Astronomers detect most distant fast radio burst to date

An international team has spotted a remote blast of cosmic radio waves lasting less than a millisecond. This 'fast radio burst' (FRB) is the most distant ever detected. Its source was pinned down by the European Southern Observatory's (ESO) Very Large Telescope (VLT) in a galaxy so far away that its light took eight billion years to reach us. The FRB is also one of the most energetic ever observed; in a tiny fraction of a second it released the equivalent of our Sun's total emission over 30 years.

The discovery of the burst, named FRB 20220610A, was made in June last year by the ASKAP radio telescope in Australia and it smashed the team's previous distance record by 50 percent.

"Using ASKAP's array of dishes, we were able to determine precisely where the burst came from," says Stuart Ryder, an astronomer from Macquarie University in Australia and the co-lead author of the study published today in Science. "Then we used [ESO's VLT] in Chile to search for the source galaxy, finding it to be older and further away than any other FRB source found to date and likely within a small group of merging galaxies."

The discovery confirms that FRBs can be used to measure the 'missing' matter between galaxies, providing a new way to 'weigh' the Universe.

Current methods of estimating the mass of the Universe are giving conflicting answers and challenging the standard model of cosmology. "If we count up the amount of normal matter in the Universe -- the atoms that we are all made of -- we find that more than half of what should be there today is missing," says Ryan Shannon, a professor at the Swinburne University of Technology in Australia, who also co-led the study. "We think that the missing matter is hiding in the space between galaxies, but it may just be so hot and diffuse that it's impossible to see using normal techniques."

"Fast radio bursts sense this ionised material. Even in space that is nearly perfectly empty they can 'see' all the electrons, and that allows us to measure how much stuff is between the galaxies," Shannon says.

Finding distant FRBs is key to accurately measuring the Universe's missing matter, as shown by the late Australian astronomer Jean-Pierre ('J-P') Macquart in 2020. "J-P showed that the further away a fast radio burst is, the more diffuse gas it reveals between the galaxies. This is now known as the Macquart relation. Some recent fast radio bursts appeared to break this relationship. Our measurements confirm the Macquart relation holds out to beyond half the known Universe," says Ryder.

"While we still don't know what causes these massive bursts of energy, the paper confirms that fast radio bursts are common events in the cosmos and that we will be able to use them to detect matter between galaxies, and better understand the structure of the Universe," says Shannon.

Read more at Science Daily

Urgent action needed to address climate change threats to coastal areas

Global coastal adaptations are 'incremental in scale', short-sighted and inadequate to address the root causes of vulnerability to climate change, according to an international team of researchers.

The 17 experts, including Prof Robert Nicholls, Professor of Climate Adaptation at the University of East Anglia (UEA), have contributed to the paper, 'Status of global coastal adaptation', which is published today in Nature Climate Change.

Prof Nicholls said: "Recent analyses conclude that despite adaptation undertaken in all regions and sectors, global action remains incremental in scale: policies and projects are usually short-sighted and single hazard-focused, inadequately address the root causes of exposure and vulnerability, and are poorly monitored. There is also little evidence of effective risk reduction in relation to implemented responses."

To address these problems, the experts say decisive action by the international policy community is needed to identify and tackle global priorities in key risk areas across countries.

Dr Alexandre Magnan, of the Institute for Sustainable Development and International Relations (IDDRI), is first author of the paper.

Dr Magnan said: "Assessing climate adaptation is a burning scientific and policy question because, as today's global climate risk will experience a two- to four-fold increase by the end of this century depending on the global greenhouse gas emissions trajectory, we need to know the current status toward addressing its consequences.

"New, alternative methods to assess adaptation are urgently needed in order carry out effective planning and action, evidence on risk reduction, capabilities and create a long-term vision."

The paper considered 61 coastal case studies to develop a locally informed perspective on the state of global coastal adaptation. It looked at both extreme events and low-onset climate change, including coastal erosion, marine flooding, sea-level rise and extremes, soil and groundwater salinization, inland flooding resulting from heavy precipitations, and permafrost thaw.

While strategies for urban coastal areas are generally more advanced than rural ones, the experts said plans for long-term adaptations remain limited.

The experts concluded that today's global coastal adaptation is half-way to the full adaptation potential.

Taking sea-level rise as one example, the experts said the risks to low-lying coasts are already detectable.

Prof Nicholls said: "By the end of the century and in the absence of ambitious adaptation efforts, these risks will become significant, widespread and possibly irreversible in atolls and arctic coasts. The lower estimates for deltas are still a concern given these geographies' population sizes and economic importance globally."

The expert group developed a qualitative structured judgment -- the Global Adaptation Progress Tracker (GAP-Track) -- to assess adaptation efforts, progress and gaps, as part of the framework for the Global Goal on Adaptation established under the Paris Agreement in 2015.

Dr Magnan said: "Countries still struggle finding a way to operationalize the Global Goal on Adaptation and to conduct the Global Stocktake (GST) series that aims to collectively track adaptation progress and gaps, with a first iteration due at COP28 in the United Arab Emirates.

"The multi-dimensional and locally grounded assessment developed in this study for coastal adaptation confirms the need to drastically scale up adaptation policy and action around the globe, from local governments and stakeholders to the international climate policy arena.

Read more at Science Daily

Study reveals our European ancestors ate seaweed and freshwater plants

For many people seaweed holds a reputation as a superfood, heralded for its health benefits and sustainability, but it appears our European ancestors were ahead of the game and were consuming the nutrient-rich plant for thousands of years.

Researchers say they have found "definitive" archaeological evidence that seaweeds and other local freshwater plants were eaten in the mesolithic, through the Neolithic transition to farming and into the Early Middle Ages, suggesting that these resources, now rarely eaten in Europe, only became marginal much more recently.

The study, published in Nature Communications, reveals that while aquatic resources were exploited, the archaeological evidence for seaweed is only rarely recorded and is almost always considered in terms of non-edible uses like fuel, food wrappings or fertilisers.

Historical accounts report laws related to collection of seaweed in Iceland, Brittany and Ireland dating to the 10th Century, while sea kale is mentioned by Pliny as a sailor's anti-scurvy remedy.

By the 18th Century seaweed was considered as famine food, and although seaweed and freshwater aquatic plants continue to be economically important in parts of Asia, both nutritionally and medicinally, there is little consumption in Europe.

The team, led by archaeologists from the universities of Glasgow and York, examined biomarkers extracted from dental calculus from 74 individuals from 28 archaeological sites across Europe, from north Scotland to southern Spain, which revealed "direct evidence for widespread consumption of seaweed and submerged aquatic and freshwater plants."

Samples where biomolecular evidence survived revealed consumption of red, green or brown seaweeds, or freshwater aquatic plants, with one sample from Orkney also containing evidence for a Brassica, most likely sea kale.

There are approximately 10,000 different species of seaweeds in the world, however only 145 species are eaten today, principally in Asia.

The researchers hope that their study will highlight the potential for including more seaweeds and other local freshwater plants in our diets today -- helping Europeans to become healthier and more sustainable.

Karen Hardy, Professor of Prehistoric Archaeology at the University of Glasgow and Principal Investigator of the Powerful Plants project, said: "Today, seaweed and freshwater aquatic plants are virtually absent from traditional, western diets and their marginalisation as they gradually changed from food to famine resources and animal fodder, probably occurred over a long period of time, as has also been detected elsewhere with some plants.

"Our study also highlights the potential for rediscovery of alternative, local, sustainable food resources that may contribute to addressing the negative health and environmental effects of over-dependence on a small number of mass-produced agricultural products that is a dominant feature of much of today's western diet, and indeed the global long-distance food supply more generally."

"It is very exciting to be able to show definitively that seaweeds and other local freshwater plants were eaten across a long period in our European past."

Co author on the paper, Dr Stephen Buckley, from the Department of Archaeology at the University of York, said "The biomolecular evidence in this study is over three thousand years earlier than historical evidence in the Far East.

"Not only does this new evidence show that seaweed was being consumed in Europe during the Mesolithic Period around 8,000 years ago when marine resources were known to have been exploited, but that it continued into the Neolithic when it is usually assumed that the introduction of farming led to the abandonment of marine dietary resources.

Read more at Science Daily

NASA's Webb captures an ethereal view of NGC 346

Filaments of dust and gas festoon this star-forming region in a new infrared image from MIRI.

One of the greatest strengths of NASA's James Webb Space Telescope is its ability to give astronomers detailed views of areas where new stars are being born. The latest example, showcased here in a new image from Webb's Mid-Infrared Instrument (MIRI), is NGC 346 -- the brightest and largest star-forming region in the Small Magellanic Cloud.

The Small Magellanic Cloud (SMC) is a satellite galaxy of the Milky Way, visible to the unaided eye in the southern constellation Tucana. This small companion galaxy is more primeval than the Milky Way in that it possesses fewer heavy elements, which are forged in stars through nuclear fusion and supernova explosions, compared to our own galaxy.

Since cosmic dust is formed from heavy elements like silicon and oxygen, scientists expected the SMC to lack significant amounts of dust. However the new MIRI image, as well as a previous image of NGC 346 from Webb's Near-Infrared Camera released in January, show ample dust within this region.

In this representative-color image, blue tendrils trace emission from material that includes dusty silicates and sooty chemical molecules known as polycyclic aromatic hydrocarbons, or PAHs. More diffuse red emission shines from warm dust heated by the brightest and most massive stars in the heart of the region. An arc at the center left may be a reflection of light from the star near the arc's center. (Similar, fainter arcs appear associated with stars at lower left and upper right.) Lastly, bright patches and filaments mark areas with abundant numbers of protostars. The research team looked for the reddest stars, and found 1,001 pinpoint sources of light, most of them young stars still embedded in their dusty cocoons.

Read more at Science Daily

'Starquakes' could explain mystery signals

Fast radio bursts, or FRBs, are an astronomical mystery, with their exact cause and origins still unconfirmed. These intense bursts of radio energy are invisible to the human eye, but show up brightly on radio telescopes. Previous studies have noted broad similarities between the energy distribution of repeat FRBs, and that of earthquakes and solar flares. However, new research at the University of Tokyo has looked at the time and energy of FRBs and found distinct differences between FRBs and solar flares, but several notable similarities between FRBs and earthquakes. This supports the theory that FRBs are caused by "starquakes" on the surface of neutron stars. This discovery could help us better understand earthquakes, the behavior of high-density matter and aspects of nuclear physics.

The vastness of space holds many mysteries. While some people dream of boldly going where no one has gone before, there is a lot we can learn from the comfort of Earth. Thanks to technological advances, we can explore the surface of Mars, marvel at Saturn's rings and pick up mysterious signals from deep space. Fast radio bursts are hugely powerful, bright bursts of energy which are visible on radio waves. First discovered in 2007, these bursts can travel billions of light years but typically last mere thousandths of a second. It has been estimated that as many as 10,000 FRBs may happen every day if we could observe the whole sky. While the sources of most bursts detected so far appear to emit a one-off event, there are about 50 FRB sources which emit bursts repeatedly.

The cause of FRBs is unknown, but some ideas have been put forward, including that they might even be alien in origin. However, the current prevailing theory is that at least some FRBs are emitted by neutron stars. These stars form when a supergiant star collapses, going from eight times the mass of our sun (on average) to a superdense core only 20-40 kilometers across. Magnetars are neutron stars with extremely strong magnetic fields, and these have been observed to emit FRBs.

"It was theoretically considered that the surface of a magnetar could be experiencing a starquake, an energy release similar to earthquakes on Earth," said Professor Tomonori Totani from the Department of Astronomy at the Graduate School of Science. "Recent observational advances have led to the detection of thousands more FRBs, so we took the opportunity to compare the now large statistical data sets available for FRBs with data from earthquakes and solar flares, to explore possible similarities."

So far, statistical analysis of FRBs has focused on the distribution of wait times between two successive bursts. However, Totani and co-author Yuya Tsuzuki, a graduate student in the same department, point out that calculating only the wait-time distribution does not take into account correlations that might exist across other bursts. So the team decided to calculate correlation across two-dimensional space, analyzing the time and emission energy of nearly 7,000 bursts from three different repeater FRB sources. They then applied the same method to examine the time-energy correlation of earthquakes (using data from Japan) and of solar flares (using records from the Hinode international mission to study the sun), and compared the results of all three phenomena.

Totani and Tsuzuki were surprised that, in contrast to other studies, their analysis showed a striking similarity between FRBs and earthquake data, but a distinct difference between FRBs and solar flares. Totani explained: "The results show notable similarities between FRBs and earthquakes in the following ways: First, the probability of an aftershock occurring for a single event is 10-50%; second, the aftershock occurrence rate decreases with time, as a power of time; third, the aftershock rate is always constant even if the FRB-earthquake activity (mean rate) changes significantly; and fourth, there is no correlation between the energies of the main shock and its aftershock."

Read more at Science Daily

Research shows wildfire smoke may linger in homes long after initial blaze

Newly published research on indoor air quality from Colorado State University shows wildfire smoke may linger in homes long after the initial blaze has been put out or winds have shifted.

The findings, published in Science Advances, show that wildfire smoke can attach to home surfaces like carpet, drapes or counters -- extending the exposure for those inside and potentially causing health problems even after an initial cleaning activity by air purifiers. However, Professor Delphine Farmer said the research also shows that simple surface cleaning -- like vacuuming, dusting or mopping -- can reduce exposure and limit risk.

The research illustrates the hidden and persistent health threats many in the Western U.S. are facing given the increase in wildfires over the last decade, she said.

"This research shows that events like the Marshall Fire in Colorado, the wildfires in Canada and the recent fires in Hawaii present serious exposure potential -- not just when they occur but well after," said Farmer, who is based in the Department of Chemistry at CSU. "This paper is a key initial step towards providing actionable and practical information on how to protect yourself and clean your home."

To better understand how smoke enters and then stays in buildings, researchers burned pine wood chips in a net zero energy residential testing facility operated by the National Institute of Standards and Technology (NIST) in Maryland. That facility is frequently used to study how different systems impact the ways energy, water and air move through a single-family house. The detailed instrumentation available for that work was perfectly suited to this research, said Dustin Poppendieck, an environmental researcher at NIST who helped coordinate the project.

"The NIST Net Zero House allowed the researchers to track the movement and transformation of chemicals in the air and onto surfaces in real time using instruments in ways that don't interfere with the behavior of the smoke," said Poppendieck.

Those smoke injection sessions occurred regularly over several days, and Farmer said the total amount applied was comparable or slightly under the particulate levels seen during the Canadian wildfires. The team then took careful measurements of air quality levels and surface conditions after opening exterior doors and windows, cleaning and use of the home's built-in air cleaning systems.

The CSU team was particularly interested in the gas-phase of compounds developing from the smoke, while other teams from the University of California San Diego, CU Boulder and the University of North Carolina Chapple Hill explored different phases and interactions across the home. The team then compared findings between states to confirm what was actually happening in the home after the burn.

Farmer said findings from this interdisciplinary research approach could also be applicable to other large air pollution events like the train derailment in East Palestine, Ohio, where the same principles of compounds sticking to surfaces are likely to occur.

Because there has not been a lot of similar indoor air research, the team leaned on previous findings from others around the effects of cigarette smoke to inform their approach. Farmer said burning nicotine causes specific compounds with well-known health concerns and that the comparison to their project findings was informative.

"Nicotine reacts on surfaces to create a particularly nasty set of compounds called nitrosamines, which is where the real concern from thirdhand smoke that is left behind comes from," she said. "Whereas with wildfire smoke, we found there was a huge diversity of organic compounds that stick to surfaces, which then slowly bleed off."

The amount, persistence and variety of compounds from the wildfire smoke in each case could potentially change the recommended approaches for cleaning the indoor spaces. Farmer said that is an area of research the team hopes to explore in the future. For now, she said the team was able to show that the amount of smoke left on surfaces was proportional to the surface area that was cleaned. That means simple cleaning and specifically addressing large but little noticed spaces that may trap harmful compounds such as cabinets and HVAC systems could be beneficial right away.

"As we continue this research, we would like to know just how effective different cleaning approaches are and when residents should move from relatively simple steps like using commercial cleaning supplies for mopping to more drastic steps like replacing the drywall altogether," Farmer said.

Farmer's team was also recently funded by the W.M. Keck Foundation to research how smog may enter and remain in the home in much the same way as wildfire smoke. That work will be particularly important in Colorado where ground-level ozone pollution is a continuing issue.

Read more at Science Daily

Researchers capture first-ever afterglow of huge planetary collision in outer space

The study, published today in Nature, reports the sighting of two ice giant exoplanets colliding around a sun-like star, creating a blaze of light and plumes of dust. Its findings show the bright heat afterglow and resulting dust cloud, which moved in front of the parent star dimming it over time.

The international team of astronomers was formed after an enthusiast viewed the light curve of the star and noticed something strange. It showed the system doubled in brightness at infrared wavelengths some three years before the star started to fade in visible light.

Co-lead author Dr Matthew Kenworthy, from Leiden University, said: "To be honest, this observation was a complete surprise to me. When we originally shared the visible light curve of this star with other astronomers, we started watching it with a network of other telescopes.

"An astronomer on social media pointed out that the star brightened up in the infrared over a thousand days before the optical fading. I knew then this was an unusual event."

The network of professional and amateur astronomers studied the star intensively including monitoring changes in the star's brightness over the next two years. The star was named ASASSN-21qj after the network of telescopes that first detected the fading of the star at visible wavelengths.

The researchers concluded the most likely explanation is that two ice giant exoplanets collided, producing the infrared glow detected by NASA's NEOWISE mission, which uses a space telescope to hunt for asteroids and comets.

Co-lead author Dr Simon Lock, Research Fellow in Earth Sciences at the University of Bristol, said: "Our calculations and computer models indicate the temperature and size of the glowing material, as well as the amount of time the glow has lasted, is consistent with the collision of two ice giant exoplanets."

The resultant expanding debris cloud from the impact then travelled in front of the star some three years later, causing the star to dim in brightness at visible wavelengths.

Over the next few years, the cloud of dust is expected to start smearing out along the orbit of the collision remnant, and a tell-tale scattering of light from this cloud could be detected with both ground-based telescopes and NASA's largest telescope in space, known as JWST.

The astronomers plan on watching closely what happens next in this system.

Read more at Science Daily

Scientists unveil detailed cell maps of the human brain and the nonhuman primate brain

A group of international scientists have mapped the genetic, cellular, and structural makeup of the human brain and the nonhuman primate brain. This understanding of brain structure, achieved by funding through the National Institutes of Health's Brain Research Through Advancing Innovative Neurotechnologies® Initiative, or The BRAIN Initiative®, allows for a deeper knowledge of the cellular basis of brain function and dysfunction, helping pave the way for a new generation of precision therapeutics for people with mental disorders and other disorders of the brain. The findings appear in a compendium of 24 papers across Science, Science Advances, and Science Translational Medicine.

"Mapping the brain's cellular landscape is a critical step toward understanding how this vital organ works in health and disease," said Joshua A. Gordon, M.D., Ph.D., director of the National Institute of Mental Health. "These new detailed cell atlases of the human brain and the nonhuman primate brain offer a foundation for designing new therapies that can target the specific brain cells and circuits involved in brain disorders."

The 24 papers in this latest BRAIN Initiative Cell Census Network (BICCN) collection detail the exceptionally complex diversity of cells in the human brain and the nonhuman primate brain. The studies identify similarities and differences in how cells are organized and how genes are regulated in the human brain and the nonhuman primate brain. For example:

• Three papers in the collection present the first atlas of cells in the adult human brain, mapping the transcriptional and epigenomic landscape of the brain. The transcriptome is the complete set of gene readouts in a cell, which contains instructions for making proteins and other cellular products. The epigenome refers to chemical modifications to a cell's DNA and chromosomes that alter the way the cell's genetic information is expressed.
• In another paper, a comparison of the cellular and molecular properties of the human brain and several nonhuman primate brains (chimpanzee, gorilla, macaque, and marmoset brains) revealed clear similarities in the types, proportions, and spatial organization of cells in the cerebral cortex of humans and nonhuman primates. Examination of the genetic expression of cortical cells across species suggests that relatively small changes in gene expression in the human lineage led to changes in neuronal wiring and synaptic function that likely allowed for greater brain plasticity in humans, supporting the human brain's ability to adapt, learn, and change.
• A study exploring how cells vary in different brain regions in marmosets found a link between the properties of cells in the adult brain and the properties of those cells during development. The link suggests that developmental programming is embedded in cells when they are formed and maintained into adulthood and that some observable cellular properties in an adult may have their origins very early in life. This finding could lead to new insights into brain development and function across the lifespan.
• An exploration of the anatomy and physiology of neurons in the outermost layer of the neocortex -- part of the brain involved in higher-order functions such as cognition, motor commands, and language -- revealed differences in the human brain and the mouse brain that suggest this region may be an evolutionary hotspot, with changes in humans reflecting the higher demands of regulating humans' more complex brain circuits.

The core aim of the BICCN, a groundbreaking effort to understand the brain's cellular makeup, is to develop a comprehensive inventory of the cells in the brain -- where they are, how they develop, how they work together, and how they regulate their activity -- to better understand how brain disorders develop, progress, and are best treated.

"This suite of studies represents a landmark achievement in illuminating the complexity of the human brain at the cellular level," said John Ngai, Ph.D., director of the NIH BRAIN Initiative. "The scientific collaborations forged through BICCN are propelling the field forward at an exponential pace; the progress -- and possibilities -- have been simply breathtaking."

Read more at Science Daily

Neanderthal gene variants associated with greater pain sensitivity

People who carry three gene variants that have bene inherited from Neanderthals are more sensitive to some types of pain, according to a new study co-led by UCL researchers.

The findings, published in Communications Biology, are the latest findings to show how past interbreeding with Neanderthals has influenced the genetics of modern humans.

The researchers found that people carrying three so-called Neanderthal variants in the gene SCN9A, which is implicated in sensory neurons, are more sensitive to pain from skin pricking after prior exposure to mustard oil.

Previous research has identified three variations in the SCN9A gene -- known as M932L, V991L, and D1908G -- in sequenced Neanderthal genomes and reports of greater pain sensitivity among humans carrying all three variants. However, prior to this study the specific sensory responses affected by these variants was unclear.

An international team led by researchers at UCL, Aix-Marseille University, University of Toulouse, Open University, Fudan University, and Oxford University, and part-funded by Wellcome, measured the pain thresholds of 1,963 people from Colombia in response to a range of stimuli.

The SCN9A gene encodes a sodium channel that is expressed at high levels in sensory neurons that detect signals from damaged tissue. The researchers found that the D1908G variant of the gene was present in around 20% of chromosomes within this population and around 30% of chromosomes carrying this variant also carried the M932L and V991L variants.

The authors found that the three variants were associated with a lower pain threshold in response to skin pricking after prior exposure to mustard oil, but not in response to heat or pressure. Additionally, carrying all three variants was associated with greater pain sensitivity than carrying only one.

When they analysed the genomic region including SCN9A using genetic data from 5,971 people from Brazil, Chile, Colombia, Mexico and Peru, the authors found that the three Neanderthal variants were more common in populations with higher proportions of Native American ancestry, such as the Peruvian population, in which the average proportion of Native American ancestry was 66%.

The authors propose that the Neanderthal variants may sensitise sensory neurons by altering the threshold at which a nerve impulse is generated. They speculate that the variants may be more common in populations with higher proportions of Native American ancestry as a result of random chance and population bottlenecks that occurred during the initial occupation of the Americas. Although acute pain can moderate behaviour and prevent further injury, the scientists that say additional research is needed to determine whether carrying these variants and having greater pain sensitivity may have been advantageous during human evolution.

Previous research by co-corresponding author Dr Kaustubh Adhikari (UCL Genetics, Evolution & Environment and The Open University) has shown that humans also inherited some genetic material from Neanderthals affecting the shape of our noses.*

Dr Adhikari commented: "In the last 15 years, since the Neanderthal genome was first sequenced, we have been learning more and more about what we have inherited from them as a result of interbreeding tens of thousands of years ago.

"Pain sensitivity is an important survival trait that enables us to avoid painful things that could cause us serious harm. Our findings suggest that Neanderthals may have been more sensitive to certain types of pain, but further research is needed for us to understand why that is the case, and whether these specific genetic variants were evolutionarily advantageous."

Read more at Science Daily

Finding explanation for Milky Way's warp

The Milky Way is often depicted as a flat, spinning disk of dust, gas, and stars. But if you could zoom out and take an edge-on photo, it actually has a distinctive warp -- as if you tried to twist and bend a vinyl LP.

Though scientists have long known through observational data that the Milky Way is warped and its edges are flared like a skirt, no one could explain why.

Now, Harvard astronomers at the Center for Astrophysics | Harvard and Smithsonian (CfA) have performed the first calculations that fully explain this phenomenon, with compelling evidence pointing to the Milky Way's envelopment in an off-kilter halo of dark matter. The work also bolsters current thinking about how the galaxy evolved and may offer clues into some of the mysteries of dark matter.

The new calculations were led by Jiwon Jesse Han, a Griffin Graduate School of Arts and Sciences student affiliated with the CfA. Published in Nature Astronomy, the work includes co-authors Charlie Conroy and Lars Hernquist, both faculty members at the CfA and in the Department of Astronomy.

Our galaxy is located inside a diffuse cloud called the stellar halo, which extends much farther out into the universe. In groundbreaking work published last year, the Harvard team deduced that the stellar halo is tilted and elliptical in shape, like a zeppelin or football.

Building on that, the team assumed the same shape for the dark matter halo, the larger entity that encompasses everything in and around the Milky Way. Dark matter makes up 80 percent of the galaxy's mass but is invisible because it doesn't interact with light, so the shape of that halo must be inferred. Using models to calculate the orbits of stars within a tilted, oblong dark matter halo, the team found a near-perfect match to existing observations of a warped, flared galaxy.

"A tilted dark halo is actually fairly common in simulations, but no one had explored its effect on the Milky Way," Conroy said. "It turns out that the tilt is an elegant way to explain both the magnitude and direction of our galaxy's wobbly disk."

Scientists had long surmised that the Milky Way formed due to a galactic collision; the astronomers' work further underscores that hypothesis.

"If the galaxy was just evolving on its own, it would have had this nice, spherical halo, this nice, flat disk," Han said. "So the fact that the halo is tilted and has a football-like shape suggests that our galaxy experienced a merger event, where two galaxies collide."

Their calculation of the dark matter halo's probable shape may also provide clues as to the properties and particle nature of dark matter itself, which remain unsolved mysteries in physics. "The fact that the galaxy is not spherical in our data implies that there is some limit to which dark matter can interact with itself," Han explained.

Read more at Science Daily