Friday, January 29, 2021

Human Evolution in Overdrive: Islands Develop Resistance to Malaria in Just 20 Generations

Researchers uncover recent traces of human adaptation in the Cabo Verde islands

 Malaria is an ancient scourge, but it’s still leaving its mark on the human genome. And now, researchers have uncovered recent traces of adaptation to malaria in the DNA of people from Cabo Verde, an island nation off the African coast.

An archipelago of ten islands in the Atlantic Ocean some 385 miles offshore from Senegal, Cabo Verde was uninhabited until the mid-1400s, when it was colonized by Portuguese sailors who brought enslaved Africans with them and forced them to work the land.

In the last 500 years, the people of Cabo Verde have evolved at a breakneck pace -- thanks to a genetic variant, inherited from their African ancestors, that protects against the ravages of malaria. 

Credit: F. Mira

The Africans who were forcibly brought to Cabo Verde carried a genetic mutation, which the European colonists lacked, that prevents a type of malaria parasite known as Plasmodium vivax from invading red blood cells. Among malaria parasites, Plasmodium vivax is the most widespread, putting one third of the world’s population at risk.

People who subsequently inherited the protective mutation as Africans and Europeans intermingled had such a huge survival advantage that, within just 20 generations, the proportion of islanders carrying it had surged, the researchers report.

Other examples of genetic adaptation in humans are thought to have unfolded over tens to hundreds of thousands of years. But the development of malaria resistance in Cabo Verde took only 500 years.

“That is the blink of an eye on the scale of evolutionary time,” said first author Iman Hamid, a Ph.D. student in assistant professor Amy Goldberg’s lab at Duke University.

It is unsurprising that a gene that protects from malaria would give people who carry it an evolutionary edge, the researchers said. One of the oldest known diseases, malaria continues to claim up to a million lives each year, most of them children.

The findings, published this month in the journal eLife, represent one of the speediest, most dramatic changes measured in the human genome, says a team led by Goldberg and Sandra Beleza of the University of Leicester.

The researchers analyzed DNA from 563 islanders. Using statistical methods they developed for people with mixed ancestry, they compared the island of Santiago, where malaria has always been a fact of life, with other islands of Cabo Verde, where the disease has been less prevalent.

The team found that the frequency of the protective mutation on Santiago is higher than expected today, given how much of the islanders’ ancestry can be traced back to Africa versus Europe.

In other words, the chances of a person surviving and having a family thanks to their genetic code -- the strength of selection -- were so great that the protective variant spread above and beyond the contributions of the Africans who arrived on Santiago’s shores. The same was not true elsewhere in the archipelago.

The team’s analyses also showed that as the protective mutation spread, nearby stretches of African-like DNA hitchhiked along with it, but only on malaria-plagued Santiago and not on other Cabo Verdean islands.

Together, the results suggest that what they were detecting was the result of adaptation in the recent past, in the few hundred years since the islands were settled, and not merely the lingering imprint of processes that happened long ago in Africa.

Humans are constantly evolving, but evidence of recent genetic adaptation -- during the last 10 to 100 generations -- has been hard to find. Part of the problem is that, on such short timescales, changes in gene frequencies can be hard to detect using traditional statistical methods.

But by using patterns of genetic ancestry to help reconstruct the Cabo Verdean islanders’ history, the researchers were able to detect evolutionary changes that previous techniques missed.

The authors hope to extend their methods to study other populations where mass migration means migrants are exposed to different diseases and environments than they were before.

“Humans are still evolving, and here we have evidence,” Hamid said.

Contacts and sources:
Robin A. Smith
Duke University

Publication: Rapid adaptation to malaria facilitated by admixture in the human population of Cabo Verde.
Iman Hamid, Katharine L Korunes, Sandra Beleza, Amy Goldberg.eLife, 2021; 10 DOI: 10.7554/eLife.63177

Diving Into Devonian Seas To Study Long Term Changes in Warming Oceans

Members of Syracuse University’s College of Arts and Sciences are shining new light on an enduring mystery—one that is millions of years in the making. Paleontologists use ancient marine faunas to test long-term changes in our warming oceans

A team of paleontologists led by Professor Cathryn Newton has increased scientists’ understanding of whether Devonian marine faunas, whose fossils are lodged in a unit of bedrock in Central New York known as the Hamilton Group, were stable for millions of years before succumbing to waves of extinctions.

Professor Cathryn Newton studies Middle Devonian marine faunas (such as these brachiopods from 380-390 million years ago), whose fossils are lodged in a unit of bedrock in Central New York.
Credit; Syracuse University

Drawing on 15 years of quantitative analysis with fellow professor Jim Brower (who died in 2018), Newton has continued to probe the structure of these ancient fossil communities, among the most renowned on Earth.

Reshaping Hypotheses 

The group’s findings, reported by the Geological Society of America (GSA), provide critical new evidence for the unusual, long-term stability of these Devonian period communities.

Newton (right) and Nicole Bonuso G’01 investigate a fossil outcrop in Morrisville, New York, in 1999. Says Bonuso, an associate professor at California State University, Fullerton: “Working with Cathy Newton and Jim Brower helped influence my career as a paleontologist. I would not be the success I am without having had them as advisors.”

Credit: Syracuse University

Such persistence, Newton says, is a longstanding scientific enigma. She and her colleagues tested the hypothesis that these ancient communities displayed coordinated stasis—a theory that attempts to explain the emergence and disappearance of species across geologic time.

Newton and Brower, along with their student Willis Newman G’93, found that Devonian marine communities vary more in species composition than the theory predicts. Newton points out that they sought not to disprove coordinated stasis but rather to gain a more sophisticated understanding of when it is applicable. “Discovering more about the dynamics of these apparently stable Devonian communities is critical,” she says. “Such knowledge has immediate significance for marine community changes in our rapidly warming seas.”
Stories in StoneLink

Since geologist James Hall Jr. first published a series of volumes on the region’s Devonian fossils and strata in the 1840s, the Hamilton Group has become a magnet for research scientists and amateur collectors alike. Today, Central New York is frequently used to test new ideas about large-scale changes in Earth’s organisms and environments.

During Middle Devonian time (approximately 380-390 million years ago), the faunal composition of the region changed little over 4-6 million years. “It’s a significant amount for marine invertebrate communities to remain stable, or ‘locked,’” explains Newton, a professor in the Department of Earth and Environmental Sciences.

She, Brower and student researchers spent years examining eight communities of animals that once dwelled in a warm, shallow sea on the northern rim of the Appalachian Basin (which, eons ago, lay south of the equator). When the organisms died, sediment from the seafloor began covering their shells and exoskeletons. Minerals from the sediment gradually seeped into their remains, causing them to fossilize. The process also preserved many of them in living position, conserving original shell materials at some sites.

These fossils currently populate exposed bedrock throughout Central New York, ranging from soft, dark, deep-water shale to hard, species-rich, shelf siltstone. “Communities near the top of the bedrock exhibit more taxonomic and ecological diversity than those at the bottom,” Newton says. “We can compare the community types and composition through time. They are remarkable sites.”
Exploring ExplanationsLink

Coordinated stasis has been a source of contention since 1995, when it was introduced. At the center of the dispute are two model-based explanations: environmental tracking and ecological locking.

Environmental tracking suggests that faunas follow their environment. “Here, periods of relative stasis are flanked by coordinated extinctions or regional disappearances. When the environment changes, so do marine faunas,” says Newton, also Professor of Interdisciplinary Sciences and Dean Emerita of Arts and Sciences.

As a teacher, scholar and mentor, Newton prepares students for a lifetime of impact. She believes her research “has the potential to change how scientists view long-term stability in ecological communities.”
Credit: Syracuse University

Ecological locking, in contrast, views marine faunas as tightly structured communities, resistant to large-scale taxonomic change. Traditionally, this model has been used to describe the stability of lower Hamilton faunas.

Newton and her colleagues analyzed more than 80 sample sites, each containing some 300 specimens. Special emphasis was placed on the Cardiff and Pecksport Members, two rock formations in the Finger Lakes region that are part of the ancient Marcellus subgroup, famed for its natural gas reserves.

“We found that lower Hamilton faunas, with two exceptions, do not have clear counterparts among upper ones. Therefore, our quantitative tests do not support the ecological locking model as an explanation for community stability in these faunas,” she continues.

Newton considers this project a final tribute to Newman, a professor of biology at the State University of New York at Cortland, who died in 2014, and Brower, who fell seriously ill while the manuscript was being finalized. “Jim knew that he likely would not live to see its publication,” says Newton, adding that Brower died as the paper was submitted to GSA.

She says this new work extends and, in some ways, completes the team’s earlier research by further analyzing community structures in the Marcellus subgroup. “It has the potential to change how scientists view long-term stability in ecological communities.”

Contacts and sources:
Rob Enslin
Syracuse University

Publication:  Cathryn R. Newton, Willis B. Newman, James C. Brower. Quantitative paleoecology of marine faunas in the lower Hamilton Group (Middle Devonian, central New York): Significance for probing models of long-term community stability. GeoScience World, 2021 DOI: 10.1130/2020.2545(09)

GameStop Bubble: Crypto-Exuberance and the Role of Fintech

GameStop is a brilliant case of the power of crowd money and the transformational role of Fintech.

Credit: University of Southampton

Dr Larisa Yarovaya, Deputy Head of the Centre for Digital Finance in the Southampton Business School assesses the long term financial implications of the GameStop scenario.

The GameStop share price rose from $145 to $450 in two days following the movement of amateur investors against Wall Street’s short sellers, coordinated via social media sites and forums such as Reddit. This is an ideal example of a stock price bubble, i.e. when the price of an asset rises at record pace without any fundamental reasons for it. What makes this bubble unique and why has this story blown up over the internet, social media and stunned the Wall Street experts?

GameStop is a video game and electronics retailer, and until recently, probably, the majority of us had not heard anything about it, neither paid attention to its stock. It was not doing particularly well during the COVID-19 pandemic, which made large hedge funds bet against it. This is an example of short selling strategy which is found to be profitable and common on Wall Street. In a short selling, investors borrow shares to sell them almost immediately at a high price with the intention to buy them back when the price will decline. This strategy normally performed by experienced investors and hedge funds.

However, growing popularity of new Fintech trading platforms, such as Robinhood, allowed a large number of individual investors to interfere in this Wall Street game. Thus, amateur investors following active discussions on online forums decided to buy GameStop stocks in contrast to the hedge funds’ bet. It was a shock for everyone that amateurs actually managed to outplay Wall Street giants, and at odds to all expert predictions, the GameStop price actually skyrocketed in a few days. The short sale strategy of hedge funds failed, and amateurs celebrated a victory.

How can Finance research better help with understanding what happened with GameStop shares?

You can read many media articles and public opinions about it in social media now, but in the Centre for Digital Finance we have explored financial bubbles, especially those that are driven by Fintech innovation for over five years already. Here are some findings that can help to understand the GameStop bubble better.

GameStop is a brilliant case of the power of crowd money and the transformational role of Fintech in the stock markets. The idea of financial liberalisation is one of the most dominant causes of Fintech popularity and various applications of Blockchain technology, such as Bitcoin, crowdfunding, peer-to-peer lending (we categorise the Blockchain applications here).

The decentralisation and freedom from authorities made cryptocurrency assets particularly attractive to amateur investors, and consequently made this asset class sensitive to social media posts and news. This news field is bubble prone. The first bubble we analysed was the Bitcoin, Ethereum bubble at the end of 2017.

However, how can the stock of companies such as GameStop become explosive if they have nothing to do with Fintech or Blockchain? This might be explained by looking at the most recent phenomenon named by Fintech experts as “Crypto-exuberance”, i.e. the situation where companies start experiencing similar behaviour as cryptocurrency markets without any particular structural changes in their business model or operations.

In one of our recent papers we identified 82 companies that changed their names in the period from 30 December 2015 to 25 June 2019, simply changing their names from, for example “Long Island Iced Tea Corp.” to “Long Blockchain Corp.” causing an astonishing share price surge following the announcement. This can be also explained by actions of amateur investors who didn’t consider the actual intentions of the companies to implement blockchain technologies in their businesses, considering only name changes.

We showed that “crypto-exuberance” is a new form of information asymmetry, beyond the investment mania documented by previous studies, or “” bubble. The recent GameStop bubble give me another reason to believe so.

GameStop excess volatility and spike in share price has also been driven by similar sentiment as crypto and Fintech movement. Online trading platforms make trading easily accessible to large a number of investors with various experience levels. For some it was a game and just a fun activity, for others, it’s almost a vigilante idea to battle with hedge funds. Thus, Facebook shut down the Robinhood Stock Traders group, while Robinhood and other trading platforms restricted the selling of GameStop shares causing further controversy and discussions on social media about lack of freedom and the very nature of capitalism. The GameStop share price fell following restrictions.

Decentralised assets and Fintech platforms are being heavily criticised by authorities and financial regulators due their explosivity and threat to the stability of the Financial System, and actions by Facebook and Robinhood are another example of this. Why are bubbles dangerous? They can destabilise financial systems and cause major losses to key actors on financial markets.

However, if there are many examples of speculative attacks conducted by large institutional investors, and short-selling itself is a speculation strategy, why should Fintech platform trading be restricted now? Did crowd money and young money threatened Wall Street? It is a strong reason to believe so. Fintech innovations will continue to challenge the financial system, regulators and traditional finance.


Contacts and sources:
University of Southampton


Geological Phenomenon Widening the Atlantic Ocean, Pushing North and South America Further from Europe and Africa

An upsurge of matter from deep beneath the Earth’s crust could be pushing the continents of North and South America further apart from Europe and Africa, new research has found.

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Credit: University of Southampton

The plates attached to the Americas are moving apart from those attached to Europe and Africa by four centimetres per year. In between these continents lies the Mid-Atlantic Ridge, a site where new plates are formed and a dividing line between plates moving to the west and those moving to the east; beneath this ridge, material rises to replace the space left by the plates as they move apart.

Credit: University of Southampton

Conventional wisdom is that this process is normally driven by distant gravity forces as denser parts of the plates sink back into the Earth. However, the driving force behind the separation of the Atlantic plates has remained a mystery because the Atlantic ocean is not surrounded by dense, sinking plates.

Credit: University of Southampton

Now a team of seismologists, led by the University of Southampton, have found evidence of an upwelling in the mantle – the material between the Earth’s crust and its core – from depths of more than 600 kilometres beneath the Mid Atlantic ridge, which could be pushing the plates from below, causing the continents to move further apart. Upwellings beneath ridges are typically thought to originate from much shallower depths of around 60 km.

The findings, published in the journal Nature provide a greater understanding of plate tectonics which causes many natural disasters around the world, including earthquakes, tsunamis and volcanic eruptions.

Credit: University of Southampton

Over two research cruises on the RV Langseth and RRV Discovery, the team deployed 39 seismometers at the bottom of the Atlantic as part of the PI-LAB (Passive Imaging of the Lithosphere-Asthenosphere Boundary) experiment and EURO-LAB (Experiment to Unearth the Rheological Oceanic Lithosphere-Asthenosphere Boundary). The data provides the first large scale and high-resolution imaging of the mantle beneath the Mid-Atlantic Ridge. This is one of only a few experiments of this scale ever conducted in the oceans and allowed the team to image variations in the structure of the Earth’s mantle near depths of 410 km and 660 km – depths that are associated with abrupt changes in mineral phases. The observed signal was indicative of a deep, sluggish and unexpected upwelling from the deeper mantle.

Lead author, Matthew Agius, a former post-doctoral fellow at the University of Southampton and currently at Università degli studi Roma Tre said: “This was a memorable mission that took us a total of 10 weeks at sea in the middle of the Atlantic Ocean. The incredible results shed new light in our understanding of how the Earth interior is connected with plate tectonics, with observations not seen before.”

Credit: University of Southampton

Dr Kate Rychert and Dr Nick Harmon from the University of Southampton and Professor Mike Kendall from the University of Oxford led the experiment and were the chief scientists on the cruises. The experiment was funded by NERC (Natural Environment Research Council, UK) and the ERC (European Research Council).

Dr Harmon said: “There is a growing distance between North America and Europe, and it is not driven by political or philosophical differences - it is caused by mantle convection!”

As well as helping scientists to develop better models and warning systems for natural disasters, plate tectonics also has an impact on sea levels, and therefore affects climate change estimates over geologic times scales.

Dr Rychert said: “This was completely unexpected. It has broad implications for our understanding of Earth’s evolution and habitability. It also demonstrates how crucial it is to gather new data from the oceans. There is so much more to explore!”

Professor Mike Kendall added: “This work is exciting and that it refutes long held assumptions that mid-ocean ridges might play a passive role in plate tectonics. It suggests that in places such as the Mid-Atlantic, forces at the ridge play an important role in driving newly-formed plates apart.”

Contacts and sources:
University of Southampton

Publication: A thin mantle transition zone beneath the equatorial Mid-Atlantic Ridge.
Matthew R. Agius, Catherine A. Rychert, Nicholas Harmon, Saikiran Tharimena, J.-Michael Kendall. Nature, 2021; 589 (7843): 562 DOI: 10.1038/s41586-020-03139-x

Does the Hellscape of Venus Support Life? The New Hypothesis

In September, a team led by astronomers in the United Kingdom announced that they had detected the chemical phosphine in the thick clouds of Venus. The team’s reported detection, based on observations by two Earth-based radio telescopes, surprised many Venus experts. Earth’s atmosphere contains small amounts of phosphine, which may be produced by life. Phosphine on Venus generated buzz that the planet, often succinctly touted as a “hellscape,” could somehow harbor life within its acidic clouds.

Since that initial claim, other science teams have cast doubt on the reliability of the phosphine detection. Now, a team led by researchers at the University of Washington has used a robust model of the conditions within the atmosphere of Venus to revisit and comprehensively reinterpret the radio telescope observations underlying the initial phosphine claim. As they report in a paper accepted to the Astrophysical Journal and posted Jan. 25 to the preprint site arXiv, the U.K.-led group likely wasn’t detecting phosphine at all.

An image of Venus compiled using data from the Mariner 10 spacecraft in 1974.

Credit: NASA/JPL-Caltech

“Instead of phosphine in the clouds of Venus, the data are consistent with an alternative hypothesis: They were detecting sulfur dioxide,” said co-author Victoria Meadows, a  University of Washington (UW0 professor of astronomy. “Sulfur dioxide is the third-most-common chemical compound in Venus’ atmosphere, and it is not considered a sign of life.”

The team behind the new study also includes scientists at NASA’s Caltech-based Jet Propulsion Laboratory, the NASA Goddard Space Flight Center, the Georgia Institute of Technology, the NASA Ames Research Center and the University of California, Riverside.

The UW-led team shows that sulfur dioxide, at levels plausible for Venus, can not only explain the observations but is also more consistent with what astronomers know of the planet’s atmosphere and its punishing chemical environment, which includes clouds of sulfuric acid. In addition, the researchers show that the initial signal originated not in the planet’s cloud layer, but far above it, in an upper layer of Venus’ atmosphere where phosphine molecules would be destroyed within seconds. This lends more support to the hypothesis that sulfur dioxide produced the signal.

This image, which shows the night side of Venus glowing in thermal infrared, was captured by Japan’s Akatsuki spacecraft

Credit .JAXA/ISAS/DARTS/Damia Bouic

Both the purported phosphine signal and this new interpretation of the data center on radio astronomy. Every chemical compound absorbs unique wavelengths of the electromagnetic spectrum, which includes radio waves, X-rays and visible light. Astronomers use radio waves, light and other emissions from planets to learn about their chemical composition, among other properties.

In 2017 using the James Clerk Maxwell Telescope, or JCMT, the U.K.-led team discovered a feature in the radio emissions from Venus at 266.94 gigahertz. Both phosphine and sulfur dioxide absorb radio waves near that frequency. To differentiate between the two, in 2019 the same team obtained follow-up observations of Venus using the Atacama Large Millimeter/submillimeter Array, or ALMA. Their analysis of ALMA observations at frequencies where only sulfur dioxide absorbs led the team to conclude that sulfur dioxide levels in Venus were too low to account for the signal at 266.94 gigahertz, and that it must instead be coming from phosphine.

In this new study by the UW-led group, the researchers started by modeling conditions within Venus’ atmosphere, and using that as a basis to comprehensively interpret the features that were seen — and not seen — in the JCMT and ALMA datasets.

“This is what’s known as a radiative transfer model, and it incorporates data from several decades’ worth of observations of Venus from multiple sources, including observatories here on Earth and spacecraft missions like Venus Express,” said lead author Andrew Lincowski, a researcher with the UW Department of Astronomy.

The team used that model to simulate signals from phosphine and sulfur dioxide for different levels of Venus’ atmosphere, and how those signals would be picked up by the JCMT and ALMA in their 2017 and 2019 configurations. Based on the shape of the 266.94-gigahertz signal picked up by the JCMT, the absorption was not coming from Venus’ cloud layer, the team reports. Instead, most of the observed signal originated some 50 or more miles above the surface, in Venus’ mesosphere. At that altitude, harsh chemicals and ultraviolet radiation would shred phosphine molecules within seconds.

“Phosphine in the mesosphere is even more fragile than phosphine in Venus’ clouds,” said Meadows. “If the JCMT signal were from phosphine in the mesosphere, then to account for the strength of the signal and the compound’s sub-second lifetime at that altitude, phosphine would have to be delivered to the mesosphere at about 100 times the rate that oxygen is pumped into Earth’s atmosphere by photosynthesis.”

The researchers also discovered that the ALMA data likely significantly underestimated the amount of sulfur dioxide in Venus’ atmosphere, an observation that the U.K.-led team had used to assert that the bulk of the 266.94-gigahertz signal was from phosphine.

“The antenna configuration of ALMA at the time of the 2019 observations has an undesirable side effect: The signals from gases that can be found nearly everywhere in Venus’ atmosphere — like sulfur dioxide — give off weaker signals than gases distributed over a smaller scale,” said co-author Alex Akins, a researcher at the Jet Propulsion Laboratory.

This phenomenon, known as spectral line dilution, would not have affected the JCMT observations, leading to an underestimate of how much sulfur dioxide was being seen by JCMT.

“They inferred a low detection of sulfur dioxide because of that artificially weak signal from ALMA,” said Lincowski. “But our modeling suggests that the line-diluted ALMA data would have still been consistent with typical or even large amounts of Venus sulfur dioxide, which could fully explain the observed JCMT signal.”

“When this new discovery was announced, the reported low sulfur dioxide abundance was at odds with what we already know about Venus and its clouds,” said Meadows. “Our new work provides a complete framework that shows how typical amounts of sulfur dioxide in the Venus mesosphere can explain both the signal detections, and non-detections, in the JCMT and ALMA data, without the need for phosphine.”

With science teams around the world following up with fresh observations of Earth’s cloud-shrouded neighbor, this new study provides an alternative explanation to the claim that something geologically, chemically or biologically must be generating phosphine in the clouds. But though this signal appears to have a more straightforward explanation — with a toxic atmosphere, bone-crushing pressure and some of our solar system’s hottest temperatures outside of the sun — Venus remains a world of mysteries, with much left for us to explore.

Additional co-authors are David Crisp at the JPL, Edward Schwieterman at UC Riverside, Giada Arney and Shawn Domagal-Goldman at the Goddard Space Flight Center, UW researcher Michael Wong, Paul Steffes at Georgia Tech and Niki Parenteau at NASA Ames. The research was funded by the NASA Astrobiology Program and performed at the NExSS Virtual Planetary Laboratory.


Contacts and sources:
James Urton
University of Washington 

Publication: Claimed detection of PH3 in the clouds of Venus is consistent with mesospheric SO2
Andrew P. Lincowski, Victoria S. Meadows, David Crisp, Alex B. Akins, Edward W. Schwieterman, Giada N. Arney, Michael L. Wong, Paul G. Steffes, M. Niki Parenteau, Shawn Domagal-Goldman.. Astrophysical Journal, 2021 [abstract]

It Shapes Galaxies: Quantum Gravity Used to Calculate Mass of Dark Matter

Scientists have calculated the mass range for Dark Matter – and it’s tighter than the science world thought.

Their findings – due to be published in Physical Letters B in March - radically narrow the range of potential masses for Dark Matter particles, and help to focus the search for future Dark Matter-hunters. The University of Sussex researchers used the established fact that gravity acts on Dark Matter just as it acts on the visible universe to work out the lower and upper limits of Dark Matter’s mass.

Credit: Greg Rakozy on Unsplash  

The results show that Dark Matter cannot be either ‘ultra-light’ or ‘super-heavy’, as some have theorised, unless an as-yet undiscovered force also acts upon it.

The team used the assumption that the only force acting on Dark Matter is gravity, and calculated that Dark Matter particles must have a mass between 10-3 eV and 107 eV. That’s a much tighter range than the 10-24 eV - 1019 GeV spectrum which is generally theorised.

What makes the discovery even more significant is that if it turns out that the mass of Dark Matter is outside of the range predicted by the Sussex team, then it will also prove that an additional force – as well as gravity - acts on Dark Matter.

Professor Xavier Calmet from the School of Mathematical and Physical Sciences at the University of Sussex, said: “This is the first time that anyone has thought to use what we know about quantum gravity as a way to calculate the mass range for Dark Matter. We were surprised when we realised no-one had done it before – as were the fellow scientists reviewing our paper.

“What we’ve done shows that Dark Matter cannot be either ‘ultra-light’ or ‘super-heavy’ as some theorise – unless there is an as-yet unknown additional force acting on it. This piece of research helps physicists in two ways: it focuses the search area for Dark Matter, and it will potentially also help reveal whether or not there is a mysterious unknown additional force in the universe.”

Folkert Kuipers, a PhD student working with Professor Calmet, at the University of Sussex, said:

“As a PhD student, it’s great to be able to work on research as exciting and impactful as this. Our findings are very good news for experimentalists as it will help them to get closer to discovering the true nature of Dark Matter.”

The visible universe – such as ourselves, the planets and stars – accounts for 25 per cent of all mass in the universe. The remaining 75 per cent is comprised of Dark Matter.

It is known that gravity acts on Dark Matter because that’s what accounts for the shape of galaxies.


Contacts and sources:
Anna Ford
University of Sussex

Publication: Theoretical bounds on dark matter masses.
Xavier Calmet, Folkert Kuipers. Physics Letters B, 2021; 814: 136068 DOI: 10.1016/j.physletb.2021.136068

Chumash Indians Used Highly Worked Shell Beads as Currency 2,000 Years Ago

Archaeologist argues the Chumash Indians were using highly worked shell beads as currency 2,000 years ago.

Chumash cupped beads from purple dwarf olive sea snails (Olivella biplicata).

 As one of the most experienced archaeologists studying California’s Native Americans, Lynn Gamble(link is external) knew the Chumash Indians had been using shell beads as money for at least 800 years.

Lynn Gamble

Credit University of California - Santa Barbara

But an exhaustive review(link is external) of some of the shell bead record led the UC Santa Barbara professor emerita of anthropology to an astonishing conclusion: The hunter-gatherers centered on the Southcentral Coast of Santa Barbara were using highly worked shells as currency as long as 2,000 years ago.

“If the Chumash were using beads as money 2,000 years ago,” Gamble said, “this changes our thinking of hunter-gatherers and sociopolitical and economic complexity. This may be the first example of the use of money anywhere in the Americas at this time.”

Although Gamble has been studying California’s indigenous people since the late 1970s, the inspiration for her research on shell bead money came from far afield: the University of Tübingen in Germany. At a symposium there some years ago, most of the presenters discussed coins and other non-shell forms of money. Some, she said, were surprised by the assumptions of California archaeologists about what constituted money.

A Chumash kit for making shell beads.
Chumash shell bead-making kit

Intrigued, she reviewed the definitions and identifications of money in California and questioned some of the long-held beliefs. Her research led to “The origin and use of shell bead money in California” in the Journal of Anthropological Archaeology.

Gamble argues that archaeologists should use four criteria in assessing whether beads were used for currency versus adornment: Shell beads used as currency should be more labor-intensive than those for decorative purposes; highly standardized beads are likely currency; bigger, eye-catching beads were more likely used as decoration; and currency beads are widely distributed.

“I then compared the shell beads that had been accepted as a money bead for over 40 years by California archaeologists to another type that was widely distributed,” she said. “For example, tens of thousands were found with just one individual up in the San Francisco Bay Area. This bead type, known as a saucer bead, was produced south of Point Conception and probably on the northern [Santa Barbara] Channel Islands, according to multiple sources of data, at least most, if not all of them.

Shell beads found in the Santa Barbara Channel region as well as elsewhere in California.
Chumash shell beads

“These earlier beads were just as standardized, if not more so, than those that came 1,000 years later,” Gamble continued. “They also were traded throughout California and beyond. Through sleuthing, measurements and comparison of standardizations among the different bead types, it became clear that these were probably money beads and occurred much earlier than we previously thought.”

As Gamble notes, shell beads have been used for over 10,000 years in California, and there is extensive evidence for the production of some of these beads, especially those common in the last 3,000 to 4,000 years, on the northern Channel Islands. The evidence includes shell bead-making tools, such as drills, and massive amounts of shell bits — detritus — that littered the surface of archaeological sites on the islands.

In addition, specialists have noted that the isotopic signature of the shell beads found in the San Francisco Bay Area indicate that the shells are from south of Point Conception.

“We know that right around early European contact,” Gamble said, “the California Indians were trading for many types of goods, including perishable foods. The use of shell beads no doubt greatly facilitated this wide network of exchange.”

Gamble’s research not only resets the origins of money in the Americas, it calls into question what constitutes “sophisticated” societies in prehistory. Because the Chumash were non-agriculturists — hunter-gatherers — it was long held that they wouldn’t need money, even though early Spanish colonizers marveled at extensive Chumash trading networks and commerce.

Recent research(link is external) on money in Europe during the Bronze Age suggests it was used there some 3,500 years ago. For Gamble, that and the Chumash example are significant because they challenge a persistent perspective among economists and some archaeologists that so-called “primitive” societies could not have had “commercial” economies.

“Both the terms ‘complex’ and ‘primitive’ are highly charged, but it is difficult to address this subject without avoiding those terms,” she said. “In the case of both the Chumash and the Bronze Age example, standardization is a key in terms of identifying money. My article on the origin of money in California is not only pushing the date for the use of money back 1,000 years in California, and possibly the Americas, it provides evidence that money was used by non-state level societies, commonly identified as ‘civilizations.’ ”

Contacts and sources:
Jim Logan
University of California - Santa Barbara

Publication: The origin and use of shell bead money in California.
Lynn H. Gamble. Journal of Anthropological Archaeology, 2020; 60: 101237 DOI: 10.1016/j.jaa.2020.101237

Light Pollution Linked to Preterm Birth Increase

In first study of its kind, researchers find that light pollution, based on a measure of skyglow, could increase the likelihood of preterm birth by 12.9%.

Jersey City skyline at night.

 Photo: iStock/AerialPerspective Works

Scientists conducted the first study to examine the fetal health impact of light pollution based on a direct measure of skyglow, an important aspect of light pollution. Using an empirical regularity discovered in physics, called Walker’s Law, a team from Lehigh, Lafayette College and the University of Colorado Denver found evidence of reduced birth weight, shortened gestational length and preterm births.

Specifically, the likelihood of a preterm birth could increase by approximately 1.48 percentage points (or 12.9%), according to the researchers, as a result of increased nighttime brightness.

Nighttime brightness is characterized by being able to see only one-fourth to one-third of the stars that are visible in the natural unpolluted night sky. The findings have been published in an article in Southern Economic Journal called “Light pollution, sleep deprivation, and infant health at birth.”

One possible biological mechanism underlying the findings, based on the existing literature, is light-pollution-induced circadian rhythm disruption, according to Muzhe Yang, a co-author of the study and a professor of economics in Lehigh's College of Business. Yang says circadian rhythm disruption can cause sleep disorders that subsequently lead to adverse birth outcomes.

"While greater use of artificial light at night (ALAN) is often associated with greater economic prosperity, our study highlights an often neglected health benefit of 'darkness,'” says Yang. "We must realize that the biological clock (i.e., the circadian rhythm) of a human body, like all lives on the earth, needs the 'darkness' as part of the light-dark cycle, in order to effectively regulate physiological functions, such as sleep."

While essential to a modern society, ALAN can disrupt a human body’s circadian rhythm and therefore become a “pollutant.” The societal benefits of ALAN, for example through increased economic activity, may be offset by ALAN’s negative externalities such as adverse health effects, say the authors.

The contribution of ALAN to the alteration of natural nocturnal lighting levels is often referred to as light pollution. Light pollution is considered a worldwide ongoing problem.

Contacts and sources:
Lori Friedman
Lehigh University

Publication: Light pollution, sleep deprivation, and infant health at birth
Laura M. Argys, Susan L. Averett, Muzhe Yang. . Southern Economic Journal, 2020; 87 (3): 849 DOI: 10.1002/soej.12477

Cannabis Use Both Helps and Hurts Entrepreneurial Creativity

When entrepreneurs dream up ideas for new businesses, cannabis use might help, and hinder, their creativity, according to a new study in the Journal of Business Venturing by Washington State University researchers.

The study found that cannabis-using entrepreneurs generated new business ideas such as a weightless, gravity-free virtual reality workout, that were more original, but less feasible, compared to those who do not use cannabis.

Credit: Washington State University

“Originality and feasibility are both crucial in entrepreneurship—one without the other limits potential value creation,” said Benjamin Warnick, lead author of the study and assistant professor in the Department of Management, Information Systems and Entrepreneurship at the WSU Carson College of Business.

Warnick and colleagues found the increased originality and decreased feasibility of cannabis users’ business ideas relative to non-users only surfaced for entrepreneurs who reported relatively strong passion for exploring new business ideas. The effect was absent for cannabis-using entrepreneurs with experience founding more than one business.

For the study, Warnick led a team of WSU researchers including Alexander Kier, assistant professor of entrepreneurship in the Carson College of Business, Carrie Cuttler, assistant professor of psychology, and Emily LaFrance, recent WSU psychology Ph.D. graduate.

The 254 entrepreneurs who participated in the study completed a new venture ideation task, generating as many ideas for a new business as possible based on virtual reality technology. The entrepreneurs also answered questions about the extent of their business experience, passion for entrepreneurship and cannabis use patterns.

A panel of experts then rated the originality and feasibility of the idea each entrepreneur identified as their best.

For the purposes of their study, the researchers separated the entrepreneurs into cannabis users and non-users. The cannabis users reported using the drug an average of nearly 20 times in the past month.

The WSU scientists’ work could ultimately play a role in helping entrepreneurs and the business community determine if, when and how cannabis use may be beneficial or detrimental to the venture creation process.

“This is the first study we know of that looks at how any kind of drug use influences new business ideation,” said Warnick, “But there is still much to explore in this area.”

Warnick noted that the cognitive effects of chronic cannabis use have been shown to last for up to a month—including increased impulsivity and free-thinking tendencies.

Results of the current study held whether or not the cannabis users reported being high at the time of the experiment, but the authors call for future research to consider how being high might influence entrepreneurs’ creativity via a randomized experiment.

While the results of the study suggest the effects of marijuana use may have some benefits in the early brainstorming stages of the venture ideation process, the researchers stressed the importance of grounding creativity in reality to successfully launch a new company.

“Our results suggest that cannabis-using entrepreneurs might benefit from non-users’ insights to develop the feasibility of their ideas,” Kier said. “This may be especially true for cannabis users who tend to get very excited about coming up with new ideas or don’t have much experience founding new businesses, since others can serve as a grounding influence, providing a reality-check on their ideas.”

As legalization of cannabis continues across the country and the stigma of the drug fades, the researchers hope their work will help paint a clearer picture of the implications of cannabis use among entrepreneurs.

“Clearly there are pros and cons to using cannabis that deserve to be investigated further,” Warnick said. “As the wave of cannabis legalization continues across the country, we need to shed light on the actual effects of cannabis not only in entrepreneurship but in other areas of business as well.”

Contacts and sources:
Will Ferguson 
Washington State University

Publication: Head in the clouds? Cannabis users' creativity in new venture ideation depends on their entrepreneurial passion and experience.
Benjamin J. Warnick, Alexander S. Kier, Emily M. LaFrance, Carrie Cuttler. Journal of Business Venturing, 2021; 36 (2): 106088 DOI: 10.1016/j.jbusvent.2020.106088

The Very Moments of Nascent Crystal Formation and Growth Caught on Camera

The crystals undergo stochastic fluctuation between crystalline and disordered states at the earliest stage of growth

Conversion of most materials into organized crystalline structure starts with the nucleation process. One everyday example that many people may be familiar with is the rapid crystalization of supercooled water after the nucleation of a seed crystal. This phenomenon has been perplexing both scientists and ordinary people alike. The nucleation process, in which the atoms gather and form the smallest crystals, has been an important scientific phenomenon that has been widely studied since the late 1800s. The classical nucleation theory states that the assembly of monomers into a crystal structure occurs in a one-directional fashion. On the other hand, there have been some who suggested that a non-classical crystallization process involving metastable intermediate crystal structures may occur in some systems. However, it has been extremely difficult to confirm these theories through direct observation because the nucleation occurs very rapidly, and the size of a nucleus can be as small as a few atoms.

Figure 1. A) The schematics of the experiment. The AuCN nanoribbons on top of a graphene membrane were irradiated with electron beams. This decomposes the ribbons to generate gold atoms, which subsequently nucleate into nanocrystals. B) Still frames of the TEM video at various points of the nucleation process. C) Lego block model representation of transition of the gold nanocrystal structure between disordered and crystalline states.

Credit IBS 

This century-old mystery has been finally solved by an international joint research team led by LEE Won Chul, Professor of Mechanical Engineering at Hanyang University Erica Campus, JEON Sungho, Postdoctoral Researcher of Mechanical Engineering at Hanyang University Erica Campus, PARK Jungwon, Professor of School of Chemical and Biological Engineering at Seoul National University and Center for Nanoparticle Research within the Institute for Basic Science (IBS), and Peter ERCIUS from Lawrence Berkeley National Laboratory. The joint research team has succeeded in observing the moment of the initial state of nanocrystal nucleation.

The scientists succeeded in filming the process where the gold atoms gather to form nanocrystals. To observe the initial state of the nucleation process, the team synthesized gold nanocrystals by emitting electron beam onto gold cyanide nanoribbons on top of a graphene membrane, which decomposes the nanoribbons into gold atoms. The synthesized specimen was observed with the high-performance transmission electron microscope (TEM) at the Lawrence Berkeley National Laboratory. The process was recorded at an atomic level spatial resolution and an ultra-high temporal resolution on a scale of milliseconds.

The TEM observation showed the abrupt disappearance and reappearance of crystal lattice structures prior to the emergence of a stable crystal structure. Through careful analysis, the team ruled out some factors which may result in such observations such as the orientation, tilt, and fast rotation of nanocrystals. Therefore, the observed results appeared to indicate that the atoms making up the nucleus randomly oscillate between the disordered and crystalline states. This structural fluctuation appeared to occur spontaneously in a stochastic manner. The team’s discovery directly challenged the longstanding nucleation theory as well as a more recent nucleation theory that has been proposed in the last two decades.

 Figure 2. A) The new thermodynamic theory behind the nucleation process that the team proposed. The energy barrier between disordered and crystalline state is relatively low when the structure has relatively fewer atoms. The energy barrier increases and the crystalline state becomes more stable as the crystal size increases. B) The fraction of time in which the atoms exist under crystalline state versus the area of the nanocrystals. C) The energy required to reach a depressed melting point versus the number of gold atoms within the crystal. D) Merger between smaller and larger nanocrystals temporarily converts the entire structure back to a disordered state.
Credit IBS 

In addition, the team found that the stability of the crystalline state increased as the size of the nanocrystals increased. For example, the nanocrystals with 2.0 nm2 areas spent approximately half of the time existing in a crystalline state. When the crystal sizes increased to above 4.0 nm2 in area, the crystals appeared to exist most of the time under a crystalline form.

In order to describe this phenomenon, the team proposed a new thermodynamic theory of crystal nucleation. The study proposed that the energy barrier between crystalline to disordered transformation tends to be very low in the earliest stage of nucleation when the cluster size is small and that it increases as more atoms are added to the structure. This can explain the spontaneous fluctuation between crystalline and disordered states in nascent crystals consisting of a few atoms. The team also pointed out in relatively smaller nanocrystals, even the addition of extra atoms can transfer enough energy into the system to transform the entire structure back to a disordered state. The energy barrier increases as the crystal grows, which reduces the probability of spontaneous reversion and stabilizes the crystalline structures in larger crystals.

Regarding these findings, Prof. Jungwon Park stated that "From a scientific point of view, we discovered a new principle of crystal nucleation process, and we proved it experimentally." Prof. Won Chul Lee mentioned that "In an engineering point of view, by reproducing the initial state of the deposition process, it can be used to achieve original technology in semiconductor materials, components, and equipment."

This research was published in the journal Science on January 29, 2021.

The TEM video of gold nanocrystal formation. The video has a temporal resolution of 10 ms and is slowed down by 2x (from 100 frames per second to 50 frames per second). The scale bar denotes 1 nm. The gold atoms repeatedly undergo reversible transitions between disordered state and crystalline state early on during the crystallization process, before becoming stabilized as the crystal grows larger.
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Credit IBS 

Contacts and sources: 
Institute for Basic Science (IBS)

Publication: Sungho Jeon, Taeyeong Heo, Sang-Yeon Hwang, Jim Ciston, Karen C. Bustillo, Bryan W. Reed, Jimin Ham, Sungsu Kang, Sungin Kim, Joowon Lim, Kitaek Lim, Ji Soo Kim, Min-Ho Kang, Ruth S. Bloom, Sukjoon Hong, Kwanpyo Kim, Alex Zettl, Woo Youn Kim, Peter Ercius, Jungwon Park, Won Chul Lee “Reversible disorder-order transitions in atomic crystal nucleation,” Science, (2021)

Plate Tectonics Dead on Venus for Past Billion Years?

A study of a giant impact crater on Venus suggests that its lithosphere was too thick to have had Earth-like plate tectonics, at least for much of the past billion years.

\At some point between 300 million and 1 billion years ago, a large cosmic object smashed into the planet Venus, leaving a crater more than 170 miles in diameter. A team of Brown University researchers has used that ancient impact scar to explore the possibility that Venus once had Earth-like plate tectonics.

For a study published in Nature Astronomy, the researchers used computer models to recreate the impact that carved out Mead crater, Venus’s largest impact basin. Mead is surrounded by two clifflike faults — rocky ripples frozen in time after the basin-forming impact. The models showed that for those rings to be where they are in relation to the central crater, Venus’s lithosphere — its rocky outer shell — must have been quite thick, far thicker than that of Earth. That finding suggests that a tectonic regime like Earth’s, where continental plates drift like rafts atop a slowly churning mantle, was likely not happening on Venus at the time of the Mead impact.

“This tells us that Venus likely had what we’d call a stagnant lid at the time of the impact,” said Evan Bjonnes, a graduate student at Brown and study’s lead author. “Unlike Earth, which has an active lid with moving plates, Venus appears to have been a one-plate planet for at least as far back as this impact.”

Mead crater, the largest impact basin on Venus, is encircled by two rocky rings, which provide valuable information about the planet's lithosphere. 
Credit: NASA

Bjonnes says the findings offer a counterpoint to recent research suggesting that plate tectonics may have been a possibility in Venus’s relatively recent past. On Earth, evidence of plate tectonics can be found all over the globe. There are huge rifts called subduction zones where swaths of crustal rock are driven down into the subsurface. Meanwhile, new crust is formed at mid-ocean ridges, sinuous mountain ranges where lava from deep inside the Earth flows to the surface and hardens into rock. Data from orbital spacecraft have revealed rifts and ridges on Venus that look a bit like tectonic features. But Venus is shrouded by its thick atmosphere, making it hard to make definitive interpretations of fine surface features.

This new study is a different way of approaching the question, using the Mead impact to probe characteristics of the lithosphere. Mead is a multi-ring basin similar to the huge Orientale basin on the Moon. Brandon Johnson, a former Brown professor who is now at Purdue University, published a detailed study of Orientale’s rings in 2016. That work showed that the final position of the rings is strongly tied to the crust’s thermal gradient — the rate at which rock temperature increases with depth. The thermal gradient influences the way in which the rocks deform and break apart following an impact, which in turn helps to determine where the basin rings end up.

Bjonnes adapted the technique used by Johnson, who is also a coauthor on this new research, to study Mead. The work showed that for Mead’s rings to be where they are, Venus’s crust must have had a relatively low thermal gradient. That low gradient — meaning a comparatively gradual increase in temperature with depth — suggests a fairly thick Venusian lithosphere.

“You can think of it like a lake freezing in winter,” Bjonnes said. “The water at the surface reaches the freezing point first, while the water at depth is a little warmer. When that deeper water cools down to similar temperatures as the surface, you get a thicker ice sheet.”

The calculations suggest that the gradient is far lower, and the lithosphere much thicker, than what you’d expect for an active-lid planet. That would mean that Venus has been without plate tectonics for as far back as a billion years ago, the earliest point at which scientists think the Mead impact occurred.

Alexander Evans, an assistant professor at Brown and study co-author, said that one compelling aspect of the findings from Mead is their consistency with other features on Venus. Several other ringed craters that the researchers looked at were proportionally similar to Mead, and the thermal gradient estimates are consistent with the thermal profile needed to support Maxwell Montes, Venus’s tallest mountain.

“I think the finding further highlights the unique place that Earth, and its system of global plate tectonics, has among our planetary neighbors,” Evans said.

Contacts and sources:
Kevin Stacy  
Brown University

Publication: Estimating Venusian thermal conditions using multiring basin morphology.
E. Bjonnes, B. C. Johnson, A. J. Evans. Nature Astronomy, 2021; DOI: 10.1038/s41550-020-01289-6

Wednesday, January 27, 2021

Puzzling Six-Exoplanet System with Rhythmic Movement Challenges Theories Of How Planets Form

Using a combination of telescopes, including the Very Large Telescope of the European Southern Observatory (ESO’s VLT), astronomers have revealed a system consisting of six exoplanets, five of which are locked in a rare rhythm around their central star. The researchers believe the system could provide important clues about how planets, including those in the Solar System, form and evolve.

This animation shows a representation of the orbits and movements of the planets in the TOI-178 system. New research by Adrien Leleu and his colleagues with several telescopes, including ESO’s Very Large Telescope, has revealed that the system boasts six exoplanets and that all but the one closest to the star are locked in a rare rhythm as they move in their orbits (represented in orange). In other words, they are in resonance. This means that there are patterns that repeat themselves rhythmically as the planets go around the star, with some planets aligning every few orbits.

In this artist’s animation, the rhythmic movement of the planets around the central star is represented through a musical harmony, created by attributing a note (in the pentatonic scale) to each of the planets in the resonance chain. This note plays when a planet completes either one full orbit or one half orbit; when planets align at these points in their orbits, they ring in resonance.
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Credit: ESO/L. Calçada

The first time the team observed TOI-178, a star some 200 light-years away in the constellation of Sculptor, they thought they had spotted two planets going around it in the same orbit. However, a closer look revealed something entirely different. “Through further observations we realised that there were not two planets orbiting the star at roughly the same distance from it, but rather multiple planets in a very special configuration,” says Adrien Leleu from the Université de Genève and the University of Bern, Switzerland, who led a new study of the system published today in Astronomy & Astrophysics.

The new research has revealed that the system boasts six exoplanets and that all but the one closest to the star are locked in a rhythmic dance as they move in their orbits. In other words, they are in resonance. This means that there are patterns that repeat themselves as the planets go around the star, with some planets aligning every few orbits. A similar resonance is observed in the orbits of three of Jupiter’s moons: Io, Europa and Ganymede. Io, the closest of the three to Jupiter, completes four full orbits around Jupiter for every orbit that Ganymede, the furthest away, makes, and two full orbits for every orbit Europa makes.

An artist’s view of the TOI-178 planetary system

Credit: ESO/L. Calçada/

The five outer exoplanets of the TOI-178 system follow a much more complex chain of resonance, one of the longest yet discovered in a system of planets. While the three Jupiter moons are in a 4:2:1 resonance, the five outer planets in the TOI-178 system follow a 18:9:6:4:3 chain: while the second planet from the star (the first in the resonance chain) completes 18 orbits, the third planet from the star (second in the chain) completes 9 orbits, and so on. In fact, the scientists initially only found five planets in the system, but by following this resonant rhythm they calculated where in its orbit an additional planet would be when they next had a window to observe the system.

More than just an orbital curiosity, this dance of resonant planets provides clues about the system’s past. “The orbits in this system are very well ordered, which tells us that this system has evolved quite gently since its birth,” explains co-author Yann Alibert from the University of Bern. If the system had been significantly disturbed earlier in its life, for example by a giant impact, this fragile configuration of orbits would not have survived.
Disorder in the rhythmic system

But even if the arrangement of the orbits is neat and well-ordered, the densities of the planets “are much more disorderly,” says Nathan Hara from the Université de Genève, Switzerland, who was also involved in the study. “It appears there is a planet as dense as the Earth right next to a very fluffy planet with half the density of Neptune, followed by a planet with the density of Neptune. It is not what we are used to.” In our Solar System, for example, the planets are neatly arranged, with the rocky, denser planets closer to the central star and the fluffy, low-density gas planets farther out.

“This contrast between the rhythmic harmony of the orbital motion and the disorderly densities certainly challenges our understanding of the formation and evolution of planetary systems,” says Leleu.
Combining techniques

To investigate the system’s unusual architecture, the team used data from the European Space Agency’s CHEOPS satellite, alongside the ground-based ESPRESSO instrument on ESO’s VLT and the NGTS and SPECULOOS, both sited at ESO’s Paranal Observatory in Chile. Since exoplanets are extremely tricky to spot directly with telescopes, astronomers must instead rely on other techniques to detect them. The main methods used are imaging transits — observing the light emitted by the central star, which dims as an exoplanet passes in front of it when observed from the Earth — and radial velocities — observing the star’s light spectrum for small signs of wobbles which happen as the exoplanets move in their orbits. The team used both methods to observe the system: CHEOPS, NGTS and SPECULOOS for transits and ESPRESSO for radial velocities.

By combining the two techniques, astronomers were able to gather key information about the system and its planets, which orbit their central star much closer and much faster than the Earth orbits the Sun. The fastest (the innermost planet) completes an orbit in just a couple of days, while the slowest takes about ten times longer. The six planets have sizes ranging from about one to about three times the size of Earth, while their masses are 1.5 to 30 times the mass of Earth. Some of the planets are rocky, but larger than Earth — these planets are known as Super-Earths. Others are gas planets, like the outer planets in our Solar System, but they are much smaller — these are nicknamed Mini-Neptunes.

Although none of the six exoplanets found lies in the star's habitable zone, the researchers suggest that, by continuing the resonance chain, they might find additional planets that could exist in or very close to this zone. ESO’s Extremely Large Telescope (ELT), which is set to begin operating this decade, will be able to directly image rocky exoplanets in a star’s habitable zone and even characterise their atmospheres, presenting an opportunity to get to know systems like TOI-178 in even greater detail.

Contacts and sources: 

Publication: Six transiting planets and a chain of Laplace resonances in TOI-178.
A. Leleu, Y. Alibert, N. C. Hara, M. J. Hooton, T. G. Wilson, P. Robutel, J.-B. Delisle, J. Laskar, S. Hoyer, C. Lovis, E. M. Bryant, E. Ducrot, J. Cabrera, J. Acton, V. Adibekyan, R. Allart, C. Allende Prieto, R. Alonso, D. Alves, D. R. Anderson, al. Astronomy & Astrophysics, 2021; DOI: 10.1051/0004-6361/202039767

NASA’s Roman Mission Will Probe Galaxy’s Core for Hot Jupiters, Brown Dwarfs

When it launches in the mid-2020s, NASA’s Nancy Grace Roman Space Telescope will explore an expansive range of infrared astrophysics topics. One eagerly anticipated survey will use a gravitational effect called microlensing to reveal thousands of worlds that are similar to the planets in our solar system. Now, a new study shows that the same survey will also unveil more extreme planets and planet-like bodies in the heart of the Milky Way galaxy, thanks to their gravitational tug on the stars they orbit.

“We were thrilled to discover that Roman will be able to offer even more information about the planets throughout our galaxy than originally planned,” said Shota Miyazaki, a graduate student at Osaka University in Japan who led the study. “It will be very exciting to learn more about a new, unstudied batch of worlds.”

Roman will primarily use the gravitational microlensing detection method to discover exoplanets – planets beyond our solar system. When a massive object, such as a star, crosses in front of a more distant star from our vantage point, light from the farther star will bend as it travels through the curved space-time around the nearer one.

  High-resolution illustration of the Roman spacecraft against a starry background. 
Credit: NASA's Goddard Space Flight Center

The result is that the closer star acts as a natural lens, magnifying light from the background star. Planets orbiting the lens star can produce a similar effect on a smaller scale, so astronomers aim to detect them by analyzing light from the farther star.

Since this method is sensitive to planets as small as Mars with a wide range of orbits, scientists expect Roman’s microlensing survey to unveil analogs of nearly every planet in our solar system. Miyazaki and his colleagues have shown that the survey also has the power to reveal more exotic worlds – giant planets in tiny orbits, known as hot Jupiters, and so-called “failed stars,” known as brown dwarfs, which are not massive enough to power themselves by fusion the way stars do.

This new study shows that Roman will be able to detect these objects orbiting the more distant stars in microlensing events, in addition to finding planets orbiting the nearer (lensing) stars.

The team’s findings are published in The Astronomical Journal.

Astronomers see a microlensing event as a temporary brightening of the distant star, which peaks when the stars are nearly perfectly aligned. Miyazaki and his team found that in some cases, scientists will also be able to detect a periodic, slight variation in the lensed starlight caused by the motion of planets orbiting the farther star during a microlensing event.

As a planet moves around its host star, it exerts a tiny gravitational tug that shifts the star’s position a bit. This can pull the distant star closer and farther from a perfect alignment. Since the nearer star acts as a natural lens, it’s like the distant star’s light will be pulled slightly in and out of focus by the orbiting planet. By picking out little shudders in the starlight, astronomers will be able to infer the presence of planets.

This animation demonstrates the xallarap effect. As a planet moves around its host star, it exerts a tiny gravitational tug that shifts the star’s position a bit. This can pull the distant star closer and farther from a perfect alignment. Since the nearer star acts as a natural lens, it’s like the distant star’s light will be pulled slightly in and out of focus by the orbiting planet. By picking out little shudders in the starlight, astronomers will be able to infer the presence of planets.
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Credits: NASA's Goddard Space Flight Center
Download high-resolution video and images from NASA’s Scientific Visualization Studio

“It’s called the xallarap effect, which is parallax spelled backward. Parallax relies on motion of the observer – Earth moving around the Sun – to produce a change in the alignment between the distant source star, the closer lens star and the observer. Xallarap works the opposite way, modifying the alignment due to the motion of the source,” said David Bennett, who leads the gravitational microlensing group at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

While microlensing is generally best suited to finding worlds farther from their star than Venus is from the Sun, the xallarap effect works best with very massive planets in small orbits, since they make their host star move the most. Revealing more distant planets will also allow us to probe a different population of worlds.

Mining the core of the galaxy

Most of the first few hundred exoplanets discovered in our galaxy had masses hundreds of times greater than Earth’s. Unlike the giant planets in our solar system, which take 12 to 165 years to orbit the Sun, these newfound worlds whirl around their host stars in as little as a few days.

These planets, now known as hot Jupiters due to their giant size and the intense heat from their host stars, weren’t expected from existing planetary formation models and forced astronomers to rethink them. Now there are several theories that attempt to explain why hot Jupiters exist, but we still aren’t sure which – if any – is correct. Roman’s observations should reveal new clues.

Even more massive than hot Jupiters, brown dwarfs range from about 4,000 to 25,000 times Earth’s mass. They’re too heavy to be characterized as planets, but not quite massive enough to undergo nuclear fusion in their cores like stars.

This illustration depicts a brown dwarf – an object that is too heavy to be characterized as a planet, but not massive enough to power itself by nuclear fusion the way stars do.
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Credits: NASA's Goddard Space Flight Center

Other planet-hunting missions have primarily searched for new worlds relatively nearby, up to a few thousand light-years away. Close proximity makes more detailed studies possible. However, astronomers think that studying bodies close to our galaxy’s core may yield new insight into how planetary systems evolve. Miyazaki and his team estimate that Roman will find around 10 hot Jupiters and 30 brown dwarfs nearer to the center of the galaxy using the xallarap effect.

The center of the galaxy is populated mainly with stars that formed around 10 billion years ago. Studying planets around such old stars could help us understand whether hot Jupiters form so close to their stars, or are born farther away and migrate inward over time. Astronomers will be able to see if hot Jupiters can maintain such small orbits for long periods of time by seeing how frequently they’re found around ancient stars.

Unlike stars in the galaxy’s disk, which typically roam the Milky Way at comfortable distances from one another, stars near the core are packed much closer together. Roman could reveal whether having so many stars so close to each other affects orbiting planets. If a star passes close to a planetary system, its gravity could pull planets out of their usual orbits.

Supernovae are also more common near the center of the galaxy. These catastrophic events are so intense that they can forge new elements, which are spewed into the surrounding area as the exploding stars die. Astronomers think this might affect planet formation. Finding worlds in this region could help us understand more about the factors that influence the planet-building process.

Roman will open up a window into the distant past by looking at older stars and planets. The mission will also help us explore whether brown dwarfs form as easily near the center of the galaxy as they do closer to Earth by comparing how frequently they’re found in each region.

By tallying up very old hot Jupiters and brown dwarfs using the xallarap effect and finding more familiar worlds using microlensing, Roman will bring us another step closer to understanding our place in the cosmos.

“We’ve found a lot of planetary systems that seem strange compared with ours, but it’s still not clear whether they’re the oddballs or we are,” said Samson Johnson, a graduate student at Ohio State University in Columbus and a co-author of the paper. “Roman will help us figure it out, while helping answer other big questions in astrophysics.”

The Nancy Grace Roman Space Telescope is managed at NASA’s Goddard Space Flight Center in Greenbelt, with participation by NASA's Jet Propulsion Laboratory and Caltech/IPAC in Pasadena, California, the Space Telescope Science Institute in Baltimore, and a science team comprising scientists from various research institutions. The primary industrial partners are Ball Aerospace and Technologies Corporation in Boulder, Colorado, L3Harris Technologies in Melbourne, Florida, and Teledyne Scientific & Imaging in Thousand Oaks, California.


Contacts and sources: 

Publication: Revealing Short-period Exoplanets and Brown Dwarfs in the Galactic Bulge Using the Microlensing Xallarap Effect with the Nancy Grace Roman Space Telescope.
Shota Miyazaki, Samson A. Johnson, Takahiro Sumi, Matthew T. Penny, Naoki Koshimoto, and Tsubasa Yamawaki. The Astronomical Journal, 2021 DOI: 10.3847/1538-3881/abcec2

Tuesday, January 26, 2021

CHEOPS Finds Unique Planetary System

The CHEOPS space telescope detects six planets orbiting the star TOI-178. Five of the planets are in a harmonic rhythm despite very different compositions – a novelty. CHEOPS is a joint mission by the European Space Agency (ESA) and Switzerland, under the aegis of the University of Bern in collaboration with the University of Geneva.

This animation shows a representation of the orbits and movements of the planets in the TOI-178 system. The system boasts six exoplanets and all but the one closest to the star are in resonance. This means that there are patterns that repeat themselves rhythmically as the planets go around the star, with some planets aligning every few orbits. In this artist’s animation, the rhythmic movement of the planets around the central star is represented through a musical harmony, created by attributing a note (in the pentatonic scale) to each of the planets in the resonance chain. This note plays when a planet completes either one full orbit or one half orbit; when planets align at these points in their orbits, they ring in resonance.
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Credit: University of Geneva.

Musical notes that sound pleasant together can form a harmony. These notes are usually in a special relationship with each other: when expressed as frequencies, their ratios result in simple fractions, such as four-thirds or three-halves. Similarly, a planetary system can also form a kind of harmony when planets, whose orbital period ratios form simple fractions, regularly attract each other with their gravity. When one planet takes three days to orbit its star and its neighbor takes two days, for example. Using the CHEOPS space telescope, scientists, led by astrophysicist Adrien Leleu of the Center for Space and Habitability of the University of Bern, the University of Geneva and the National Center of Competence in Research PlanetS, found such relationships between five of six planets orbiting the star TOI-178, located over 200 light years away from Earth. The results were published in the journal Astronomy and Astrophysics.

A missing piece in an unexpected puzzle

“This result surprised us, as previous observations with the Transiting Exoplanet Survey Satellite (TESS) of NASA pointed toward a three planets system, with two planets orbiting very close together. We therefore observed the system with additional instruments, such as the ground based ESPRESSO spectrograph at the European Southern Observatory (ESO)’s Paranal Observatory in Chile, but the results were inconclusive.”, Leleu remembers. When he and his colleagues first proposed to investigate the system more closely, they were therefore not sure what they would find. The high precision and target-pointing agility of CHEOPS was required to bring clarity, but that turned out to be more difficult than expected. “After analyzing the data from eleven days of observing the system with CHEOPS, it seemed that there were more planets than we had initially thought”, Leleu says. The team identified a possible solution with five planets and decided to invest another day of precious observation time on the system to confirm. They found that there were indeed five planets present with orbital periods of around 2, 3, 6, 10 and 20 days respectively.

Artist's impression of the TOI-178 system with the planet in the foreground orbiting most distantly around the star.

Credit: © ESO

While a system with five planets would have been quite a remarkable finding in itself, Leleu and his colleagues noticed that there might be more to the story: the system appeared to be in harmony. “Our theory implied that there could be an additional planet in this harmony; however its orbital period needed to be very nearly 15 days.”, Leleu explains. To check if their theory was in fact true, the team scheduled yet another observation with CHEOPS, at the exact time that this missing planet would pass by – if it existed. But then, an accident threatened to cancel their plans.
Prediction confirmed despite near-collision

“Just before the time of the observation, a piece of space debris threatened to collide with the CHEOPS satellite”, as co-author and Professor of Astrophysics at the University of Bern, Yann Alibert, recalls. Therefore, the control center of the European Space Agency (ESA) initiated an evasive maneuver of the satellite and all observations were interrupted. “But to our great relief, this manoeuver was done very efficiently and the satellite could resume observations just in time to capture the mysterious planet passing by”, as Nathan Hara, co-author and astrophysicist from the University of Geneva reports. “A few days later, the data clearly indicated the presence of the additional planet and thus confirmed that there were indeed six planets in the TOI-178 system”, Hara explains.
A system that challenges current understanding

Thanks to the precision of CHEOPS’ measurements as well as previous data from the TESS mission, the ESO’s spectrograph ESPRESSO, and others, the scientists could not only measure the periods and sizes of the planets of 1.1 to 3 times the radius of the Earth, but also estimate their densities. With that came another surprise: compared to the harmonic, orderly way the planets orbit around their star, their densities appear to be a wild mixture.

“It is the first time we observe something like this”, as ESA Project Scientist Kate Isaak points out and adds that “in the few systems we know with such a harmony, the density of planets steadily decreases as we move away from the star. In the TOI-178 system, a dense, terrestrial planet like Earth appears to be right next to a very fluffy planet with half the density of Neptune followed by one very similar to Neptune”.

As Adrien Leleu concludes, “the system therefore turned out to be one that challenges our understanding of the formation and evolution of planetary systems”.


Contacts and sources:
University of Bern

Publication: Six transiting planets and a chain of Laplace resonances in TOI-178.
A. Leleu, Y. Alibert, N. C. Hara, M. J. Hooton, T. G. Wilson, P. Robutel, J.-B. Delisle, J. Laskar, S. Hoyer, C. Lovis, E. M. Bryant, E. Ducrot, J. Cabrera, J. Acton, V. Adibekyan, R. Allart, C. Allende Prieto, R. Alonso, D. Alves, D. R. Anderson, al. Astronomy & Astrophysics, 2021; DOI: 10.1051/0004-6361/202039767

Saturn’s Tilt Caused by Its Moons

Two scientists from CNRS and Sorbonne University working at the Institute of Celestial Mechanics and Ephemeris Calculation (Paris Observatory - PSL/CNRS) have just shown that the influence of Saturn's satellites can explain the tilt of the rotation axis of the gas giant. Their work, published on 18 January 2021 in the journal Nature Astronomy, also predicts that the tilt will increase even further over the next few billion years.

Artist’s impression of the migration of Titan and the tilt of Saturn.

Credit:  © Coline SAILLENFEST / IMCCE

Rather like David versus Goliath, it appears that Saturn’s tilt may in fact be caused by its moons. This is the conclusion of recent work carried out by scientists from the CNRS, Sorbonne University and the University of Pisa, which shows that the current tilt of Saturn’s rotation axis is caused by the migration of its satellites, and especially by that of its largest moon, Titan.

Recent observations have shown that Titan and the other moons are gradually moving away from Saturn much faster than astronomers had previously estimated. By incorporating this increased migration rate into their calculations, the researchers concluded that this process affects the inclination of Saturn’s rotation axis: as its satellites move further away, the planet tilts more and more.

A schematic animation showing Titan’s migration and Saturn entering into resonance. The frame is rotating, so the axis stops moving when resonance is achieved.

Credit: © Melaine SAILLENFEST / IMCCE

The decisive event that tilted Saturn is thought to have occurred relatively recently. For over three billion years after its formation, Saturn’s rotation axis remained only slightly tilted. It was only roughly a billion years ago that the gradual motion of its satellites triggered a resonance phenomenon that continues today: Saturn’s axis interacted with the path of the planet Neptune and gradually tilted until it reached the inclination of 27° observed today.

These findings call into question previous scenarios. Astronomers were already in agreement about the existence of this resonance. However, they believed that it had occurred very early on, over four billion years ago, due to a change in Neptune’s orbit. Since that time, Saturn’s axis was thought to have been stable. In fact, Saturn’s axis is still tilting, and what we see today is merely a transitional stage in this shift. Over the next few billion years, the inclination of Saturn’s axis could more than double.

The research team had already reached similar conclusions about the planet Jupiter, which is expected to undergo comparable tilting due to the migration of its four main moons and to resonance with the orbit of Uranus: over the next five billion years, the inclination of Jupiter’s axis could increase from 3° to more than 30°.


Contacts and sources: 
François Maginiot

Publication: The large obliquity of Saturn explained by the fast migration of Titan. Melaine Saillenfest, Giacomo Lari and Gwenaël Boué. Nature Astronomy, 18 January 2021.