Aug 22, 2017

Climate Change Is Causing Fish to Shrink

Measuring the size of cod caught in the North Sea. New research helps to explain why climate change is causing fish to shrink in size.
Fishermen over the past several years have noted that fish appear to be shrinking. That observation was validated in 2014 by research that found commercially important fish stocks in the North Sea, such as sole, herring, and haddock, have decreased in maximum body size over a 40-year period. Scientists suspected that climate change was the culprit, but were unsure how warming waters could lead to fish shrinkage across entire species.

New research published in the journal Global Change Biology describes the mechanism that is likely causing fish to shrink. Lead author Daniel Pauly, a principal investigator with the Sea Around Us project at the University of British Columbia, said the findings apply to animals with gills, such as fish, sharks, squid, and lobsters.

Pauly's co-author William Cheung, director of science for the Nippon Foundation Nereus Program at the university, explained that these species and many others are ectotherms, meaning that their body temperature depends on environmental temperature.

“As the oceans warm up,” Cheung said, “their bodies will do so as well. Higher temperature within the scope that the fish can tolerate generally increases the rate of biochemical reactions in the fish’s body and thus increases their body metabolic rate.”

Metabolic rate refers to an animal’s oxygen consumption, which also naturally increases as fish grow into adulthood because their body mass becomes larger.

Graphic showing how climate change can cause the bodies of certain marine species to shrink in size
One might wonder why fish and other marine ectotherms aren’t just taking in ever more oxygen to coincide with this natural growth due to maturation and the rise of ocean temperatures. They don’t because at a certain point they cannot keep up.

The researchers point out that the surface area of an animal’s gills — where oxygen is obtained — does not grow at the same pace as the rest of its body.

“This is because gills, in order to work, must function as a two-dimensional surface (width by height) and thus cannot grow as fast as the three-dimensional volume (width by height by depth) they have to supply with oxygen,” Pauly said.

He and Cheung liken how a fish gill works to a car radiator. Both are made up of numerous thin layers that allow for the transfer of heat, which permits cooling. But both can only work in two dimensions because air or water pass through only once.

“There is not much that fish can do to solve this problem,” Pauly said. “They can have bigger gills — just as sports cars have bigger radiators — but ultimately, the weight always catches up, and the ratio of gill surface to body weight becomes too low.”

The researchers believe this set of principles, which they have named the Gill-Oxygen Limitation Theory helps to explain why so many populations of marine species are shrinking. They and others predict that the reductions will be in the range of 20–30 percent if ocean temperatures continue to climb due to climate change.

At the higher end of that range is one of the world’s most important commercial fish: tuna.

“Tunas are active, mobile, and fast-swimming animals that need a lot of oxygen to maintain their lifestyle,” Cheung said. “In fact, they have to keep swimming non-stop in order to get more water through their gills to obtain sufficient oxygen. Thus, when temperature increases, they are particularly susceptible to not having sufficient oxygen to support their body growth.”

He added that for a 2 degree Celsius (3.6 degree Fahrenheit) increase in water temperature, which is approximately what is expected to occur in oceans around the world by the mid-21st century, tunas such as the Atlantic bluefin tuna will potentially decrease in body size by 30 percent.

Sharks, many of which are already threatened with extinction, are also predicted to decrease in size, especially larger species.

In the case of tuna, haddock, cod, and other fish consumed by humans, shrinkage is predicted to decrease potential fisheries production. Since marine ecosystems are structured in part by the body size of organisms — basically larger fish eat smaller fish — the projected changes to body sizes will likely affect predator and prey interactions, as well as ecosystem structure and functions, Cheung said.

He said the most effective way to prevent these problems from occurring is to mitigate carbon dioxide emissions.

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The Asteroid That Killed the Dinosaurs Caused Catastrophic Climate Change

The last days of dinosaurs during the Cretaceous Period, caused by a giant asteroid impact at Chicxulub off the coast of Mexico.
Most schoolchildren learn the dinosaurs died out when an asteroid hit the earth.

Fortunately, schoolchildren are spared the gory details.

Scientists now believe that the asteroid that slammed into Mexico’s Yucatan Peninsula 66 million years ago was 6 miles wide — almost big enough to cover San Francisco — and caused cataclysmic destruction on a scale comparable to global thermonuclear war. In the aftermath, about three-quarters of all species on Earth died out.

The asteroid, named Chicxulub, sent huge tsunamis surging across the seas, and caused massive earthquakes and volcanoes. But that was just the beginning.

A massive amount of vaporized rock was propelled high above Earth, where it condensed into tiny particles and fell back down to the surface. Heated by friction, the descending cloud of rock dust reached temperatures hot enough to spark fires, literally broiling the Earth’s surface along with plant and animal life.

In other words, dinosaurs living far away from the Yucatan Peninsula were flambéed from above by the cloud of scorching rock particles falling on them. A thin layer of molten particles is still observable to geologists today.

New research, however, now suggests that following the asteroid strike global temperatures plunged in a way analogous to the planetary cooling thought to follow a global nuclear war, commonly known as nuclear winter.

The resulting wildfires sparked by the broiling rock dust sent so much soot back up into the sky the sun was blackened out completely for most of the next two years, shutting down photosynthesis and dramatically cooling the planet in one of the most significant known episodes of climate change in Earth’s history.

Global temperatures plummeted by 50 degrees Fahrenheit on land and 20°F over the oceans.

On land, temperatures returned to normal in about seven years, though they were still a couple of degrees Celsius below normal 15 years later, according to Charles Bardeen of the National Center for Atmospheric Research, who led a study of Earth’s climate following the impact. The results were published in the journal Proceedings of the National Academy of Sciences.

Bardeen and his colleagues from NASA and the University of Colorado Boulder used advanced computer models to simulate the climate’s reaction during the years after the asteroid landed.

Rampant, sudden wildfires caused by the meteor impact cooled global temperatures in a way that is thought to be likely following widespread detonations of nuclear weapons, Bardeen said.

“Fires created by an asteroid impact and fires created by a nuclear war can put large amounts of soot high up above where the rain happens, so they can exist for a longer period of time and have these global consequences,” Bardeen said. “As long as that soot gets injected above where the rain would happen, it can stay in the atmosphere for a long time.”

Yet, perhaps surprisingly, the dinosaur-killing asteroid brought climate consequences that likely far exceeded those of a modern day limited nuclear war.

A war between India and Pakistan, where perhaps 100 Hiroshima-sized nuclear weapons are used, would probably put enough soot into the atmosphere to have a 1-2°C impact on the atmosphere,” Bardeen said.

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Bacteria Covered in Semiconductor Crystals Outcompete Plants at Photosynthesis

In nature, plants use photosynthesis to convert sunlight into chemicals and energy. But this process is actually not very efficient because chlorophyll, the pigment that makes photosynthesis possible, only responds to one wavelength of light.

Now scientists have devised a way to take the light-harvesting efficiency of a semiconductor that can absorb more wavelengths of sunlight and combine it with the catalytic power of a bacterium to more efficiently convert light, water, and carbon dioxide (CO2) into chemicals, which can in turn be used to develop fuels, polymers, and pharmaceuticals.

The combination is described as a form of “cyborg bacteria.”

“The best path forward is to take the best of both worlds,” chemist Kelsey K. Sakimoto told Seeker. He began researching this organism in Peidong Yang’s lab at the University of California, Berkeley, and is now a post-doctoral fellow at Harvard University.

“With a higher efficiency light harvester you can begin to outcompete natural photosynthesis,” Sakimoto said.

To convert CO2 into products, researchers can produce very complex items in a simple way that chemists can’t even begin to think about doing with conventional chemistry.

In their experiments, Sakimoto and his colleagues achieved a solar-to-chemical conversion efficiency of around 80 percent. Conventional solar panels convert sunlight at an efficiency around 20 percent. Natural photosynthesis has a conversion efficiency that, theoretically, maxes out at 12 percent, according to Sakimoto.

The research team will present its findings today at the 254th National Meeting & Exposition of the American Chemical Society (ACS).

The team’s work focuses on the bacterium Moorella thermoacetica, which can be found in soil and at the bottom of stagnant ponds. As part of its normal respiration, it naturally uses hydrogen to turn CO2 into acetic acid, a versatile chemical that can form the basis of fuels and plastics that are otherwise derived from petrochemicals.

Moorella thermoacetica has another attribute that makes it ideal for this purpose: When it encounters the toxic metal cadmium in the environment, it turns it into tiny particles of cadmium sulfide on its outer cell wall so that it doesn’t get inside, where it can be harmful.

“It's basically a stress response that they have on the back burner if they encounter these conditions,” said Sakimoto. “So we tap this stress response and induce it by adding some cadmium.”

Cadmium sulfide nanocrystals function like tiny solar panels. In fact, some of the earliest solar panels were made using cadmium sulfide as a light-absorbing semiconductor.

The bacterium uses the cadmium sulfide like a piece of equipment that absorbs sunlight and transfers that energy to produce a molecule that the bacteria can eat. In doing so, CO2 is turned into acetic acid.

An advantage of using this bacteria to produce acetic acid is that chemists can make large amounts of it relatively simply.

“One of the reasons we opted for a free-living system in which the semiconductors are directly attached to the bacteria is that you can make giant vats of this stuff and [the bacteria] will kind of chug along happily like micro algae,” Sakimoto remarked.

In these quantities, it’s easier and cheaper to expose the bacteria to cadmium rather than hydrogen, which would require an expensive, energy-intensive system called an electrolysis reactor.

“The nanoparticles accomplish all of that in a single step,” said Sakimoto. “Having the microbes make all the equipment itself simplifies the process even further.”

In vats under the sun, the bacteria would self-replicate without producing waste.

The acetate produced would then be harnessed to make other products. Previous researchers have shown that genetically engineered E. coli bacteria can turn acetic acid into fuels, such as butanol, as well as into biopolymers to make plastics and into various compounds that are useful in a variety of pharmaceuticals.

Sakimoto believes it’s worthwhile to do some “bioprospecting” for other examples of bacteria that could be tapped to create chemicals. The fact that Moorella thermoacetica produced cadmium sulfide nanoparticles as a stress response was documented as a curious observation in a paper, he said — it was essentially a side note.

“The first, easiest step is to go back and look through the old biological and microbiological literature with the lens of a chemist or a material chemist to see what has been already discovered that other fields of science haven't really found a use,” he said.

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X-Ray Reveals Ancient Roman Portrait Covered in Mt. Vesuvius Ash

An iron element map (right) made with new X-ray technology reveals the underlying craftsmanship hidden beneath a damaged portrait of a Roman woman (left).
For centuries, the ancient Roman resort town of Herculaneum was buried under 66 feet of volcanic material. The city on the Italian coast, along with nearby Pompeii, was destroyed during an eruption of Mount Vesuvius in 79 AD. Excavations in the mid-19th century uncovered much of Herculaneum, including its large “House of the Mosaic Atrium,” but an ancient painting in the house went almost unnoticed, until now.

A newly developed portable macro X-ray fluorescence instrument, ELIO by XGLab SRL, revealed the Roman woman in the portrait that has been subjected to molten lava, volcanic ash, grime, salt, and humidity over the years. As if that weren’t rough treatment enough, its exposure since it was excavated 70 years ago has caused much of it to deteriorate.

The portable X-ray instrument was brought directly to the site at Herculaneum, where the noninvasive analysis of the mid-1st century AD painting occurred.

“As far as we know, this is the first study of an ancient Roman wall painting — or any other historical wall painting — in situ, in its original setting,” Eleonora Del Federico, a professor of chemistry at the Pratt Institute who studies artists’ materials and conservation, told Seeker. “The technique is fairly new, and has been used for studies at museums on Rembrandts, Picassos and Van Goghs, among others.”

The ELIO device scanning the Roman portrait within the House of the Mosaic Atrium at Herculaneum.
While ELIO works best at just over a half an inch away from an artwork’s surface, the instrument never actually touches a painting. It is not difficult to operate, but ELIO is not cheap and the data analysis and interpretation of the results it provides require specialized training.

Del Federico, who conducted this latest research in conjunction with the Herculaneum Conservation Project, will present her findings today at the 254th National Meeting & Exposition of the American Chemical Society in Washington, DC.

Her analysis revealed that an artist created a sketch of the young woman with an iron-based pigment, and then put highlighting around the woman’s eyes in the sketch with a lead pigment. High levels of potassium in the woman’s cheeks in the artwork suggest that a green Earth pigment was used as an underpainting to help create a flesh-toned color.

“We were very surprised at the complexity and sophistication of the painting technique, the use of color, mixture of pigments and layering,” Del Federico said.

Images of the early Roman painting showing the various elements revealed by the macro X-ray fluorescence instrument.
She explained that the painting method actually involved two primary techniques. The first, known as fresco, involved applying pigments on a wet surface of lime mortar, which consists of a mixture of calcium hydroxide and sand and/or pumice stone. The second, called secco, involved applying pigments with organic binders to the surface once the lime mortar had set.

Together, these methods were used to contour the portrait and to give realistic-looking volume to the subject’s face, cheeks and nose.

ELIO allowed Del Federico to create an “iron map” highlighting the woman’s primary features.

“When we look at the map of iron atoms, it reveals a beautiful young woman caught in a moment of deep thought,” she said. “You can always feel her presence, talk to her and feel her humanity, at least for me. She was gone by the years of exposure to the elements, and now she is back to life.”

The portrait is not signed, so the artist, for now, remains a mystery. Intriguingly, a similar portrait known as “Saffo” is on exhibit at the National Archaeological Museum of Naples. It is possible that both portraits were created by an artist who was given the honorary title “pictor imaginarius.” Many painters worked in early Roman towns, but the “pictor imaginarius” was among the most skilled, and would be brought in to tackle prominent wall areas requiring greater expertise.

A sketch of the woman in the early Roman painting created with an iron-based pigment.
As for who the woman was in the Herculaneum portrait, she remains a mystery for now, too. Del Federico said that she is possibly wearing a tiara. The House of the Mosaic Atrium “was indeed a well-to-do household, but not necessarily aristocratic.”

Roger Ling, a professor of classical art and archaeology at the University of Manchester, believes that a portrait such as this functioned as “a symbol of aristocratic luxury by which householders liked to surround themselves.”

Del Federico added, “A good quality wall painting was a sign of status.”

Read more at Seeker

Aug 18, 2017

Archaeologists uncover ancient trading network in Vietnam

The excavation site at Rach Nui in Southern Vietnam.
A team of archaeologists from The Australian National University (ANU) has uncovered a vast trading network which operated in Vietnam from around 4,500 years ago up until around 3,000 years ago.

A new study shows a number of settlements along the Mekong Delta region of Southern Vietnam were part of a sophisticated scheme where large volumes of items were manufactured and circulated over hundreds of kilometres.

Lead researcher Dr Catherine Frieman School of the ANU School of Archaeology and Anthropology said the discovery significantly changes what was known about early Vietnamese culture.

"We knew some artefacts were being moved around but this shows evidence for a major trade network that also included specialist tool-makers and technological knowledge. It's a whole different ball game," Dr Frieman said.

"This isn't a case of people producing a couple of extra items on top of what they need. It's a major operation."

The discovery was made after Dr Frieman, an expert in ancient stone tools, was brought in to look at a collection of stone items found by researchers at a site called Rach Nui in Southern Vietnam.

Dr Frieman found a sandstone grinding stone used to make tools such as axe heads out of stone believed to come from a quarry located over 80 kilometres away in the upper reaches of the Dong Nai River valley.

"The Rach Nui region had no stone resources. So the people must have been importing the stone and working it to produce the artefacts," she said.

"People were becoming experts in stone tool making even though they live no-where near the source of any stone."

Dr Phillip Piper of the ANU School of Archaeology and Anthropology, an expert in Vietnamese archaeology, is working to map the transition from hunting and gathering to farming across Southeast Asia.

"Vietnam has an amazing archaeological record with a number of settlements and sites that provide significant information on the complex pathways from foraging to farming in the region" Dr Piper said.

"In southern Vietnam, there are numerous archaeological sites of the Neolithic period that are relatively close together, and that demonstrate considerable variation in material culture, methods of settlement construction and subsistence.

Read more at Science Daily

Mechanisms explaining positional diversity of the hindlimb in tetrapod evolution

In the snake embryo, onset of GDF11 function in the prospective vertebra region is later than in other vertebrates' embryos, resulting in a longer flank.
In the evolution of tetrapods, the position of the hindlimb has diversified along with the vertebral formula, which is the number of small bones forming the vertebra. Tetrapods, as the name implies, are species that have four feet. However, this group also includes many other animals without four or any feet, such as snakes and birds. This is because tetrapods include all the organisms, living and extinct, that descended from the last common ancestor of amphibians, reptiles and mammals, even if they have secondarily lost their "four feet."

Although researchers have long studied tetrapod anatomy, how the species-specific position of the body parts of these species -- for example, the hindlimb position along the body -- are formed in early development remains unclear. Elucidating this mystery will be a major step in evolution biology.

This crucial piece of the puzzle has finally been found by a team of researchers from Nagoya University in Japan. The researchers demonstrated that a protein called GDF11, which is involved in embryonic development, plays a vital role in the eventual position of the sacral vertebrae and the hindlimb. The study results were published in July 2017 in Nature Ecology & Evolution.

"In laboratory mice that do not produce the protein GDF11, we have noted that the sacral vertebrae and the hindlimbs are shifted more to the back," said Yoshiyuki Matsubara, researcher at the Division of Biological Science and first author of the study.

To arrive at that conclusion, the research team started by analyzing the expression pattern of the gene of interest and examining the relationship between the pattern and the prospective position of the spine and hindlimb at different development stages in chicken embryos. Next, they tested whether hindlimb positioning can be manipulated by changing the timing of GDF11 activity in the embryos. Lastly, to fully elucidate the role of GDF11 in diversification of the hindlimb position in tetrapods, the team examined the correlation between Gdf11 expression and hindlimb positioning in eight tetrapod species, including the African clawed frog, Chinese soft-shelled turtle, ocelot gecko, Japanese striped snake, chick, quail, emu and mouse.

"Our results also suggest that species-specific hindlimb positioning may have been an effect of the change in the timing or rate of events in the gene that expresses GDF11 during embryonic development," said Takayuki Suzuki, last author of the study.

According to their conclusion, snakes have a long trunk because initiation timing of Gdf11 expression in the developmental stage is much later than that in other tetrapod species.

Read more at Sience Daily

Observations of Red Supergiant Antares Shed Light on the Final Moments of Dying Stars

Antares and Scorpius
One day, our sun will become a red giant, growing so large that it will swallow Earth. That hasn't yet happened, of course, which is fortunate for us on Earth. However, it means scientists must look beyond the solar system to study the full evolutionary cycles of stars and their mechanisms at each stage.

A new study led by Keiichi Ohnaka, a researcher at Catholic University of the North in Chile, sought to understand how the distant red supergiant star Antares manages to expel so much matter off its surface as it nears the end of its life and nears its finale as a spectacular supernova.

The study demonstrated improved techniques for discovering what could be behind atmospheric motion on Antares, while showing that there are still mysteries surrounding what, exactly, causes the star's turbulent churning.

"With this study, we can open a new window to observe stars other than the sun … in a similar way that we observe the sun," Ohnaka told "We can then apply this technique to investigate other problems — not only supergiants, like Antares, but also other types of stars and other unsolved problems."

Antares is a red supergiant star, and its large size makes it an ideal candidate for study from Earth. The star is so bright that it was given its name to mean "anti-Ares," likely because its reddish color seemed to oppose that of the shiny planet Mars, named after Ares, the ancient Greek god of war. Because it is so large, Antares is an ideal first subject for scientists to study to gain a better understanding of how stars other than Earth's sun manage to exist and function. Indeed, Antares's diameter is estimated to be 883 times larger than that of the sun. Antares is also known as Alpha Scorpii, meaning it's the brightest star in the constellation Scorpius. The red star is visible in the August night sky.

How can astronomers study distant stars? They certainly cannot travel there with today's technology: A spacecraft flying at the speed of light would take 600 years to arrive at Antares. Ohnaka's group used the European Southern Observatory's Very Large Telescope Interferometer (VLTI) in Cerro Paranal, Chile, to observe the motion of the carbon monoxide gas in Antares's atmosphere.

Until now, scientists have relied on optical and ultraviolet spectroscopy to understand stars, which means they look at light to analyze the chemical compositions of stars. That method is also used to study the sun, but has its limitations. For example, though it can indicate what a star is made of, it cannot show the mechanics of atmospheric gas movement, which could answer questions about what processes Antares experiences. The use of interferometry allows Ohnaka to capture more precise images of the outer parts of distant Antares' atmosphere, down to very small measurements of angles known as milliarseconds. According to Ohnaka, the observations his group made with VLTI's multiple telescopes over the course of five nights in April 2014 were combined to paint a detailed picture of how the gas in Antares' outer atmosphere was moving.

Ohnaka's technical use of VLTI is an important preliminary step in understanding the end stages of stars, according to John Monnier, an astronomer at the University of Michigan who was not involved in the study.

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Antimony Poisoning — Not Lead — May Have Contributed to the Roman Empire’s Fall

A section of the Anio Vetus aqueduct stands in the countryside near Tivoli, 30 kilometers out of Rome, on September 28, 2013.
Lead often takes the blame for the fall of the Roman Empire. Lead water pipes, lead cooking vessels, and lead utensils poisoned unwitting Romans, causing neurological damage, fertility disorders, and other problems — or so the story goes.

But researchers who published a study in the journal Toxicology Letters now claim the theory could be wrong.

Studying a 40-milligram fragment of an ancient lead pipe from Pompeii — the Italian city destroyed by the eruption of the volcano Mt. Vesuvius almost 2,000 year ago — the researchers discovered antimony, a chemical that’s even more toxic than lead.

Given how the inside of lead pipes calcify quickly, forming a barrier between the poisonous lead and the drinking water flowing through the pipe, antimony might have been the real culprit in bringing down one of the world’s great civilizations, said Kaare Lund Rasmussen, a study co-author and an expert in archaeological chemistry at the University of Southern Denmark.

“This is the first time that you see that it is possible they died of antimony poisoning instead of lead poisoning or both,” he said.

A grey metal-like chemical used in making lead batteries, electronics, and other products, antimony is especially common in groundwater near volcanoes, so Rasmussen said it’s crucial to look at pipes in other Roman cities. He expected Italian researchers who have the best access to Roman archeological sites would likely lead that inquiry.

“It’s only one sample,” said Rasmussen. “We know we should measure more.”

A lead pipe sample is analyzed at University of Southern Denmark.
But there’s little doubt Pompeiians were imbibing antimony that quickly causes vomiting, diarrhea, and dehydration, unlike lead poisoning that can take months or even years to develop, he said. Severe antimony poisoning can also damage the liver and kidneys and trigger cardiac arrest.

Rasmussen didn’t know how or why Pompeiians and other Romans might have kept drinking the water if it caused sickness. But he noted that today plenty of people continue to eat unhealthful foods despite health warnings even when those foods might even make them sick — think 39-cent hamburgers, fries, and strawberry shakes.

The levels of antimony in Roman water lines also might have been slight, so the casual water drinker might not have made a connection between quenching their thirst and an upset stomach, he added. “Maybe it’s not so acutely toxic,” he said. “Maybe it was just half or one-tenth of what’s lethal. Then after a while you die from it.”

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Aug 17, 2017

Astrophysicists predict Earth-like planet in star system only 16 light years away

This is the GJ832 system.
Astrophysicists at the University of Texas at Arlington have predicted that an Earth-like planet may be lurking in a star system just 16 light years away.

The team investigated the star system Gliese 832 for additional exoplanets residing between the two currently known alien worlds in this system. Their computations revealed that an additional Earth-like planet with a dynamically stable configuration may be residing at a distance ranging from 0.25 to 2.0 astronomical unit (AU) from the star.

"According to our calculations, this hypothetical alien world would probably have a mass between 1 to 15 Earth's masses," said the lead author Suman Satyal, UTA physics researcher, lecturer and laboratory supervisor. The paper is co-authored by John Griffith, UTA undergraduate student and long-time UTA physics professor Zdzislaw Musielak.

The astrophysicists published their findings this week as "Dynamics of a probable Earth-Like Planet in the GJ 832 System" in The Astrophysical Journal.

UTA Physics Chair Alexander Weiss congratulated the researchers on their work, which underscores the University's commitment to data-driven discovery within its Strategic Plan 2020: Bold Solutions | Global Impact.

"This is an important breakthrough demonstrating the possible existence of a potential new planet orbiting a star close to our own," Weiss said. "The fact that Dr. Satyal was able to demonstrate that the planet could maintain a stable orbit in the habitable zone of a red dwarf for more than 1 billion years is extremely impressive and demonstrates the world class capabilities of our department's astrophysics group."

Gliese 832 is a red dwarf and has just under half the mass and radius of our sun. The star is orbited by a giant Jupiter-like exoplanet designated Gliese 832b and by a super-Earth planet Gliese 832c. The gas giant with 0.64 Jupiter masses is orbiting the star at a distance of 3.53 AU, while the other planet is potentially a rocky world, around five times more massive than the Earth, residing very close its host star -- about 0.16 AU.

For this research, the team analyzed the simulated data with an injected Earth-mass planet on this nearby planetary system hoping to find a stable orbital configuration for the planet that may be located in a vast space between the two known planets.

Gliese 832b and Gliese 832c were discovered by the radial velocity technique, which detects variations in the velocity of the central star, due to the changing direction of the gravitational pull from an unseen exoplanet as it orbits the star. By regularly looking at the spectrum of a star -- and so, measuring its velocity -- one can see if it moves periodically due to the influence of a companion.

"We also used the integrated data from the time evolution of orbital parameters to generate the synthetic radial velocity curves of the known and the Earth-like planets in the system," said Satyal, who earned his Ph.D. in Astrophysics from UTA in 2014. "We obtained several radial velocity curves for varying masses and distances indicating a possible new middle planet," the astrophysicist noted.

For instance, if the new planet is located around 1 AU from the star, it has an upper mass limit of 10 Earth masses and a generated radial velocity signal of 1.4 meters per second. A planet with about the mass of the Earth at the same location would have radial velocity signal of only 0.14 m/s, thus much smaller and hard to detect with the current technology.

Read more at Science Daily

Four Earth-sized planets detected orbiting the nearest sun-like star

This illustration compares the four planets detected around the nearby star tau Ceti (top) and the inner planets of our solar system (bottom).
A new study by an international team of astronomers reveals that four Earth-sized planets orbit the nearest sun-like star, tau Ceti, which is about 12 light years away and visible to the naked eye. These planets have masses as low as 1.7 Earth mass, making them among the smallest planets ever detected around nearby sun-like stars. Two of them are super-Earths located in the habitable zone of the star, meaning they could support liquid surface water.

The planets were detected by observing the wobbles in the movement of tau Ceti. This required techniques sensitive enough to detect variations in the movement of the star as small as 30 centimeters per second.

"We are now finally crossing a threshold where, through very sophisticated modeling of large combined data sets from multiple independent observers, we can disentangle the noise due to stellar surface activity from the very tiny signals generated by the gravitational tugs from Earth-sized orbiting planets," said coauthor Steven Vogt, professor of astronomy and astrophysics at UC Santa Cruz.

According to lead author Fabo Feng of the University of Hertfordshire, UK, the researchers are getting tantalizingly close to the 10-centimeter-per-second limit required for detecting Earth analogs. "Our detection of such weak wobbles is a milestone in the search for Earth analogs and the understanding of the Earth's habitability through comparison with these analogs," Feng said. "We have introduced new methods to remove the noise in the data in order to reveal the weak planetary signals."

The outer two planets around tau Ceti are likely to be candidate habitable worlds, although a massive debris disc around the star probably reduces their habitability due to intensive bombardment by asteroids and comets.

The same team also investigated tau Ceti four years ago in 2013, when coauthor Mikko Tuomi of the University of Hertfordshire led an effort in developing data analysis techniques and using the star as a benchmark case. "We came up with an ingenious way of telling the difference between signals caused by planets and those caused by star's activity. We realized that we could see how star's activity differed at different wavelengths and use that information to separate this activity from signals of planets," Tuomi said.

The researchers painstakingly improved the sensitivity of their techniques and were able to rule out two of the signals the team had identified in 2013 as planets. "But no matter how we look at the star, there seem to be at least four rocky planets orbiting it," Tuomi said. "We are slowly learning to tell the difference between wobbles caused by planets and those caused by stellar active surface. This enabled us to essentially verify the existence of the two outer, potentially habitable planets in the system."

Sun-like stars are thought to be the best targets in the search for habitable Earth-like planets due to their similarity to the sun. Unlike more common smaller stars, such as the red dwarf stars Proxima Centauri and Trappist-1, they are not so faint that planets would be tidally locked, showing the same side to the star at all times. Tau Ceti is very similar to the sun in its size and brightness, and both stars host multi-planet systems.

The data were obtained by using the HARPS spectrograph (European Southern Observatory, Chile) and Keck-HIRES (W. M. Keck Observatory, Mauna Kea, Hawaii).

Read more at Science Daily