in human infancy.

When over the course of development do humans become conscious? When the seventeenth-century French philosopher René Descartes was asked about infant consciousness by his critics, he eventually suggested that infants might have thoughts, albeit ones that are simpler than those of adults. Hundreds of years later, the issue of when human beings become conscious is a question which remains a challenge for psychologists and philosophers alike.

But now, in response to a recent article in Trends in Cognitive Sciences, two academics from the University of Birmingham have suggested an improved way to help scientists and researchers identify when babies become conscious.

In a Letter to the Editor, also published in Trends in Cognitive Sciences, Dr Henry Taylor, Associate Professor of Philosophy, and Andrew Bremner, Professor of Developmental Psychology, have explored a new approach which is being proposed, that involves identifying markers of consciousness in adults, and then measuring when babies start to exhibit larger numbers of these in development.

Dr Taylor says: "For example, imagine that in adults, we know that a certain very specific behaviour, or a specific pattern of brain activation always comes along with consciousness. Then, if we can identify when this behaviour or brain activation arises in babies, we have good reason to think that this is when consciousness emerges in babies. Behaviours and brain activations like this are what we call 'markers' of consciousness."

This kind of approach is desperately needed since babies (unlike adults) cannot tell you what they are conscious of. Professor Bremner said: "It is really hard to establish when babies become conscious. This is mostly because infants can't report their experiences and, as most parents will know, can be rather uncooperative particularly when it comes to experimental tasks. As we can't just ask babies when they become conscious, the best approach is to try to identify a broad range of markers of consciousness, which appear in early development and late development, and then group them together, this could help us identify when consciousness emerges."

In the recent article the researchers (Prof. Tim Bayne and colleagues) suggested four specific markers of consciousness, some of which are present in the late stages of gestation, and others which are found in early infancy. Based on this, the study argues that consciousness emerges early (from the last prenatal trimester).

But Professor Bremner and Dr Taylor say that this ignores other markers of consciousness. Previous research has identified a separate cluster of markers. These include:

• Pointing (bringing a social partner's attention to an object and checking). • Intentional control (intentional means-end coordination of actions -- e.g., pulling a support to retrieve a distal object). • Explicit memory (deferred imitation of actions).

Dr Taylor said: "One of the complicated issues is that it does not look like all the markers point to the same age for the emergence of consciousness. The ones mentioned by Bayne and colleagues suggest somewhere between the third trimester of pregnancy and early infancy, but other markers suggest the age might be around one year old. In fact, at the really extreme end, some markers only emerge at around 3-4 years. Because there are so many different markers of consciousness which appear in early and late development it is extremely hard to come to a conclusion."

Professor Bremner concluded: "We propose that a broad approach to markers, including those that emerge in early and late stage, is needed. We also recommend that a range of developmental models of the onset of consciousness should be considered. For instance, it may be that some markers emerge in one cluster in early development, with others in a later cluster. As well as this there may be a continuous and gradual emergence of certain markers stretching over gestation and throughout early life.

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Astrophysicist's research could provide a hint in the search for dark matter

Dark matter is one of science's greatest mysteries. Although it is believed to make up about 85 percent of the cosmos, scientists know very little about its fundamental nature. Research by Clemson University postdoctoral fellow Alex McDaniel provides some of the most stringent constraints on the nature of dark matter yet. It also revealed a small hint of a signal that, if real, could be confirmed in the next decade or so.

Dark matter is one of science's greatest mysteries.

It doesn't absorb, reflect or emit light, so we can't see it. But its presence is implied by the gravitational effects it appears to have on galaxies.

Although dark matter makes up about 85 percent of the cosmos, scientists know very little about its fundamental nature.

Theories abound, and research by Clemson University postdoctoral fellow Alex McDaniel provides some of the most stringent constraints on the nature of dark matter yet.

His research also reveals a small hint of a signal that, if real, could be confirmed sometime in the next decade or so.

"With data collection and new discoveries in the future, this small hint could potentially turn into a very concrete detection of a dark matter model," McDaniel said.

Detecting dark matter would be groundbreaking.

"Dark matter is one of the most important things in astrophysics, and we know next to nothing about it. Discovering it will be a tremendous breakthrough," said Marco Ajello, an associate professor in the Clemson Department of Physics and Astronomy and McDaniel's adviser.

"Whoever discovers may win a Nobel Prize. It's that big."

In this work, McDaniel and collaborators were searching dwarf galaxies for dark matter that self-annihilates into ordinary matter and gamma rays, a form of light at the highest energy levels.

Dwarf galaxies are ideal for study because they are small, rich in dark matter and mostly lack other astrophysics phenomena such as gas, dust and supernova that could contaminate the findings.

"We look for these because, ideally, they give us a clean signal or allow us to rule out certain particle theories," McDaniel said.

Some models predict that dark matter has a certain mass or cross section, which is the probability of a specific event occurring due to the interaction of particles.

That would determine what researchers would expect to see in gamma rays.

If they don't see that, they can rule out those masses and cross sections, he said.

"In this paper, we do more ruling out, saying that dark matter can't have those masses or cross section," said Chris Karwin, a former postdoc at Clemson and a co-author of the study.

Karwin is now a postdoctoral fellow at the NASA Goddard Space Flight Center.

"But compared to previous studies, we do start to see a hint of something that might be a signal from these systems."

McDaniel's study uses the larger samples that include additional discovered dwarf galaxies and larger amounts of data than previous studies.

He included about 50 dwarf galaxies in his study but said that with new, more powerful telescopes coming online in the near future, he expects that number to increase to 150-200.

"The new telescopes are basically dwarf galaxy detectors," he said.

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Say hello to biodegradable microplastics

Microplastics are tiny, nearly indestructible fragments shed from everyday plastic products. As we learn more about microplastics, the news keeps getting worse. Already well-documented in our oceans and soil, we're now discovering them in the unlikeliest of places: our arteries, lungs and even placentas. Microplastics can take anywhere from 100 to 1,000 years to break down and, in the meantime, our planet and bodies are becoming more polluted with these materials every day.

Finding viable alternatives to traditional petroleum-based plastics and microplastics has never been more important. New research from scientists at the University of California San Diego and materials-science company Algenesis shows that their plant-based polymers biodegrade -- even at the microplastic level -- in under seven months. The paper, whose authors are all UC San Diego professors, alumni or former research scientists, appears in Nature Scientific Reports.

"We're just starting to understand the implications of microplastics. We've only scratched the surface of knowing the environmental and health impacts," stated Professor of Chemistry and Biochemistry Michael Burkart, one of the paper's authors and an Algenesis co-founder. "We're trying to find replacements for materials that already exist, and make sure these replacements will biodegrade at the end of their useful life instead of collecting in the environment. That's not easy."

"When we first created these algae-based polymers about six years ago, our intention was always that it be completely biodegradable," said another of the paper's authors, Robert Pomeroy, who is also a professor of chemistry and biochemistry and an Algenesis co-founder. "We had plenty of data to suggest that our material was disappearing in the compost, but this is the first time we've measured it at the microparticle level."

Putting it to the test

To test its biodegradability, the team ground their product into fine microparticles, and used three different measurement tools to confirm that, when placed in a compost, the material was being digested by microbes.

The first tool was a respirometer. When the microbes break down compost material, they release carbon dioxide (CO2), which the respirometer measures. These results were compared to the breakdown of cellulose, which is considered the industry standard of 100% biodegradability. The plant-based polymer matched the cellulose at almost one hundred percent.

Next the team used water flotation. Since plastics are not water soluble and they float, they can easily be scooped off the surface of water. At intervals of 90 and 200 days, almost 100% of the petroleum-based microplastics were recovered, meaning none of it had biodegraded. On the other hand, after 90 days, only 32% of the algae-based microplastics were recovered, showing that more than two thirds of it had biodegraded. After 200 days, only 3% was recovered indicating that 97% of it had disappeared.

The last measurement involved chemical analysis via gas chromatography/mass spectrometry (GCMS), which detected the presence of the monomers used to make the plastic, indicating that the polymer was being broken to its starting plant materials. Scanning-electron microscopy further showed how microorganisms colonize the biodegradable microplastics during composting.

"This material is the first plastic demonstrated to not create microplastics as we use it," said Stephen Mayfield, a paper coauthor, School of Biological Sciences professor and co-founder of Algenesis. "This is more than just a sustainable solution for the end-of-product life cycle and our crowded landfills. This is actually plastic that is not going to make us sick."

Creating an eco-friendly alternative to petroleum-based plastics is only one part of the long road to viability. The ongoing challenge is to be able to use the new material on pre-existing manufacturing equipment that was originally built for traditional plastic, and here Algenesis is making progress. They have partnered with several companies to make products that use the plant-based polymers developed at UC San Diego, including Trelleborg for use in coated fabrics and RhinoShield for use in the production of cell phone cases.

"When we started this work, we were told it was impossible," stated Burkart. "Now we see a different reality. There's a lot of work to be done, but we want to give people hope. It is possible."

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Your dog understands that some words 'stand for' objects

It's no surprise that your dog can learn to sit when you say "sit" and come when called. But a study appearing March 22 in the journal Current Biology has made the unexpected discovery that dogs generally also know that certain words "stand for" certain objects. When dogs hear those words, brain activity recordings suggest they activate a matching mental representation in their minds.

"Dogs do not only react with a learned behavior to certain words," says Marianna Boros of the Department of Ethology at the Eötvös Loránd University, Budapest, Hungary, one of the paper's co-first authors. "They also don't just associate that word with an object based on temporal contiguity without really understanding the meaning of those words, but they activate a memory of an object when they hear its name."

Word understanding tests with individuals who do not speak, such as infants and animals, usually require active choice, the researchers say. They're asked to show or get an object after hearing its name. Very few dogs do well on such tests in the lab, often fetching objects correctly at a rate expected by chance.

The researchers wanted to look closer at dogs' implicit understanding of object words by measuring brain activity using non-invasive EEG without asking them to act. The idea was that this might offer a more sensitive measure of their understanding of language.

In their studies, they had 18 dog owners say words for toys their dogs knew and then present the objects to them. Sometimes they presented the matching toy, while other times they would present an object that didn't match. For example, an owner would say, "Zara, look, the ball," and present the object while the dog's brain activity was captured on EEG.

The brain recording results showed a different pattern in the brain when the dogs were shown a matching object versus a mismatched one. That's similar to what researchers have seen in humans and is widely accepted as evidence that they understand the words. The researchers also found a greater difference in those patterns for words that dogs knew better, offering further support for their understanding of object words. Interestingly, while the researchers thought this ability might depend on having a large vocabulary of object words, their findings showed that it doesn't.

"Because typical dogs learn instruction words rather than object names, and there are only a handful of dogs with a large vocabulary of object words, we expected that dogs' capacity for referential understanding of object words will be linked to the number of object words they know; but it wasn't," says Lilla Magyari, also of Eötvös Loránd University and University of Stavanger and the other co-first author.

"It doesn't matter how many object words a dog understands -- known words activate mental representations anyway, suggesting that this ability is generally present in dogs and not just in some exceptional individuals who know the names of many objects," Boros added.

The discovery that dogs as a species may generally have a capacity to understand words in a referential way, just as humans do, might reshape the way scientists think about the uniqueness of how humans use and understand language, the researchers say. That has important implications for theories and models of language evolution. For dog owners, it's also an important realization.

"Your dog understands more than he or she shows signs of," Magyari says. "Dogs are not merely learning a specific behavior to certain words, but they might actually understand the meaning of some individual words as humans do."

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Study reveals 'cozy domesticity' of prehistoric stilt-house dwellers in England's ancient marshland

A major report on the remains of a stilt village that was engulfed in flames almost 3,000 years ago reveals in unprecedented detail the daily lives of England's prehistoric fenlanders.

Must Farm, a late Bronze Age settlement, dates to around 850BC, with University of Cambridge archaeologists unearthing four large wooden roundhouses and a square entranceway structure -- all of which had been constructed on stilts above a slow-moving river.

The entire hamlet stood approximately two metres above the riverbed, with walkways bridging some of the main houses, and was surrounded by a two-metre-high fence of sharpened posts.

The settlement was less than a year old when it was destroyed by a catastrophic fire, with buildings and their contents collapsing into the muddy river below. The combination of charring and waterlogging led to exceptional preservation. The site has been described as "Britain's Pompeii."

Years of research conducted on thousands of artefacts from the site have now shown that early Fen folk had surprisingly comfortable lifestyles, with domestic layouts similar to modern homes, meals of "honey-glazed venison" and clothes of fine flax linen, and even a recycling bin.

The settlement-on-stilts also contained a stack of spears with shafts over three metres long, as well as a necklace with beads from as far away as Denmark and Iran, and a human skull rendered smooth by touch, perhaps a memento of a lost loved one.

The Cambridge archaeologists say the site provides a unique "blueprint" for the circular architecture, home interiors and overall domesticity of those who inhabited the swampy fenland of East Anglia some eight centuries before Romans set foot on British shores.

Full findings from the Must Farm site -- excavated by the Cambridge Archaeological Unit (CAU) in 2015-16 after its discovery on the edge of Whittlesey near Peterborough -- are published in two reports, both made available by Cambridge's McDonald Institute for Archaeological Research.

"These people were confident and accomplished home-builders. They had a design that worked beautifully for an increasingly drowned landscape," said CAU's Mark Knight, report co-author and excavation director.

"While excavating the site there was a sense that its Bronze Age residents had only just left. You could almost see and smell their world, from the glint of metal tools hanging on wattled walls to the sharp milkiness of brewed porridge."

'Mirror' of ancient home interiors

The ruins of five structures were uncovered, along with walkways and fencing, but the original settlement was likely twice as big -- half the site was removed by 20th century quarrying -- with researchers saying it may have held up to sixty occupants in family units.

The river running underneath the community would have been shallow, sluggish and thick with vegetation. This cushioned the scorched remains where they fell, creating an archaeological "mirror" of what had stood above -- allowing researchers to map the layout of the structures.

One of the main roundhouses, with almost fifty square metres of floor space, appeared to have distinct activity zones comparable to rooms in a modern home.

"Conducting research on Must Farm is a bit like getting an estate agent's tour of a Bronze Age stilt house," said David Gibson, report co-author and Archaeological Manager at CAU.

Ceramic and wooden containers, including tiny cups, bowls, and large storage jars, were found in the northeast quadrant of "Structure One," the location of a kitchen. Some pots were even nested: designed to stack inside one another to save space.

Metal tools were stored along the building's eastern side, while the empty northwest area was probably reserved for sleeping. The southeast space had lots of cloth fragments, along with bobbins and loom weights. This was close to a likely entrance, where extra light would have helped with textile work.

The roundhouse's southwest quadrant was reserved for keeping lambs indoors. There was no evidence of humans dying in the fire, but several young sheep had been trapped and burnt alive.

Skeletal remains showed the lambs were three to six months old, suggesting the settlement was destroyed sometime in late summer or early autumn. Evidence that the wooden architecture was still "green" confirms construction took place around nine months to a year earlier.

Tool kits, textiles and a token of good luck

Household inventories were remarkably consistent. All the roundhouses contained a metalwork "tool kit" that included sickles (crop-harvesting blades) along with axes and curved "gouges" used to hack and chisel wood, as well as hand-held razors for cutting hair.

Most buildings had objects for making textiles, from spindle whorls to thread bobbins, although the distribution suggests that "spinning" -- the process of twisting fibres together -- was conducted in three of the roundhouses, but Structure One was where this yarn got converted to fabrics.

The textiles are the finest of this period found in Europe, with details such as "pile tufts" that would have given garments a soft, almost velvety feel, and "tubular selvedge" for neat seams and hems.

Each roundhouse roof had three layers: insulating straw topped by turf and completed with clay -- making them warm and waterproof but still well ventilated. "In a freezing winter, with winds cutting across the Fens, these roundhouses would have been pretty cosy," said CAU project archaeologist Dr Chris Wakefield.

Structure Four, a smaller square building, may also have acted as the settlement's entrance. A large wooden bucket had been kept within, containing several damaged bronze objects and worn axe-heads, waiting to be smelted down and recycled into new tools.

Encircling the footprint of each roundhouse were "middens," haloes of rubbish dumped from the stilt village above, included broken pots, butchered animal bone, and "coprolites" or fossilised faeces. Some human coprolites had parasite eggs, suggesting inhabitants struggled with intestinal worms.

One item, however, had been placed in the silt directly beneath Structure One: an intact hafted axe, perhaps a token of good fortune, or an offering to some kind of spirit on completion of the build.

'Meaty porridge'

Despite millennia in the mud, many artefacts still bore traces of daily life -- along with its sudden interruption as inhabitants abandoned their possessions to escape the blaze.

For example, a pottery bowl with the finger-marks of its maker captured in the clay was found still holding its final meal: a wheat-grain porridge mixed with animal fats (possibly goat or red deer). The wooden spatula used for stirring was resting against the inside of the bowl.

"It appears the occupants saved their meat juices to use as toppings for porridge," said Dr Chris Wakefield. "The site is providing us with hints of recipes for Bronze Age breakfasts and roast dinners."

"Chemical analyses of the bowls and jars showed traces of honey along with ruminant meats such as deer, suggesting these ingredients were combined to create a form of prehistoric honey-glazed venison."

The stilt-house dwellers even had favourite cuts of meat, often only bringing the forelegs of a boar back for roasting, for example. Preferred aquatic dishes included pike and bream.

Several small dog skulls suggest the animals were kept domestically, perhaps as pets but also to help flush out prey on a hunt. Dog coprolites show they fed on scraps from their owners' meals.

Must Farm's residents used the local woodlands -- evidence suggests within a two-mile radius -- to hunt boar and deer, graze sheep, and harvest crops such as wheat and flax as well as wood for construction. Waterways were vital for transporting all these materials.

The remains of nine log-boats, canoes hollowed from old tree trunks, were found upstream, dating from across the Bronze and into the Iron Age, included some that were contemporary to Must Farm.

"Boat journeys through reed swamps to the woodlands would have been made many times during the site's short life," said Wakefield. "In summer, that meant traversing clouds of mosquitos."

Much of what was retrieved from Must Farm were everyday items, the Bronze Age equivalent to the TV remotes and coffee mugs of our own lives. However, some items would have been precious.

A necklace of beads made from glass, amber, siltstone and shale had been lost in the fire. In fact, decorative beads were found right across the site. All but one of Must Farm's 49 glass beads came from far-flung places, including Northern and Eastern Europe, and even the Middle East.

"Such items would gradually make their way across thousands of miles in a long series of small trades," said Wakefield.

Up in flames…

The researchers say that, while the Bronze Age could be violent, and aspects of the site's structure are clearly defensive, its location may be as much to do with resources. Spears found on site, up to 3.4 metres in length, as well as swords, were as likely to be used in animal hunts as on rival groups.

A few human remains were recovered, including the skull of an adult woman polished by repeated touch -- a sign this may have been a keepsake of love rather than war.

"The cause of the fire that tore through the settlement will probably never be known," said CAU's David Gibson. "Some argue it may have come under attack, as the occupants never returned for their goods, which would have been fairly easy to retrieve from the shallow waters."

However, others think it more likely to have been an accident. If an internal fire took hold in one of the roundhouses, it would spread between the tightknit structures within minutes.

Added Gibson: "A settlement like this would have had a shelf-life of maybe a generation, and the people who built it had clearly constructed similar sites before. It may be that after the fire, they simply started again."

"There is every possibility that the remains of many more of these stilted settlements are buried across Fenland, waiting for us to find them."

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Scientists find one of the most ancient stars that formed in another galaxy

The first generation of stars transformed the universe. Inside their cores, simple hydrogen and helium fused into a rainbow of elements. When these stars died, they exploded and sent these new elements across the universe. The iron running in your veins and the calcium in your teeth and the sodium powering your thoughts were all born in the heart of a long-dead star.

No one has been able to find one of those first generation of stars, but scientists have announced a unique finding: a star from the second generation that originally formed in a different galaxy from ours.

"This star provides a unique window into the very early element-forming process in galaxies other than our own," said Anirudh Chiti, a University of Chicago postdoctoral fellow and first author on a paper announcing the findings. "We have built up an idea of the how these stars that were chemically enriched by the first stars look like in the Milky Way, but we don't yet know if some of these signatures are unique, or if things happened similarly across other galaxies."

The paper was published March 20 in Nature Astronomy.

'Fishing needles out of haystacks'

Chiti specializes in what is called stellar archaeology: Reconstructing how the earliest generations of stars changed the universe. "We want to understand what the properties of those first stars were and what were the elements they produced," said Chiti.

But no one has yet managed to directly see these first-generation stars, if any remain in the universe. Instead, Chiti and his colleagues look for stars that formed from the ashes of that first generation.

It's hard work, because even the second generation of stars is now incredibly ancient and rare. Most stars in the universe, including our own sun, are the result of tens to thousands of generations, building up more and more heavy elements each time. "Maybe fewer than 1 in 100,000 stars in the Milky Way is one of these second-gen stars," he said. "You really are fishing needles out of haystacks."

But it's worth it to get snapshots of what the universe looked like back in time. "In their outer layers, these stars preserve the elements near where they formed," he explained. "If you can find a very old star and get its chemical composition, you can understand what the chemical composition of the universe was like where that star formed, billions of years ago."

An intriguing oddity

For this study, Chiti and his colleagues aimed their telescopes at an unusual target: the stars that make up the Large Magellanic Cloud.

The Large Magellanic Cloud is a bright swath of stars visible to the naked eye in the Southern Hemisphere. We now think it was once a separate galaxy that was captured by the Milky Way's gravity just a few billion years ago. This makes it particularly interesting because its oldest stars were formed outside the Milky Way -- giving astronomers a chance to learn about whether conditions in the early universe all looked the same, or were different in other places.

The scientists searched for evidence of these particularly ancient stars in the Large Magellanic Cloud and catalogued ten of them, first with the European Space Agency's Gaia satellite and then with the Magellan Telescope in Chile.

One of these stars immediately jumped out as an oddity. It had much, much less of the heavier elements in it than any other star yet seen in the Large Magellanic Cloud. This means it was probably formed in the wake of the first generation of stars -- so it had not yet built up heavier elements over the course of repeated star births and deaths.

Mapping out its elements, the scientists were surprised to see that it had a lot less carbon than iron compared to what we see in Milky Way stars.

"That was very intriguing, and it suggests that perhaps carbon enhancement of the earliest generation, as we see in the Milky Way, was not universal," Chiti said. "We'll have to do further studies, but it suggests there are differences from place to place.

"I think we're filling out the picture of what the early element enrichment process looked like in different environments," he said.

Their findings also corroborated other studies that have suggested that the Large Magellanic Cloud made much fewer stars early on compared to the Milky Way.

Read more at Science Daily

Icy impacts: Planetary scientists use physics and images of impact craters to gauge the thickness of ice on Europa

Sometimes planetary physics is like being in a snowball fight. Most people, if handed an already-formed snowball, can use their experience and the feel of the ball to guess what kind of snow it is comprised of: packable and fluffy, or wet and icy.

Using nearly the same principles, planetary scientists have been able to study the structure of Europa, Jupiter's icy moon.

Europa is a rocky moon, home to saltwater oceans twice the volume of Earth's, encased in a shell of ice.

Scientists have long thought that Europa may be one of the best places in our solar system to look for nonterrestrial life.

The likelihood and nature of that life, though, heavily depend on the thickness of its icy shell, something astronomers have not yet been able to ascertain.

A team of planetary science experts including Brandon Johnson, an associate professor, and Shigeru Wakita, a research scientist, in the Department of Earth, Atmospheric, and Planetary Sciences in Purdue University's College of Science, announced in a new paper published in Science Advances [ES1] that Europa's ice shell is at least 20 kilometers thick.

To reach their conclusion, the scientists studied large craters on Europa, running a variety of models to determine what combination of physical characteristics could have created such a surface structure.

"This is the first work that has been done on this large crater on Europa," Wakita said.

"Previous estimates showed a very thin ice layer over a thick ocean. But our research showed that there needs to be a thick layer -- so thick that convection in the ice, which has previously been debated, is likely."

Using data and images from the spacecraft Galileo, which studied Europa in 1998, Johnson analyzed the impact craters to decode truths about Europa's structure.

An expert in planetary physics and colossal collisions, Johnson has studied almost every major planetary body in the solar system.

Scientists have long debated the thickness of Europa's ice shell; no one has visited to measure it directly, so scientists are creatively using the evidence at hand: the craters on Europa's icy surface.

"Impact cratering is the most ubiquitous surface process shaping planetary bodies," Johnson said.

"Craters are found on almost every solid body we've ever seen. They are a major driver of change in planetary bodies. When an impact crater forms, it is essentially probing the subsurface structure of a planetary body. By understanding the sizes and shapes of craters on Europa and reproducing their formation with numerical simulations, we're able to infer information about how thick its ice shell is."

Europa is a frozen world, but the ice shelters a rocky core.

The icy surface, though, is not stagnant. Plate tectonics and convection currents in the oceans and the ice itself refresh the surface fairly frequently.

This means the surface itself is only 50 million to 100 million years old -- which sounds old to short-lived organisms like humans, but is young as far as geological periods go.

That smooth, young surface means that craters are clearly defined, easier to analyze and not very deep.

Their impacts tell scientists more about the icy shell of the moon and the water ocean below, rather than conveying much information about its rocky heart.

Read more at Science Daily