Origins of life: Chemical evolution in a tiny Gulf Stream

 Chemical reactions driven by the geological conditions on the early Earth might have led to the prebiotic evolution of self-replicating molecules. Scientists at Ludwig-Maximilians Universitaet (LMU) in Munich now report on a hydrothermal mechanism that could have promoted the process.

Life is a product of evolution by natural selection. That's the take-home lesson from Charles Darwin's book "The Origin of Species," published over 150 years ago. But how did the history of life on our planet begin? What kind of process could have led to the formation of the earliest forms of the biomolecules we now know, which subsequently gave rise to the first cell? Scientists believe that, on the (relatively) young Earth, environments must have existed, which were conducive to prebiotic, molecular evolution. A dedicated group of researchers is engaged in attempts to define the conditions under which the first tentative steps in the evolution of complex polymeric molecules from simple chemical precursors could have been feasible. "To get the whole process started, prebiotic chemistry must be embedded in a setting in which an appropriate combination of physical parameters causes a non-equilibrium state to prevail," explains LMU biophysicist Dieter Braun. Together with colleagues based at the Salk Institute in San Diego, he and his team have now taken a big step toward the definition of such a state. Their latest experiments have shown the circulation of warm water (provided by a microscopic version of the Gulf Stream) through pores in volcanic rock can stimulate the replication of RNA strands. The new findings appear in the journal Physical Review Letters.

As the carriers of hereditary information in all known lifeforms, RNA and DNA are at the heart of research into the origins of life. Both are linear molecules made up of four types of subunits called bases, and both can be replicated -- and therefore transmitted. The sequence of bases encodes the genetic information. However, the chemical properties of RNA strands differ subtly from those of DNA. While DNA strands pair to form the famous double helix, RNA molecules can fold into three-dimensional structures that are much more varied and functionally versatile. Indeed, specifically folded RNA molecules have been shown to catalyze chemical reactions both in the test-tube and in cells, just as proteins do. These RNAs therefore act like enzymes, and are referred to as 'ribozymes'. The ability to replicate and accelerate chemical transformations motivated the formulation of the 'RNA world' hypothesis. This idea postulates that, during early molecular evolution, RNA molecules served both as stores of information like DNA, and as chemical catalysts. The latter role is performed by proteins in today's organisms, where RNAs are synthesized by enzymes called RNA polymerases.

Ribozymes that can link short RNA strands together -- and some that can replicate short RNA templates -- have been created by mutation and Darwinian selection in the laboratory. One of these 'RNA polymerase' ribozymes was used in the new study.

Acquisition of the capacity for self-replication of RNA is viewed as the crucial process in prebiotic molecular evolution. In order to simulate conditions under which the process could have become established, Braun and his colleagues set up an experiment in which a 5-mm cylindrical chamber serves as the equivalent of a pore in a volcanic rock. On the early Earth, porous rocks would have been exposed to natural temperature gradients. Hot fluids percolating through rocks below the seafloor would have encountered cooler waters at the sea-bottom, for instance. This explains why submarine hydrothermal vents are the environmental setting for the origin of life most favored by many researchers. In tiny pores, temperature fluctuations can be very considerable, and give rise to heat transfer and convection currents. These conditions can be readily reproduced in the laboratory. In the new study, the LMU team verified that such gradients can greatly stimulate the replication of RNA sequences.

One major problem with ribozyme-driven scenario for replication of RNA is that the initial result of the process is a double-stranded RNA. To achieve cyclic replication, the strands must be separated ('melted'), and this requires higher temperatures, which are likely to unfold -- and inactivate -- the ribozyme. Braun and colleagues have now demonstrated how this can be avoided. "In our experiment, local heating of the reaction chamber creates a steep temperature gradient, which sets up a combination of convection, thermophoresis and Brownian motion," says Braun. Convection stirs the system, while thermophoresis transports molecules along the gradient in a size-dependent manner. The result is a microscopic version of an ocean current like the Gulf Stream. This is essential, as it transports short RNA molecules into warmer regions, while the larger, heat-sensitive ribozyme accumulates in the cooler regions, and is protected from melting. Indeed, the researchers were astonished to discover that the ribozyme molecules aggregated to form larger complexes, which further enhances their concentration in the colder region. In this way, the lifetimes of the labile ribozymes could be significantly extended, in spite of the relatively high temperatures. "That was a complete surprise," says Braun.

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New class of laser beam doesn't follow normal laws of refraction

 University of Central Florida researchers have developed a new type of laser beam that doesn't follow long-held principles about how light refracts and travels.

The findings, which were published recently in Nature Photonics, could have huge implications for optical communication and laser technologies.

"This new class of laser beams has unique properties that are not shared by common laser beams," says Ayman Abouraddy, a professor in UCF's College of Optics and Photonics and the study's principal investigator.

The beams, known as spacetime wave packets, follow different rules when they refract, that is when they pass through different materials. Normally, light slows down when it travels into a denser material.

"In contrast, spacetime wave packets can be arranged to behave in the usual manner, to not change speed at all, or even to anomalously speed up in denser materials," Abouraddy says. "As such, these pulses of light can arrive at different points in space at the same time."

"Think about how a spoon inside a water-filled glass looks broken at the point where the water and air meet," Abouraddy says. "The speed of light in air is different from the speed of light in water. And so, the light rays wind up bending after they cross the surface between air to water, and so apparently the spoon looks bent. This is a well-known phenomenon described by Snell's Law."

Although Snell's Law still applies, the underlying change in velocity of the pulses is no longer applicable for the new laser beams, Abouraddy says. These abilities are counter to Fermat's Principle that says light always travels such that it takes the shortest path, he says.

"What we find here, though, is no matter how different the materials are that light passes through, there always exists one of our spacetime wave packets that could cross the interface of the two materials without changing its velocity," Abouraddy says. "So, no matter what the properties of the medium are, it will go across the interface and continue as if it's not there."

For communication, this means the speed of a message traveling in these packets is no longer affected by traveling through different materials of different densities.

"If you think of a plane trying to communicate with two submarines at the same depth but one is far away and the other one's close by, the one that's farther away will incur a longer delay than the one that's close by," Abouraddy says. "We find that we can arrange for our pulses to propagate such that they arrive at the two submarines at the same time. In fact, now the person sending the pulse doesn't even need to know where the submarine is, as long as they are at the same depth. All those submarines will receive the pulse at the same time so you can blindly synchronize them without knowing where they are."

Abouraddy's research team created the spacetime wave packets by using a device known as a spatial light modulator to reorganize the energy of a pulse of light so that its properties in space and time are no longer separate. This allows them to control the "group velocity" of the pulse of light, which is roughly the speed at which the peak of the pulse travels.

Previous work has shown the team's ability to control the group velocity of the spacetime wave packets, including in optical materials. The current study built upon that work by finding they could also control the spacetime wave packets' speed through different media. This does not contradict special relativity in any way, because it applies to the propagation of the pulse peak rather than to the underlying oscillations of the light wave.

"This new field that we're developing is a new concept for light beams," Abouraddy says. "As a result, everything we look into using these beams reveals new behavior. All the behavior we know about light really takes tacitly an underlying presumption that its properties in space and time are separable. So, all we know in optics is based on that. It's a built-in assumption. It's taken to be the natural state of affairs. But now, breaking that underlying assumption, we're starting to see new behavior all over the place."

Co-authors of the study were Basanta Bhaduri, lead author and a former research scientist with UCF's College of Optics and Photonics, now with Bruker Nano Surfaces in California, and Murat Yessenov, a doctoral candidate in the college.

Bhaduri became interested in Abouraddy's research after reading about it in journals, such as Optics Express and Nature Photonics, and joined the professor's research team in 2018. For the study, he helped develop the concept and designed the experiments, as well as carried out measurements and analyzed data.

He says the study results are important in many ways, including the new research avenues it opens.

"Space-time refraction defies our expectations derived from Fermat's principle and offers new opportunities for molding the flow of light and other wave phenomena," Bhaduri says.

Yessenov's roles included data analysis, derivations and simulations. He says he became interested in the work by wanting to explore more about entanglement, which in quantum systems is when two well-separated objects still have a relation to each other.

"We believe that spacetime wave packets have more to offer and many more interesting effects can be unveiled using them," Yessenov says.

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Hubble uses Earth as proxy for identifying oxygen on potentially habitable exoplanets

Taking advantage of a total lunar eclipse, astronomers using NASA's Hubble Space Telescope have detected Earth's own brand of sunscreen -- ozone -- in our atmosphere. This method simulates how astronomers and astrobiology researchers will search for evidence of life beyond Earth by observing potential "biosignatures" on exoplanets (planets around other stars).

Hubble did not look at Earth directly. Instead, the astronomers used the Moon as a mirror to reflect sunlight, which had passed through Earth's atmosphere, and then reflected back towards Hubble. Using a space telescope for eclipse observations reproduces the conditions under which future telescopes would measure atmospheres of transiting exoplanets. These atmospheres may contain chemicals of interest to astrobiology, the study of and search for life.

Though numerous ground-based observations of this kind have been done previously, this is the first time a total lunar eclipse was captured at ultraviolet wavelengths and from a space telescope. Hubble detected the strong spectral fingerprint of ozone, which absorbs some of the sunlight. Ozone is important to life because it is the source of the protective shield in Earth's atmosphere.

On Earth, photosynthesis over billions of years is responsible for our planet's high oxygen levels and thick ozone layer. That's one reason why scientists think ozone or oxygen could be a sign of life on another planet, and refer to them as biosignatures.

"Finding ozone is significant because it is a photochemical byproduct of molecular oxygen, which is itself a byproduct of life," explained Allison Youngblood of the Laboratory for Atmospheric and Space Physics in Boulder, Colorado, lead researcher of Hubble's observations.

Although ozone in Earth's atmosphere had been detected in previous ground-based observations during lunar eclipses, Hubble's study represents the strongest detection of the molecule to date because ozone -- as measured from space with no interference from other chemicals in the Earth's atmosphere -- absorbs ultraviolet light so strongly.

Hubble recorded ozone absorbing some of the Sun's ultraviolet radiation that passed through the edge of Earth's atmosphere during a lunar eclipse that occurred on January 20 to 21, 2019. Several other ground-based telescopes also made spectroscopic observations at other wavelengths during the eclipse, searching for more of Earth's atmospheric ingredients, such as oxygen and methane.

"One of NASA's major goals is to identify planets that could support life," Youngblood said. "But how would we know a habitable or an uninhabited planet if we saw one? What would they look like with the techniques that astronomers have at their disposal for characterizing the atmospheres of exoplanets? That's why it's important to develop models of Earth's spectrum as a template for categorizing atmospheres on extrasolar planets."

Her paper is available online in The Astronomical Journal.

Sniffing Out Planetary Atmospheres

The atmospheres of some extrasolar planets can be probed if the alien world passes across the face of its parent star, an event called a transit. During a transit, starlight filters through the backlit exoplanet's atmosphere. (If viewed close up, the planet's silhouette would look like it had a thin, glowing "halo" around it caused by the illuminated atmosphere, just as Earth does when seen from space.)

Chemicals in the atmosphere leave their telltale signature by filtering out certain colors of starlight. Astronomers using Hubble pioneered this technique for probing exoplanets. This is particularly remarkable because extrasolar planets had not yet been discovered when Hubble was launched in 1990 and the space observatory was not initially designed for such experiments.

So far, astronomers have used Hubble to observe the atmospheres of gas giant planets and super-Earths (planets several times Earth's mass) that transit their stars. But terrestrial planets about the size of Earth are much smaller objects and their atmospheres are thinner, like the skin on an apple. Therefore, teasing out these signatures from Earth-sized exoplanets will be much harder.

That's why researchers will need space telescopes much larger than Hubble to collect the feeble starlight passing through these small planets' atmospheres during a transit. These telescopes will need to observe planets for a longer period, many dozens of hours, to build up a strong signal.

To prepare for these bigger telescopes, astronomers decided to conduct experiments on a much closer and only known inhabited terrestrial planet: Earth. Our planet's perfect alignment with the Sun and Moon during a total lunar eclipse mimics the geometry of a terrestrial planet transiting its star.

But the observations were also challenging because the Moon is very bright, and its surface is not a perfect reflector because it is mottled with bright and dark areas. The Moon is also so close to Earth that Hubble had to try and keep a steady eye on one select region, despite the Moon's motion relative to the space observatory. So, Youngblood's team had to account for the Moon's drift in their analysis.

Where There's Ozone, There's Life?

Finding ozone in the skies of a terrestrial extrasolar planet does not guarantee that life exists on the surface. "You would need other spectral signatures in addition to ozone to conclude that there was life on the planet, and these signatures cannot necessarily be seen in ultraviolet light," Youngblood said.

On Earth, ozone is formed naturally when oxygen in the Earth's atmosphere is exposed to strong concentrations of ultraviolet light. Ozone forms a blanket around Earth, protecting it from harsh ultraviolet rays.

"Photosynthesis might be the most productive metabolism that can evolve on any planet, because it is fueled by energy from starlight and uses cosmically abundant elements like water and carbon dioxide," said Giada Arney of NASA's Goddard Space Flight Center in Greenbelt, Maryland, a co-author of the science paper. "These necessary ingredients should be common on habitable planets."

Seasonal variability in the ozone signature also could indicate seasonal biological production of oxygen, just as it does with the growth seasons of plants on Earth.

But ozone can also be produced without the presence of life when nitrogen and oxygen are exposed to sunlight. To increase confidence that a given biosignature is truly produced by life, astronomers must search for combinations of biosignatures. A multiwavelength campaign is needed because each of the many biosignatures are more easily detected at wavelengths specific to those signatures.

"Astronomers will also have to take the developmental stage of the planet into account when looking at younger stars with young planets. If you wanted to detect oxygen or ozone from a planet similar to the early Earth, when there was less oxygen in our atmosphere, the spectral features in optical and infrared light aren't strong enough," Arney explained. "We think Earth had low concentrations of ozone before the mid-Proterozoic geological period (between roughly 2.0 billion to 0.7 billion years ago) when photosynthesis contributed to the build up of oxygen and ozone in the atmosphere to the levels we see today. But because the ultraviolet-light signature of ozone features is very strong, you would have a hope of detecting small amounts of ozone. The ultraviolet may therefore be the best wavelength for detecting photosynthetic life on low-oxygen exoplanets."

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This fruit attracts birds with an unusual way of making itself metallic blue

There's a reason why blue fruits are so rare: the pigment compounds that make fruits blue are relatively uncommon in nature. But the metallic blue fruits of Viburnum tinus, a popular landscaping plant in Europe, get their color a different way. Instead of relying solely on pigments, the fruits use structural color to reflect blue light, something that's rarely seen in plants. Researchers reporting August 6 in the journal Current Biology show that the fruits use nanostructures made of lipids in their cell walls, a previously unknown mechanism of structural color, to get their striking blue -- which may also double as a signal to birds that the fruits are full of nutritious fats.

"Structural color is very common in animals, especially birds, beetles, and butterflies, but only a handful of plant species have ever been found to have structural color in their fruits," says co-first author Miranda Sinnott-Armstrong, a postdoctoral researcher at the University of Colorado-Boulder. "This means that V. tinus, in addition to showing a completely novel mechanism of structural color, is also one of the few known structurally colored fruits."

Senior author Silvia Vignolini, a physical chemist at the University of Cambridge, has been interested in the plants for nearly 10 years. "I actually found this Viburnum in a garden in Italy and observed that they looked weird, so we measured them at the time but didn't have conclusive results. It was kind of always on the back of my mind," she says. As her team grew, they become more interested in V. tinus and eventually had the capability to examine the structure of the fruits using electron microscopy. "Before we got the images, we were just seeing all these blobs," she says. "When we found out that those blobs were lipids, we got very excited."

While most plants have cell walls made of cellulose, used to make cotton and paper, V. tinus fruit cells have much thicker walls with thousands of globular lipids arranged in layers that reflect blue light. The structure formed by this so-called lipid multilayer allows the fruits to create their vibrant blue color while containing no blue pigment. "This is very strange because globular lipids like these are not usually found in this arrangement in the cell wall, as they are normally stored inside the cell and used for transport," says co-first author Rox Middleton, a physicist who studied the optical response of the fruits during her PhD and is now a postdoctoral researcher at the University of Bristol. "We also believe that this lipid may contribute to the fruit's nutrition. That means that the fruit can demonstrate how nutritious it is by being a beautiful, shiny blue."

This extra nutrition would be important for V. tinus's main consumers: birds that disperse the plant's seeds. Although the researchers can't say for sure whether the lipids are used as fat by the birds that consume them, there is reason to believe they might be. If so, the researchers suggest that the metallic blue color made by the lipid multilayer could indicate to the birds that if they see this striking blue, the fruit in question will have enough nutrients to make it a worthwhile meal. "While birds have been shown to be attracted to blue fruits," says Vignolini, "other blue fruits that we have studied essentially don't have any nutritional value."

Going forward, the researchers want to see how widespread blue structural color is in fruits to understand its ecological significance. They had never seen this type of lipid multilayer in a biomaterial before, but since their discovery, they've begun to take notice of other species. "We actually realize now that there are some older electron microscopy pictures from other plants where you can see the blobs. The researchers didn't know that they were lipids at the time, or that lipids could even form this type of structure, but our research suggests that they very well could be, meaning this structure may not be limited to Viburnum," Vignolini says.

Additionally, learning how V. tinus can use such a unique mechanism to make color may have implications for how we color our own foods. "There are lots of problems connected to food coloration," says Vignolini. She adds that once this mechanism is better understood, it could potentially be used to create a healthier, more sustainable food colorant.

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Non-invasive nerve stimulation boosts learning of foreign language sounds

New research by neuroscientists at the University of Pittsburgh and University of California San Francisco (UCSF) revealed that a simple, earbud-like device developed at UCSF that imperceptibly stimulates a key nerve leading to the brain could significantly improve the wearer's ability to learn the sounds of a new language. This device may have wide-ranging applications for boosting other kinds of learning as well.

Mandarin Chinese is considered one of the hardest languages for native English speakers to learn, in part because the language -- like many others around the world -- uses distinctive changes in pitch, called "tones," to change the meaning of words that otherwise sound the same. In the new study, published today in npj Science of Learning (a Nature partner journal), researchers significantly improved the ability of native English speakers to distinguish between Mandarin tones by using precisely timed, non-invasive stimulation of the vagus nerve -- the longest of the 12 cranial nerves that connect the brain to the rest of the body. What's more, vagus nerve stimulation allowed research participants to pick up some Mandarin tones twice as quickly.

"Showing that non-invasive peripheral nerve stimulation can make language learning easier potentially opens the door to improving cognitive performance across a wide range of domains," said lead author Fernando Llanos, Ph.D., a postdoctoral researcher in Pitt's Sound Brain Lab.

"This is one of the first demonstrations that non-invasive vagus nerve stimulation can enhance a complex cognitive skill like language learning in healthy people," said Matthew Leonard, Ph.D., an assistant professor, Department of Neurological Surgery, UCSF Weill Institute for Neurosciences, whose team developed the nerve stimulation device. Leonard is a senior author of the new study, alongside Bharath Chandrasekaran, Ph.D., professor and vice chair of research, Department of Communication Science and Disorders, Pitt School of Health and Rehabilitation Sciences, and director of the Sound Brain Lab.

Researchers used a non-invasive technique called transcutaneous vagus nerve stimulation (tVNS), in which a small stimulator is placed in the outer ear and can activate the vagus nerve using unnoticeable electrical pulses to stimulate one of the nerve's nearby branches.

For their study, the researchers recruited 36 native English-speaking adults and trained them to identify the four tones of Mandarin Chinese in examples of natural speech, using a set of tasks developed in the Sound Brain Lab to study the neurobiology of language learning.

Participants who received imperceptible tVNS paired with two Mandarin tones that are typically easier for English speakers to tell apart showed quick improvements in learning to distinguish these tones. By the end of the training, those participants were 13% better on average at classifying tones and reached peak performance twice as quickly as control participants who wore the tVNS device but never received stimulation.

"There's a general feeling that people can't learn the sound patterns of a new language in adulthood, but our work historically has shown that's not true for everyone," Chandrasekaran said. "In this study, we are seeing that tVNS reduces those individual differences more than any other intervention I've seen."

"This approach may be leveling the playing field of natural variability in language learning ability," added Leonard. "In general, people tend to get discouraged by how hard language learning can be, but if you could give someone 13% to 15% better results after their first session, maybe they'd be more likely to want to continue."

The researchers now are testing whether longer training sessions with tVNS can impact participants' ability to learn to discriminate two tones that are harder for English speakers to differentiate, which was not significantly improved in the current study.

Stimulation of the vagus nerve has been used to treat epilepsy for decades and has recently been linked to benefits for a wide range of issues ranging from depression to inflammatory disease, though exactly how these benefits are conferred remains unclear. But most of these findings have used invasive forms of stimulation involving an impulse generator implanted in the chest. By contrast, the ability to evoke significant boosts to learning using simple, non-invasive vagus nerve stimulation could lead to significantly cheaper and safer clinical and commercial applications.

The researchers suspect tVNS boosts learning by broadly enhancing neurotransmitter signaling across wide swaths of the brain to temporarily boost attention to the auditory stimulus being presented and promote long-term learning, though more research is needed to verify this mechanism.

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Placebos prove powerful even when people know they're taking one

How much of a treatment is mind over matter? It is well documented that people often feel better after taking a treatment without active ingredients simply because they believe it's real -- known as the placebo effect.

A team of researchers from Michigan State University, University of Michigan and Dartmouth College is the first to demonstrate that placebos reduce brain markers of emotional distress even when people know they are taking one.

Now, evidence shows that even if people are aware that their treatment is not "real" -- known as nondeceptive placebos -- believing that it can heal can lead to changes in how the brain reacts to emotional information.

"Just think: What if someone took a side-effect free sugar pill twice a day after going through a short convincing video on the power of placebos and experienced reduced stress as a result?," said Darwin Guevarra, MSU postdoctoral fellow and the study's lead author. "These results raise that possibility."

The new findings, published in the most recent edition of the journal Nature Communications, tested how effective nondeceptive placebos -- or, when a person knows they are receiving a placebo -- are for reducing emotional brain activity.

"Placebos are all about 'mind over matter," said Jason Moser, co-author of the study and professor of psychology at MSU. "Nondeceptive placebos were born so that you could possibly use them in routine practice. So rather than prescribing a host of medications to help a patient, you could give them a placebo, tell them it can help them and chances are -- if they believe it can, then it will."

To test nondeceptive placebos, the researchers showed two separate groups of people a series of emotional images across two experiments. The nondeceptive placebo group members read about placebo effects and were asked to inhale a saline solution nasal spray. They were told that the nasal spray was a placebo that contained no active ingredients but would help reduce their negative feelings if they believed it would. The comparison control group members also inhaled the same saline solution spray, but were told that the spray improved the clarity of the physiological readings the researchers were recording.

The first experiment found that the nondeceptive placebos reduced participants' self-reported emotional distress. Importantly, the second study showed that nondeceptive placebos reduced electrical brain activity reflecting how much distress someone feels to emotional events, and the reduction in emotional brain activity occurred within just a couple of seconds.

"These findings provide initial support that nondeceptive placebos are not merely a product of response bias -- telling the experimenter what they want to hear -- but represent genuine psychobiological effects," said Ethan Kross, co-author of the study and a professor of psychology and management at the University of Michigan.

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New Guinea has the world's richest island flora

Almost 20 times the size of Switzerland, New Guinea is the world's largest tropical island. It features a complex mosaic of ecosystems ? from lowland jungles to high-elevation grasslands with peaks higher than Mont Blanc. Botanists have long known that this mega-diverse wilderness area is home to a large number of plant species. Efforts to identify and name thousands of plants collected in New Guinea and archived in herbaria all over the world have been ongoing since the 17th century.

However, since researchers have worked mostly independently from each other, a great uncertainty remains as to the exact number of plant species, with conflicting estimates ranging from 9,000 to 25,000. "Compared to other areas like Amazonia, for which plant checklists were recently published, New Guinea remained the 'Last Unknown'," says Rodrigo Cámara-Leret, a postdoctoral researcher in the lab of Prof. Jordi Bascompte in the UZH Department of Evolutionary Biology and Environmental Studies. Under his lead, 99 scientists from 56 institutions and 19 countries have now built the first expert-verified checklist for the 13,634 vascular plant species of New Guinea and its surrounding islands.

Merging databases and human knowledge

The researchers began their large-scale collaborative effort by compiling a list of plant names from online catalogues, institutional repositories and datasets curated by taxonomists. After standardizing the scientific names, 99 experts on New Guinea flora checked almost 25,000 species names derived from over 700,000 individual specimens. For this, they reviewed the list of original names in their plant family of expertise and assessed whether these names were correctly assigned in the online platforms. Finally, an independent comparison was performed between the list accepted by experts and a list contained in Plants of the World Online for New Guinea.

Tremendous, mostly endemic plant diversity

The resulting checklist contains 13,634 plants, demonstrating that New Guinea has the world's richest island flora ? with about 20% more species than Madagascar or Borneo. By far the most species-rich family are the orchids and almost a third of the species are trees. One particularly remarkable finding is that 68% of the plants are endemic ? they are only found in the region. "Such high endemic species richness is unmatched in tropical Asia," says Cámara-Leret, "It means that Indonesia and Papua New Guinea, the two states into which the island is divided, have a unique responsibility for the survival of this irreplaceable biodiversity."

Foundation for research and protection

The new authoritative checklist will improve the accuracy of biogeographic and ecological studies, help focus DNA sequencing on species-rich groups with high endemism, and facilitate the discovery of more species by taxonomists. Thousands of specimens remain unidentified in the collections and many unknown species have yet to be discovered in the wild. "We estimate that in the next 50 years, 3,000 to 4,000 species will be added," says Michael Kessler, co-author of the study and scientific curator of the Botanical Garden of the University of Zurich. These efforts will be important for conservation planning and modelling the impact of changes in climate and land use.

The collaboration also underscores that expert knowledge is still essential in the digital era ? reliance on online platforms alone would have erroneously inflated species counts by one fifth. However, many of the New Guinea plants experts are already or soon to be retired, and almost half of them are non-residents. The researchers therefore advocate building a critical mass of resident plant taxonomists.

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Calcium-rich supernova examined with x-rays for first time

Called "calcium-rich supernovae," these stellar explosions are so rare that astrophysicists have struggled to find and subsequently study them. The nature of these supernovae and their mechanism for creating calcium, therefore, have remained elusive.

Now a Northwestern University-led team has potentially uncovered the true nature of these rare, mysterious events. For the first time ever, the researchers examined a calcium-rich supernova, dubbed SN 2019ehk, with X-ray imaging, providing an unprecedented glimpse into the star during the last month of its life and ultimate explosion.

The study, which includes data from W. M. Keck Observatory on Maunakea in Hawaii, is published in the August 5, 2020 issue of The Astrophysical Journal.

The new findings revealed that a calcium-rich supernova is a compact star that sheds an outer layer of gas during the final stages of its life. When the star explodes, its matter collides with the loose material in that outer shell, emitting bright X-rays. The overall explosion causes intensely hot temperatures and high pressure, driving a chemical reaction that produces calcium.

"These events are so few in number that we have never known what produced calcium-rich supernova," said lead author Wynn Jacobson-Galan, an NSF Graduate Research Fellow at Northwestern University. "By observing what this star did in its final month before it reached its critical, tumultuous end, we peered into a place previously unexplored, opening new avenues of study within transient science."

"Before this event, we had indirect information about what calcium-rich supernovae might or might not be," said senior author Raffaella Margutti, an assistant professor of physics and astronomy at Northwestern University and a member of CIERA (Center for Interdisciplinary Exploration and Research in Astrophysics). "Now, we can confidently rule out several possibilities."

'THE RICHEST OF THE RICH'

While all calcium comes from stars, calcium-rich supernovae pack the most powerful punch. Typical stars create small amounts of calcium slowly through burning helium throughout their lives. Calcium-rich supernovae, on the other hand, produce massive amounts of calcium within seconds.

"The explosion is trying to cool down," Margutti explained. "It wants to give away its energy, and calcium emission is an efficient way to do that."

Using Keck Observatory's Low Resolution Imaging Spectrometer (LRIS), the researchers discovered SN 2019ehk emitted the most calcium ever observed in a singular astrophysical event.

"The beautiful Keck spectrum revealed it wasn't just calcium-rich," Margutti said. "It was the richest of the rich."

'A GLOBAL COLLABORATION WAS IGNITED'

Amateur astronomer Joel Shepherd first spotted the bright burst in April 2019 while using his new telescope to view Messier 100 (M100), a spiral galaxy located 55 million light years from Earth. After seeing a bright orange dot appear in the frame, he immediately reported the discovery to the astronomical community.

"As soon as the world knew that there was a potential supernova in M100, a global collaboration was ignited," Jacobson-Galan said. "Every single country with a prominent telescope turned to look at this object."

The worldwide follow-up operation moved so quickly, the supernova was observed just 10 hours after exploding. Leading observatories such as NASA's Swift Satellite, Lick Observatory, and Keck Observatory were among the telescopes triggered to examine SN 2019ehk in optical wavelengths.

University of California Santa Barbara graduate student Daichi Hiramatsu was the first to trigger Swift to study SN 2019ehk in the X-ray and ultraviolet. The X-ray emission detected with Swift only lingered for five days before completely disappearing.

"In the world of transients, we have to discover things very, very fast before they fade," Margutti said. "Initially, no one was looking for X-rays. Daichi noticed something and alerted us to the strange appearance of what looked like X-rays. We looked at the images and realized something was there. It was much more luminous than anybody would have ever thought. There were no preexisting theories that predicted calcium-rich transients would be so luminous in X-ray wavelengths."

UNCOVERING NEW CLUES

SN 2019ehk's brief luminosity told another a story about its nature. The Northwestern researchers believe the star shed an outer layer of gas in its final days. When the star exploded, its material collided with this outer layer to produce a bright, energetic burst of X-rays.

"The luminosity tells us how much material the star shed and how close that material was to the star," Jacobson-Galan said. "In this case, the star lost a very small amount of material right before it exploded. That material was still nearby."

Although the Hubble Space Telescope had been observing M100 for the past 25 years, the powerful device never registered the star -- which was experiencing its final evolution -- responsible for SN 2019ehk. The researchers used the Hubble images to examine the supernova site before the explosion occurred and say this is yet another clue to the star's true nature.

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Sun’s bubble of influence may be shaped like a deflated croissant

Scientists have developed a new prediction of the shape of the bubble surrounding our solar system using a model developed with data from NASA missions.

All the planets of our solar system are encased in a magnetic bubble, carved out in space by the Sun's constantly outflowing material, the solar wind. Outside this bubble is the interstellar medium -- the ionized gas and magnetic field that fills the space between stellar systems in our galaxy. One question scientists have tried to answer for years is on the shape of this bubble, which travels through space as our Sun orbits the center of our galaxy. Traditionally, scientists have thought of the heliosphere as a comet shape, with a rounded leading edge, called the nose, and a long tail trailing behind.

Research published in Nature Astronomy in March and featured on the journal's cover for July provides an alternative shape that lacks this long tail: the deflated croissant.

The shape of the heliosphere is difficult to measure from within. The closest edge of the heliosphere is more than ten billion miles from Earth. Only the two Voyager spacecraft have directly measured this region, leaving us with just two points of ground-truth data on the shape of the heliosphere.

From near Earth, we study our boundary to interstellar space by capturing and observing particles flying toward Earth. This includes charged particles that come from distant parts of the galaxy, called galactic cosmic rays, along with those that were already in our solar system, travel out towards the heliopause, and are bounced back towards Earth through a complex series of electromagnetic processes. These are called energetic neutral atoms, and because they are created by interacting with the interstellar medium, they act as a useful proxy for mapping the edge of the heliosphere. This is how NASA's Interstellar Boundary Explorer, or IBEX, mission studies the heliosphere, making use of these particles as a kind of radar, tracing out our solar system's boundary to interstellar space.

To make sense of this complex data, scientists use computer models to turn this data into a prediction of the heliosphere's characteristics. Merav Opher, lead author of the new research, heads a NASA- and NSF-funded DRIVE Science Center at Boston University focused on the challenge.

This latest iteration of Opher's model uses data from NASA planetary science missions to characterize the behavior of material in space that fills the bubble of the heliosphere and get another perspective on its borders. NASA's Cassini mission carried an instrument, designed to study particles trapped in Saturn's magnetic field, that also made observations of particles bouncing back towards the inner solar system. These measurements are similar to IBEX's, but provide a distinct perspective on the heliosphere's boundary.

Additionally, NASA's New Horizons mission has provided measurements of pick-up ions, particles that are ionized out in space and are picked up and move along with the solar wind. Because of their distinct origins from the solar wind particles streaming out from the Sun, pick-up ions are much hotter than other solar wind particles -- and it's this fact that Opher's work hinges on.

"There are two fluids mixed together. You have one component that is very cold and one component that is much hotter, the pick-up ions," said Opher, a professor of astronomy at Boston University. "If you have some cold fluid and hot fluid, and you put them in space, they won't mix -- they will evolve mostly separately. What we did was separate these two components of the solar wind and model the resulting 3D shape of the heliosphere."

Considering the solar wind's components separately, combined with Opher's earlier work using the solar magnetic field as a dominant force in shaping the heliosphere, created a deflated croissant shape, with two jets curling away from the central bulbous part of the heliosphere, and notably lacking the long tail predicted by many scientists.

"Because the pick-up ions dominate the thermodynamics, everything is very spherical. But because they leave the system very quickly beyond the termination shock, the whole heliosphere deflates," said Opher.

The shape of our shield

The shape of the heliosphere is more than a question of academic curiosity: The heliosphere acts our solar system's shield against the rest of the galaxy.

Energetic events in other star systems, like supernova, can accelerate particles to nearly the speed of light. These particles rocket out in all directions, including into our solar system. But the heliosphere acts as a shield: It absorbs about three-quarters of these tremendously energetic particles, called galactic cosmic rays, that would make their way into our solar system.

Those that do make it through can wreak havoc. We're protected on Earth by our planet's magnetic field and atmosphere, but technology and astronauts in space or on other worlds are exposed. Both electronics and human cells can be damaged by the effects of galactic cosmic rays -- and because galactic cosmic rays carry so much energy, they're difficult to block in a way that's practical for space travel. The heliosphere is spacefarers' main defense against galactic cosmic rays, so understanding its shape and how that influences the rate of galactic cosmic rays pelting our solar system is a key consideration for planning robotic and human space exploration.

The heliosphere's shape is also part of the puzzle for seeking out life on other worlds. The damaging radiation from galactic cosmic rays can render a world uninhabitable, a fate avoided in our solar system because of our strong celestial shield. As we learn more about how our heliosphere protects our solar system -- and how that protection may have changed throughout the solar system's history -- we can look for other star systems that might have similar protection. And part of that is the shape: Are our heliospheric lookalikes long-tailed comet shapes, deflated croissants, or something else entirely?

Whatever the heliosphere's true shape, an upcoming NASA mission will be a boon for unraveling these questions: the Interstellar Mapping and Acceleration Probe, or IMAP.

IMAP, slated for launch in 2024, will map the particles streaming back to Earth from the boundaries of the heliosphere. IMAP will build on the techniques and discoveries of the IBEX mission to shed new light on the nature of the heliosphere, interstellar space, and how galactic cosmic rays make their way into our solar system.

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Scientists discover the switch that makes human brown fat burn energy

An international research team have discovered how to activate brown fat in humans, which may lead to new treatments for type 2 diabetes and obesity. The results of the collaboration between the Centre de recherche du Centre hospitalier universitaire de Sherbrooke (CRCHUS) and the Novo Nordisk Foundation Center for Basic Metabolic Research (CBMR) at the University of Copenhagen were published today in Cell Metabolism.

Brown fat burns energy and generates heat -- a process called thermogenesis -- after being activated by cold temperature or chemical signals. Humans have small deposits of brown fat, and scientists have long hypothesized that finding alternative ways to pharmacologically activate the fat could help improve metabolism.

Scientists have now discovered that beta2-adrenergic receptors (b2-AR) in brown fat cells are responsible for stimulating thermogenesis. According to Dr. Denis Blondin from CRCHUS, the finding could explain why most clinical trials, which have attempted to induce BAT to burn energy, have performed poorly.

"We show that perhaps we were aiming for the wrong target all along. In contrast to rodents, human BAT is activated through the stimulation of the beta2-adrenergic receptor, the same receptor responsible for the release of fat from our white adipose tissue."

Unlocking the therapeutic potential of brown fat

According to Associate Professor Camilla Schéele at CBMR, this finding has clear therapeutic applications. "Activation of brown fat burns calories, improves insulin sensitivity and even affects appetite regulation. Our data reveals a previously unknown key to unlocking these functions in humans, which would potentially be of great gain for people living with obesity or type 2 diabetes."

A second phase of research will begin in the autumn, which will attempt to validate the finding by activating brown fat with drugs that target b2-AR, explains Professor André Carpentier from CRCHUS:

"Our next step will be to use a drug that specifically activate that target on brown fat and determine how much it could be of use to burn fat and calories in humans. Once this is done, studies in patients with type 2 diabetes will start to determine if this approach can be useful to improve the metabolic control of the disease."

From Science Daily