Nov 5, 2016
The object QSO B0218+357 is a blazar, a specific type of black hole. Researchers now assume that there is a supermassive black hole at the center of every galaxy. Black holes, into which matter is currently plunging are called active black holes. They emit extremely bright jets. If these bursts point towards Earth, the term blazar is used.
Full moon prevents the first MAGIC observation
The event now described in "Astronomy & Astrophysics" took place 7 billion years ago, when the universe was not even half its present age. "The blazar was discovered initially on 14 July 2014 by the Large Area Telescope (LAT) of the Fermi satellite," explains Razmik Mirzoyan, scientist at the Max Planck Institute for Physics and spokesperson for the MAGIC collaboration. "The gamma ray telescopes on Earth immediately fixed their sights on the blazer in order to learn more about this object."
One of these telescopes was MAGIC, on the Canary Island of La Palma, specialized in high-energy gamma rays. It can capture photons -- light particles -- whose energy is 100 billion times higher than the photons emitted by our Sun and a thousand times higher than those measured by Fermi-LAT. The MAGIC scientists were initially out of luck, however: A full moon meant the telescope was not able to operate during the time in question.
Gravitational lens deflects ultra-high-energy photons
Eleven days later, MAGIC got a second chance, as the gamma rays emitted by QSO B0218+357 did not take the direct route to Earth: One billion years after setting off on their journey, they reached the galaxy B0218+357G. This is where Einstein's General Theory of Relativity came into play.
This states that a large mass in the universe, a galaxy, for example, deflects light of an object behind it. In addition, the light is focused as if by a gigantic optical lens -- to a distant observer, the object appears to be much brighter, but also distorted. The light beams also need different lengths of time to pass through the lens, depending on the angle of observation.
This gravitational lens was the reason that MAGIC was able, after all, to measure QSO B0218+357 -- and thus the most distant object in the high-energy gamma ray spectrum. "We knew from observations undertaken by the Fermi space telescope and radio telescopes in 2012 that the photons that took the longer route would arrive 11 days later," says Julian Sitarek (University of ?ódz, Poland), who led this study. "This was the first time we were able to observe that high-energy photons were deflected by a gravitational lens."
Read more at Science Daily
|Close-up of the ornamental white feathers on a pair of Crescent Honeyeaters, Phylidonyris pyrrhopterus, one of the species of birds examined in this study.|
Tropical birds are well known for their colorful appearance: vibrantly colored macaws, parakeets and parrots are widely considered to be the quintessential birds of this region. The popularity of these birds leads many to assume that tropical climates are home to a greater proportion of colorful birds than temperate climates. But do birds evolve to become more colorful when they move to the tropics? Research from Dr. Nicholas Friedman, who is part of the Biodiversity and Biocomplexity Unit at the Okinawa Institute of Science and Technology Graduate University (OIST), helps answer this question.
As part of his research in collaboration with Vladimír Remeš at Palacký University in the Czech Republic, Friedman headed to Australia to examine the feathers of different birds across the country and its neighboring tropical islands to see if there was a correlation between geographical climate zone and color pattern. Australia is home to a rich mixture of species, many of which are found nowhere else. The fact that Australian species were geographically isolated from the rest of the world for so long makes it an excellent place to study evolution. A trip to Australia as a young man contributed to Charles Darwin's pivotal work on evolution, On the Origin of Species.
Friedman began his study at the Australian National Wildlife Collection, where he examined bird specimens from different regions of Australia. A total of 137 different species from two major songbird families were examined. Songbirds originated in Australia nearly 30 million years ago. Research suggests that these birds began diversifying there before colonizing other parts of the world. The familial relationships of the birds that Friedman examined were compared using an evolutionary tree based on the birds' DNA. Friedman then used a special instrument to measure the color of the feathers in particular places on the birds. Birds can see a wider range of colors than humans can, and many are even able to see colors in the UV spectrum in addition to those in the 'visible' spectrum, so the differences in color patterns between birds may appear more pronounced to birds than they appear to humans. Next, Friedman used data from satellites to describe the geographical region each species lives in. He looked at vegetation, precipitation, and humidity of each region, then combined this data with the evolutionary relationships and color measurements of the birds.
The results of this study, published in Global Ecology and Biogeography, show that bird species do not evolve more colorful feathers in the tropics compared to their cousins in temperate climates. "If you look at birds in the tropics, there are a lot of colorful birds that stand out. But there are really more species in general there, and there are just as many more of the little brown ones" describes Friedman. "Instead, birds living in the harsh arid climates of inland Australia tended to have fancier colors than those in the lush tropical islands. Since desert birds have to scramble for mates during the wet season, we think they may be evolving colors that can attract mates quickly."
Meanwhile, birds thriving in climates with more precipitation and vegetation are darker in color overall, while desert birds tend to be lighter. "The pattern is really clear" Friedman reports, "birds living in the desert tend to be more grey on their backs, while birds living in the forest have evolved to be more of a dark green -- we think they are evolving these colors to match their background." This would be an example of natural selection, in this case more camouflaged organisms can survive and pass on their genes.
Read more at Science Daily
Nov 4, 2016
The spacecraft made many discoveries, including finding several moons at each system. But long after Voyager 2 left Uranus behind in 1989, and with fewer spacecraft exploring the outer solar system, we are still finding new satellites. Some, surprisingly, are from old Voyager data being reanalyzed with new techniques.
Other finds are from the venerable Hubble Space Telescope, which has been in Earth orbit since April 1990. It shows that even decades after Voyager, there are likely new moons waiting to be found -- especially with the sharper eye of the James Webb Space Telescope slated to start working in 2018.
Part of the secret appears to be the Cassini factor. Scientists have been learning a lot about ring behavior, and how satellites affect them, since the mission has been examining Saturn in 2004. Recently, scientists applied that understanding to the Uranus system, using data from Voyager obtained in 1986. They found regular patterns in the rings that suggest there could be moonlets there.
"There were some very clear periodic variations in the structure of the alpha and the beta rings," said University of Idaho physics researcher Matthew Hedman, who was a participant in the experiment led by doctoral student Rob Chancia, in an interview with Seeker. "The opacity of the ring just changed in a periodic way over a couple of kilometers. The thing that was weird about the structure was it had different wavelengths in different places. It wasn't the same kind all the way around the ring, which a lot of ring structures are."
|A composite Hubble Space Telescope image showing Neptune (color) and a new moon (black and white).|
But here's where the story stops, at least for now. Hedman and his graduate students will publish the results shortly in the Astronomical Journal in the hopes that somebody more experienced in spacecraft imaging can find moonlets. Hedman will continue investigating and comparing ring structures across the solar system, as not everything yet can be explained by moons.
One researcher who may carry the torch is a veteran moon-hunter himself. The SETI Institute's Mark Showalter was the one who first described moonlet rakes. He's been processing spacecraft images since Voyager; he was a grad student when the spacecraft passed by Saturn, and was doing his postdoctoral work during the Uranus and Neptune encounters.
Thirty years of moon-hunting came in very handy for him in 2013, when his team announced they had discovered yet another moon around Neptune, using Hubble. So how could Voyager go right past the moon and not easily find it? The camera was built on 1970s technology, and it was working in low light, Showalter said. He also found the Uranian moons Cupid and Mab (using Hubble) in 2003; one was practically invisible in Voyager data when he looked again, while the other one was barely detectable.
One of his next projects will be looking again at Uranus to see if those moonlets are there, he said. "I do have a lot of Hubble data of the Uranus system," he said in an interview. "Now that I know where to look, based on Rob and Matt's results, I do plan to do a search of the existing archive of Hubble data from Uranus for any chance to pick out these little objects."
|A moon is spotted around the dwarf planet Makemake in this Hubble Space Telescope Image from April 2015.|
Other moon mysteries lie in other parts of the solar system. When New Horizons was on its way to Pluto, the moons Styx and Kerberos were found in 2011 and 2012, respectively. Nix was also found in 2005, the year before it launched. (All three finds included researchers part of the "Pluto Companion Search Team", who were tasked specifically for New Horizons' flight.) Previously, only the moon Charon was known — discovered in 1978.
"The Pluto team is intrigued that such a small [dwarf] planet can have such a complex collection of satellites," NASA said in a 2012 statement. "The new discovery provides additional clues for unraveling how the Pluto system formed and evolved. The favored theory is that all the moons are relics of a collision between Pluto and another large Kuiper belt object billions of years ago."
Read more at Discovery News
Dubbed the Paris Agreement, it's the first-ever deal binding all the world's nations, rich and poor, to a commitment to cap global warming caused mainly from the burning of coal, oil and gas.
"A historic day for the planet," said the office of President Francois Hollande of France, host to the 2015 negotiations that yielded the breakthrough pact.
"Humanity will look back on Nov. 4, 2016, as the day that countries of the world shut the door on inevitable climate disaster," UN climate chief Patricia Espinosa and Moroccan Foreign Minister Salaheddine Mezouar said in a joint statement.
Mezouar will preside over the UN meeting opening in Marrakesh on Monday.
"It is also a moment to look ahead with sober assessment and renewed will over the task ahead," they said.
This meant drastically and urgently cutting emissions, which requires political commitment and considerable financial investment.
The urgency was brought home by a UN report Thursday warning that emissions trends were steering the world towards climate "tragedy."
By 2030, said the UN Environment Programme, annual emissions will be 13 to 15 billion tons of carbon dioxide equivalent (CO2e) higher than the desired level of 46 billion tons.
The 2014 level was about 58 billion tons.
2016 is on track to become the hottest year on record, and carbon dioxide levels in the atmosphere passed an ominous milestone in 2015.
On Friday, the Eiffel Tower in Paris as well as public buildings in Marrakesh, Adelaide, Brussels, New Delhi and Sao Paulo were to be lit in green to mark the entry into force of the pact meant to stop the rot.
That historic agreement was finally endorsed in the French capital last December, after years of complex and divisive negotiations, but the ratification was reached with record speed.
At least 55 parties to the UN's climate convention (UNFCCC), responsible for at least 55 percent of global greenhouse gas emissions, had to ratify it for it to take effect.
It passed the threshold last month, and by Friday had been ratified by 97 of the 197 UNFCCC parties, representing 67.5 precent of emissions, according to France's environment minister Segolene Royal, the outgoing president of the UN talks.
"It is a magnificent day, concluding years of hard work," Royal told journalists in Paris.
"We must maintain this extraordinary momentum by encouraging countries to continue ratifying the deal, and by moving full steam ahead with our preparations to put it into action across the world," Europe's climate commissioner Miguel Canete added in a statement.
A major doubt looms over the process, however, as diplomats gear up for 11 days of talks in Morocco to discuss way of putting the agreement's political undertakings into practice.
U.S. Republican nominee Donald Trump has threatened to "cancel" Washington's participation in the agreement if he is elected president on Nov. 8.
Read more at Discovery News
The site, known as Warratyi, shows Aboriginal Australians settled the arid interior of the country around 49,000 years ago — some 10,000 years earlier than previously thought.
The shelter, about 550 kilometers north of Adelaide, also contains the first reliably dated evidence of human interaction with megafauna.
Artefacts excavated at the site also push back the earliest-known dates on the development of key bone and stone axe technologies and the use of ochre in Australia.
Lead author Giles Hamm, a consultant archaeologist and doctoral student at La Trobe University, found the site with local Adnyamathanha elder Clifford Coulthard while surveying gorges in the northern Flinders Ranges.
"A man getting out of the car to go to the toilet led to the discovery of one of the most important sites in Australian pre-history."
Mr Hamm said during a survey of the gorge they noticed a rock shelter with a blackened roof about 20 meters above the creek bed.
"Immediately when we saw that we thought, 'Wow, that's people lighting fires inside that rock shelter, that's human activity'," he said.
At the time they had no idea how significant the find was, Mr Hamm admitted, and thought maybe it would reach back about 5,000 years.
Working with the Adnyamathanha people over the past nine years, Mr Hamm and colleagues recovered from the one-meter-deep excavations around 4,300 artifacts and 200 bone fragments from 16 mammals and one reptile.
Importantly dating of the artifacts and fossil finds show humans occupied the site from 49,000 to 46,000 years ago.
Mr Hamm said the significance of the site was the combination of its age and geographic location.
The previous oldest-known site in the arid zone, located at Puritjarra in western Central Australia, is around 38,000 years old.
However, Mr Hamm said it was likely the climate was more favorable when they arrived.
"They got there before it became really arid," he said.
"In one sense they were trapped in the Flinders Ranges because once the climate changed [due to the last glacial maximum] it was too risky to move out of these well-watered ranges that had these permanent springs."
It was a view supported by palaeoanthropologist Michael Westaway at Griffith University, who was part of a recent genomic study that confirmed modern Aboriginal Australians are the descendants of the first people to inhabit Australia and showed they adapted genetically to survive in the desert.
"Our DNA paper suggested the arid center at 50,000 years ago was not really a barrier to the movement of people, and this seems to be what Giles is suggesting — people were able to migrate south quite quickly," Dr Westaway said.
Among the other significant artifact finds at the site was the earliest-known use of ochre in Australia and South-East Asia around 49,000-46,000 years ago.
Mr Hamm said they had pushed back the dates on the development of technologies such as bone needles (40,000-38,000 years ago), wood-handled stone tools (at least 24,000 years ago) and gypsum use (40,000-33,000 years ago).
The site also provided reliably dated evidence of hafted axe technology about 38,000 years ago.
Co-author Professor Gavin Prideaux pointed to the discovery of bones from the extinct giant wombat-like Diprotodon optatum and eggs from an ancient giant bird as important evidence of interaction with ancient humans which would have an impact on the debate over the extinction of megafauna.
Professor Prideaux, from Flinders University's School of Biological Sciences, said the only previous site in Australia where megafauna remains and human artifacts had been found together was Cuddie Springs in NSW, which had become the subject of controversy over the accuracy of dating.
"One good thing about this study ... is there's no doubt there are megafauna remains in the form of Diprotodon and a giant bird in that rock shelter in a well-dated, well-stratified context sometime between 45,000 and 50,000 years ago," Professor Prideaux said.
"The only way those bones and shells got there [because of the steep incline up to the rock shelter] is because people brought them there [to eat] ... in terms of megafauna that's the really significant finding."
Read more at Discovery News
Muddy waters rushed into my family's home as well as into the homes of thousands of Florentines. The flood came with little warning, claiming the lives of 34 people. Raging torrents entered streets, houses, shops, museums, churches and libraries.
Thousands of frescoes, paintings, sculptures and rare books were destroyed or terribly damaged by slime in one of the greatest cultural disasters of modern times.
Such was the devastation that an army of young volunteers — known as "the mud angels" — came from all over Europe and America to help rescue Florence's treasures.
The prompt intervention of restorers and new methods of restoration in the following decades made it possible to salvage almost all of the damaged artworks.
One masterpiece, however, was considered beyond saving. Giorgio Vasari's "Last Supper," a large painting on five wooden panels, remained for four decades in storage, and restorers did not even dare to touch the cracked panels.
Today, Vasari's "Last Supper," the last major flood-damaged artwork that remained untreated, has been returned to public viewing in Santa Croce Church.
"It's a dream that has become reality," Marco Ciatti, head of the renowned restoration center Opificio delle Pietre Dure (OPD) in Florence, said.
More than 8 feet high and 21 feet across, Vasaris' painting was commissioned by the nuns of the Murate convent in Florence. Vasari was best known for writing one of the first great books of art history, "Lives of the Most Excellent Italian Painters, Sculptors." He was also a painter and architect.
The nuns' cloistered rule prohibited male artists from staying in the convent, so Vasari split the painting of Christ and his disciples into five portable poplar panels so he could work on the piece elsewhere and then transport it into the convent in parts. He completed the monumental painting in 1546.
After being moved several times, the "Last Supper" was installed at the museum of Santa Croce Church. When the river flooded, it remained completely immersed in filthy, oily water for at least 12 hours.
In the first hours after the flood, a team of restorers, led by art conservator Umberto Baldini, separated the panels and attached protective sheets of Japanese paper all over them in a desperate attempt to prevent the paint from flaking off.
"We can now say that system has worked. However, the glue used to attach the paper was a very strong acrylic resin which over the decades became an impermeable plate," Ciatti told Seeker.
|One of the panels as it appeared 10 years ago.|
Ciatti's team had to face several issues. First, there was the problem of the wood support and the ground layer underneath the painting. Consisting of a binder, chalk and animal glue, this layer was the surface for the paint.
"As the wood panels dried, they shrank, stressing the painting's surface. Meanwhile the chalk and glue, which are soluble in water, degraded dramatically," Ciatti said.
"The contraction of the wood and the decohesion of the ground layer caused the painted surface to detach," he added.
Meanwhile, restorers faced another problem: how to peel the paper and the resin away without removing Vasari's paint.
Ten years ago, Roberto Bellucci, senior painting conservator at the Opificio, figured out how to remove the paper layer and the acrylic resin used as a glue. During my visit at the Opificio, I was lucky to see a bearded St. Peter emerging from the paper crust for the first time in 40 years.
Surprisingly, the blue and yellow of St. Peter's clothes were still vivid and looked much as they did before the flood.
"The color was still there, beneath the dirt, the glue and the paper. Without Baldini's emergency intervention, the painting would have been lost forever," Ciatti said.
|Restoration of Giorgio Vasari's Last Supper|
Senior painting conservator Ciro Castelli returned the wood to its original size by taking advantage of the splits that had opened in the waterlogged panels. Tiny slivers of poplar wood were inserted in the gaps to counter the contraction of the wood.
Using special synthetic resins, Bellucci managed to restore adhesion of the flaked paint to the surface, while securing the ground layer.
"The result is amazing. It went beyond my expectations. Our success is due to innovative products and technologies, but most of all to the dexterity of our restorers," Ciatti said.
The "Last Supper" now appears in all its glory of vibrant color, light and shadow.
Ciatti explained that any minor loss of color in the painting was not caused by the flood but likely by previous restoration efforts. He found inscriptions describing at least two interventions on the painting in 1594 and 1718.
Read more at Discovery News
Over the past several years, people with a degenerative eye disease could recover some vision through a high-tech prosthetic system. Patients went from complete darkness to seeing crude outlines of objects and people. Now Second Sight, the company behind that bionic eye, is developing neurotechnology that promises to do the same for millions worldwide who are blind from other causes.
Recently the company announced they had completed a successful proof of concept study at UCLA. A team there sent wireless signals to the brain of a blind patient through a simple device, which produced spots of light for her.
"It told us that yes, you can stimulate the visual cortex, you can produce a spot of light, and the patient can see that spot and localize it," Second Sight president and CEO Will McGuire told Seeker. Those results are informing the creation of a new product for artificial vision called Orion I that the company hopes to begin testing next year.
Orion I differs from Second Sight's current Argus II system, which has FDA approval to treat patients in the advanced stages of a degenerative disease that destroys the retina known as retinitis pigmentosa. Eventually the person can't tell whether the sun is out or an overhead light is turned on, McGuire explained.
Argus II has three main components: eyewear containing a video camera that captures and transmits footage, a small wearable video processing unit and a tiny electronics package that must be surgically implanted in the eye by a specialist. The glasses transmit imaging data in real time to 60 electrodes that are attached to the retina. These electrodes light up in patterns that replicate what the camera sees.
Second Sight, which has offices in California and Switzerland, has treated around 200 patients with the Argus II. McGuire said that just under 400,000 people worldwide have legal blindness from retinitis pigmentosa.
However, an estimated six million people globally are blindness for other reasons including cancer, trauma, glaucoma and diabetes. In those cases, the eye or optical nerve is completely nonfunctioning. Stimulating the retina won't help. Instead, the Second Sight team wants to bypass the retina and go straight to the surface of the brain responsible for vision.
Read more at Discovery News
Nov 3, 2016
The great power of MUSE is that it creates thousands of images of the nebula at the same time, each at a different wavelength of light. This allows astronomers to map out the chemical and physical properties of the material at different points in the nebula.
Images of similar structures, the famous Pillars of Creation* in the Eagle Nebula and formations in NGC 3603, were combined with the ones displayed here. In total ten pillars have been observed, and in so doing a clear link was observed between the radiation emitted by nearby massive stars and the features of the pillars themselves.
In an ironic twist, one of the first consequences of the formation of a massive star is that it starts to destroy the cloud from which it was born. The idea that massive stars will have a considerable effect on their surroundings is not new: such stars are known to blast out vast quantities of powerful, ionising radiation -- emission with enough energy to strip atoms of their orbiting electrons. However, it is very difficult to obtain observational evidence of the interplay between such stars and their surroundings.
The team analysed the effect of this energetic radiation on the pillars: a process known as photoevaporation, when gas is ionised and then disperses away. By observing the results of photoevaporation -- which included the loss of mass from the pillars -- they were able to deduce the culprits. There was a clear correlation between the amount of ionising radiation being emitted by nearby stars, and the dissipation of the pillars.
Read more at Science Daily
|Amphibians are a group that is highly sensitive to global warming due to the permeability of their skin and their complex lifecycle, which combines an aquatic stage as larvae and a terrestrial stage when young and as adults.|
Global warming is causing not only a general increase in temperatures, but also an increase in the frequency and intensity of extreme weather events, such as flooding, heat waves and droughts. These environmental changes pose a challenge for many organisms, among them amphibians, who have to change their behaviour, physiology and life strategies in order to survive.
Researchers at the Universities of Lisbon (Portugal) and Uppsala (Sweden) studied the behaviour of three kinds of amphibians that inhabit the Iberian Peninsula: the European tree frog (Hyla arborea), the Mediterranean tree frog (Hyla meridionalis) and the Iberian painted frog (Discoglosus galganoi) to find out what effect heat waves can have on their diets.
As Germán Orizaola, co-author of the study published in the journal Ecology and a researcher at the Swedish university states "Among the many challenges climate change poses to natural ecosystems, the effect it can have on the dietary preferences of living organisms is a field of study that has been attracting researchers' attention in recent years."
Amphibians are a group that is highly sensitive to global warming due to the permeability of their skin and their complex lifecycle, which combines an aquatic stage as larvae and a terrestrial stage when young and as adults. "In fact, they are already experiencing sharp declines in population and extinction on a global scale, and they have become the focus of several research and conservation programmes in recent decades," the scientist explains.
A vegetable-based, animal-based or mixed diet
The researchers conducted a laboratory experiment in which they exposed the larvae of these three species to various kinds of heat waves, which varied in duration and intensity, by increasing the temperature of the water where they were growing.
"The larvae were kept in three different sets of conditions: with a solely vegetable-based diet, solely animal-based or a mixed diet. This third situation allowed us to assess whether they modified their diets towards a greater or lower percentage of vegetable matter," Orizaola adds.
They also examined the relationship between various carbon and nitrogen isotopes in the tissue of larvae with a mixed diet and compared them with those of exclusively vegetable-based or animal-based 'menus'. This enabled them to reconstruct the type of diet larvae exposed to a combined diet selected..
"Our results indicated first that larvae of various species have a diet adapted to the conditions under which they reproduce. The painted frog, which reproduces when it is cold, has a carnivorous diet, while the Mediterranean tree frog, which reproduces during the hottest season of the year, maintains a vegetarian diet," the investigator notes.
The most important result is that these larvae have very flexible dietary habits. All three species increased the percentage of vegetables consumed during heat waves. By analysing these larvae's rates of survival, growth and development, reduced effectiveness of the carnivorous diet in favour of a vegetarian diet was discovered in hot conditions.
Read more at Science Daily
Robert Korty, associate professor in the Department of Atmospheric Sciences at Texas A&M, along with colleagues from China, Norway, and the University of Wisconsin, have had their work published in the current issue of PNAS (Proceedings of the National Academy of Sciences).
The team studied storm development from the Pliocene era, roughly three million years ago, and chose that time period because it was the last time Earth had as much carbon dioxide as it does now, and the changes in climate from it can play a major role in storm formation and intensity.
Using computer models and simulations, the team found an increase in the average intensity during the period and the storms most often moved into higher latitudes -- to a more northward direction.
"There seems to be a limit on how strong these ancient storms might be, but the number getting close to the limit appears to be larger during warmer periods," Korty explains.
"They reached their peak intensity at higher latitudes, following an expansion of tropical conditions with warming. It is consistent with smaller changes in the same patterns that we have observed over recent decades and project to continue over the next 100 years. I think it gives us greater confidence in some trends we are witnessing about how storms may change in future years."
Researchers today know that the oceans continued to be relatively warm during the Pliocene era, though there has been some uncertainty where waters were warmest. Their study found that the increase in average intensity and in the poleward expansion occurred regardless of where the greatest change in temperatures occurred in the Pliocene.
Read more at Science Daily
That this symbiotic relationship arose during a time of massive worldwide coral-reef expansion suggests that the interconnection of algae and coral is crucial for the health of coral reefs, which provide habitat for roughly one-fourth of all marine life. Reefs are threatened by a trend in ocean warming that has caused corals to expel algae and turn white, a process called coral bleaching.
Published in the journal Science Advances, the study found strong evidence of this coral-algae relationship in fossilized coral skeletons dating back more than 210 million years to the late Triassic period, a time when the first dinosaurs appeared and Earth's continents were a single land mass known as Pangea. Although symbiosis is recognized to be important for the success of today's reefs, it was less clear that that was the case with ancient corals.
"It is important to know how far back in time symbiosis evolved because it gives insight into how important symbiosis is to the health of coral reefs," said Daniel Sigman, Princeton's Dusenbury Professor of Geological and Geophysical Sciences and a member of the Princeton Environmental Institute. "It appears that the origin of symbiosis corresponds to the rise of coral reefs in general."
In addition to confirming that symbiosis dates back to the Triassic, the study found that the corals inhabited nutrient-poor marine environments -- not unlike today's subtropical waters -- where algae-coral symbiosis played a major role in driving reef development.
"The onset of symbiosis with algae was highly profitable for corals," said lead author Jaroslaw Stolarski, a professor of biogeology at the Institute of Paleobiology at the Polish Academy of Sciences. "It allowed them to survive in very nutrient-poor waters, and at the same time grow and expand."
Algae belonging to the group known as dinoflagellates live inside the corals' tissues. The algae use photosynthesis to produce nutrients, many of which they pass to the corals' cells. The corals in turn emit waste products in the form of ammonium, which the algae consume as a nutrient.
This relationship keeps the nutrients recycling within the coral rather than drifting away in ocean currents and can greatly increase the coral's food supply. Symbiosis also helps build reefs -- corals that host algae can deposit calcium carbonate, the hard skeleton that forms the reefs, up to 10 times faster than non-symbiotic corals.
Finding out when symbiosis began has been difficult because dinoflagellates have no hard or bony parts that fossilize. Instead, the researchers looked for three types of signatures in the coral fossils that indicate the past presence of algae: fossil microstructures, levels of different types of carbon and oxygen, and levels of two forms of nitrogen.
First author Katarzyna Frankowiak of the Institute of Paleobiology at the Polish Academy of Sciences conducted the microstructural analysis with assistance from Marcelo Kitahara of the Federal University of Sao Paulo in Brazil, Maciej Mazur of the University of Warsaw, and Anders Meibom of the Ecole Polytechnique Federale de Lausanne and the Universite de Lausanne. Their analysis revealed regularly spaced patterns of growth consistent with the symbiotic corals' reliance on algal photosynthesis, which only takes place during daylight.
Frankowiak and Anne Gothmann, who earned her Ph.D. from Princeton's Department of Geosciences in 2015 and is now a postdoctoral researcher at the University of Washington, measured the ratios of different types of oxygen and carbon and found that the results matched what would be expected when symbiosis occurs.
The third approach, determining the forms of nitrogen -- which derive in part from the ammonium the corals had excreted -- was conducted by Xingchen (Tony) Wang, who earned his doctoral degree in geosciences from Princeton in 2016 and is now a postdoctoral research fellow working with Sigman.
The nitrogen atoms, which are trapped in the fossil's calcium-carbonate matrix, come in two forms, or isotopes, that vary only by how many neutrons they have: 14N has seven neutrons while 15N has eight neutrons, making it slightly heavier. By studying modern corals, researchers knew that symbiotic corals contain a lower ratio of 15N to 14N compared to non-symbiotic corals. The team found that the fossilized corals also had a low 15N-to-14N ratio, indicating they were symbiotic.
"Although algae were not present in the fossils, they left behind chemical signatures," Wang said. "We found strong evidence that the fossilized coral were symbiotic and that they lived in a nutrient-poor environment. We were able to link the environmental conditions from 200 million years ago to the evolution of corals."
George Stanley, a professor of geosciences at the University of Montana, had earlier explored the question of when symbiosis first evolved in corals. "This confirms a hypothesis that my colleagues and I put forth 20 years ago," said Stanley, who is familiar with the research but had no role in it. "It is really exciting to see this confirmation."
The fossils used in the study were collected in a mountainous region in Antalya, Turkey. During their lifetime, they lived in a shallow sunlit body of water called the Tethys Sea.
Read more at Science Daily
Nov 2, 2016
Freakishly mild weather coupled with a warmer-than-normal ocean are in large part responsible for the great sea ice slowdown of 2016. It's just the latest piece of evidence that 2016 is on another level when it comes to signs that the climate is changing.
The turn of the calendar toward winter and rapidly dwindling daylight usually equate to the growth of sea ice in the Arctic. After hitting a minimum in early September, sea ice regrowth got off to a blistering start. But it's speedy recolonization of the Arctic Ocean slowed to a crawl in October.
Preliminary data published by the Japanese space agency and visualized by Zach Labe, a Ph.D. student at the University of California, Irvine, show that it's the slowest regrowth on record. That includes a period at the end of October where it appears sea ice didn't grow at all.
Large areas of ice were missing at the end of October in the western Beaufort and Chukchi seas north of Alaska and the Kara and Barents seas that sit above Russia. Ted Scambos, a scientist at the National Snow and Ice Data Center, said it looks like sea ice is about 232,000 square miles below the previous record and 965,000 square miles below the October average. For perspective, the latter is an area slightly larger than the eastern half of the U.S. (and the former is roughly the size of Texas).
The main reason for the slow growth is it's been relatively warm by Arctic standards almost all month. The Arctic Ocean has been an astonishing 7°F above normal on average in October (again, this is based on preliminary data) with a number of areas much warmer than that with temperatures ranging up to 18°F warmer than usual.
"There is a strong high pressure over Scandinavia which is helping to transport warm air from the north Atlantic towards the Arctic," Julienne Stroeve, a scientist at NSIDC, said. "Ocean temperatures are also quite a bit above normal especially in the Chukchi and East Siberian Sea so that is also contributing."
It's the latest piece of dismal sea ice news in 2016. This year set a record low for the winter maximum, besting the previous record set just a year ago. Sea ice reached its the second-lowest minimum ever recorded in the region, trailing only 2012.
The lack of ice this summer allowed the Crystal Serenity, a luxury cruise ship, to traverse the Northwest Passage. There have also been a number of other months with record low sea ice this year.
Compounding the sea ice misery in the Arctic is the disappearance of sea ice that's been around for four years or more. That older sea ice essentially acts like the foundation of a house, helping support the growth of new, younger sea ice. It's also thicker and harder and less prone to melting. Without it, younger sea ice is being built on shaky ground and melts more easily each summer.
Read more at Discovery News
All of this could be explained by a big collision that took place between the Earth and a Mars-sized object early in the evolution of our solar system, according to University of Maryland researchers. After the big crash about 4.5 billion years ago, Earth's spin would have spun up. Our planet also would have tilted to an extreme degree, lying practically on its side.
Today, the system we have is much smoother thanks to gravitational interactions between the Earth, moon and sun. But these characteristics could be leftovers of what happened in ancient solar system history.
"Despite smart people working on this problem for 50 years, we're still discovering surprisingly basic things about the earliest history of our world," said Matija Cuk, a scientist at the SETI Institute and lead researcher for the simulations, in a statement. "It's quite humbling."
|A mosaic of images the NASA Galileo spacecraft took of the moon in 1992, on its way to Jupiter.|
Here's the challenge: according to physics, the debris ring (which also represents the moon's orbit immediately after it was formed) should have been in Earth's equatorial plane. Over time, tidal interactions between the Earth and the moon pushed the moon further away.
At that point, the moon's orbit should have shifted to the ecliptic, which is the path the Earth takes around the sun. In reality, however, the moon's orbit has a five degree tilt away from the ecliptic. But a new model by the science team suggests an alternate scenario, where the Earth spun very fast and the impact changed Earth's tilt to somewhere between 60 and 80 degrees.
|The Earth and the moon captured in a single image by the Galileo spacecraft in 1992, eight days after it made a close flyby of Earth.|
"Such a stalemate can last for millions of years, during which Earth kept losing its spin while the moon did not go into a wider orbit. Instead, its orbit became more tilted. Once the Earth had lost enough of its original spin, the moon broke out of this stalled state and continued its outward journey."
Read more at Discovery News
The two mummified cubs, nicknamed Uyan and Dina after the Uyandina River where they were found, were just about 1 week old when they died, likely crushed by "extensive collapse of the sediments in the den," the study's researchers wrote in a summary of their research. The report was presented as a poster here on Wednesday (Oct. 26) at the 2016 Society of Vertebrate Paleontology meeting.
"They were squished to death," said study co-researcher Olga Potapova, the collections curator at the Mammoth Site of Hot Springs, South Dakota.
The last known cave lion lived in what is now Alaska about 14,000 years ago, Potapova said. Little is known about the development of cave lions from cubs into adults, making the finding an extraordinary one, because it tells researchers about how these ancient cubs grew in comparison with their modern-day relatives, the lion (Panthera leo).
For instance, Uyan's body, which was more intact than Dina's, weighs about 6 lbs. (2.8 kilograms), which is about 4.6 lbs. (2.1 kg) heavier than a modern lion newborn, Potapova told Live Science. She added that because newborn lions don't have any identifiable sex characteristics, it's unclear whether Uyan and Dina were male or female.
Uyan's body is about the size of an adult house cat, approximately 17 inches (43 centimeters) long, Potapova said. At about 3 inches (7 cm) long, the cub's tail is just about 23 percent of its body length, "which is significantly smaller than that in modern lions," whose tails are about 60 percent of their body length, Potapova said.
Moreover, Uyan's legs had yet to grow long enough for walking, but the little one could likely crawl, Potapova said. Uyan was also a furry cub, with fur about 1.2 inches (3 cm) long on its body, Potapova noted.
Dina and Uyan were so young, they likely couldn't see yet, Potapova said. "Dina's eyelids were tightly closed, while in Uyan, the left eye was closed, but the right eyelids were positioned a little apart," Potapova wrote on the poster. However, it's unclear whether Uyan's right eyelids were already open when the animal died, or if they opened postmortem, Potapova said.
But modern lions don't open their eyes for two to three weeks after birth, and they can't even see properly for another week after that. So, given Uyan's young age at time of death, it's likely that the animal's eyes were closed when it died, Potapova said.
In modern lion cubs, the milk (baby) teeth erupt when the cub is about 3 weeks old, and permanent canines replace them when the cub is about 3 months old. However, a computer tomography (CT) scan of Uyan and Dina showed that although the cubs were still toothless, the milk and canine teeth were already erupting below the gum line in both animals.
"The advanced development of Uyan's dentition indicates that the milk teeth were likely to be shed at a sooner time, possibly at 2 months," the researchers wrote in the poster. [My, What Sharp Teeth! 12 Living and Extinct Saber-Toothed Animals]
However, because the cubs were still toothless, they likely fed by suckling milk from their mother. Uyan's stomach was empty, but a CT scan of the gut showed that the cub likely had milk just a few hours before dying, Potapova said.
Along with the cave lion mummies, which lived between 29,000 and 57,000 years ago, the researchers also found bones of approximately the same age belonging to a wooly mammoth, steppe bison, reindeer and wolf, along with two large brown bear skulls on the Uyandina's banks, Potapova said. However, these bones were collected about a year after the cubs' discovery, and so those fossils may not be from the exact same site where the cubs were found.
Read more at Discovery News
St. Anne's Well was found on the lands of a private farm on the border between the townships of Rainhill and Sutton St Helens, near Liverpool, UK.
According to Historic England Heritage, which commissioned the excavation, "the well had become completely filled with earth due to ploughing."
"When we first got to the well we found that there was very little indication of it on the surface, but after excavation it was found to be in reasonable condition," Jamie Quartermaine, an archaeologist who supervised the dig, told Discovery News.
The well was built of local sandstone blocks and consisted of a shallow square basin with two steps leading down into the bottom.
"The fabric of the well is consistent with a Medieval date," Quartermaine said.
The archaeologist noted that St. Anne is quite commonly associated with holy wells.
"This well was probably a late Medieval foundation as the cult of St. Anne did not become widespread in England until after the end of the 14th century," Quartermaine said.
The dating is important. Alexandra Walsham, professor of modern history at Cambridge's Trinity College, told Seeker that "a Medieval past for many healing wells was assumed or even invented by later antiquaries, especially in the 19th century."
After descending the steps, pilgrims submerged themselves in the pool, which was about 4 feet deep. Water seeped in from below the floor, while a stone conduit, now lost, took water from the overflow of the well, which measures 6.5 feet by 6.5 feet.
According to Historic England Heritage, local legend suggests St. Anne's Well was associated with a nearby priory of about 12 monks, which was lost during Henry VIII's draconian dissolution of the monasteries.
The legend said the priory held an extensive estate from which the monks had an income. The story goes that St. Anne had bathed in the well, which was reputed to have healing powers for eye and skin afflictions.
"The well attracted numbers of pilgrims, necessitating the building of a small three-roomed structure around the well and the custodianship of two of the monks," Quartermaine said.
According to local folklore, a dispute rose in the 16th century about boundaries and access to the well between the prior, Father Delwaney, and Hugh Darcy, the estate manager of the neighboring landowner.
One day, when the two stood nearby the well, Darcy predicted the prior would not be in position for much longer. Two days later the king's commissioners arrived and took possession of the priory and the well.
Father Delwaney promptly understood Darcy's role in the action as he was clearly known to the commissioners.
"With teeth tightly clenched, and his face white with suppressed passion," the prior hissed out his curse, according to a 1877 report on local legends in the St. Helens Leader.
Darcy would be dead within a year and a day, Delwaney predicted. He then collapsed and died himself.
A series of disgraces fell on Darcy: three months after the curse, his only son died of a mysterious illness. He suffered financial losses and "plunged recklessly into dissipation," according to the St. Helens Leader.
Read more at Discovery News
Nov 1, 2016
|This example demonstrates the relationship between size and number: usually, more items will take up more space in the shopping cart, unless you have a few larger, denser items.|
The most widely accepted theory today suggests people are born with a "sense of numbers," an innate ability to recognize different quantities, like the number of items in a shopping cart, and that this ability improves with age. Early math curricula and tools for diagnosing math-specific learning disabilities such as dyscalculia, a brain disorder that makes it hard to make sense of numbers and math concepts, have been based on that consensus.
Ph.D. students Naama Katzin and Maayan Harel and Prof. Avishai Henik, all from the BGU Department of Psychology and the Zlotowski Center for Neuroscience, collaborated with Dr. Tali Leibovich from the Numerical Cognition Laboratory at the Department of Psychology & Brain and Mind Institute, University of Western Ontario. Dr. Leibovich was formerly a Ph.D. researcher at BGU's Department of Brain and Cognitive Sciences and the Zlotowski Center.
"If we are able to understand how the brain learns math, and how it understands numbers and more complex math concepts that shape the world we live in, we will be able to teach math in a more intuitive and enjoyable way," says Dr. Leibovich. "This study is the first step in achieving this goal."
The study challenges the prevalent "sense of numbers" theory. Other theories suggest that a "sense of magnitude" that enables people to discriminate between different "continuous magnitudes," such as the density of two groups of apples or total surface area of two pizza trays, is even more basic and automatic than a sense of numbers.
The researchers argue that understanding the relationship between size and number is critical for the development of higher math abilities. By combining number and size (e.g., area, density and perimeter), we can make faster and more efficient decisions.
Take for example the dilemma over choosing the quickest checkout line at the grocery store. While most people intuitively get behind someone with a less filled-looking cart, a fuller-looking cart with fewer, larger items may actually be quicker. The way we make these kinds of decisions reveals that people use the natural correlation between number and continuous magnitudes to compare magnitudes.
The researchers also urge colleagues to consider the roles other factors, such as language and cognitive control, play in acquiring numerical concepts. While the theoretical models presented in this review may raise more questions than answers, the researchers hope their hypothesis will reveal new ways of identifying dyscalculia, which can currently only be diagnosed in school-aged children. By this stage, children with the disorder are already lagging behind their peers.
Read more at Science Daily
|How do different brain regions interact when long-term memories are formed?|
The hippocampus has been the focus of intense scrutiny by memory researchers since the late 1950s, when it was surgically removed from a patient known as H.M. -- who was thereafter unable to form new memories. It was largely unknown what role the neocortex played in memory or how the two regions interacted. In their experiments, the Tübingen researchers placed test subjects at a computer screen and into a virtual maze, where they had to find hidden objects. The longer the test persons moved through the maze, the better they became at understanding how it was set out and where the hidden objects were. While the test subjects were carrying out the task, their brain activity was recorded by an MRI scanner.
In order to identify the brain region responsible for spatial memory, the researchers had a special trick. During one part of the experiment the maze did not change. This enabled the participants to slowly build up a spatial representation of it in their memories. In another part of the experiment, the maze changed constantly, so that the test subjects could not recognize it or learn a set path around it. "The comparison of the MRI images from the two mazes reveals which brain regions were specifically contributing to the formation of spatial memories," says Svenja Brodt, a doctoral candidate at the Graduate Training Center of Neuroscience and lead author of the study. "We were suprised that the activity of the precuneus, a region at the back of the neocortex, steadily increased, while the activity in the hippocampus steadily fell," Brodt explains. And communication between the two regions also fell during the learning process, according to Brodt.
"These results enable us to demonstrate that the long-term, neocortical traces of memory are formed right when the information is first gathered," says Dr. Monika Schönauer, who supervised the study. She said the pace of this process was astounding. Researchers had always assumed that the process took place very slowly, lasting weeks or months. Professor Steffen Gais explains: "The astonishing thing is that the hippocampus ceases to participate in learning after such a short time." The number of repetitions appeared to have a key influence on how quickly a long-term, stable memory was formed in the neocortex.
Read more at Science Daily
That's according to scientists from California State University, who spoke about the ancient fish at a meeting of the Society of Vertebrate Paleontology.
"These giant, spike-toothed salmon were amazing fish," said Julia Sankey, who led a team of researchers in a study of the extinct creatures. "You can picture them getting scooped out of the proto-Tuolumne River [near Modesto in central Calif.] by large bears 5 million years ago."
And that scooping must have been a tricky task. Even large bears would likely have had their paws full: The super-salmon could weigh up to 400 pounds.
The unusual teeth of the giant fish were the focus of the team's work. The researchers think it's likely the fish was a filter feeder, just like modern sockeye Pacific salmon, which open wide and take in plankton as they move.
If not for dining, what, then, was the purpose of the teeth?
To find out, Sankey and her colleagues compared dozens of tooth fossils from the animal that were found in freshwater and saltwater environments. The freshwater teeth were longer and more sharply curved, with clear evidence of wear, while those from saltwater sites were consistently smaller and lacked the worn-down look, indicating there was a change in the teeth before spawning.
That difference told the researchers that the large, spiky teeth were likely used for displaying and fighting among the giant salmon during spawning season. The finding dovetailed nicely with the behavior of most modern salmon species. Born in freshwater rivers and streams, they head out to salt water to live much of their lives, before moving back upstream to fresh water to spawn, after which all Pacific salmon and many other species die in a matter of weeks.
Before they migrate, though, salmon undergo physical changes, particularly to their skulls, the researchers noted. And modern males will fight with each other in defense of eggs they have fertilized. The ancient giant salmon, then, had particularly rough-house weapons at its disposal.
From Discovery News
Melanesians retain both Neanderthal and Denisovan ancestry in their genes. Neanderthals and Denisovans were both extinct populations of humans in our genus, Homo. The new research, presented recently at the American Society of Human Genetics Annual Meeting in Vancouver, B.C., may add yet another layer to the ancestry of many Pacific Islanders.
Their mystery relative "could have been a population relative to Denisova, or something more distantly related," Ryan Bohlender, lead author of the new research, told Seeker.
Melanesians to this day have an extremely unusual trait: they often have the darkest skin in the world outside of Africa, yet about one-fourth of them have blonde afros. Their unique appearance must be due to their intricate ancestry, which involved a lot of admixture. That's when two or more previously isolated populations within a species mix. In their case, it looks like the interbreeding included modern humans (Homo sapiens), Neanderthals, Denisovans and the mystery human.
Bohlender, who is a postdoctoral researcher at the University of Texas MD Anderson Cancer Center, and his colleagues created an estimation tool to better determine how our histories interacted with those of Neanderthals and Denisovans. The scientists then looked to see how well the computer model predicted the pattern of variation seen in various existing populations.
"We find that the answer is, reasonably well in Europe and East Asia, and less well in Melanesia," Bohlender said.
"Given the poor fit in Melanesia, something appears to be different there and one way for things to differ is additional admixture from some other hominin (early human) that we didn't include in the model."
The estimation tool also indicates that the early human population in Africa was about 50 percent larger than previously believed. It also suggests that Neanderthals diverged from our lineage 440,000 years ago, which is 100,000 years later than previously thought.
Why there was an archaic-modern human separation at that time is yet another mystery.
If you are Melanesian, then you are about 2 percent Neanderthal, between 3–4 percent Denisovan and also likely retain an additional small percentage of DNA from the mystery human ancestor, based on the new research.
"I think there is no such thing as a purebred modern human," Joshua Akey, who conducted some of the earlier research, told Seeker.
"All of our genomes are a mosaic of different ancestries, and admixture is a recurring theme throughout human evolutionary history," continued Akey, who is a researcher at the University of Washington's Department of Genome Science.
Interbreeding happened in Africa too, other studies indicate. A 2012 paper, for example, found DNA for yet another mystery human species in the genomes of hunter-gatherer people who live in Cameroon and Tanzania.
As for what all of this interbreeding means for us, it seems that the news is both good and bad. On the positive side, Bohlender said that "there are regions that have directly benefited from archaic DNA, like high altitude adaptation in Tibet." Today's Tibetans can therefore thank their Denisovan relatives for the ability to breathe easier than the rest of us while in the thinner air of mountainous areas.
Read more at Discovery News
Oct 31, 2016
|The cheetah is social, like primates, yet unlike primates its frontal lobe is relatively small. Why? It may be a consequence of its unusual skull shape, an adaptation for high-speed pursuits.|
Arguably, the fact that people and monkeys have particularly large frontal lobes is linked to their social nature. But cheetahs are also social creatures and their frontal lobes are relatively small. And leopards are solitary beasts, yet their frontal lobes are actually enlarged.
So what gives? Sharleen Sakai, lead investigator of the National Science Foundation-funded research, said the findings suggest that multiple factors beyond sociality may influence brain anatomy in carnivores.
"Studying feline brain evolution has been a bit like herding cats," said Sakai, MSU professor of psychology and neuroscience. "Our findings suggest the factors that drive brain evolution in wild cats are likely to differ from selection pressures identified in primate brain evolution."
Sakai and colleagues examined 75 wild feline skulls, representing 13 species, obtained from museum collections, including those at MSU. The researchers used computed tomography (CT) scans and sophisticated software to digitally "fill in" the areas where the brains would have been. From that process, they determined brain volume.
Sakai's lab is interested in uncovering the factors that influence the evolution of the carnivore brain. One explanation for large brains in humans and primates is the effect of sociality. The idea is that dealing with social relationships is more demanding than living alone and results in bigger brains, especially a bigger frontal cortex.
"We wanted to know if this idea, called the 'social brain' hypothesis, applied to other social mammals, especially carnivores and, in particular, wild cats," Sakai said.
Of the 13 wild feline species examined, 11 are solitary and two -- lions and cheetahs -- are social.
Here are some of the key findings of the research:
*Surprisingly, overall brain size did not differ, on average, between the social and solitary species of wild cats. But the part of the brain that includes the frontal cortex did differ between the two species.
*The female lion had the largest frontal cortex. Female lions are highly social, working together to protect and feed their young, hunt large prey and defend their territory. In contrast, males may live alone and may be dominant in a pride for only a few years. The larger frontal cortex in females compared to male lions and the other wild cats may reflect the lionesses' demands of processing social information necessary for life in the pride.
*The social cheetahs, in contrast, had the smallest overall brains and the smallest frontal cortex of the wild cats. Small brains weigh less and require less energy, factors that might contribute to the cheetah's remarkable running speeds. "Cheetah brain anatomy is distinctive and differs from other wild cats," Sakai said. "The size and shape of its brain may be a consequence of its unusual skull shape, an adaptation for high-speed pursuits."
Read more at Science Daily
|Left: Image of Saturn's rings taken by the Cassini spacecraft. Right: Image of Uranus' rings taken by the Hubble Space Telescope.|
The lead author of the paper is HYODO Ryuki (Kobe University, Graduate School of Science), and co-authors are Professor Sébastien Charnoz (Institute de Physique du Globe/Université Paris Diderot), Professor OHTSUKI Keiji (Kobe University, Graduate School of Science), and Project Associate Professor GENDA Hidenori (Earth-Life Science Institute, Tokyo Institute of Technology).
The giant planets in our solar system have very diverse rings. Observations show that Saturn's rings are made of more than 95% icy particles, while the rings of Uranus and Neptune are darker and may have higher rock content. Since the rings of Saturn were first observed in the 17th century, investigation of the rings has expanded from earth-based telescopes to spacecraft such as Voyagers and Cassini. However, the origin of the rings was still unclear and the mechanisms that lead to the diverse ring systems were unknown.
The present study focused on the period called the Late Heavy Bombardment that is believed to have occurred 4 billion years ago in our solar system, when the giant planets underwent orbital migration. It is thought that several thousand Pluto-sized (one fifth of Earth's size) objects from the Kuiper belt existed in the outer solar system beyond Neptune. First the researchers calculated the probability that these large objects passed close enough to the giant planets to be destroyed by their tidal force during the Late Heavy Bombardment. Results showed that Saturn, Uranus and Neptune experienced close encounters with these large celestial objects multiple times.
Next the group used computer simulations to investigate disruption of these Kuiper belt objects by tidal force when they passed the vicinity of the giant planets. The results of the simulations varied depending on the initial conditions, such as the rotation of the passing objects and their minimum approach distance to the planet. However they discovered that in many cases fragments comprising 0.1-10% of the initial mass of the passing objects were captured into orbits around the planet. The combined mass of these captured fragments was found to be sufficient to explain the mass of the current rings around Saturn and Uranus. In other words, these planetary rings were formed when sufficiently large objects passed very close to giants and were destroyed.
The researchers also simulated the long-term evolution of the captured fragments using supercomputers at the National Astronomical Observatory of Japan. From these simulations they found that captured fragments with an initial size of several kilometers are expected to undergo high-speed collisions repeatedly and are gradually shattered into small pieces. Such collisions between fragments are also expected to circularize their orbits and lead to the formation of the rings observed today.
This model can also explain the compositional difference between the rings of Saturn and Uranus. Compared to Saturn, Uranus (and also Neptune) has higher density (the mean density of Uranus is 1.27g cm-3, and 1.64g cm-3 for Neptune, while that of Saturn is 0.69g cm-3). This means that in the cases of Uranus (and Neptune), objects can pass within close vicinity of the planet, where they experience extremely strong tidal forces. (Saturn has a lower density and a large diameter-to-mass ratio, so if objects pass very close they will collide with the planet itself). As a result, if Kuiper belt objects have layered structures such as a rocky core with an icy mantle and pass within close vicinity of Uranus or Neptune, in addition to the icy mantle, even the rocky core will be destroyed and captured, forming rings that include rocky composition. However if they pass by Saturn, only the icy mantle will be destroyed, forming icy rings. This explains the different ring compositions.
Read more at Science Daily
|While it is well known that changes to the mean climate can affect ecosystems, little is known about the impact of short-term extreme climatic events (ECEs) such as heatwaves, heavy rainfall or droughts.|
Researchers investigated the impact of Extreme Climatic Events (ECEs) on butterfly populations. The study shows that the impact can be significantly positive and negative, but questions remain as to whether the benefits outweigh the negative effects.
While it is well known that changes to the mean climate can affect ecosystems, little is known about the impact of short-term extreme climatic events (ECEs) such as heatwaves, heavy rainfall or droughts.
Osgur McDermott-Long, PhD student and lead author from the School of Environmental Sciences at UEA, said: "This is the first study to examine the effects of extreme climate events across all life stages of the UK butterflies from egg to adult butterfly. We wanted to identify sensitive life stages and unravel the role that life history traits play in species sensitivity to ECEs."
The researchers used data from the UK Butterfly Monitoring Scheme (UKBMS), a high-quality long-term dataset of UK butterfly abundances collected from over 1,800 sites across the UK, spanning 37 years, to examine the effects of weather data and extreme events (drought, extremes of rain, heat and cold) on population change.
The team looked at resident species of butterflies, those which only breed once in a year, and those having more than one brood annually. Multi-brood species were found to be more vulnerable than single brood species and in general extremes of temperature rather than precipitation were found to influence changes in butterfly populations.
Dr Aldina Franco, co-author said: "A novel finding of this study was that precipitation during the pupal (cocoon) life-stage was detrimental to over one quarter of the species. This study also found that extreme heat during the 'overwintering' life stage was the most detrimental extreme weather event affecting over half of UK species. This may be due to increased incidents of disease or potentially extreme hot temperatures acting as a cue for butterflies or their larvae to come out from overwintering too early and subsequently killed off by temperatures returning to colder conditions."
In addition to the negative impacts, the authors found that some life stages may benefit from climatic extreme weather, with extreme heat in the adult stage causing a positive population change in over one third of the UK species.
Dr Franco, added: "This is not an unexpected finding given that butterflies are warm loving creatures. Years with extreme warm summers and winters may have mixed effects. For example, this year was terrible for butterflies, although the summer was warm the number of butterflies counted during the Big Butterfly Count was particularly low. Our study indicates that this could have resulted from the detrimental effects of the warm winter, for example the recent low counts1 of Gatekeeper, Common Blue, Comma, Peacock and Small Tortoiseshell butterflies could be explained by our results due to their negative response to warm winters which was just experienced2."
Mr McDermott Long said: "The study has demonstrated previously unknown sensitivities of our UK butterflies to extreme climatic events, which are becoming more frequent with climate change. Some of these effects are undoubtedly putting future populations at risk, such as extremely warm winters, however we've seen that warm and even climatically extreme hot summers may actually benefit butterflies.
Further research is needed regarding the balance of the importance that these variables could have, to see if the benefits of warmer summers will be outweighed by the detrimental winter effects."
Dr Tom Brereton from Butterfly Conservation and a co-author of the study, said: "If we are to mitigate against extreme events as part of conservation efforts, in particular, we need a better understanding of the habitat conditions which can lead to successful survival of adult, pupal and overwintering life stages of UK butterflies in these situations."
Read more at Science Daily
The recently completed Five-hundred-meter Aperture Spherical radio Telescope, or "FAST," occupies a valley in the southwestern Guizhou province of China. With a diameter of 500 meters, this monstrous telescope is almost 200 meters wider than the famous Arecibo Observatory in Puerto Rico. And now FAST will join the Breakthrough Listen SETI project to "listen in" on the strange star.
Though the likelihood of actually finding any chatty aliens around the star is slim, great mystery still surrounds the cause of some dramatic dimming events. NASA's Kepler space telescope recorded these events as transits that caused the star to dip in brightness of up to 22%. Kepler looks for exoplanets by detecting their transits (i.e. as a planet orbiting another star passes in front, blocking a tiny fraction of starlight). Typically, these transit events block a fraction of one percent of starlight.
Add to these unprecedented transit events the fact the star has apparently been dimming for over a century, and astronomers have been presented with a quandary: what is blocking the light from Tabby's Star?
One hypothesis put forward is that the dramatic transits were caused by a cloud of comets, but that explanation has fallen short of proving the source of the anomaly. Most likely is that Tabby's Star's weirdness is being caused by some overlooked phenomenon, or a completely new natural phenomenon that has yet to be understood.
But say if the cause isn't natural? What if there's an advanced alien civilization building some kind of "Dyson Sphere"-like structure — basically a star-enshrouding solar array that is designed to harness all the star's energy? Unlikely as it may sound and, as Occam's Razor dictates, aliens are the least likely explanation, Breakthrough Listen will study the star and it now has a powerful new tool to add to its growing arsenal of radio antennae.
It was announced that FAST would be joining Breakthrough Listen earlier this month, and now it looks like hopes are high that it will be committed specifically to the monitoring of Tabby's Star despite a busy observing schedule.
"The FAST telescope will be absolutely incredible for conducting extremely sensitive searches of Tabby's star for evidence of technologically produced radio emissions," Andrew Siemion, director of the Berkeley SETI Research Center and co-director of Breakthrough Listen, told the South China Morning Post. "We are very excited to work with our colleagues in China on conducting SETI observations with FAST, including of Tabby's star. Within its frequency range, FAST is the most sensitive telescope in the world capable of conducting SETI observations of Tabby's star, and will be able to detect the weakest signals."
Read more at Discovery News