Technical

The shape of water: What water molecules look like on the surface of materials

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Understanding the various molecular interactions and structures that arise among surface water molecules would enable scientists and engineers to develop all sorts of novel hydrophobic/hydrophilic materials or improve existing ones. For example, the friction caused by water on ships could be reduced through materials engineering, leading to higher efficiency. Other applications include, but are not limited to, medical implants and anti-icing surfaces for airplanes. However, the phenomena that occur in surface water are so complicated that Tokyo University of Science, Japan, has established a dedicated research center, called “Water Frontier Science and Technology,” where various research groups tackle this problem from different angles (theoretical analysis, experimental studies, material development, and so on). Prof Takahiro Yamamoto leads a group of scientists at this center, and they try to solve this mystery through simulations of the microscopic structures, properties, and functions of water on the surface of materials.

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For this study in particular, which was published in the Japanese Journal of Applied Physics, the researchers from Tokyo University of Science, in collaboration with researchers from the Science Solutions Division, Mizuho Information & Research Institute, Inc., focused on the interactions between water molecules and graphene, a charge-neutral carbon-based material that can be made atomically flat. “Surface water on carbon nanomaterials such as graphene has attracted much attention because the properties of these materials make them ideal for studying the microscopic structure of surface water,” explains Prof Yamamoto. It had been already pointed out in previous studies that water molecules on graphene tend to form stable polygonal (2D) shapes in both surface water and “free” water (water molecules away from the surface of the material). Moreover, it had been noted that the probability of finding these structures was drastically different in surface water than in free water. However, the differences between surface and free water have to be established, and the transition between the two is difficult to analyze using conventional simulation methods.

Considering this situation, the research team decided to combine a method taken from data science, called persistent homology (PH), with simulations of molecular dynamics. PH allows for the characterization of data structures, including those contained in images/graphics, but it can also be used in materials science to find stable 3D structures between molecules. “Our study represents the first time PH was used for a structural analysis of water molecules,” remarks Prof Yamamoto. With this strategy, the researchers were able to obtain a better idea of what happens to surface water molecules as more layers of water are added on top.

When a single layer of water molecules is laid on top of graphene, the water molecules align so that their hydrogen atoms form stable polygonal structures with different numbers of sides through hydrogen bonds. This “fixes” the orientation and relative position of these first-layer water molecules, which are now forming shapes parallel to the graphene layer. If a second layer of water molecules is added, the molecules from the first and second layers form 3D structures called tetrahedrons, which resemble a pyramid but with a triangular base. Curiously, these tetrahedrons are mostly pointing downwards (towards the graphene layer), because this orientation is “energetically favorable.” In other words, the order from the first layer translates to the second one to form these 3D structures with a consistent orientation. However, as a third and more layers are added, the tetrahedrons that form don’t necessarily point downwards and instead appear to be free to point in any direction, swayed by the surrounding forces. “These results confirm that the crossover between surface and free water occurs within only three layers of water,” explains Prof Yamamoto.

The researchers have provided a video of one of their simulations where these 2D and 3D structures are highlighted, allowing one to understand the full picture. “Our study is a good example of the application of modern data analysis techniques to gain new and important insights,” adds Prof Yamamoto. What’s more, these predictions should not be hard to measure experimentally on graphene through atomic-force microscopy techniques, which would, without a doubt, confirm the existence of these structures and further validate the combination of techniques used. Prof Yamamoto concludes: “Although graphene is a rather simple surface and we could expect more complicated water structures on other types of materials, our study provides a starting point for discussions of more realistic surface effects, and we expect it will lead to the control of surface properties.”

Bilingual children are strong, creative storytellers, study shows

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Bilingual children use as many words as monolingual children when telling a story, and demonstrate high levels of cognitive flexibility, according to new research by University of Alberta scientists.

“We found that the number of words that bilingual children use in their stories is highly correlated with their cognitive flexibility — the ability to switch between thinking about different concepts,” said Elena Nicoladis, lead author and professor in the Department of Psychology in the Faculty of Science. “This suggests that bilinguals are adept at using the medium of storytelling.”

Vocabulary is a strong predictor of school achievement, and so is storytelling. “These results suggest that parents of bilingual children do not need to be concerned about long-term school achievement, said Nicoladis. “In a storytelling context, bilingual kids are able to use this flexibility to convey stories in creative ways.”

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The research examined a group of French-English bilingual children who have been taught two languages since birth, rather than learning a second language later in life. Results show that bilingual children used just as many words to tell a story in English as monolingual children. Participants also used just as many words in French as they did in English when telling a story.

Previous research has shown that bilingual children score lower than monolingual children on traditional vocabulary tests, meaning this results are changing our understanding of multiple languages and cognition in children.

“The past research is not surprising,” added Nicoladis. “Learning a word is related to how much time you spend in each language. For bilingual children, time is split between languages. So, unsurprisingly, they tend to have lower vocabularies in each of their languages. However, this research shows that as a function of storytelling, bilingual children are equally strong as monolingual children.”

This research used a new, highly sensitive measure for examining cognitive flexibility, examining a participant’s ability to switch between games with different rules, while maintaining accuracy and reaction time. This study builds on previous research examining vocabulary in bilingual children who have learned English as a second language.

New rules illuminate how objects absorb and emit light

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Princeton researchers have uncovered new rules governing how objects absorb and emit light, fine-tuning scientists’ control over light and boosting research into next-generation solar and optical devices.

The discovery solves a longstanding problem of scale, where light’s behavior when interacting with tiny objects violates well-established physical constraints observed at larger scales.

New rules illuminate how objects absorb and emit light
New rules illuminate how objects absorb and emit light

“The kinds of effects you get for very small objects are different from the effects you get from very large objects,” said Sean Molesky, a postdoctoral researcher in electrical engineering and the study’s first author. The difference can be observed in moving from a molecule to a grain of sand. “You can’t simultaneously describe both things,” he said.

The problem stems from light’s famous shapeshifting nature. For ordinary objects, light’s movement can be described by straight lines, or rays. But for microscopic objects, light’s wave properties take over and the neat rules of ray optics break down. The effects are significant. In important modern materials, observations at the micron scale showed infrared light radiating at millions of times more energy per unit area than ray optics predicts.

The new rules, published in Physical Review Letters on Dec. 20, tell scientists how much infrared light an object of any scale can be expected to absorb or emit, resolving a decades-old discrepancy between big and small. The work extends a 19th-century concept, known as a blackbody, into a useful modern context. Blackbodies are idealized objects that absorb and emit light with maximum efficiency.

“There’s been a lot of research done to try to understand in practice, for a given material, how one can approach these blackbody limits,” said Alejandro Rodriguez, an associate professor of electrical engineering and the study’s principal investigator. “How can we make a perfect absorber? A perfect emitter?”

“It’s a very old problem that many physicists — including Planck, Einstein and Boltzmann — tackled early on and laid the foundations for the development of quantum mechanics.”

A large body of previous work has shown that structuring objects with nanoscale features can enhance absorption and emission, effectively trapping photons in a tiny hall of mirrors. But no one had defined the fundamental limits of the possible, leaving open major questions about how to assess a design.

No longer confined to brute-force trial and error, the new level of control will allow engineers to optimize designs mathematically for a wide range of future applications. The work is especially important in technologies like solar panels, optical circuits and quantum computers.

Currently, the team’s findings are specific to thermal sources of light, like the sun or like an incandescent bulb. But the researchers hope to generalize the work further to agree with other light sources, like LEDs, fireflies, or arcing bolts of electricity.

The research was supported in part by the National Science Foundation, the Cornell Center for Materials Research, the Defense Advanced Research Projects Agency and the National Science and Engineering Research Council of Canada.

Unprecedented and worrying rise in sea levels

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A new study led by Simon Fraser University’s Dean of Science, Prof. Paul Kench, has discovered new evidence of sea-level variability in the central Indian Ocean.

The study, which provides new details about sea levels in the past, concludes that sea levels in the central Indian Ocean have risen by close to a meter in the last two centuries.

Prof. Kench says, “We know that certain types of fossil corals act as important recorders of past sea levels. By measuring the ages and the depths of these fossil corals, we are identifying that there have been periods several hundred years ago that the sea level has been much lower than we thought in parts of the Indian Ocean.”

He says understanding where sea levels have been historically, and what happens as they rise, will provide greater insights into how coral reefs systems and islands may be able to respond to the changes in sea levels in the future.

Unprecedented and worrying rise in sea levels
Unprecedented and worrying rise in sea levels

Underscoring the serious threat posed to coastal cities and communities in the region, the ongoing study, which began in 2017, further suggests that if such acceleration continues over the next century, sea levels in the Indian Ocean will have risen to their highest level ever in recorded history.

A new tomato ideal for urban gardens and even outer space

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Farmers could soon be growing tomatoes bunched like grapes in a storage unit, on the roof of a skyscraper, or even in space. That’s if a clutch of new gene-edited crops prove as fruitful as the first batch.

The primary goal of this new research is to engineer a wider variety of crops that can be grown in urban environments or other places not suitable for plant growth, said Cold Spring Harbor Laboratory Professor and HHMI Investigator Zach Lippman, who leads the lab that designed the ‘urban agriculture tomatoes.’

A new tomato ideal for urban gardens and even outer space
A new tomato ideal for urban gardens and even outer space

These new gene-edited tomato plants look nothing like the long vines you might find growing in a backyard garden or in agricultural fields. The most notable feature is their bunched, compact fruit. They resemble a bouquet whose roses have been replaced by ripe cherry tomatoes. They also mature quickly, producing ripe fruit that’s ready for harvest in under 40 days. And you can eat them.

“They have a great small shape and size, they taste good, but of course that all depends on personal preference,” Lippman said.

Most importantly, they’re eco-friendly.

“This demonstrates how we can produce crops in new ways, without having to tear up the land as much or add excessive fertilizer that runs off into rivers and streams,” Lippman said. “Here’s a complementary approach to help feed people, locally and with a reduced carbon footprint.”

That’s good news for anyone concerned about climate change. Earlier this year, the UN Intergovernmental Panel on Climate Change (IPCC) warned that more than 500 million people are living on land already degraded by deforestation, changing weather patterns, and overuse of viable cropland. By shifting some of the burden of growing the world’s crops to urban and other areas, there’s hope that desperate land mismanagement will slow.

Urban agricultural systems often call for compact plants that can be slotted or stacked into tight spaces, such as in tiered farming in warehouses or in converted storage containers. To make up for crop yield constrained by limited space, urban farms can operate year-round in climate-controlled conditions. That’s why it’s beneficial to use plants that can be grown and harvested quickly. More harvests per year results in more food, even if the space used is very small.

Lippman and his colleagues created the new tomatoes by fine-tuning two genes that control the switch to reproductive growth and plant size, the SELF PRUNING (SP) and SP5G genes, which caused the plant to stop growing sooner and flower and fruit earlier. But Lippman’s lab knew it could only modify the SP sister genes only so much before trading flavor or yield for even smaller plants.

“When you’re playing with plant maturation, you’re playing with the whole system, and that system includes the sugars, where they’re made, which is the leaves, and how they’re distributed, which is to the fruits,” Lippman said.

Searching for a third player, Lippman’s team recently discovered the gene SIER, which controls the lengths of stems. Mutating SIER with the CRISPR gene-editing tool and combining it with the mutations in the other two flowering genes created shorter stems and extremely compact plants.

Lippman is refining this technique, published in the latest issues of Nature Biotechnology, and hopes others will be inspired to try it on other fruit crops like kiwi. By making crops and harvests shorter, Lippman believes that agriculture can reach new heights.

“I can tell you that NASA scientists have expressed some interest in our new tomatoes,” he said.

While the first ship to Mars probably won’t have its own farm, astronauts may still get to test their green thumbs with urbanized, space-faring tomatoes.

Nightside barrier gently brakes ‘bursty’ plasma bubbles

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The solar wind that pummels the Earth’s dayside magnetosphere causes turbulence, like air over a wing. Physicists at Rice University have developed new methods to characterize how that influences space weather on the nightside.

It’s rarely quiet up there. The solar wind streams around the Earth and cruises off into the night, but closer to the planet, parcels of plasma get caught in the turbulence and sink back toward Earth. That turbulence causes big ripples in the plasma.

With the help of several spacecraft and computational tools developed over the past decade, Rice scientists led by space plasma physicist Frank Toffoletto can now assess the ripples, called buoyancy waves, caused by the turbulence.

Nightside barrier gently brakes 'bursty' plasma bubbles
Nightside barrier gently brakes ‘bursty’ plasma bubbles

These waves, or oscillations, have been observed in the thin layer of magnetic flux along the base of the plasma sheet that tails away from the planet’s nightside. The Rice theory is the first to quantify their motion.

The theory adds another element to the Rice Convection Model, an established, decades-in-the-making algorithm that helps scientists calculate how the inner and middle magnetosphere will react to events like solar storms that threaten satellites, communications and power grids on Earth.

The new paper in JGR Space Physics by Toffoletto, emeritus professor Richard Wolf and former graduate student Aaron Schutza starts by describing the bubbles — “bursty bulk flows” predicted by Wolf and Rice alumnus Duane Pontius in 1990 — that fall back toward Earth through the plasma tail.

Functionally, they’re the reverse of buoyant air bubbles that bob up and down in the atmosphere because of gravity, but the plasma bubbles respond to magnetic fields instead. The plasma bubbles lose most of their momentum by the time they touch down at the theoretical, filamentlike boundary between the inner plasma sheet and the protective plasmasphere.

Nightside barrier gently brakes 'bursty' plasma bubbles
Nightside barrier gently brakes ‘bursty’ plasma bubbles

That sets the braking boundary into a gentle oscillation, which lasts mere minutes before stabilizing again. Toffoletto compared the motion to a plucked guitar string that quickly returns to equilibrium.

“The fancy name for this is the eigenmode,” he said. “We’re trying to figure out the low-frequency eigenmodes of the magnetosphere. They haven’t been studied very much, though they appear to be associated with dynamic disruptions to the magnetosphere.”

Toffoletto said the Rice team has in recent years discovered through simulations that the magnetosphere doesn’t always respond in a linear fashion to the steady driving force of the solar wind.

“You get all kinds of wave modes in the system,” he said, explaining that bursty bulk flows are one such mode. “Every time one of these things come flying in, when they hit the inner region, they basically reach their equilibrium point and oscillate with a certain frequency. Finding that frequency is what this paper is all about.”

As measured by the THE MIS spacecraft, the periods of these waves are a few minutes and the amplitudes are often bigger than the Earth.

“Understanding the natural frequency of the system and how it behaves can tell us a lot about the physical properties of plasma on the night side, its transport and how it might be related to the aurora,” he said. “A lot of these phenomena show up in the ionosphere as auroral structures, and we don’t understand where these structures come from.”

Toffoletto said the models suggest buoyant waves may play a role in the formation of the ring current that consists of charged particles that flow around Earth as well as magnetospheric substorms, all of which are connected to the aurora.

He said that no more than a decade ago, many magnetosphere simulations “would look very uniform, kind of boring.” The Rice group is collaborating with the Applied Physics Laboratory to include the Rice Convection Model in a newly developed global magnetosphere code called “Gamera,” named after the fictional Japanese monster.

“Now, with such higher-resolution models and much better numerical methods, these structures are starting to show up in the simulations,” Toffoletto said. “This paper is one little piece of the puzzle we’re putting together of how the system behaves. All this plays a big role in understanding how space weather works and how that in turn impacts technology, satellites and ground-based systems.”

The Rice Convection Model itself was refreshed this month in a paper led by recent Rice alumnus Jian Yang, now an associate professor of Earth and space sciences at the Southern University of Science and Technology, Shenzhen, China.

New polymer material may help batteries become self-healing, recyclable

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Lithium-ion batteries are notorious for developing internal electrical shorts that can ignite a battery’s liquid electrolytes, leading to explosions and fires. Engineers at the University of Illinois have developed a solid polymer-based electrolyte that can self-heal after damage — and the material can also be recycled without the use of harsh chemicals or high temperatures.

New polymer material may help batteries become self-healing, recyclable
New polymer material may help batteries become self-healing, recyclable

 

The new study, which could help manufacturers produce recyclable, self-healing commercial batteries, is published in the Journal of the American Chemical Society.

As lithium-ion batteries go through multiple cycles of charge and discharge, they develop tiny, branchlike structures of solid lithium called dendrites, the researchers said. These structures reduce battery life, cause hotspots and electrical shorts, and sometimes grow large enough to puncture the internal parts of the battery, causing explosive chemical reactions between the electrodes and electrolyte liquids.

There has been a push by chemists and engineers to replace the liquid electrolytes in lithium-ion batteries with solid materials such as ceramics or polymers, the researchers said. However, many of these materials are rigid and brittle resulting in poor electrolyte-to-electrode contact and reduced conductivity.

“Solid ion-conducting polymers are one option for developing nonliquid electrolytes,” said Brian Jing, a materials science and engineering graduate student and study co-author. “But the high-temperature conditions inside a battery can melt most polymers, again resulting in dendrites and failure.”

Past studies have produced solid electrolytes by using a network of polymer strands that are cross-linked to form a rubbery lithium conductor. This method delays the growth of dendrites; however, these materials are complex and cannot be recovered or healed after damage, Jing said.

To address this issue, the researchers developed a network polymer electrolyte in which the cross-link point can undergo exchange reactions and swap polymer strands. In contrast to linear polymers, these networks actually get stiffer upon heating, which can potentially minimize the dendrite problem, the researchers said. Additionally, they can be easily broken down and resolidified into a networked structure after damage, making them recyclable, and they restore conductivity after being damaged because they are self-healing.

“This new network polymer also shows the remarkable property that both conductivity and stiffness increase with heating, which is not seen in conventional polymer electrolytes,” Jing said.

“Most polymers require strong acids and high temperatures to break down,” said materials science and engineering professor and lead author Christopher Evans. “Our material dissolves in water at room temperature, making it a very energy-efficient and environmentally friendly process.”

The team probed the conductivity of the new material and found its potential as an effective battery electrolyte to be promising, the researchers said, but acknowledge that more work is required before it could be used in batteries that are comparable to what is in use today.

“I think this work presents an interesting platform for others to test,” Evans said. “We used a very specific chemistry and a very specific dynamic bond in our polymer, but we think this platform can be reconfigured to be used with many other chemistries to tweak the conductivity and mechanical properties.”

Scientists find iron ‘snow’ in Earth’s core

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The Earth’s inner core is hot, under immense pressure and snow-capped, according to new research that could help scientists better understand forces that affect the entire planet.

The snow is made of tiny particles of iron — much heavier than any snowflake on Earth’s surface — that fall from the molten outer core and pile on top of the inner core, creating piles up to 200 miles thick that cover the inner core.

Scientists find iron 'snow' in Earth's core
Scientists find iron ‘snow’ in Earth’s core

The image may sound like an alien winter wonderland. But the scientists who led the research said it is akin to how rocks form inside volcanoes.

“The Earth’s metallic core works like a magma chamber that we know better of in the crust,” said Jung-Fu Lin, a professor in the Jackson School of Geosciences at The University of Texas at Austin and a co-author of the study.

The study is available online and will be published in the print edition of the journal JGR Solid Earth on December 23.

Youjun Zhang, an associate professor at Sichuan University in China, led the study. The other co-authors include Jackson School graduate student Peter Nelson; and Nick Dygert, an assistant professor at the University of Tennessee who conducted the research during a postdoctoral fellowship at the Jackson School.

The Earth’s core can’t be sampled, so scientists study it by recording and analyzing signals from seismic waves (a type of energy wave) as they pass through the Earth.

However, aberrations between recent seismic wave data and the values that would be expected based on the current model of the Earth’s core have raised questions. The waves move more slowly than expected as they passed through the base of the outer core, and they move faster than expected when moving through the eastern hemisphere of the top inner core.

Scientists find iron 'snow' in Earth's core
Scientists find iron ‘snow’ in Earth’s core

The study proposes the iron snow-capped core as an explanation for these aberrations. The scientist S.I. Braginkskii proposed in the early 1960s that a slurry layer exists between the inner and outer core, but prevailing knowledge about heat and pressure conditions in the core environment quashed that theory. However, new data from experiments on core-like materials conducted by Zhang and pulled from more recent scientific literature found that crystallization was possible and that about 15% of the lowermost outer core could be made of iron-based crystals that eventually fall down the liquid outer core and settle on top of the solid inner core.

“It’s sort of a bizarre thing to think about,” Dygert said. “You have crystals within the outer core snowing down onto the inner core over a distance of several hundred kilometers.”

The researchers point to the accumulated snow pack as the cause of the seismic aberrations. The slurry-like composition slows the seismic waves. The variation in snow pile size — thinner in the eastern hemisphere and thicker in the western — explains the change in speed.

“The inner-core boundary is not a simple and smooth surface, which may affect the thermal conduction and the convections of the core,” Zhang said.

The paper compares the snowing of iron particles with a process that happens inside magma chambers closer to the Earth’s surface, which involves minerals crystalizing out of the melt and glomming together. In magma chambers, the compaction of the minerals creates what’s known as “cumulate rock.” In the Earth’s core, the compaction of the iron contributes to the growth of the inner core and shrinking of the outer core.

And given the core’s influence over phenomena that affects the entire planet, from generating its magnetic field to radiating the heat that drives the movement of tectonic plates, understanding more about its composition and behavior could help in understanding how these larger processes work.

Bruce Buffet, a geosciences professor at the University of California, Berkley who studies planet interiors and who was not involved in the study, said that the research confronts longstanding questions about the Earth’s interior and could even help reveal more about how the Earth’s core came to be.

“Relating the model predictions to the anomalous observations allows us to draw inferences about the possible compositions of the liquid core and maybe connect this information to the conditions that prevailed at the time the planet was formed,” he said. “The starting condition is an important factor in Earth becoming the planet we know.”

NASA maps inner Milky Way, sees cosmic ‘candy cane’

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A feature resembling a candy cane appears at the center of this colorful composite image of our Milky Way galaxy’s central zone. But this is no cosmic confection. It spans 190 light-years and is one of a set of long, thin strands of ionized gas called filaments that emit radio waves.

This image includes newly published observations using an instrument designed and built at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. Called the Goddard-IRAM Superconducting 2-Millimeter Observer (GISMO), the instrument was used in concert with a 30-meter radio telescope located on Pico Veleta, Spain, operated by the Institute for Radio Astronomy in the Millimeter Range headquartered in Grenoble, France.

NASA maps inner Milky Way, sees cosmic 'candy cane'
NASA maps inner Milky Way, sees cosmic ‘candy cane’

“GISMO observes microwaves with a wavelength of 2 millimeters, allowing us to explore the galaxy in the transition zone between infrared light and longer radio wavelengths,” said Johannes Staguhn, an astronomer at Johns Hopkins University in Baltimore who leads the GISMO team at Goddard. “Each of these portions of the spectrum is dominated by different types of emission, and GISMO shows us how they link together.”

GISMO detected the most prominent radio filament in the galactic center, known as the Radio Arc, which forms the straight part of the cosmic candy cane. This is the shortest wavelength at which these curious structures have been observed. Scientists say the filaments delineate the edges of a large bubble produced by some energetic event at the galactic center, located within the bright region known as Sagittarius A about 27,000 light-years away from us. Additional red arcs in the image reveal other filaments.

“It was a real surprise to see the Radio Arc in the GISMO data,” said Richard Arendt, a team member at the University of Maryland, Baltimore County and Goddard. “Its emission comes from high-speed electrons spiraling in a magnetic field, a process called synchrotron emission. Another feature GISMO sees, called the Sickle, is associated with star formation and may be the source of these high-speed electrons.”

Two papers describing the composite image, one led by Arendt and one led by Staguhn, were published on Nov. 1 in the Astrophysical Journal.

The image shows the inner part of our galaxy, which hosts the largest and densest collection of giant molecular clouds in the Milky Way. These vast, cool clouds contain enough dense gas and dust to form tens of millions of stars like the Sun. The view spans a part of the sky about 1.6 degrees across — equivalent to roughly three times the apparent size of the Moon — or about 750 light-years wide.

To make the image, the team acquired GISMO data, shown in green, in April and November 2012. They then used archival observations from the European Space Agency’s Herschel satellite to model the far-infrared glow of cold dust, which they then subtracted from the GISMO data. Next, they added, in blue, existing 850-micrometer infrared data from the SCUBA-2 instrument on the James Clerk Maxwell Telescope near the summit of Maunakea, Hawaii. Finally, they added, in red, archival longer-wavelength 19.5-centimeter radio observations from the National Science Foundation’s Karl G. Jansky Very Large Array, located near Socorro, New Mexico. The higher-resolution infrared and radio data were then processed to match the lower-resolution GISMO observations.

The resulting image essentially color codes different emission mechanisms.

Blue and cyan features reveal cold dust in molecular clouds where star formation is still in its infancy. Yellow features, such as the Arches filaments making up the candy cane’s handle and the Sagittarius B1 molecular cloud, reveal the presence of ionized gas and show well-developed star factories; this light comes from electrons that are slowed but not captured by gas ions, a process also known as free-free emission. Red and orange regions show areas where synchrotron emission occurs, such as in the prominent Radio Arc and Sagittarius A, the bright source at the galaxy’s center that hosts its supermassive black hole.

ESO observations reveal black holes’ breakfast at the cosmic dawn

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Astronomers using ESO’s Very Large Telescope have observed reservoirs of cool gas around some of the earliest galaxies in the Universe. These gas halos are the perfect food for super massive black holes at the centre of these galaxies, which are now seen as they were over 12.5 billion years ago. This food storage might explain how these cosmic monsters grew so fast during a period in the Universe’s history known as the Cosmic Dawn.

“We are now able to demonstrate, for the first time, that primordial galaxies do have enough food in their environments to sustain both the growth of super massive black holes and vigorous star formation,” says Emanuele Paolo Farina, of the Max Planck Institute for Astronomy in Heidelberg, Germany, who led the research published today in The Astrophysical Journal. “This adds a fundamental piece to the puzzle that astronomers are building to picture how cosmic structures formed more than 12 billion years ago.”

ESO observations reveal black holes' breakfast at the cosmic dawn
ESO observations reveal black holes’ breakfast at the cosmic dawn

Astronomers have wondered how super massive black holes were able to grow so large so early on in the history of the Universe. “The presence of these early monsters, with masses several billion times the mass of our Sun, is a big mystery,” says Farina, who is also affiliated with the Max Planck Institute for Astrophysics in Garching bei München. It means that the first black holes, which might have formed from the collapse of the first stars, must have grown very fast. But, until now, astronomers had not spotted ‘black hole food’ — gas and dust — in large enough quantities to explain this rapid growth.

To complicate matters further, previous observations with ALMA, the Atacama Large Millimeter/sub millimeter Array, revealed a lot of dust and gas in these early galaxies that fuelled rapid star formation. These ALMA observations suggested that there could be little left over to feed a black hole.

To solve this mystery, Farina and his colleagues used the MUSE instrument on ESO’s Very Large Telescope in the Chilean Atacama Desert to study quasars — extremely bright objects powered by super massive black holes which lie at the centre of massive galaxies. The study surveyed 31 quasars that are seen as they were more than 12.5 billion years ago, at a time when the Universe was still an infant, only about 870 million years old. This is one of the largest samples of quasars from this early on in the history of the Universe to be surveyed.

The astronomers found that 12 quasars were surrounded by enormous gas reservoirs: halos of cool, dense hydrogen gas extending 100,000 light years from the central black holes and with billions of times the mass of the Sun. The team, from Germany, the US, Italy and Chile, also found that these gas halos were tightly bound to the galaxies, providing the perfect food source to sustain both the growth of super massive black holes and vigorous star formation.

The research was possible thanks to the superb sensitivity of MUSE, the Multi Unit Spectroscopic Explorer, on ESO’s VLT, which Farina says was “a game changer” in the study of quasars. “In a matter of a few hours per target, we were able to delve into the surroundings of the most massive and voracious black holes present in the young Universe,” he adds. While quasars are bright, the gas reservoirs around them are much harder to observe. But MUSE could detect the faint glow of the hydrogen gas in the halos, allowing astronomers to finally reveal the food stashes that power super massive black holes in the early Universe.

In the future, ESO’s Extremely Large Telescope will help scientists reveal even more details about galaxies and super massive black holes in the first couple of billion years after the Big Bang. “With the power of the ELT, we will be able to delve even deeper into the early Universe to find many more such gas nebulae,” Farina concludes.