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Exposure to particular sources of air pollution is harmful to children’s learning and memory

A new USC study involving 8,500 children from across the country reveals that a form of air pollution, largely the product of agricultural emissions, is linked to poor learning and memory performance in 9- and 10-year-olds.
The specific component of fine particle air pollution, or PM2.5, ammonium nitrate, is also implicated in Alzheimer’s and dementia risk in adults, suggesting that PM2.5 may cause neurocognitive harm across the lifespan. Ammonium nitrate forms when ammonia gas and nitric acid, produced by agricultural activities and fossil fuel combustion, respectively, react in the atmosphere.
The findings appear in Environmental Health Perspectives.
“Our study highlights the need for more detailed research on particulate matter sources and chemical components,” said senior author Megan Herting, an associate professor of population and public health sciences at the Keck School of Medicine of USC. “It suggests that understanding these nuances is crucial for informing air quality regulations and understanding long-term neurocognitive effects.”
For the last several years, Herting has been working with data from the largest brain study across America, known as the Adolescent Brain Cognitive Development Study, or ABCD, to understand how PM2.5 may affect the brain.
PM2.5, a key indicator of air quality, is a mixture of dust, soot, organic compounds and metals that come in a range of particle sizes less than 2.5 micrometers in diameter. PM2.5 can travel deep into the lungs, where these particles can pass into the bloodstream, and bypass the blood-brain barrier, causing serious health problems.
Fossil fuel combustion is one of the largest sources of PM2.5, especially in urban areas, but sources like wildfires, agriculture, marine aerosols and chemical reactions are also important.
In 2020, Herting and her colleagues published a paper in which they looked at PM2.5 as a whole, and its potential impact on cognition in children, and did not find a relationship.
For this study, they used special statistical techniques to look at 15 chemical components in PM2.5 and their sources. That’s when ammonium nitrate — which is usually a result of agricultural and farming operations — in the air appeared as a prime suspect.
“No matter how we examined it, on its own or with other pollutants, the most robust finding was that ammonium nitrate particles were linked to poorer learning and memory,” Herting said. “That suggests that overall PM2.5 is one thing, but for cognition, it’s a mixture effect of what you’re exposed to.”
For their next project, the researchers hope to look at how these mixtures and sources may map on to individual differences in brain phenotypes during child and adolescent development.
In addition to Herting, other study authors include Rima Habre, Kirthana Sukumaran, Katherine Bottenhorn, Jim Gauderman, Carlos Cardenas-Iniguez, Rob McConnell and Hedyeh Ahmadi, all of the Keck School of Medicine; Daniel A. Hackman of the USC Suzanne Dworak-Peck School of Social Work; Kiros Berhane of the Columbia University Mailman School of Public Health; Shermaine Abad of University of California, San Diego; and Joel Schwartz of the Harvard T.H. Chan School of Public Health.
The research was supported by grants from the National Institutes of Health [NIEHS R01ES032295, R01ES031074, P30ES007048] and the Environmental Protection Agency [RD 83587201, RD 83544101].
Evolutionary paths vastly differ for birds, bats

New Cornell University research has found that, unlike birds, the evolution of bats’ wings and legs is tightly coupled, which may have prevented them from filling as many ecological niches as birds.
“We initially expected to confirm that bat evolution is similar to that of birds, and that their wings and legs evolve independently of one another. The fact we found the opposite was greatly surprising,” said Andrew Orkney, postdoctoral researcher in the laboratory of Brandon Hedrick, assistant professor biomedical sciences.
Both researchers are co-corresponding authors of research published on Nov. 1 in Nature Ecology and Evolution.
Because legs and wings perform different functions, researchers had previously thought that the origin of flight in vertebrates required forelimbs and hindlimbs to evolve independently, allowing them to adapt to their distinct tasks more easily. Comparing bats and birds allows for the testing of this idea because they do not share a common flying ancestor and, therefore, constitute independent replicates to study the evolution of flight.
The researchers observed in both bats and birds that the shapes of the bones within a species’ wing (handwing, radius, humerus), or within a species’ leg (femur and tibia) are correlated — meaning that within a limb, bones evolve together. However, when looking at the correlation across legs and wings, results are different: Bird species show little to no correlation, whereas bats show strong correlation.
This means that, contrary to birds, bats’ forelimbs and hindlimbs did not evolve independently: When the wing shape changes — either increases or shrinks, for example — the leg shape changes in the same direction.
“We suggest that the coupled evolution of wing and leg limits bats’ capability to adapt to new ecologies,” Hedrick said.
Following their discovery, the team began re-examining the evolution of bird skeletons in greater depth.
“While we showed that the evolution of birds’ wings and legs is independent, and it appears this is an important explanation for their evolutionary success,” Orkney said, “we still don’t know why birds are able to do this or when it began to occur in their evolutionary history.”
More resources needed to protect birds in Germany

Member states of the European Union are obliged to designate Special Protection Areas (SPAs) as part of the Natura 2000 network. These areas are designed to guarantee the preservation and restoration of bird populations. However, due to the paucity of data about rare species, it was not known how well these areas worked. Researchers at the University of Göttingen and Dachverband Deutscher Avifaunisten (DDA) developed citizen science platforms as a new data source to evaluate the effectiveness of the 742 protected areas for birds across Germany. This research shows that although these areas are well placed, their effectiveness varies greatly. When protected areas were compared with unprotected sites that showed similar geographical characteristics, only a few species thrived better inside the SPAs. The results were published in the journal Biological Conservation.
Citizen science platforms enable thousands of people to contribute to research with their observations — whether a single blackbird at a bird feeder or a long list of species seen during a day trip to the seashore. The study used the platform ornitho.de (https://www.ornitho.de/), which contains more than 90 million records. The advantage of such platforms is that they provide almost complete coverage of the country. However, the poorly standardised and unsystematic data collection process means that there are multiple sources of error. For this reason, the researchers limited their analysis just to particularly valuable, complete lists that provide information on all birds registered during an observation. To find out how the protected areas fared, the researchers compared them with areas that were not protected but had similar natural features.
The analyses showed that 62 per cent of the species studied were more likely to be found in a Special Protection Area than outside it. Dr Femke Pflüger, first author of the study, based at the DDA and Göttingen University’s Department of Conservation Biology, highlights these positive findings: “Conservationists obviously did a good job in selecting the right areas in the 2000s.” However, a comparison over time showed more mixed results and she adds: “For the period 2012 to 2022, we were only able to identify positive developments in protected areas for 17 per cent of the species. These concerned mainly meadow birds such as black-tailed godwits and curlews, which have benefited from targeted habitat management.” For 83 per cent of the species, there was either no measurable effect or the development was less favourable inside the protected areas than outside. The study also defined situations as ‘effective protection’ if the probability of finding a species decreased over time, both inside and outside the protected areas, but to a lesser extent within them.
Professor Johannes Kamp, Head of the Department of Conservation Biology at the University of Göttingen who led the analyses, says: “This shows that designating a Special Protection Area is not enough to stop a downward trend. The areas need better staffing and funding to restore habitats and to target measures specifically to support endangered species.” Dr Jakob Katzenberger, who coordinates the DDA’s research, is delighted that thousands of citizens contributed: “We were able to show that collecting biodiversity data from online platforms has huge potential. It was possible to track large-scale changes in birdlife really effectively.”
This research was made possible thanks to funding by the German Federal Agency for Nature Conservation (BfN) as part of the project ‘Implementation of measures for nationwide harmonised bird monitoring in EU special protection areas’.
New Huntington’s treatment prevents protein aggregation

Scientists at Northwestern and Case Western Reserve universities have developed the first polymer-based therapeutic for Huntington’s disease, an incurable, debilitating illness that causes nerve cells to break down in the brain.
Patients with Huntington’s disease have a genetic mutation that triggers proteins to misfold and clump together in the brain. These clumps interfere with cell function and eventually lead to cell death. As the disease progresses, patients lose the ability to talk, walk, swallow and concentrate. Most patients die within 10 to 20 years after symptoms first appear.
The new treatment leverages peptide-brush polymers, which act as a shield to prevent proteins from binding to one another. In studies in mice, the treatment successfully rescued neurons to reverse symptoms. The treated mice also experienced no significant side effects, confirming the therapy is nontoxic and well tolerated.
Although the treatment needs further testing, the researchers imagine it potentially someday could be administered as a once-weekly injection to delay disease onset or reduce symptoms in patients with the genetic mutation.
The study will be published on Friday (Nov. 1), in the journal Science Advances.
“Huntington’s is a horrific, insidious disease,” said Northwestern’s Nathan Gianneschi, who led the polymer therapeutic development. “If you have this genetic mutation, you will get Huntington’s disease. It’s unavoidable; there’s no way out. There is no real treatment for stopping or reversing the disease, and there is no cure. These patients really need help. So, we started thinking about a new way to address this disease. The misfolded proteins interact and aggregate. We’ve developed a polymer that can fight those interactions.”
Gianneschi is the Jacob and Rosaline Cohn Professor of Chemistry at Northwestern’s Weinberg College of Arts and Sciences and professor of materials science and engineering and biomedical engineering at Northwestern’s McCormick School of Engineering as well as in Pharmacology at Feinberg School of Medicine. He also is a member of the International Institute of Nanotechnology. Gianneschi co-led the study with Xin Qi, the Jeanette M. and Joseph S. Silber Professor of Brain Sciences and co-director of the Center for Mitochondrial Research and Therapeutics, at Case Western Reserve University.
Promising peptide
The new study builds on previous work from Qi’s laboratory at Case Western Reserve. In 2016, Qi and her team identified a protein (valosin-containing protein or VCP) that abnormally binds to the mutant Huntington protein, causing protein aggregates. These aggregates accumulate within a cell’s mitochondria, an organelle that generates the energy needed to power a cell’s biochemical reactions. Without functioning mitochondria, the cells become dysfunctional and then self-destruct.
As part of that study, Qi also uncovered a naturally occurring peptide that disrupts the interaction between the VCP and the mutant Huntington protein. In cells exposed to the peptide, both the VCP and mutant Huntington protein bound to the peptide — instead of each other.
“Qi’s team identified a peptide that comes from the mutant protein itself and basically controls the protein-protein interface,” Gianneschi said. “That peptide inhibited mitochondrial death, so it showed promise.”
Pulling apart proteins like Velcro
But the peptide, by itself, faced several limitations. Because they are easily broken down by enzymes, peptides have a short lifespan in the body and often have difficulty effectively entering cells. For the peptide to inhibit Huntington’s disease, it needs to cross the blood-brain barrier in large enough quantities to prevent large-scale protein aggregation.
“The peptide has a very small footprint with respect to the protein interfaces,” Gianneschi said. “The proteins stick to each other like Velcro. In this analogy, one protein has hooks and the other has loops. The peptide, on its own, is like trying to undo a patch of Velcro by pulling apart one hook and loop at a time. By the time you get to the bottom of the patch, the top has already come back together and resealed. We needed something big enough to disrupt the entire interface.”
To overcome these obstacles, Gianneschi and his team developed a biocompatible polymer that displays multiple copies of the active peptide. The new structure has a polymer backbone with peptides attached like branches. Not only does the structure protect the peptides from destructive enzymes, it also helps them cross the blood-brain barrier and enter cells.
Experimental results
In laboratory experiments, Gianneschi and his team injected the protein-like polymer into a mouse model of Huntington’s disease. The polymers stayed in the body 2,000 times longer than traditional peptides. In biochemical and neuropathological examinations, the researchers found the treatment prevented mitochondrial fragmentation to preserve the health of brain cells. According to Gianneschi, the mice with Huntington’s disease also lived longer and behaved more like normal mice.
“In one study, the mice are examined in an open field test,” Gianneschi said. “In the animals with Huntington’s, as the disease progresses, they stay along the edges of the box. Whereas normal animals cross back and forth to explore the space. The treated animals with Huntington’s disease started to do the same thing. It’s quite compelling when you see animals behave more normally than they would otherwise.”
Next, Gianneschi will continue to optimize the polymer, with plans to explore its use in other neurodegenerative diseases.
“My childhood friend was diagnosed with Huntington’s at age 18 through a genetic test,” Gianneschi said. “He’s now in an assisted living facility because he needs 24-hour, full-time care. I remain highly motivated — both personally and scientifically — to continue traveling down the path.”
GPs demand protection from Budget tax hike
GPs are warning that a rise to National Insurance from next April could force them to cut staff.
Research uses lasers to detect landmines, underground objects

Enough landmines are buried underground worldwide to circle Earth twice at the equator, but the identification and removal of these explosives is costly and time-consuming.
New University of Mississippi research could help solve the problem.
Vyacheslav Aranchuk, principal scientist in the National Center for Physical Acoustics, presented his research on laser multibeam vibration sensor technology at the Optica Laser Congress and Exhibition, held last week in Osaka, Japan. Aranchuk’s laser vibration sensing technology can detect landmines in the ground much faster than previous techniques.
“There are tens of millions of landmines buried around the world, and more every day as conflicts continue,” Aranchuk said. “There are military applications for this technology in ongoing conflicts and humanitarian applications after the conflicts are over.”
There are more than 110 million active landmines worldwide and landmines or other s left behind from previous wars injured or killed 4,710 people in 2022. More than 85% of landmine casualties were civilians, and half of the civilian casualties were children. Seventy countries worldwide still live with the risk of active landmines each day, including current and former war zones.
Landmines are easy to make and can cost as little as $3 apiece, but identification and disposal can cost up to $1,000 per mine to remove.
Current landmine detection mostly relies on handheld metal detectors, a technique that is dangerous and time-consuming, Aranchuk said. Metal detectors and ground-penetrating radar are not effective in finding plastic landmines.
Aranchuk’s research team developed a laser vibration sensor in 2019 that could find buried objects at a safe distance from a moving vehicle with 30 laser beams formed in a line.
The researchers’ latest technology can form a vibration map of the ground in less than a second. It uses a 34 x 23 matrix array of beams — which roughly forms the shape of a rectangle.
“Most of the modern mines are made of plastic, so they are harder targets for traditional methods of detection that look for metal,” he said. “That’s why the NCPA developed this method of detection.”
Like the 2019 technology, Aranchuk’s laser multi-beam differential interferometric sensor, or LAMBDIS, can be used from a moving vehicle, further increasing the speed at which buried landmines can be detected.
Boyang Zhang, a former postdoctoral researcher at the NCPA from Nantong, China, co-authored the report.
“Metal detectors often generate false positives by detecting any metallic object, and (ground-penetrating radar) can be hindered by certain soil conditions or materials,” Zhang said. “In contrast, laser-acoustic detection uses a combination of laser and acoustic sensing, which allows it to detect landmines from a distance with greater accuracy.
“It reduces false positives and enhances safety by keeping operators farther from the detection zone.”
To find buried objects — explosive or otherwise — the researchers create ground vibration and then cast a two-dimensional array of laser beams at the ground. Ground vibration induces small variations to the frequency of reflected laser light which are used to create a vibration image of the area. A buried landmine vibrates differently than the surrounding soil and appears as a red blob in the vibration image.
“The working principle is based on inference of light,” Aranchuk said. “We send beams to the ground and the interference of light scattered back from different points on the ground produces signals which processing reveals vibration magnitude at each point of the ground surface.”
While the technology is intended to detect landmines, its applications could be numerous, the researchers said.
“Beyond landmine detection, LAMBDIS technology can be adapted for other purposes, such as assessment of bridges and other engineering structures, vibration testing and non-destructive inspection of materials in automotive and aerospace industry, and in biomedical applications,” he said.
The next phase of Aranchuk’s research aims to investigate LAMBDIS’s performance for different buried objects and in different soil conditions.
This material is based on work supported by the U.S. Department of the Navy’s Office of Naval Research under award No. N00014-18-2489.
Trees cool better than reflective roofs in vulnerable Houston neighborhoods

As heatwaves become more intense, cities are looking for strategies that can help keep neighborhoods cooler. A new tool developed by researchers at The University of Texas at Austin has already helped identify potential solutions in Houston, a city where the impact of heat can vary significantly in different communities.
Researchers Kwun Yip Fung, Zong-Liang Yang, and Dev Niyogi at the UT Jackson School of Geosciences, along with colleagues from Spain and Canada, have created a new physics-based computer modeling framework that integrates indices of human comfort and social vulnerability with heat island mitigation strategies and a state-of-the-art urban climate modeling system.
The work was published in PNAS Nexus.
When the researchers applied the index to Houston, they discovered that trees, rather than roof treatments, provided the best relief from the heat in the most vulnerable areas. Vulnerability is assessed based on sensitivity factors such as socioeconomic status, household composition, and minority status as well as adaptive capacity factors such as housing type and access to transportation.
Heat islands occur in cities where structures such as buildings and roads absorb the sun’s heat more than natural landscapes such as trees and grass. This higher heat leads to increased energy consumption from air conditioning, increased emissions from using more electricity, and compromises human health and comfort. This heat island effect can vary in different parts of the city, leading to differences in impact.
Most people are familiar with wind chill indexes used in the winter to describe how cold temperatures and wind interact to make people feel colder. Similarly, the heat index relies on both temperature and humidity to describe how conditions can make people feel hotter. Before this study, little research had been done to quantitively assess how the sun beating down on people makes them feel in an urban setting.
“If construction workers work under direct sunlight versus under the shade of tree cover, the comfort level will be very different,” said Yang.
The universal thermal comfort index combines human comfort based on temperature, humidity, wind speed, and radiation. The researchers said it could be used in any community.
In their study, the researchers considered three different heat island mitigation strategies: painting roofs white to increase solar reflectance; planting vegetation on roofs to increase evaporation through the plants; and planting more trees, which increases evaporation and provides shade. In a generic city block, painting roofs white led to the biggest decrease in the index, especially during the day.
However, looking at different neighborhoods in Houston, the results became more nuanced.
The U.S. Centers for Disease Control and Prevention has developed a social vulnerability index as a measure of how sensitive neighborhoods are to socioeconomic factors and their capacity for adaptation. Classifying the neighborhoods in Houston according to this vulnerability index and then applying the human comfort index revealed that while painting roofs white was the best cooling option in places with low vulnerabilities, in places with higher vulnerabilities, planting trees was a better strategy.
“Now that we have developed the index of cooling and we have the vulnerability data, if we combine both of them, we can see which methods provide more cooling for those vulnerable neighborhoods,” said lead author Fung, who conducted the research as part of his doctoral studies at the Jackson School.
The research revealed that places with high vulnerabilities also had more available space where trees could be planted, so the potential for adding trees was greater. They also had less roof area available for painting white or planting with vegetation.
“Now that we know the vulnerable neighborhoods have more space for planting trees, we should prioritize trees at those regions,” said Fung. “And in those less vulnerable neighborhoods, we should prioritize other strategies like cool roofs and green roofs.”
Applying the methodology to other cities may require other considerations. For example, in arid places like Arizona, trees would need to be selected for heat and drought tolerance. In northern cities, a lack of air conditioning plays a role in communities that are vulnerable to heat.
The new methodology could also be used to develop hybrid strategies, combining both rooftop treatments and tree planting, as well as other strategies such as reflective pavements.
“We see this as a baseline, but we are still exploring,” said Fung. “Now that the index and the methodology have been developed, they can be applied to many other scenarios.”
The reasons flowers wilt could explain how plants spend (and save) their energy

A study in the journal Plant Biology by researchers from Macquarie University and international collaborators has shown for the first time, that plants reuse resources from wilting flowers to support future reproduction.
Lead author Honorary Professor Graham Pyke from Macquarie University says the findings help explain a common but poorly understood plant process.
“Our research delivers the first direct demonstration that plants can salvage resources from wilting flowers and reuse these resources to promote future reproduction,” Professor Pyke says.
These resources include the energy and chemical makeup of the petals — including carbohydrates and nutrients like nitrogen and phosphorus.
Running the trials
The three-year study focused on Blandfordia grandiflora, commonly known as Christmas Bells, which mostly flowers in December.
This perennial plant species with colourful red and yellow flowers, native to eastern Australia, is often sold in flower markets in Australia and internationally.
Commercially-grown stems of Christmas Bells produce anything from two or three flowers to a dozen or more.
“Our research takes place on a plantation containing several hectares of native wet heath where Christmas bells flower quite profusely, along with a commercial shadehouse,” says Professor Pyke.
The team used a variety of techniques to control pollination and flower wilting then checked the effect on seed production and reflowering.
To their surprise, the researchers found that plants did not use the resources from wilted flowers to improve short-term reproduction by either the same flowers or other flowers on the same plant.
“These plants salvage resources invested in reproduction during one flowering season and reuse these resources during the next flowering,” Professor Pyke says.
To do this, Blandfordia grandiflora transfers resources from its wilting flowers, storing this ‘chemical energy’ underground in corms and roots to then help produce new flowering stems in the subsequent season, generally a year later.
Plant economics
Professor Pyke says the plant world is a fascinating realm of resource management and economic strategy.
“Plant economics are all about trade-offs,” he says. “Plants must make decisions about where to allocate their limited resources; investing in one area means they can’t invest as much in another.”
This concept of resource allocation is what led Professor Pyke to investigate the phenomenon of flower wilting, which for years scientists have speculated might be a way for plants to shift valuable resources to other processes.
“We were in for a surprise,” says Professor Pyke. “It turns out the plants were playing a longer game than we anticipated, not using their reclaimed resources immediately, but saving them for the next flowering season.”
Professor Pyke says plants have evolved diverse strategies for managing their flowers after they’ve served their primary reproductive function, with wilting just one of several possible approaches.
Not all plants follow the flower wilt pattern; flowers will still bloom on some plants long after they can be fertilised and after they stop producing nectar.
“Flowers make the whole plant more attractive to pollinators even when they are just there as part of the overall display,” he says.
Some plants will even drop their blooms well before they wilt. “For example, jacaranda flowers that seem perfectly good will just drop to the ground; frangipani trees will also shed intact flowers rather than that have them wilt.”
Testing theories
The study tested resource reuse in different ways.
One experiment compared seed production between plants with flowers allowed to wilt and those with petals removed to prevent wilting. Another prevented seed production in all flowers — but allowed wilting in one group of plants.
“We can easily prevent seed production by snipping off the stigma,” says Professor Pyke.
Results showed plants with wilting flowers were more likely to reflower the next season than those where wilting was prevented.
The study also considered other factors that might influence seed production, such as flowering stem height, number of flowers per stem, and flower position.
Taller flowering stems, for example, produced more seeds and heavier seeds, as did stems with more flowers. But flowers positioned lower down on the plant tended to have fewer seeds, and seeds that weighed less.
“Our findings pave the way for further research into other plant species, and how they recover and reuse the resources from wilting flowers,” Professor Pyke says.
Further research could explore what these salvaged resources are made of, how plants move and change them, and whether the benefits of saving these resources outweigh the costs of making flowers in the first place.
NASA’s Hubble, Webb probe surprisingly smooth disk around Vega

In the 1997 movie “Contact,” adapted from Carl Sagan’s 1985 novel, the lead character scientist Ellie Arroway (played by actor Jodi Foster) takes a space-alien-built wormhole ride to the star Vega. She emerges inside a snowstorm of debris encircling the star — but no obvious planets are visible.
It looks like the filmmakers got it right.
A team of astronomers at the University of Arizona, Tucson used NASA’s Hubble and James Webb space telescopes for an unprecedented in-depth look at the nearly 100-billion-mile-diameter debris disk encircling Vega. “Between the Hubble and Webb telescopes, you get this very clear view of Vega. It’s a mysterious system because it’s unlike other circumstellar disks we’ve looked at,” said Andras Gáspár of the University of Arizona, a member of the research team. “The Vega disk is smooth, ridiculously smooth.”
The big surprise to the research team is that there is no obvious evidence for one or more large planets plowing through the face-on disk like snow tractors. “It’s making us rethink the range and variety among exoplanet systems,” said Kate Su of the University of Arizona, lead author of the paper presenting the Webb findings.
Webb sees the infrared glow from a disk of particles the size of sand swirling around the sizzling blue-white star that is 40 times brighter than our Sun. Hubble captures an outer halo of this disk, with particles no bigger than the consistency of smoke that are reflecting starlight.
The distribution of dust in the Vega debris disk is layered because the pressure of starlight pushes out the smaller grains faster than larger grains. “Different types of physics will locate different-sized particles at different locations,” said Schuyler Wolff of the University of Arizona team, lead author of the paper presenting the Hubble findings. “The fact that we’re seeing dust particle sizes sorted out can help us understand the underlying dynamics in circumstellar disks.”
The Vega disk does have a subtle gap, around 60 AU (astronomical units) from the star (twice the distance of Neptune from the Sun), but otherwise is very smooth all the way in until it is lost in the glare of the star. This shows that there are no planets down at least to Neptune-mass circulating in large orbits, as in our solar system, say the researchers.
“We’re seeing in detail how much variety there is among circumstellar disks, and how that variety is tied into the underlying planetary systems. We’re finding a lot out about the planetary systems — even when we can’t see what might be hidden planets,” added Su. “There’s still a lot of unknowns in the planet-formation process, and I think these new observations of Vega are going to help constrain models of planet formation.”
Disk Diversity
Newly forming stars accrete material from a disk of dust and gas that is the flattened remnant of the cloud from which they are forming. In the mid-1990s Hubble found disks around many newly forming stars. The disks are likely sites of planet formation, migration, and sometimes destruction. Fully matured stars like Vega have dusty disks enriched by ongoing “bumper car” collisions among orbiting asteroids and debris from evaporating comets. These are primordial bodies that can survive up to the present 450-million-year age of Vega (our Sun is approximately ten times older than Vega). Dust within our solar system (seen as the Zodiacal light) is also replenished by minor bodies ejecting dust at a rate of about 10 tons per second. This dust is shoved around by planets. This provides a strategy for detecting planets around other stars without seeing them directly — just by witnessing the effects they have on the dust.
“Vega continues to be unusual,” said Wolff. “The architecture of the Vega system is markedly different from our own solar system where giant planets like Jupiter and Saturn are keeping the dust from spreading the way it does with Vega.”
For comparison, there is a nearby star, Fomalhaut, which is about the same distance, age and temperature as Vega. But Fomalhaut’s circumstellar architecture is greatly different from Vega’s. Fomalhaut has three nested debris belts.
Planets are suggested as shepherding bodies around Fomalhaut that gravitationally constrict the dust into rings, though no planets have been positively identified yet. “Given the physical similarity between the stars of Vega and Fomalhaut, why does Fomalhaut seem to have been able to form planets and Vega didn’t?” said team member George Rieke of the University of Arizona, a member of the research team. “What’s the difference? Did the circumstellar environment, or the star itself, create that difference? What’s puzzling is that the same physics is at work in both,” added Wolff.
First Clue to Possible Planetary Construction Yards
Located in the summer constellation Lyra, Vega is one of the brightest stars in the northern sky. Vega is legendary because it offered the first evidence for material orbiting a star — presumably the stuff for making planets — as potential abodes of life. This was first hypothesized by Immanuel Kant in 1775. But it took over 200 years before the first observational evidence was collected in 1984. A puzzling excess of infrared light from warm dust was detected by NASA’s IRAS (Infrared Astronomy Satellite). It was interpreted as a shell or disk of dust extending twice the orbital radius of Pluto from the star.
In 2005, NASA’s infrared Spitzer Space Telescope mapped out a ring of dust around Vega. This was further confirmed by observations using submillimeter telescopes including Caltech’s Submillimeter Observatory on Mauna Kea, Hawaii, and also the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, and ESA’s (European Space Agency’s) Herschel Space Telescope, but none of these telescopes could see much detail. “The Hubble and Webb observations together provide so much more detail that they are telling us something completely new about the Vega system that nobody knew before,” said Rieke.
Two papers (Wolff et al. and Su et. al.) from the Arizona team will be published in The Astrophysical Journal.
