Jun 19, 2021

Scientists detect signatures of life remotely

Left hands and right hands are almost perfect mirror images of each other. But whatever way they are twisted and turned, they cannot be superimposed onto each other. This is why the left glove simply won't fit the right hand as well as it fits the left. In science, this property is referred to as chirality.

Just like hands are chiral, molecules can be chiral, too. In fact, most molecules in the cells of living organisms, such as DNA, are chiral. Unlike hands, however, that usually come in pairs of left and right, the molecules of life almost exclusively occur in either their "left-handed" or their "right-handed" version. They are homochiral, as researchers say. Why that is, is still not clear. But this molecular homochirality is a characteristic property of life, a so-called biosignature.

As part of the MERMOZ project (see info box), an international team led by the University of Bern and the National Centre of Competence in Research NCCR PlanetS, has now succeeded in detecting this signature from a distance of 2 kilometers and at a velocity of 70 kph. Jonas Kühn, MERMOZ project manager of the University of Bern and co-author of the study that has just been published in the journal Astronomy and Astrophysics, says: "The significant advance is that these measurements have been performed in a platform that was moving, vibrating and that we still detected these biosignatures in a matter of seconds."

An instrument that recognizes living matter

"When light is reflected by biological matter, a part of the light's electromagnetic waves will travel in either clockwise or counterclockwise spirals. This phenomenon is called circular polarization and is caused by the biological matter's homochirality. Similar spirals of light are not produced by abiotic non-living nature," says the first author of the study Lucas Patty, who is a MERMOZ postdoctoral researcher at the University of Bern and member of the NCCR PlanetS,

Measuring this circular polarization, however, is challenging. The signal is quite faint and typically makes up less than one percent of the light that is reflected. To measure it, the team developed a dedicated device called a spectropolarimeter. It consists of a camera equipped with special lenses and receivers capable of separating the circular polarization from the rest of the light.

Yet even with this elaborate device, the new results would have been impossible until recently. "Just 4 years ago, we could detect the signal only from a very close distance, around 20 cm, and needed to observe the same spot for several minutes to do so," as Lucas Patty recalls. But the upgrades to the instrument he and his colleagues made, allow a much faster and stable detection, and the strength of the signature in circular polarisation persists even with distance. This rendered the instrument fit for the first ever aerial circular polarization measurements.

Useful measurements on earth and in space

Using this upgraded instrument, dubbed FlyPol, they demonstrated that within mere seconds of measurements they could differentiate between grass fields, forests and urban areas from a fast moving helicopter. The measurements readily show living matter exhibiting the characteristic polarization signals, while roads, for example, do not show any significant circular polarization signals. With the current setup, they are even capable of detecting signals coming from algae in lakes.

After their successful tests, the scientists now look to go even further. "The next step we hope to take, is to perform similar detections from the International Space Station (ISS), looking down at the Earth. That will allow us to assess the detectability of planetary-scale biosignatures. This step will be decisive to enable the search for life in and beyond our Solar System using polarization," says MERMOZ principal investigator and co-author Brice-Olivier Demory, professor of astrophysics at the University of Bern and member of the NCCR PlanetS says.

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Unraveling the origin of Alzheimer's disease

Case Western Reserve University researchers studying prions -- misfolded proteins that cause lethal incurable diseases -- have identified for the first time surface features of human prions responsible for their replication in the brain.

The ultimate goal of the research is to help design a strategy to stop prion disease in humans -- and, ultimately, to translate new approaches to work on Alzheimer's and other neurodegenerative diseases.

Scientists have yet to discover the exact cause of Alzheimer's disease, but largely agree that protein issues play a role in its emergence and progression. Alzheimer's disease afflicts more than 6 million people in the U.S., and the Alzheimer's Association estimates that their care will cost an estimated $355 billion this year.

Research was done at the Safar Laboratory in the Department of Pathology and the Center for Proteomics and Bioinformatics at Case Western Reserve University School of Medicine, and at Case Western Reserve's Center for Synchrotron Bioscience at Brookhaven Laboratories in New York. Jiri Safar, professor of pathology, neurology and neurosciences at the Case Western Reserve School of Medicine, leads the work. The report, "Structurally distinct external domains drive replication of major human prions," was published in the June 17 issue of PLOS Pathogens.

Prions were first discovered in the late 1980s as a protein-containing biological agent that could replicate itself in living cells without nucleic acid. The public health impact of medically transmitted human prion diseases -- and also animal transmissions of bovine spongiform encephalopathy (BSE, "mad cow disease") prions -- dramatically accelerated the development of a new scientific concept of self-replicating protein.

Human prions can bind to neighboring normal proteins in the brain, and cause microscopic holes. In essence, they turn brains into sponge-like structures and lead to dementia and death. These discoveries led to the ongoing scientific debate on whether prion-like mechanisms may be involved in the origin and spread of other neurodegenerative disorders in humans.

"Human prion diseases are conceivably the most heterogenous neurodegenerative disorders, and a growing body of research indicates that they are caused by distinct strains of human prions," Safar said. "However, the structural studies of human prions have lagged behind the recent progress in rodent laboratory prions, in part because of their complex molecular characteristics and prohibitive biosafety requirements necessary for investigating disease which is invariably fatal and has no treatment."

The researchers developed a new three-step process to study human prions:

  • Human brain-derived prions were first exposed to a high-intensity synchrotron X-ray beam. That beam created hydroxyl radical species which, with short bursts of light, selectively and progressively changed the prion's surface chemical composition. The unique properties of this type of light source include its enormous intensity; it can be millions of times brighter than light from the sun to the Earth.
  • The rapid chemical modifications of prions by short bursts of light were monitored with anti-prion antibodies. The antibodies recognize the prion surface features, and mass spectrometry that identifies exact sites of prion-specific, strain-based differences, providing an even more precise description of the prion's defects.
  • Illuminated prions were then allowed to replicate in a test tube. The progressive loss of their replication activity as the synchrotron modifies them helped identify key structural elements responsible for prions' replication and propagation in the brain.

"The work is a critical first step for identifying sites of structural importance that reflect differences between prions of different diagnosis and aggressiveness," said Mark Chance, vice dean for research at the School of Medicine and a co-investigator on the work. "Thus, we can now envision designing small molecules to bind to these sites of nucleation and replication and block progression of human prion disease in patients."

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First evidence that medieval plague victims were buried individually with 'considerable care'

In the mid-14th century Europe was devastated by a major pandemic -- the Black Death -- which killed between 40 and 60 per cent of the population. Later waves of plague then continued to strike regularly over several centuries.

Plague kills so rapidly it leaves no visible traces on the skeleton, so archaeologists have previously been unable to identify individuals who died of plague unless they were buried in mass graves.

Whilst it has long been suspected that most plague victims received individual burial, this has been impossible to confirm until now.

By studying DNA from the teeth of individuals who died at this time, researchers from the After the Plague project, based at the Department of Archaeology, University of Cambridge, have identified the presence of Yersinia Pestis, the pathogen that causes plague.

These include people who received normal individual burials at a parish cemetery and friary in Cambridge and in the nearby village of Clopton.

Lead author Craig Cessford of the University of Cambridge said, "These individual burials show that even during plague outbreaks individual people were being buried with considerable care and attention. This is shown particularly at the friary where at least three such individuals were buried within the chapter house. Cambridge Archaeological Unit conducted excavations on this site on behalf of the University in 2017."

"The individual at the parish of All Saints by the Castle in Cambridge was also carefully buried; this contrasts with the apocalyptic language used to describe the abandonment of this church in 1365 when it was reported that the church was partly ruinous and 'the bones of dead bodies are exposed to beasts'."

The study also shows that some plague victims in Cambridge did, indeed, receive mass burials.

Yersinia Pestis was identified in several parishioners from St Bene't's, who were buried together in a large trench in the churchyard excavated by the Cambridge Archaeological Unit on behalf of Corpus Christi College.

This part of the churchyard was soon afterwards transferred to Corpus Christi College, which was founded by the St Bene't's parish guild to commemorate the dead including the victims of the Black Death. For centuries, the members of the College would walk over the mass burial every day on the way to the parish church.

Read more at Science Daily

Jun 18, 2021

Hubble data confirms galaxies lacking dark matter

The most accurate distance measurement yet of ultra-diffuse galaxy (UDG) NGC1052-DF2 (DF2) confirms beyond any shadow of a doubt that it is lacking in dark matter. The newly measured distance of 22.1 +/-1.2 megaparsecs was obtained by an international team of researchers led by Zili Shen and Pieter van Dokkum of Yale University and Shany Danieli, a NASA Hubble Fellow at the Institute for Advanced Study.

"Determining an accurate distance to DF2 has been key in supporting our earlier results," stated Danieli. "The new measurement reported in this study has crucial implications for estimating the physical properties of the galaxy, thus confirming its lack of dark matter."

The results, published in Astrophysical Journal Letters on June 9, 2021, are based on 40 orbits of NASA's Hubble Space Telescope, with imaging by the Advanced Camera for Surveys and a "tip of the red giant branch" (TRGB) analysis, the gold standard for such refined measurements. In 2019, the team published results measuring the distance to neighboring UDG NGC1052-DF4 (DF4) based on 12 Hubble orbits and TRGB analysis, which provided compelling evidence of missing dark matter. This preferred method expands on the team's 2018 studies that relied on "surface brightness fluctuations" to gauge distance. Both galaxies were discovered with the Dragonfly Telephoto Array at the New Mexico Skies observatory.

"We went out on a limb with our initial Hubble observations of this galaxy in 2018," van Dokkum said. "I think people were right to question it because it's such an unusual result. It would be nice if there were a simple explanation, like a wrong distance. But I think it's more fun and more interesting if it actually is a weird galaxy."

In addition to confirming earlier distance findings, the Hubble results indicated that the galaxies were located slightly farther away than previously thought, strengthening the case that they contain little to no dark matter. If DF2 were closer to Earth, as some astronomers claim, it would be intrinsically fainter and less massive, and the galaxy would need dark matter to account for the observed effects of the total mass.

Dark matter is widely considered to be an essential ingredient of galaxies, but this study lends further evidence that its presence may not be inevitable. While dark matter has yet to be directly observed, its gravitational influence is like a glue that holds galaxies together and governs the motion of visible matter. In the case of DF2 and DF4, researchers were able to account for the motion of stars based on stellar mass alone, suggesting a lack or absence of dark matter. Ironically, the detection of galaxies deficient in dark matter will likely help to reveal its puzzling nature and provide new insights into galactic evolution.

While DF2 and DF4 are both comparable in size to the Milky Way galaxy, their total masses are only about one percent of the Milky Way's mass. These ultra-diffuse galaxies were also found to have a large population of especially luminous globular clusters.

This research has generated a great deal of scholarly interest, as well as energetic debate among proponents of alternative theories to dark matter, such as Modified Newtonian dynamics (MOND). However, with the team's most recent findings -- including the relative distances of the two UDGs to NGC1052 -- such alternative theories seem less likely. Additionally, there is now little uncertainty in the team's distance measurements given the use of the TRGB method. Based on fundamental physics, this method depends on the observation of red giant stars that emit a flash after burning through their helium supply that always happens at the same brightness.

"There's a saying that extraordinary claims require extraordinary evidence, and the new distance measurement strongly supports our previous finding that DF2 is missing dark matter," stated Shen. "Now it's time to move beyond the distance debate and focus on how such galaxies came to exist."

 Read more at Science Daily

A new rapid assessment to promote climate-informed conservation and nature-based solutions

A new article, published as a Perspective in the journal Conservation Science and Practice, introduces a rapid assessment framework that can be used as a guide to make conservation and nature-based solutions more robust to future climate.

Climate change poses risks to conservation efforts, if practitioners assume a future climate similar to the past or present. For example, more frequent and intense disturbances, such as wildfire or drought-induced tree mortality, can threaten projects that are designed to enhance habitat for forest-dependent species and sequester carbon. Overlooking such climate-related risks can result in failed conservation investments and negative outcomes for people, biodiversity, and ecosystem integrity as well as lead to carbon-sink reversal. Drawing from lessons learned from a decade of funding over 100 adaptation initiatives through the WCS Climate Adaptation Fund, the authors offer a simple framework that enables users to rapidly assess how -- and by what means -- climate change will require innovation beyond business-as-usual conservation practice.

This tractable assessment encourages practitioners and funders to use the "what, when, where, why, and who" -- or the "5Ws" -- of climate-informed action as a tool in project design and implementation. The "what," for example, means considering whether climate variability and projected changes will require taking new actions or modifying existing actions. The "who" asks users to consider: by whom, with whom, who benefits and who might bear potential harm or tradeoffs from project implementation and anticipated outcomes.

Using the 5Ws in practice can result in doing conservation differently in the warming world and help practitioners achieve their desired objectives. They use available science and local knowledge to address climate risks to traditional investments in reforestation, fire management, watershed restoration, and habitat protection. Take reforestation as an example: a traditional approach might aim to enhance habitat and carbon sequestration using seed or seedlings from historically-dominant tree species. Tree mortality due to unsuitable climate conditions could then lead to unexpected habitat degradation and reductions in carbon sequestration. A climate-informed approach favors native species that are expected to thrive under future climate. Seed or seedlings can be sourced from warmer and/or drier locations to assist migration to climatically-suitable areas. The 5Ws facilitates this process of figuring out what, if anything, should be done differently from the status quo.

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First months decisive for immune system development

Many diseases caused by a dysregulated immune system, such as allergies, asthma and autoimmunity, can be traced back to events in the first few months after birth. To date, the mechanisms behind the development of the immune system have not been fully understood. Now, researchers at Karolinska Institutet show a connection between breast milk, beneficial gut bacteria and the development of the immune system. The study is published in Cell.

"A possible application of our results is a preventative method for reducing the risk of allergies, asthma and autoimmune disease later in life by helping the immune system to establish its regulatory mechanisms," says the paper's last author Petter Brodin, paediatrician and researcher at the Department of Women's and Children's Health, Karolinska Institutet. "We also believe that certain mechanisms that the study identifies can eventually lead to other types of treatment for such diseases, not just a prophylactic."

The incidence of autoimmune diseases such as asthma, type 1 diabetes and Crohn's disease is increasing in children and adolescents in parts of the world. These diseases are debilitating, but not as common in low-income countries as they are in Europe and the USA.

It has long been known that the risk of developing these diseases is largely determined by early life events; for instance, there is a correlation between the early use of antibiotics and a higher risk of asthma. It is also known that breastfeeding protects against most of these disorders.

There is a link between specific, protective bacteria on the skin and in the airways and gut and a lower risk of immunological diseases. However, there is still much to learn about how these bacteria form the immune system.

Researchers at Karolinska Institutet, Evolve Biosystems, Inc, the University of California Davis, University of Nebraska, Lincoln, and University of Nevada, Reno studied how the neonatal immune system adapts to and is shaped by the many bacteria, viruses, nutrients and other environmental factors to which the baby is exposed during the first few months of life.

Earlier research has shown that bifidobacteria are common in breastfed babies in countries with a low incidence of autoimmune diseases.

Breast milk is rich in HMOs (Human milk oligosaccharides), which babies are unable to metabolise on their own. The production of these complex sugars are instead associated with the evolutionary advantage of nourishing specific gut bacteria that play an important part in their immune system. Bifidobacteria are one such bacterial class.

"We found that babies whose intestinal flora can break down HMOs have less inflammation in the blood and gut," says professor Brodin. "This is probably because of the uniquely good ability of the bifidobacteria to break down HMOs, to expand in nursing babies and to have a beneficial effect on the developing immune system early in life."

Babies who were breastfed and received additional bifidobacteria had higher intestinal levels of the molecules ILA and Galectin-1. ILA (indole-3-lactic acid) is needed to convert HMO molecules into nutrition; Galectin-1 is central to the activation of the immune response to threats and attacks.

According to the researchers, Galectin-1 is a newly discovered and critical mechanism for preserving bacteria with beneficial, anti-inflammatory properties in the intestinal flora.

The results are based on 208 breastfed babies born at Karolinska University Hospital between 2014 and 2019. The researchers also used novel methods to analyse the immune system even from small blood samples. Additionally, a second cohort developed by the University of California in which infants were exclusively breastfed and half were fed B. infantis supplement were analyzed for enteric inflammation.

One limitation of the study is that the researchers were unable to study the immune system direct in the gut and had to resort to blood samples. Not all aspects of the gut immune system can be seen in the blood, but it is not ethically defensible to take intestinal biopsies from healthy neonates.

The researchers now hope to follow the participant babies for a longer time to see which ones develop atopic eczema, asthma and allergies.

Read more at Science Daily

Most cancer cells grown in a dish have little in common with cancer cells in people, research finds

In a bid to find or refine laboratory research models for cancer that better compare with what happens in living people, Johns Hopkins Medicine scientists report they have developed a new computer-based technique showing that human cancer cells grown in culture dishes are the least genetically similar to their human sources.

The finding, they say, should help focus more resources on cancer research models such as genetically engineered mice and 3D balls of human tissue known as "tumoroids" to better evaluate human cancer biology and treatments, and the genetic errors responsible for cancer growth and progress.

"It may not be a surprise to scientists that cancer cell lines are genetically inferior to other models, but we were surprised that genetically engineered mice and tumoroids performed so very well by comparison," says Patrick Cahan, Ph.D., associate professor of biomedical engineering at The Johns Hopkins University and the Johns Hopkins University School of Medicine and lead investigator of the new study.

The new technique, dubbed CancerCellNet, uses computer models to compare the RNA sequences of a research model with data from a cancer genome atlas to compare how closely the two sets match up.

The researchers found that, on average, genetically engineered mice and tumoroids have RNA sequences most closely aligned with the genome atlas baseline data in 4 out of every 5 tumor types they tested, including breast, lung and ovarian cancers.

The investigators say their work adds to evidence that cancer cell lines grown in the laboratory have less parity with their human source because of the complex differences between a human cell's natural environment and a laboratory growth environment. "Once you take tumors out of their natural environment, cell lines start to change," says Cahan.

Scientists worldwide rely on a range of research models to improve their understanding of cancer and other disease biology and develop treatments for conditions. Among the most widely used cancer research models are cell lines created by extracting cells from human tumors and growing them with various nutrients in laboratory flasks.

Researchers also use mice that have been genetically engineered to develop cancer. In other cases, they implant human tumors into mice, a process called xenografting, or use tumoroids.

To evaluate how well any of these research models align with what may be happening in people, scientists often transplant lab-cultured cells or cells from tumoroids or xenografts into mice and see if the cells behave as they should -- that is, grow and spread and retain the genetic hallmarks of cancer. However, the Johns Hopkins researchers say this process is expensive, time-consuming and scientifically challenging.

The goal of the new work was to develop a computational approach to evaluating research models in a less cumbersome and accurate way. A report on the work was published April 29 in Genome Medicine, and the researchers have filed for a provisional patent on what they named CancerCellNet.

The new technique is based on genetic information about cellular RNA, a molecular string of chemicals similar to DNA and an intermediate set of instructions cells used to translate DNA into the manufacture of proteins.

"RNA is a pretty good surrogate for cell type and cell identity, which are key to determining whether lab-developed cells resemble their human counterparts," says Cahan. "RNA expression data is very standardized and available to researchers, and less subject to technical variation that can confound a study's results."

First, Cahan and his team had to choose a standard set of data that acted as a baseline to compare the research models. Data from The Cancer Genome Atlas served as the so-called "training" data, which includes RNA expression information of hundreds of patient tumor samples, and their corresponding stage, grade and other tumor information.

They also tested their CancerCellNet tool by applying it to data where the tumor type was already known, such as from the International Human Genome Sequencing Consortium.

Members of the research team combed through The Cancer Genome Atlas data to determine 22 types of tumors to study. They used the genome atlas data as the baseline for comparing RNA expression data from 657 cancer cell lines grown in labs worldwide, some of which were established decades ago, 415 xenografts, 26 genetically engineered mouse models and 131 tumoroids.

In one example from the study, prostate cancer cells from a line called PC3 start to look genetically more like bladder cancer, he notes. It's also possible, he says, that the cell line was originally labeled incorrectly or it could have actually been derived from bladder cancer. But the bottom line was that from a genetic standpoint, the prostate cancer cell line was not a representative surrogate for what happens in a typical human with prostate cancer.

Read more at Science Daily

Jun 17, 2021

How a supermassive black hole originates

Supermassive black holes, or SMBHs, are black holes with masses that are several million to billion times the mass of our sun. The Milky Way hosts an SMBH with mass a few million times the solar mass. Surprisingly, astrophysical observations show that SMBHs already existed when the universe was very young. For example, a billion solar mass black holes are found when the universe was just 6% of its current age, 13.7 billion years. How do these SMBHs in the early universe originate?

A team led by a theoretical physicist at the University of California, Riverside, has come up with an explanation: a massive seed black hole that the collapse of a dark matter halo could produce.

Dark matter halo is the halo of invisible matter surrounding a galaxy or a cluster of galaxies. Although dark matter has never been detected in laboratories, physicists remain confident this mysterious matter that makes up 85% of the universe's matter exists. Were the visible matter of a galaxy not embedded in a dark matter halo, this matter would fly apart.

"Physicists are puzzled why SMBHs in the early universe, which are located in the central regions of dark matter halos, grow so massively in a short time," said Hai-Bo Yu, an associate professor of physics and astronomy at UC Riverside, who led the study that appears in Astrophysical Journal Letters. "It's like a 5-year-old child that weighs, say, 200 pounds. Such a child would astonish us all because we know the typical weight of a newborn baby and how fast this baby can grow. Where it comes to black holes, physicists have general expectations about the mass of a seed black hole and its growth rate. The presence of SMBHs suggests these general expectations have been violated, requiring new knowledge. And that's exciting."

A seed black hole is a black hole at its initial stage -- akin to the baby stage in the life of a human.

"We can think of two reasons," Yu added. "The seed -- or 'baby' -- black hole is either much more massive or it grows much faster than we thought, or both. The question that then arises is what are the physical mechanisms for producing a massive enough seed black hole or achieving a fast enough growth rate?"

"It takes time for black holes to grow massive by accreting surrounding matter," said co-author Yi-Ming Zhong, a postdoctoral researcher at the Kavli Institute for Cosmological Physics at the University of Chicago. "Our paper shows that if dark matter has self-interactions then the gravothermal collapse of a halo can lead to a massive enough seed black hole. Its growth rate would be more consistent with general expectations."

In astrophysics, a popular mechanism used to explain SMBHs is the collapse of pristine gas in protogalaxies in the early universe.

"This mechanism, however, cannot produce a massive enough seed black hole to accommodate newly observed SMBHs -- unless the seed black hole experienced an extremely fast growth rate," Yu said. "Our work provides an alternative explanation: a self-interacting dark matter halo experiences gravothermal instability and its central region collapses into a seed black hole."

The explanation Yu and his colleagues propose works in the following way:

Dark matter particles first cluster together under the influence of gravity and form a dark matter halo. During the evolution of the halo, two competing forces -- gravity and pressure -- operate. While gravity pulls dark matter particles inward, pressure pushes them outward. If dark matter particles have no self-interactions, then, as gravity pulls them toward the central halo, they become hotter, that is, they move faster, the pressure increases effectively, and they bounce back. However, in the case of self-interacting dark matter, dark matter self-interactions can transport the heat from those "hotter" particles to nearby colder ones. This makes it difficult for the dark matter particles to bounce back.

Yu explained that the central halo, which would collapse into a black hole, has angular momentum, meaning, it rotates. The self-interactions can induce viscosity, or "friction," that dissipates the angular momentum. During the collapse process, the central halo, which has a fixed mass, shrinks in radius and slows down in rotation due to viscosity. As the evolution continues, the central halo eventually collapses into a singular state: a seed black hole. This seed can grow more massive by accreting surrounding baryonic -- or visible -- matter such as gas and stars.

"The advantage of our scenario is that the mass of the seed black hole can be high since it is produced by the collapse of a dark matter halo," Yu said. "Thus, it can grow into a supermassive black hole in a relatively short timescale."

The new work is novel in that the researchers identify the importance of baryons -- ordinary atomic and molecular particles -- for this idea to work.

"First, we show the presence of baryons, such as gas and stars, can significantly speed up the onset of the gravothermal collapse of a halo and a seed black hole could be created early enough," said Wei-Xiang Feng, Yu's graduate student and a co-author on the paper. "Second, we show the self-interactions can induce viscosity that dissipates the angular momentum remnant of the central halo. Third, we develop a method to examine the condition for triggering general relativistic instability of the collapsed halo, which ensures a seed black hole could form if the condition is satisfied."

Over the past decade, Yu has explored novel predictions of dark matter self-interactions and their observational consequences. His work has shown that self-interacting dark matter can provide a good explanation for the observed motion of stars and gas in galaxies.

Read more at Science Daily

Study of young chaotic star system reveals planet formation secrets

A team of scientists using the Atacama Large Millimeter/submillimeter Array (ALMA) to study the young star Elias 2-27 have confirmed that gravitational instabilities play a key role in planet formation, and have for the first time directly measured the mass of protoplanetary disks using gas velocity data, potentially unlocking one of the mysteries of planet formation. The results of the research are published today in two papers in The Astrophysical Journal.

Protoplanetary disks -- planet-forming disks made of gas and dust that surround newly formed young stars -- are known to scientists as the birthplace of planets. The exact process of planet formation, however, has remained a mystery. The new research, led by Teresa Paneque-Carreño -- a recent graduate of the Universidad de Chile and PhD student at the University of Leiden and the European Southern Observatory, and the primary author on the first of the two papers -- focuses on unlocking the mystery of planet formation.

During observations, scientists confirmed that the Elias 2-27 star system -- a young star located less than 400 light-years away from Earth in the constellation Ophiuchus -- was exhibiting evidence of gravitational instabilities which occur when planet-forming disks carry a large fraction of the system's stellar mass. "How exactly planets form is one of the main questions in our field. However, there are some key mechanisms that we believe can accelerate the process of planet formation," said Paneque-Carreño. "We found direct evidence for gravitational instabilities in Elias 2-27, which is very exciting because this is the first time that we can show kinematic and multi-wavelength proof of a system being gravitationally unstable. Elias 2-27 is the first system that checks all of the boxes."

Elias 2-27's unique characteristics have made it popular with ALMA scientists for more than half a decade. In 2016, a team of scientists using ALMA discovered a pinwheel of dust swirling around the young star. The spirals were believed to be the result of density waves, commonly known to produce the recognizable arms of spiral galaxies -- like the Milky Way Galaxy -- but at the time, had never before been seen around individual stars.

"We discovered in 2016 that the Elias 2-27 disk had a different structure from other already studied systems, something not observed in a protoplanetary disk before: two large-scale spiral arms. Gravitational instabilities were a strong possibility, but the origin of these structures remained a mystery and we needed further observations," said Laura Pérez, Assistant Professor at the Universidad de Chile and the principal investigator on the 2016 study. Together with collaborators, she proposed further observations in multiple ALMA bands that were analyzed with Paneque-Carreño as a part of her M.Sc. thesis at Universidad de Chile.

In addition to confirming gravitational instabilities, scientists found perturbations -- or disturbances -- in the star system above and beyond theoretical expectations. "There may still be new material from the surrounding molecular cloud falling onto the disk, which makes everything more chaotic," said Paneque-Carreño, adding that this chaos has contributed to interesting phenomena that have never been observed before, and for which scientists have no clear explanation. "The Elias 2-27 star system is highly asymmetric in the gas structure. This was completely unexpected, and it is the first time we've observed such vertical asymmetry in a protoplanetary disk."

Cassandra Hall, Assistant Professor of Computational Astrophysics at the University of Georgia, and a co-author on the research, added that the confirmation of both vertical asymmetry and velocity perturbations -- the first large-scale perturbations linked to spiral structure in a protoplanetary disk -- could have significant implications for planet formation theory. "This could be a 'smoking gun' of gravitational instability, which may accelerate some of the earliest stages of planet formation. We first predicted this signature in 2020, and from a computational astrophysics point of view, it's exciting to be right."

Paneque-Carreño added that while the new research has confirmed some theories, it has also raised new questions. "While gravitational instabilities can now be confirmed to explain the spiral structures in the dust continuum surrounding the star, there is also an inner gap, or missing material in the disk, for which we do not have a clear explanation."

One of the barriers to understanding planet formation was the lack of direct measurement of the mass of planet-forming disks, a problem addressed in the new research. The high sensitivity of ALMA Band 6, paired with Bands 3 and 7, allowed the team to more closely study the dynamical processes, density, and even the mass of the disk. "Previous measurements of protoplanetary disk mass were indirect and based only on dust or rare isotopologues. With this new study, we are now sensitive to the entire mass of the disk," said Benedetta Veronesi -- a graduate student at the University of Milan and postdoctoral researcher at École normale supérieure de Lyon, and the lead author on the second paper. "This finding lays the foundation for the development of a method to measure disk mass that will allow us to break down one of the biggest and most pressing barriers in the field of planet formation. Knowing the amount of mass present in planet-forming disks allows us to determine the amount of material available for the formation of planetary systems, and to better understand the process by which they form."

Read more at Science Daily

A quarter of adults don't want children -- and they're still happy

Parenting is one of life's greatest joys, right? Not for everyone. New research from Michigan State University psychologists examines characteristics and satisfaction of adults who don't want children.

As more people acknowledge they simply don't want to have kids, Jennifer Watling Neal and Zachary Neal, both associate professors in MSU's department of psychology, are among the first to dive deeper into how these "child-free" individuals differ from others.

"Most studies haven't asked the questions necessary to distinguish 'child-free' individuals -- those who choose not to have children -- from other types of nonparents," Jennifer Watling Neal said. "Nonparents can also include the 'not-yet-parents' who are planning to have kids, and 'childless' people who couldn't have kids due to infertility or circumstance. Previous studies simply lumped all nonparents into a single category to compare them to parents."

The study -- published June 16 in PLOS ONE -- used a set of three questions to identify child-free individuals separately from parents and other types of nonparents. The researchers used data from a representative sample of 1,000 adults who completed MSU's State of the State Survey, conducted by the university's Institute for Public Policy and Social Research.

"After controlling for demographic characteristics, we found no differences in life satisfaction and limited differences in personality traits between child-free individuals and parents, not-yet-parents, or childless individuals," Zachary Neal said. "We also found that child-free individuals were more liberal than parents, and that people who aren't child-free felt substantially less warm toward child-free individuals."

Beyond findings related to life satisfaction and personality traits, the research unveiled additional unexpected findings.

"We were most surprised by how many child-free people there are," Jennifer Watling Neal said. "We found that more than one in four people in Michigan identified as child-free, which is much higher than the estimated prevalence rate in previous studies that relied on fertility to identify child-free individuals. These previous studies placed the rate at only 2% to 9%. We think our improved measurement may have been able to better capture individuals who identify as child-free."

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