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Wednesday, July 1, 2015

Hallucigenia: One of the Most Bizarre Creatures Ever Discovered

A new analysis of one of the most bizarre-looking fossils ever discovered has definitively sorted its head from its tail, and turned up a previously unknown ring of teeth, which could help answer some of the questions around the early development of moulting animals.

A new study of an otherworldly creature from half a billion years ago – a worm-like animal with legs, spikes and a head difficult to distinguish from its tail – has definitively identified its head for the first time, and revealed a previously unknown ring of teeth and a pair of simple eyes. 

Left: Hallucigenia sparsa from the Burgess Shale (Royal Ontario Museum 61513) The fossil is 15 mm long. Right: Colour reconstruction of Hallucigenia sparsa.
Credit: Left: Jean-Bernard Caron Right: Danielle Dufault


The results, published in the journal Nature, have helped scientists reconstruct what the common ancestor of everything from tiny roundworms to huge lobsters might have looked like. Researchers from the University of Cambridge, the Royal Ontario Museum and the University of Toronto have found that the creature, known as Hallucigenia due to its strange appearance, had a throat lined with needle-like teeth, a previously unidentified feature which could help connect the dots between it, modern velvet worms and arthropods – the group which contains modern insects, spiders and crustaceans. 


Arthropods, velvet worms (onychophorans) and water bears (tardigrades) all belong to the massive group of animals that moult, known as ecdysozoans. Though Hallucigenia is not the common ancestor of all ecdysozoans, it is a precursor to velvet worms. Finding this mouth arrangement in Hallucigenia helped scientists determine that velvet worms originally had the same configuration – but it was eventually lost through evolution. 

“The early evolutionary history of this huge group is pretty much uncharted,” said Dr Martin Smith, a postdoctoral researcher in Cambridge’s Department of Earth Sciences, and the paper’s lead author. “While we know that the animals in this group are united by the fact that they moult, we haven’t been able to find many physical characteristics that unite them.” 

“It turns out that the ancestors of moulting animals were much more anatomically advanced than we ever could have imagined: ring-like, plate-bearing worms with an armoured throat and a mouth surrounded by spines,” said Dr Jean-Bernard Caron, Curator of Invertebrate Palaeontology at the Royal Ontario Museum and Associate Professor in the Departments of Earth Sciences and Ecology & Evolutionary Biology at the University of Toronto. 

“We previously thought that neither velvet worms nor their ancestors had teeth. But Hallucigenia tells us that actually, velvet worm ancestors had them, and living forms just lost their teeth over time.” Hallucigenia was just one of the weird creatures that lived during the Cambrian Explosion, a period of rapid evolutionary development starting about half a billion years ago, when most major animal groups first emerge in the fossil record. 

At first, Hallucigenia threw palaeontologists for a bit of a loop. When it was identified in the 1970s, it was reconstructed both backwards and upside down: the spines along its back were originally thought to be legs, its legs were thought to be tentacles along its back, and its head was mistaken for its tail. Right side up and right way round, Hallucigenia still looks pretty strange: it had pairs of lengthy spines along its back, seven pairs of legs ending in claws, and three pairs of tentacles along its neck. The animals were between 10 and 50 millimetres in length and lived on the floor of the Cambrian oceans.  

More significantly, Hallucigenia’s unearthly appearance has made it difficult to link it to modern animal groups and to find its home in the Tree of Life. In 2014, research from Cambridge partially solved this problem by studying the structure of Hallucigenia’s claws, which helped definitively link it to modern velvet worms. In the new work, researchers used electron microscopy to examine fossils from the collections of the Royal Ontario Museum and the Smithsonian Institution, definitively sorting Hallucigenia’s front from back, and making some surprising observations.

“Prior to our study there was still some uncertainty as to which end of the animal represented the head, and which the tail,” said Smith. “A large balloon-like orb at one end of the specimen was originally thought to be the head, but we can now demonstrate that this actually wasn’t part of the body at all, but a dark stain representing decay fluids or gut contents that oozed out as the animal was flattened during burial.”

Identifying this end as the tail led Caron to revisit the fossils and dig away the sediment that was covering the head: the animals died as they were buried in a mudslide, and their floppy head often ended up pointing down into the mud. “This let us get the new images of the head,” said Caron.

“When we put the fossils in the electron microscope, we were initially hoping that we might find eyes, and were astonished when we also found the teeth smiling back at us!” The new images show an elongated head with a pair of simple eyes, which sat above a mouth with a ring of teeth.

In addition, Hallucigenia’s throat was lined with needle-shaped teeth. The fossils originated in the Burgess Shale of Yoho National Park in western Canada, one of the world’s richest sources of fossils from the Cambrian period.

The ring of teeth that surrounded Hallucigenia’s mouth probably helped to generate suction, flexing in and out, like a valve or a plunger, in order to suck its food into its throat. The researchers speculate that the teeth in the throat worked like a ratchet, keeping food from slipping out of the mouth each time it took another ‘suck’ at its food. “These teeth resemble those we see in many early moulting animals, suggesting that a tooth-lined throat was present in a common ancestor,” said Caron.

“So where previously there was little reason to think that arthropod mouths had much in common with the mouths of animals such as penis worms, Hallucigenia tells us that arthropods and velvet worms did ancestrally have round-the-mouth plates and down-the-throat teeth – they just lost or simplified them later.” The material for this study was collected between 1992 and 2000 and represents more than 165 additional Hallucigenia specimens – including many rare orientations and well-preserved specimens.

Parks Canada, which holds jurisdiction over the Burgess Shale sites located in Yoho and Kootenay national parks, is thrilled by this discovery and eager to share this exciting new piece of the ever-unfolding Burgess Shale story with their visitors. The research was funded by Clare College, Cambridge, the Natural Sciences and Engineering Research Council of Canada, and the Royal Ontario Museum.



Contacts and sources:
Sarah Collins
University of Cambridge

Women’s Faces Get Redder during Ovulation

Previous studies have shown that men find female faces more attractive when the women are ovulating, but the visual clues that allow this are unclear. Now, new research investigating whether it might be to do with subtle changes in skin colour has shown that women's faces do increase in redness during ovulation, but the levels of change are just under the detectable range of the human eye.

Credit: Greg Peverill-Conti

Researchers say this may mean that facial redness in females was once an involuntary signal for optimal fertility, but has since been "dampened" by evolution as it is more beneficial for females to hide or control outward signs of peak fertility.

Involuntarily signalling ovulation can prevent longer-term investment from males. In primate species that advertise ovulation, males only express sexual interest in females when they appear to be fertile. In humans, ovulation is less conspicuous and sexual behaviour is not restricted to the period of peak fertility.

The research, published today in the open-access journal PLOS ONE, is the most complete objective study of female faces during the ovulatory cycle, say researchers. Twenty-two women were photographed without make-up at the same time every working day for at least one month in the same environment and using a scientific camera modified to more accurately capture colour (usually used for studying camouflage in wildlife).

A computer programme was designed to select an identical patch of cheek from each photograph. The participants also self-tested for hormone changes at key times dictated by the research team's "period maths".

A surge in luteinising hormone told researchers that ovulation would occur in roughly the next 24 hours, so they knew which photographs were taken when the women were most fertile. The team converted the imagery into red/green/blue (RGB) values to measure colour levels and changes.

They found that redness varied significantly across the ovulatory cycle, peaking at ovulation and remaining high during the latter stages of the cycle after oestrogen levels have fallen. Skin redness then dips considerably once menstruation begins. The research suggests facial redness closely maps fluctuations in body temperature during the cycle.

However, when running the results through models of human visual perception, the largest average difference in redness was 0.6 units. A change of 2.2 units are needed to be detectable to the naked human eye.

"Women don't advertise ovulation, but they do seem to leak information about it, as studies have shown they are seen as more attractive by men when ovulating," said Dr Hannah Rowland, from the University of Cambridge's Zoology Department, who led the study with Dr Robert Burriss, a psychologist from Northumbria University.

"We had thought facial skin colour might be an outward signal for ovulation, as it is in other primates, but this study shows facial redness is not what men are picking up on - although it could be a small piece of a much larger puzzle," she said.

Primates, including humans, are attracted to red, say the study's authors. Women may subconsciously augment the naturally-occurring facial redness during ovulation through make-up such as blusher or red clothing, they say.

"As far back as the 1970s, scientists were speculating that involuntary signals of fertility such as skin colour changes might be replaced with voluntary signals, such as clothing and behaviour," said Burriss. "Some species of primate advertise their fertility through changes in the colour of their faces. Even if humans once advertised ovulation in this way, it appears that we don't anymore."

It may be that, during ovulation, women have a greater propensity for blushing when around men they find attractive, say the researchers. "Other research has shown that when women are in the fertile phase of their cycle they are more flirtatious and their pupils dilate more readily, but only when they are thinking about or interacting with attractive men," said Burriss. "We will need to do more research to find out if skin redness changes in the same way".

Rowland and Burriss first conceived of the experiment seven years ago, but it wasn't until Rowland arrived at Cambridge that they were able to do the research, thanks to the University's collegiate system. "We were able to recruit undergraduates in a number of colleges and photograph the women just before they had dinner in the college hall every evening. The collegiate routines and networks were vital to collecting data with such regularity," said Rowland.



Contacts and sources:
University of Cambridge


Palaeolake Mega-Chad: Largest Lake in the World Disappeared, Once Covered 360,000 Square Kilometers in Sahara 6,000 Year Ago

Researchers from Royal Holloway, Birkbeck and Kings College, University of London used satellite images to map abandoned shore lines around Palaeolake Mega-Chad, and analysed sediments to calculate the age of these shore lines, producing a lake level history spanning the last 15,000 years.

At its peak around 6,000 years ago, Palaeolake Mega-Chad was the largest freshwater lake on Earth, with an area of 360,000 km2. Now today’s Lake Chad is reduced to a fraction of that size, at only 355 km2. The drying of Lake Mega-Chad reveals a story of dramatic climate change in the southern Sahara, with a rapid change from a giant lake to desert dunes and dust, due to changes in rainfall from the West African Monsoon. 

Image courtesy of Charlie Bristow

The research, published this week in the journal Proceedings of the National Academy of Sciences of the United States of America confirms earlier suggestions that the climate change was abrupt, with the southern Sahara drying in just a few hundred years.

Part of the Palaeolake Mega-Chad basin that has dried completely is the Bodélé depression, which lies in remote northern Chad. The Bodélé depression is the World’s single greatest source of atmospheric dust, with dust being blown across the Atlantic to South America, where it is believed to be helping to maintain the fertility of tropical rainforests. However, the University of London team’s research shows that a small lake persisted in the Bodélé depression until about 1,000 years ago. This lake covered the parts of the Bodélé depression which currently produce most dust, limiting the dust potential until recent times.

The rivers, lake area and catchment area of Lake Megachad overlaid on the DEM of the Chad basin. Lakes are marked in blue, rivers in black and marshlands in green. When rivers flow into sand seas they often disappear in the dunes fields, and thus appear to terminate abruptly. This is probably because the channels are obscured by moving sand. Intermittent channel reaches can often be detected amongst the dunes in both the DEM and Landsat TM imagery suggesting they were once much more extensive 

“The Amazon tropical forest is like a giant hanging basket” explains Dr Simon Armitage from the Department of Geography at Royal Holloway. “In a hanging basket, daily watering quickly washes soluble nutrients out of the soil, and these need to be replaced using fertiliser if the plants are to survive. Similarly, heavy washout of soluble minerals from the Amazon basin means that an external source of nutrients must be maintaining soil fertility. As the World’s most vigorous dust source, the Bodélé depression has often been cited as a likely source of these nutrients, but our findings indicate that this can only be true for the last 1,000 years,” he added. 

Location of the palaeolake shoreline complexes identified in this research.  
Image by Nick Drake

The field work carried out by Professor Charlie Bristow, Professor Nick Drake and Dr Armitage was made possible by Royal Geographical Society grants for expeditions to Chad in 2005 and northern Nigeria in 2008. Additional sample analyses were funded by the Natural Environment Research Council.


Contacts and sources:
Royal Holloway, University of London

Round Trip to Mars: LED Lights Could Grow Plants for Voyage


A Purdue University study shows that targeting plants with red and blue LEDs provides energy-efficient lighting in contained environments, a finding that could advance the development of crop-growth modules for space exploration.

Research led by Cary Mitchell, professor of horticulture, and then-master's student Lucie Poulet found that leaf lettuce thrived under a 95-to-5 ratio of red and blue light-emitting diodes, or LEDs, placed close to the plant canopy. The targeted LED lighting used about 90 percent less electrical power per growing area than traditional lighting and an additional 50 percent less energy than full-coverage LED lighting.

A study by Purdue University researchers showed that LEDs are an efficient light source for growing crops in space.

Credit: Lucie Poulet

The study suggests that this model could be a valuable component of controlled-environment agriculture and vertical farming systems in space and on Earth, Mitchell said.

"Everything on Earth is ultimately driven by sunlight and photosynthesis," he said. "The question is how we can replicate that in space. If you have to generate your own light with limited energy resources, targeted LED lighting is your best option. We're no longer stuck in the era of high-power lighting and large, hot, fragile lamps."

One of the major obstacles to long-duration space exploration is the need for a bioregenerative life-support system - an artificial, self-contained ecosystem that mimics Earth's biosphere. A round-trip voyage to Mars for a crew of six, for example, could take about 1,000 days and would require more food, water and oxygen than current space vehicles can carry. Developing a module for efficiently growing crops would allow a space crew to grow food on long voyages and on the moon or Mars, said Poulet, now a doctoral student at Blaise Pascal University in France.

"If we can design a more energy-efficient system, we can grow vegetables for consumption for longer space travel," she said. "I can imagine a greenhouse on the moon."

The main challenge to creating a crop-growth module for space travel has been the staggering energy cost of the 600- to 1,000-watt conventional high-pressure sodium lamps traditionally used to mimic sunlight and stimulate plant photosynthesis in contained environments. The lamps also scorch plants if placed too close and require a filtration system to absorb the excess heat they create.

"Lighting was taking about 90 percent of the energy demand," Poulet said. "You'd need a nuclear reactor to feed a crew of four people on a regular basis with plants grown under traditional electric lights."

To design a more efficient system, Poulet and Mitchell turned to high-intensity LEDs, which require about 1 watt each and are much smaller and longer lasting than traditional lights. Because they emit no radiant heat, LEDs are also cool enough to be positioned close to the plant canopy and at strategic positions to maximize the amount of light that reaches the leaves.

"Instead of the minimum 4-foot separation we had between conventional lamps and lettuce, we could get LEDs as close as 4 centimeters away from the leaves," Mitchell said.

The researchers also optimized the ratio of red to blue lights, providing leaf lettuce with the best combination of lightwaves for photosynthesis and growth. Their lighting system slashed the amount of energy needed for plant growth by "an order of magnitude" compared with traditional lighting, Poulet said.

Mitchell said targeted LEDs could also help make controlled-environment agriculture on Earth more economically viable by reducing lighting costs.

The next step in research, he said, is to fine-tune when to increase and decrease lighting according to plant growth stage to optimize growing conditions and save energy.



Contacts and sources: 
Natalie van Hoose
Purdue University

The paper was published in Life Sciences in Space Research and is available at http://www.sciencedirect.com/science/article/pii/S2214552414000327.

First Time: Astronomers Witnessing Birth of a Planet

Astronomers at ETH Zurich have confirmed the existence of a young giant gas planet still embedded in the midst of the disk of gas and dust surrounding its parent star. For the first time, scientists are able to directly study the formation of a planet at a very early stage.

The formation of a giant gas planet near the star HD 100546 (left) is not yet complete, allowing astronomers to observe the process.
Artist’s impression: ESO / L. Calçada)

Observing time at the European Southern Observatory (ESO) on Paranal Mountain is a very precious commodity – and yet the Very Large Telescope (VLT) in Chile spent an entire night with a high-resolution infrared camera pointed at a single object in the night sky. The data collected by the Naco optics instrument enabled an international team headed by ETH Zurich’s Sascha Quanz to confirm its earlier hypothesis: that a young gas planet – presumed not unlike Jupiter in our own solar system – is orbiting the star designated HD 100546.

At “just” 335 light years away, HD 100546 is one of our near cosmic neighbours, and its age of five to ten million years makes it relatively young in astronomical terms. Like many young stars, it is surrounded by a massive disk of gas and dust. The outer reaches of this disk are home to the protoplanet, which lies at a distance from its parent star that is some fifty times greater than the distance between the Earth and the Sun.

Flung to the outskirts – an unlikely scenario

The team first postulated the existence of this young planet in an initial research paper published back in 2013. At the time, however, the researchers were still debating another possible explanation for the data they had collected, namely that the observed object might be a more massive – albeit older – giant planet that had formed further inside the circumstellar disk before being hurled outward. “It’s a scenario we still can’t rule out completely,” Quanz admits. “But it’s much less likely than our explanation, which suggests that what we’re seeing is the birth of a planet.”

If the object were an older planet that had formed earlier and closer to the star, its ejection trajectory would have to meet certain conditions for the researchers to be able to observe it now: It would have to be ejected directly in the plane of the gas and dust disk and at precisely the right time. “That would be a pretty huge coincidence,” says Quanz. This is why the team prefers the more natural interpretation, which at any rate is unusual enough. 

In addition, their latest observations have convinced the researchers that the signal they are picking up cannot be coming from a background source. “The best explanation for the observed phenomena is that a new planet is actually in the process of formation, embedded in the disk surrounding its parent star” – that was the conclusion of the study, which is published in the Astrophysical Journal. The study was conducted within the framework of “PlanetS”, one of Switzerland’s National Centres of Competence in Research.

Cosmic laboratory

Named HD 100546 b, the planet is the first object of its kind to be discovered. “It provides us with unique observational data on what happens when a gas giant is formed,” Quanz says. Previously, scientists investigated how, where and when giant planets form in the disks surrounding young stars only in theory or using computer simulations. “Now we have a kind of ‘laboratory’ that can give us empirical data,” Quanz explains.

In the meantime, other astronomers have found two more young stars that appear to be harbouring young giant planets, although these seem to be in a somewhat later evolutionary phase as, thanks to their orbital motion, they have already cleared large gaps in the disks they are embedded in. No largely cleared gaps have been found in the vicinity of HD 100546 b.

“Our object still seems to be surrounded by a lot of dust and gas,” Quanz says. Besides the parent star’s circumstellar disk, there may also be a smaller, circumplanetary disk encircling the newly formed planet from where matter is accreted onto the planet.

Thermal radiation from a large area

Based on their observations in three different wavelength bands, the researchers were able to derive an initial estimate for the object’s size and temperature. Their estimate puts the average temperature of the area – which has a diameter corresponding to seven times that of Jupiter’s – at over 600 degrees Celsius. 

The fact that thermal radiation is emanating from such a large area suggests that its source is a combination of a young planet and a circumplanetary disk. Future observations using the Alma radio telescope in Chile’s Atacama Desert should confirm whether or not the protoplanet is in fact encircled by its own disk, as well as provide indications regarding the disk’s mass and size.

And it’s quite possible that HD 100546 may yet supply further insights: Based on earlier observations of the star, the astronomers suspect that there might be a second planet orbiting it. If so, it would be approximately five times closer to the star than HD 100546 b is. So the astronomers may even be able to observe the formation of several planets in a single system. However, the existence of the second, inner planet is yet to be confirmed. That would come as no surprise, though, as many of the almost 2,000 exoplanets discovered so far belong to multi-planetary systems – just like our solar system.


Contacts and sources:
By: Barbara Vonarburg
ETH Zurich 


Citation:  Quanz SP, Amara A, Meyer MR, Girard JH, Kenworthy MA, Kasper M: Confirmation and characterization of the protoplanet HD 100546 b, Astrophysical Journal, 1. Juli 2015, doi: 10.1088/0004-637X/807/1/64

A Deep, Dark Mystery in California

UC Santa Barbara geologist Jim Boles has found evidence of helium leakage from the Earth’s mantle along a 30-mile stretch of the Newport-Inglewood Fault Zone in the Los Angeles Basin. Using samples of casing gas from two dozen oil wells ranging from LA’s Westside to Newport Beach in Orange County, Boles discovered that more than one-third of the sites — some of the deepest ones — show evidence of high levels of helium-3 (3He).

The Newport-Inglewood fault was responsible for the 4.9 magnitude Inglewood earthquake in 1920 and the 6.4 magnitude Long Beach earthquake in 1933.
Photo Credit:  Sonia Fernandez

Considered primordial, 3He is a vestige of the Big Bang. Its only terrestrial source is the mantle. Leakage of 3He suggests that the Newport-Inglewood fault is deeper than scientists previously thought. Boles’s findings appear in Geochemistry, Geophysics, Geosystems (G-Cubed), an electronic journal of the American Geophysical Union and the Geochemical Society.

“The results are unexpected for the area, because the LA Basin is different from where most mantle helium anomalies occur,” said Boles, professor emeritus in UCSB’s Department of Earth Science. “The Newport-Inglewood fault appears to sit on a 30-million-year-old subduction zone, so it is surprising that it maintains a significant pathway through the crust.”

A geologic cross section of the Los Angeles Basin from the southwest to northeast. This profile intersects the Newport-Inglewood Fault Zone at Long Beach. 
Credit: UC Santa Barbara

When Boles and his co-authors analyzed the 24 gas samples, they found that high levels of 3He inversely correlate with carbon dioxide (CO2), which Boles noted acts as a carrier gas for 3He. An analysis showed that the CO2 was also from the mantle, confirming leakage from deep inside the Earth.

Blueschist found at the bottom of nearby deep wells indicates that the Newport-Inglewood fault is an ancient subduction zone — where two tectonic plates collide — even though its location is more than 40 miles west of the current plate boundary of the San Andreas Fault System. Found 20 miles down, blueschist is a metamorphic rock only revealed when regurgitated to the surface via geologic upheaval.

The cylinders Jim Boles used to gather casing gas samples from oil wells along the Newport-Inglewood fault, where he found evidence of helium-3.

Credit:  Sonia Fernandez

“About 30 million years ago, the Pacific plate was colliding with the North American plate, which created a subduction zone at the Newport-Inglewood fault,” Boles explained. “Then somehow that intersection jumped clear over to the present San Andreas Fault, although how this occurred is really not known. This paper shows that the mantle is leaking more at the Newport-Inglewood fault zone than at the San Andreas Fault, which is a new discovery.”

The study’s findings contradict a scientific hypothesis that supports the existence of a major décollement — a low-angle thrust fault — below the surface of the LA Basin. “We show that the Newport-Inglewood fault is not only deep-seated but also directly or indirectly connected with the mantle,” Boles said.

“If the décollement existed, it would have to cross the Newport-Inglewood fault zone, which isn’t likely,” he added. “Our findings indicate that the Newport-Inglewood fault is a lot more important than previously thought, but time will tell what the true importance of all this is.”

Study co-authors include Grant Garven of Tufts University; Hilario Camacho of Occidental Oil and Gas Corp.; and John Lupton of the National Oceanic and Atmospheric Administration’s Pacific Marine Environmental Laboratory.

This research was supported by the U.S. Department of Energy’s Office of Science and Office of Basic Energy Sciences and by the NOAA Pacific Marine Environmental Laboratory.

 

Contacts and sources: 
By Julie Cohen
UC Santa Barbara

Asteroid Disaster Planning, Software Predicts Impact Locations and Effects

PhD researcher Dr Clemens Rumpf has developed a software (named ARMOR) that can predict the impact locations of asteroids and their impact effects. Here he discusses Asteroid Day and how ARMOR can help disaster planning against asteroid impact.

June  30th was Asteroid Day and this initiative aims to inform the public and raise awareness about the possibility that asteroids can collide with the Earth in the future.

The specific date was chosen because in 1908, on the same day, a 30-metre sized object entered the atmosphere over a forest region in Siberia and exploded in mid-air. The resulting shock wave and heat levelled the forest over an area larger than Greater London. In fact, about twice a year, an asteroid causes an explosion in the atmosphere that releases the energy equivalent to the Hiroshima bomb.

Every line on this image is the path of a known asteroid that could hit Earth
Credit: NASA/JPL/Caltech

What’s more, everybody can see asteroid hits first hand when one looks up into the night sky and happens to see a shooting star that leaves its bright streak against the starry background. A shooting star is typically only a grain sized particle that burn up in the atmosphere but it is the same mechanism as a larger scale asteroid collision, only with less consequences. Asteroids are part of our natural environment and we have lived with them as long as we have existed.

Even though there is a regular influx of cosmic material onto the Earth, an asteroid impact only rarely causes damage. Usually, asteroids are too small, explode too high or enter the atmosphere over uninhabited territory, such as the oceans that cover 70 per cent of the Earth’s surface. However, in time intervals that can be measured in tens or even hundreds of years, an asteroid impact causes significant damage.

This diagram maps the data gathered from 1994-2013 on small asteroids impacting Earth's atmosphere to create very bright meteors, technically called "bolides" and commonly referred to as "fireballs". Sizes of red dots (daytime impacts) and blue dots (nighttime impacts) are proportional to the optical radiated energy of impacts measured in billions of Joules (GJ) of energy, and show the location of impacts from objects about 1 meter (3 feet) to almost 20 meters (60 feet) in size. 
Image Credit: Planetary Science

A relatively small impact event occurred over the Russian city of Chelyabinsk in 2013. Here, a 17 metre-sized object caused a shock wave that shattered windows and glass shards injured about 1500 people. Impacting asteroids can measure hundreds of metres in diameter and have the potential to cause significant damage to our civilisation. Such an event may lie many years in the future but the potential damage that could be caused is reason enough to research asteroids and learn about their potential for natural disaster.

In contrast to other natural disasters, such as earthquakes, an asteroid impact is predictable. Shortly after an asteroid is discovered, its impact probability and its impact time can be calculated to hour level accuracy even if the potential impact is tens of years in the future. In addition, the impact location can be constraint to lie within a so called ‘impact corridor’ as shown in this image. Because of uncertainty in the observations of asteroids, the impact point prediction does not produce a point but a corridor that typically stretches across half the globe.

ARMOR 
Credit: University of Southampton

In order to make use of the favourable condition that an asteroid impact is predictable, the asteroid needs to be discovered before it impacts the Earth. Currently, we know of only about 1 per cent of the asteroids that can impact the Earth in the future. This means that the next asteroid impact will likely happen without warning, just like in Chelyabinsk. What is needed now are telescopes that help us discover all potentially threatening asteroids.

Space-based telescopes, such as the Sentinel mission proposed by the B612 Foundation or NASA’s proposed NeoCam mission, would be able to discover most of the remaining asteroids within 10 years. The observations of such telescopes would also help reduce uncertainty in the observational data. Less uncertainty means that we can make a clearer statement about whether or not an asteroid hits. Similarly, better observations collapse the impact corridor to smaller width and allow to make better predictions about where a potential impact might occur.

Considering the entire asteroid population and averaged over a long period of many years, any region on Earth has equal likelihood to be impacted by an asteroid. The average impact distribution can be likened to a pile of many transparent, sharp images stacked above each other. Stacked together, the sharp images produce a blurred picture with little distinguishable information. But taken by themselves, each individual image represents the day to day knowledge of where an asteroid impact is most likely to occur. One such snapshot image is shown here:

Asteroid impact probability
Credit: University of Southampton

The current knowledge of the asteroid impact probability distribution changes over time because new observations improve our knowledge. But information, such as shown in the last figure, can help disaster planning because it is our current best guess of where an asteroid impact might occur. Usually, impact probabilities are low, similar to winning the jackpot in the lottery. This is the daily situation that we live in and not very worrisome. However, some asteroids stand out and in 2004 the asteroid Apophis had a 3 per cent probability to impact in the year 2029. In such a scenario, it is important to know where the impact can occur and what the consequences might be.

The close approach of 99942 Apophis (previously better known by its provisional designation 2004 MN4) to the Earth and Moon on Friday, April 13, 2029 The small white bar indicates uncertainty in the range of possible positions.

Credit: NASA/Marco Polo - Wikipedia

To support decision making with respect to the asteroid threat, we have developed a software (named ARMOR) that can predict the impact locations of asteroids and their impact effects. The figures shown here are results of this research that have also been presented to an audience of world experts at the Planetary Defense Conference in April 2015.

An asteroid impact can be averted by altering the trajectory of an asteroid. Our long-term goal is to support asteroid deflection mission design by including the knowledge of where the asteroid could impact and what damage it could cause into the deflection mission design process.

Asteroid Apophis was discovered on June 19, 2004. 
Asteroid Apophis was discovered on June 19, 2004.
Image credit: UH/IA
Asteroids are part of our natural environment and smaller specimens collide with the Earth on a regular basis. Typically, a harmless shooting star is the result but a large asteroid impact can cause damage on global scale. Telescopes are the next step to enable further investigation of this natural hazard. Early observations make it possible to predict the impact location and even enable deflection of the asteroid such that no impact occurs. We are not in a critical situation at the moment and the continued effort of the dedicated planetary defence community aims to ensure that we are prepared when the next Tunguska asteroid is discovered.



Contacts and sources:
University of Southampton

Tuesday, June 30, 2015

Little Black-Hole Monsters Unexpectedly Rapidly Suck Up Surrounding Matter

Using the Subaru Telescope, researchers at the Special Astrophysical Observatory in Russia and Kyoto University in Japan have found evidence that enigmatic objects in nearby galaxies - called ultra-luminous X-ray sources (ULXs) - exhibit strong outflows that are created as matter falls onto their black holes at unexpectedly high rates. 

The strong outflows suggest that the black holes in these ULXs must be much smaller than expected. Curiously, these objects appear to be "cousins" of SS 433, one of the most exotic objects in our own Milky Way Galaxy. The team's observations help shed light on the nature of ULXs, and impact our understanding of how supermassive black holes in galactic centers are formed and how matter rapidly falls onto those black holes.

Multi-color optical image around the ULX "X-1" (indicated by the arrow) in the dwarf galaxy Holmberg II, is located in the direction of the constellation Ursa Major, at a distance of 11 million light-years. The image size corresponds to 1,100 × 900 light-years at the galaxy. The red color represents spectral line emission from hydrogen atoms.

Credit: Special Astrophysical Observatory/Hubble Space Telescope
X-ray observations of nearby galaxies have revealed these exceptionally luminous sources at off-nuclear positions that radiate about million times higher power than the Sun. The origins of ULXs have been a subject of heated debate for a long time. The basic idea is that a ULX is a close binary system consisting of a black hole and a star. As matter from the star falls onto the black hole, an accretion disk forms around the black hole. As the gravitational energy of the material is released, the innermost part of the disk is heated up to a temperature higher than 10 million degrees, which causes it to emit strong X-rays.

The unsolved key question about these objects asks: what is the mass of the black hole in these bright objects? ULXs are typically more than a hundred times more luminous than known black hole binaries in the Milky Way, whose black hole masses are at most 20 times the mass of the Sun.

This is a schematic view of ULXs (looking from upper side) and SS 433 (looking from left side). Strong X-rays are emitted from the inner region of the supercritical accretion disk. Powerful winds are launched from the disk, which eventually emit spectral lines of helium ions and hydrogen atoms.

Credit: Kyoto University

There are two different black hole scenarios proposed to explain these objects: (1) they contain very "big" black holes that could be more than a thousand times more massive than the Sun (Note 1), or (2) they are relatively small black holes, "little monsters" with masses no more than a hundred times that of the Sun, that shine at luminosities exceeding theoretical limits for standard accretion (called "supercritical (or super-Eddington) accretion," Note 2). Such supercritical accretion is expected to produce powerful outflow in a form of a dense disk wind.

To understand which scenario explains the observed ULXs researchers observed four objects: Holmberg II X-1, Holmberg IX X-1, NGC 4559 X-7, NGC 5204 X-1, and took high-quality spectra with the FOCAS instrument on Subaru Telescope for four nights. Image 1 shows an optical multi-color image toward Holmberg II X-1 as observed with Hubble Space Telescope. The object X-1, indicated by the arrow, is surrounded by a nebula (colored in red), which is most likely the gas heated by strong radiation from the ULX.

The team discovered a prominent feature in the optical spectra of all the ULXs observed. It is a broad emission line from helium ions, which indicates the presence of gas heated to temperatures of several tens of thousands of degrees in the system. In addition, they found that the width of the hydrogen line, which is emitted from cooler gas (with a temperature of about 10,000 K), is broader than the helium line. The width of a spectral line reflects velocity dispersion of the gas and shows up due to the Doppler effect caused by a distribution of the velocities of gas molecules. These findings suggest that the gas must be accelerated outward as a wind from either the disk or the companion star and that it is cooling down as it escapes.

Distant ULXs and a Similar Mysterious Object in the Milky Way:

The activity of these ULXs in distant galaxies is very similar to a mysterious object in our own Milky Way. The team noticed that the same line features are also observed at SS 433, a close binary consisting of an A-type star and most probably a black hole with a mass less than 10 times that of the Sun. SS 433 is famous for its persistent jets with a velocity of 0.26 times the speed of light. It is the only confirmed system that shows supercritical accretion (that is, an excessive amount of accretion that results in a very powerful outflow). By contrast, such features have not been observed from "normal" black hole X-ray binaries in the Milky Way where sub-critical accretion takes place.

After carefully examining several possibilities, the team concluded that huge amounts of gas are rapidly falling onto "little monster" black holes in each of these ULXs, which produces a dense disk wind flowing away from the supercritical accretion disk. They suggest that "bona-fide" ULXs with luminosities of about million times that of the Sun must belong to a homogeneous class of objects, and SS 433 is an extreme case of the same population. In these, even though the black hole is small, very luminous X-ray radiation is emitted as the surrounding gas falls onto the disk at a huge rate.

Image 3 is a schematic view of the ULXs (upper side) and SS 433 (lower side). If the system is observed from a vertical direction, it's clear that the central part of the accretion disk emits intense X-rays. If SS 433 were observed in the same direction, it would be recognized as the brightest X-ray source in the Milky Way. In reality, since we are looking at SS 433 almost along the disk plane, our line-of-sight view towards the inner disk is blocked by the outer disk. The accretion rate is inferred to be much larger in SS 433 than in the ULXs, which could explain the presence of persistent jets in SS 433.

Such "supercritical accretion" is thought to be a possible mechanism in the formation of supermassive black holes at galactic centers in very short time periods (which are observed very early in cosmic time). The discovery of these phenomena in the nearby universe has significant impacts on our understanding of how supermassive black holes are formed and how matter rapidly falls onto them.

There are still some remaining questions: What are the typical mass ranges of the black holes in ULXs? In what conditions can steady baryonic jets as observed in SS 433 be produced? Dr. Yoshihiro Ueda, a core member of the team, expresses his enthusiasm for future research in this area. "We would like to tackle these unresolved problems by using the new X-ray observations by ASTRO-H, planned to be launched early next year, and by more sensitive future X-ray satellites, together with multi-wavelength observations of ULXs and SS 433," he said.


Contacts and sources:
Yoshihiro Ueda
Associate Professor, Kyoto University

Hideaki Fujiwara
Subaru Telescope, National Astronomical Observatory of Japan

This work has been published online in Nature Physics on 2015 June 1 (Fabrika et al. 2015, "Supercritical Accretion Discs in Ultraluminous X-ray Sources and SS 433", 10.1038/nphys3348). The research was supported by the Japan Society for the Promotion of Science's KAKENHI Grant number 26400228.

Authors:  Sergei Fabrika (Special Astrophysical Observatory, Russia; Kazan Federal University, Russia)
Yoshihiro Ueda (Department of Astronomy, Kyoto University, Japan)
Alexander Vinokurov (Special Astrophysical Observatory, Russia)
Olga Sholukhova (Special Astrophysical Observatory, Russia)
Megumi Shidatsu (Department of Astronomy, Kyoto University, Japan)

Notes:

1. Generally, black holes with masses between about 100 and about 100,000 times that of the Sun are called "intermediate-mass black holes," although there is no strict definition for the mass range.

2. In a spherically symmetric case, matter cannot fall onto a central object when the radiation pressure exceeds the gravity. This luminosity is called the Eddington limit, which is proportional to the mass of the central object. When matter is accreted at rates higher than that corresponding to the Eddington limit, it is called "supercritical (or super-Eddington) accretion." In the case of non-spherical geometry, such as disk accretion, supercritical accretion may happen.

Seeing a Supernova in a New Light

Type Ia supernovae are the "standard candles" astrophysicists use to chart distance in the Universe. But are these dazzling exploding stars truly all the same? To answer this, scientists must first understand what causes stars to explode and become supernovae. 

Supernova 3C58, first observed in the year 1181 AD by Chinese and Japanese astronomers, was imaged by the Chandra telescope in X-ray emissions. 

Credit: Weizmann Institute of Science, NASA/CXC/SAO

Recently, a unique collaborative project between the California Institute of Technology (Caltech) and the Weizmann Institute of Science provided a rare glimpse of the process. Their findings were published in Nature.

The project, called the Palomar Transient Factory, is a robotic telescope system based in Southern California that scans the night sky for changes. In May, halfway around the world at the Weizmann Institute, Dr. Ilan Sagiv realized that one of the bright new lights the Palomar telescope had pinpointed was, indeed, a supernova - just four days into the explosion - and he sounded the alert sending the Swift Space Telescope on NASA's Swift Satellite to observe the blast. But the Swift Telescope also observed in an unusual way - in the invisible, ultraviolet range.

"Ultraviolet is crucial," says the Weizmann Institute's Prof. Avishay Gal-Yam of the Particle Physics and Astrophysics Department, "because initially, supernova blasts are so energetic that the most important information can only be gathered in short wavelengths. And it can only be seen from a space telescope, because the ultraviolet wavelengths are filtered out in the Earth's atmosphere."

The researchers collected observations ranging from the energetic X-ray and UV all the way to the radio wavelengths, the latter effort led by the Institute's Dr. Assaf Horesh. Caltech graduate student Yi Cao, who was the lead author on the paper, and his advisor Prof. S. Kulkarni, compared the figures from the observations to various models to see which fit. Astrophysicists mostly agree that the exploding stars that become type Ia supernova are extremely dense, old stars called white dwarfs. But a number of models have been proposed to explain what makes them suddenly blow up.

Ultraviolet observation enabled the researchers to see something they had never seen before: a unique, brief spike in the high-energy radiation very early on. This spike, says Gal-Yam, fits a model in which a dwarf star has a giant companion. "The white dwarf is the mass of the Sun packed into a sphere the size of the Earth, while its companion is around 50-100 times bigger around than the Sun." Material flows from the diffuse star to the dense one until, at some point the pressure from the added mass causes the smaller star to detonate. The radiation spike is caused by the initial material thrown off in the blast slamming into the companion.

Gal-Yam says that the group's findings show, among other things, the importance of ultraviolet-range observations. He is hopeful that the ULTRASAT mini-satellite planned by the Weizmann Institute's Prof. Eli Waxman, together with other researchers, the Israeli Space Agency and NASA, which will observe in the ultraviolet range, will help researchers discover whether this explosive process is common to type Ia supernovae.



Contacts and sources:
Yael Edelman
Weizmann Institute of Science

Game Changer: Pulsed Electric Fields Rejuvenate Skin

A Tel Aviv University (TAU) researcher harnessed pulsed electric fields to rejuvenate epidermal function and appearance

Americans spend over $10 billion a year on products and surgery in their quest to find a "fountain of youth," with little permanent success. Botulinum toxin -- notably Botox -- which smoothes lines and wrinkles to rejuvenate the aging face has been the number one nonsurgical procedure in the U.S. since 2000. But injections of this toxic bacterium are only a temporary solution and carry many risks, some neurological.

Credit: TAU

A team of Tel Aviv University (TAU) and Harvard Medical School researchers has now devised a non-invasive technique that harnesses pulsed electric fields to generate new skin tissue growth. According to their research, the novel non-invasive tissue stimulation technique, utilizing microsecond-pulsed, high-voltage, non-thermal electric fields, produces scarless skin rejuvenation and may revolutionize the treatment of degenerative skin diseases.

The study, published recently in Scientific Reports, was led by Dr. Alexander Golberg of TAU's Porter School of Environmental Studies and the Center for Engineering in Medicine at Massachusetts General Hospital, Harvard Medical School, and Shriners Burns Hospital in Boston, in collaboration with Dr. William J. Austen, Jr. from the Department of Plastic Surgery at Massachusetts General Hospital and Dr. Martin L. Yarmush at the Center for Engineering in Medicine at Massachusetts General Hospital, Harvard Medical School, and Shriners Burns Hospital in Boston, along with other prominent researchers.

An (effective) shock to the system

"Pulsed electrical field technology has many advantages, which have already proved effective -- for example, in food preservation, tumor removal, and wound disinfection," said Dr. Golberg. "Our new application may jumpstart the secretion of new collagen and capillaries in problematic skin areas. Considering that, in the modern era of aging populations and climate change, degenerative skin diseases affect one in three adults over the age of 60, this has the potential to be an healthcare game changer."

Current therapies to rejuvenate skin use various physical and chemical methods to affect cells and the extracellular matrix, but they induce unsightly scarring. Pulsed electric fields, however, affect only the cell membrane itself, preserving the extracellular matrix architecture and releasing multiple growth factors to spark new cell and tissue growth. By inducing nanoscale defects on the cell membranes, electric fields cause the death of a small number of cells in affected areas. The released growth factors increase the metabolism of the remaining cells, generating new tissue.

"We have identified in rats the specific pulsed electric field parameters that lead to prominent proliferation of the epidermis, formation of microvasculature, and secretion of new collagen at treated areas without scarring," said Dr. Golberg. "Our results suggest that pulsed electric fields can improve skin function and potentially serve as a novel non-invasive skin therapy for multiple degenerative skin diseases."

The researchers are currently developing a low-cost device for use in clinical trials in order to test the safety and efficacy of the technology in humans.


Contacts and sources: 
George Hunka
American Friends of Tel Aviv University

NASA Monitors a Waking Black Hole

NASA's Swift satellite detected a rising tide of high-energy X-rays from the constellation Cygnus on June 15, just before 2:32 p.m. EDT. About 10 minutes later, the Japanese experiment on the International Space Station called the Monitor of All-sky X-ray Image (MAXI) also picked up the flare.

Credit: NASA

On June 15, NASA's Swift caught the onset of a rare X-ray outburst from a stellar-mass black hole in the binary system V404 Cygni. Astronomers around the world are watching the event. In this system, a stream of gas from a star much like the sun flows toward a 10 solar mass black hole. Instead of spiraling toward the black hole, the gas accumulates in an accretion disk around it. Every couple of decades, the disk switches into a state that sends the gas rushing inward, starting a new outburst.

Credits: NASA's Goddard Space Flight Center

The outburst came from V404 Cygni, a binary system located about 8,000 light-years away that contains a black hole. Every couple of decades the black hole fires up in an outburst of high-energy light, becoming an X-ray nova. Until the Swift detection, it had been slumbering since 1989.

An X-ray nova is a bright, short-lived X-ray source that reaches peak intensity in a few days and then fades out over a period of weeks or months. The outburst occurs when stored gas abruptly rushes toward a neutron star or black hole. By studying the patterns of the X-rays produced, astronomers can determine the kind of object at the heart of the eruption.

"Relative to the lifetime of space observatories, these black hole eruptions are quite rare," said Neil Gehrels, Swift's principal investigator at NASA's Goddard Space Flight Center in Greenbelt, Maryland. "So when we see one of them flare up, we try to throw everything we have at it, monitoring across the spectrum, from radio waves to gamma rays."

Astronomers classify this type of system as a low-mass X-ray binary. In V404 Cygni, a star slightly smaller than the sun orbits a black hole 10 times its mass in only 6.5 days. The close orbit and strong gravity of the black hole produce tidal forces that pull a stream of gas from its partner. The gas travels to a storage disk around the black hole and heats up to millions of degrees, producing a steady stream of X-rays as it falls inward.

But the disk flips between two dramatically different conditions. In its cooler state, the gas resists inward flow and just collects in the outer part of the disk like water behind a dam. Inevitably the build-up of gas overwhelms the dam, and a tsunami of hot bright gas rushes toward the black hole.

Astronomers relish the opportunity to collect simultaneous multiwavelength data on black hole binaries, especially one as close as V404 Cygni. In 1938 and 1956, astronomers caught V404 Cygni undergoing outbursts in visible light. During its eruption in 1989, the system was observed by Ginga, an X-ray satellite operated by Japan, and instruments aboard Russia's Mir space station.

"Right now, V404 Cygni shows exceptional variation at all wavelengths, offering us a rare chance to add to this unique data set," said Eleonora Troja, a Swift team member at Goddard.

Ongoing or planned satellite observations of the outburst involve NASA's Swift satellite, Chandra X-ray Observatory and Fermi Gamma-ray Space Telescope, as well as Japan's MAXI, the European Space Agency's INTEGRAL satellite, and the Italian Space Agency's AGILE gamma-ray mission. Ground-based facilities following the eruption include the 10.4-meter Gran Telescopio Canarias operated by Spain in the Canary Islands, the University of Leicester's 0.5-meter telescope in Oadby, U.K., the Nasu radio telescope at Waseda University in Japan, and amateur observatories.

V404 Cygni has flared many times since the eruption began, with activity ranging from minutes to hours. "It repeatedly becomes the brightest object in the X-ray sky -- up to 50 times brighter than the Crab Nebula, which is normally one of the brightest sources," said Erik Kuulkers, the INTEGRAL project scientist at ESA's European Space Astronomy Centre in Madrid. "It is definitely a 'once in a professional lifetime' opportunity."

In a single week, flares from V404 Cygni generated more than 70 "triggers" of the Gamma-ray Burst Monitor (GBM) aboard Fermi. This is more than five times the number of triggers seen from all objects in the sky in a typical week. The GBM triggers when it detects a gamma-ray flare, then it sends numerous emails containing increasingly refined information about the event to scientists on duty.

Every time the GBM recovered from one trigger, V404 Cygni set it off again, resulting in a torrent of emails. The event prompted David Yu, a GBM scientist at the Max Planck Institute of Extraterrestrial Physics in Garching, Germany, to comment on social media: "Achievement Unlocked: Mailbox spammed by a blackhole."


Contacts and sources:
Francis Reddy
NASA  Goddard Space Flight Center,

The Earth Explodes, Atoms Tear Apart, The End of Everything: The Big Rip


The universe can be a very sticky place, but just how sticky is a matter of debate.

That is because for decades cosmologists have had trouble reconciling the classic notion of viscosity based on the laws of thermodynamics with Einstein's general theory of relativity. However, a team from Vanderbilt University has come up with a fundamentally new mathematical formulation of the problem that appears to bridge this long-standing gap.

This is a timeline of life of the universe that ends in a Big Rip.

Credit: Jeremy Teaford, Vanderbilt University

The new math has some significant implications for the ultimate fate of the universe. It tends to favor one of the more radical scenarios that cosmologists have come up with known as the "Big Rip." It may also shed new light on the basic nature of dark energy.

The new approach was developed by Assistant Professor of Mathematics Marcelo Disconzi in collaboration with physics professors Thomas Kephart and Robert Scherrer and is described in a paper published earlier this year in the journal Physical Review D.

"Marcelo has come up with a simpler and more elegant formulation that is mathematically sound and obeys all the applicable physical laws," said Scherrer.

The type of viscosity that has cosmological relevance is different from the familiar "ketchup" form of viscosity, which is called shear viscosity and is a measure of a fluid's resistance to flowing through small openings like the neck of a ketchup bottle. Instead, cosmological viscosity is a form of bulk viscosity, which is the measure of a fluid's resistance to expansion or contraction. The reason we don't often deal with bulk viscosity in everyday life is because most liquids we encounter cannot be compressed or expanded very much.

Disconzi began by tackling the problem of relativistic fluids. Astronomical objects that produce this phenomenon include supernovae (exploding stars) and neutron stars (stars that have been crushed down to the size of planets).

Scientists have had considerable success modeling what happens when ideal fluids - those with no viscosity - are boosted to near-light speeds. But almost all fluids are viscous in nature and, despite decades of effort, no one has managed to come up with a generally accepted way to handle viscous fluids traveling at relativistic velocities. In the past, the models formulated to predict what happens when these more realistic fluids are accelerated to a fraction of the speed of light have been plagued with inconsistencies: the most glaring of which has been predicting certain conditions where these fluids could travel faster than the speed of light.

"This is disastrously wrong," said Disconzi, "since it is well-proven experimentally that nothing can travel faster than the speed of light."

These problems inspired the mathematician to re-formulate the equations of relativistic fluid dynamics in a way that does not exhibit the flaw of allowing faster-than-light speeds. He based his approach on one that was advanced in the 1950s by French mathematician André Lichnerowicz.

Next, Disconzi teamed up with Kephart and Scherrer to apply his equations to broader cosmological theory. This produced a number of interesting results, including some potential new insights into the mysterious nature of dark energy.

In the 1990s, the physics community was shocked when astronomical measurements showed that the universe is expanding at an ever-accelerating rate. To explain this unpredicted acceleration, they were forced to hypothesize the existence of an unknown form of repulsive energy that is spread throughout the universe. Because they knew so little about it, they labeled it "dark energy."

Most dark energy theories to date have not taken cosmic viscosity into account, despite the fact that it has a repulsive effect strikingly similar to that of dark energy. "It is possible, but not very likely, that viscosity could account for all the acceleration that has been attributed to dark energy," said Disconzi. "It is more likely that a significant fraction of the acceleration could be due to this more prosaic cause. As a result, viscosity may act as an important constraint on the properties of dark energy."

Another interesting result involves the ultimate fate of the universe. Since the discovery of the universe's run-away expansion, cosmologists have come up with a number of dramatic scenarios of what it could mean for the future.

One scenario, dubbed the "Big Freeze," predicts that after 100 trillion years or so the universe will have grown so vast that the supplies of gas will become too thin for stars to form. As a result, existing stars will gradually burn out, leaving only black holes which, in turn, slowly evaporate away as space itself gets colder and colder.

An even more radical scenario is the "Big Rip." It is predicated on a type of "phantom" dark energy that gets stronger over time. In this case, the expansion rate of the universe becomes so great that in 22 billion years or so material objects begin to fall apart and individual atoms disassemble themselves into unbound elementary particles and radiation.

The key value involved in this scenario is the ratio between dark energy's pressure and density, what is called its equation of state parameter. If this value drops below -1 then the universe will eventually be pulled apart. Cosmologists have called this the "phantom barrier." In previous models with viscosity the universe could not evolve beyond this limit.

In the Desconzi-Kephart-Scherrer formulation, however, this barrier does not exist. Instead, it provides a natural way for the equation of state parameter to fall below -1.

"In previous models with viscosity the Big Rip was not possible," said Scherrer. "In this new model, viscosity actually drives the universe toward this extreme end state."

According to the scientists, the results of their pen-and-paper analyses of this new formulation for relativistic viscosity are quite promising but a much deeper analysis must be carried out to determine its viability. The only way to do this is to use powerful computers to analyze the complex equations numerically. In this fashion the scientists can make predictions that can be compared with experiment and observation.



Contacts and sources:
David Salisbury
Vanderbilt University

Monday, June 29, 2015

Lightning Research Deepens Understanding of Sprite Formation

A new study led by Florida Institute of Technology Professor Ningyu Liu has improved our understanding of a curious luminous phenomenon that happens 25 to 50 miles above thunderstorms.

A sprite as captured in this pseudo-color, composite photo recorded from an aircraft by a high-speed, high-sensitivity camera.
Credit: Florida Institute of Technology

These spectacular phenomena, called sprites, are fireworks-like electrical discharges, sometimes preceded by halos of light, in earth's upper atmosphere. It has been long thought that atmospheric gravity waves play an important role in the initiation of sprites but no previous studies, until this team's recent findings, provided convincing arguments to support that idea.

In this high-speed video captured from an airplane of the luminous phenomenon known as a sprite, a halo first appears and persists for a short while, and sprite elements are initiated from the bottom of the halo in an explosive manner and form a spectacular fireworks-like display. Researchers led by Florida Institute of Technology's Ningyu Liu have now provided a clearer understanding of the atmospheric mechanisms that lead to sprite formation.
Credit: Florida Institute of Technology

The research, published in the June 29 issue of Nature Communications, includes comprehensive computer-simulation results from a novel sprite initiation model and dramatic images of a sprite event, and provides a clearer understanding of the atmospheric mechanisms that lead to sprite formation.

Understanding the conditions of sprite formation is important, in part, because they can interfere with or disrupt long-range communication signals by changing the electrical properties of the lower ionosphere.

Predicted by Nobel laureate C. T. R. Wilson in 1924 but not discovered until 1989, sprites are triggered by intense cloud-to-ground lightning strokes. They typically last a few to tens of milliseconds; they are bright enough to be seen with dark-adapted naked eyes at night; and only the most powerful lightning strokes can cause them.

The study, conducted by Liu, a Florida Tech professor of physics and space sciences, and collaborators Joseph Dwyer, a former professor at Florida Tech now at University of New Hampshire, Hans Stenbaek-Nielsen from University of Alaska Fairbanks, and Matthew McHarg from the United States Air Force Academy, investigated how sprites are initiated.

According to Liu, the perturbations in the upper atmosphere created by atmospheric gravity waves can grow in the electric field produced by lightning and eventually lead to sprites.

"Perturbations with small size and large amplitude are best for initiating sprites," Liu said. "If the size of the perturbation is too large, sprite initiation is impossible; if the magnitude of the perturbation is small, it requires a relatively long time for sprites to be initiated."

To validate their model, the team analyzed a sprite event captured simultaneously by high-speed, high-sensitivity cameras on two aircraft during an observation mission sponsored by the Japanese broadcasting corporation NHK. The high-speed images show that a relatively long-lasting sprite halo preceded the fast initiation of sprite elements, exactly as predicted by the model.

Hamid Rassoul, an atmospheric physicist and the dean of Florida Tech's College of Science, said the findings will be critical to future researchers.

"They will allow scientists to study not only sprites but also the mesospheric perturbations, which are difficult, if not impossible, to observe," he said.

Liu added, "Our findings also suggest that small, dim glows in the upper atmosphere may be frequently caused by intense lightning but elude the detection. There may be many interesting phenomena waiting for discovery with more sensitive imaging systems."





Contacts and sources:
Adam Lowenstein
Florida Institute of Technology 


More on the study can be found at the Nature Communications website http://www.nature.com/ncomms/2015/150629/ncomms8540/full/ncomms8540.html.

Saturday, June 27, 2015

Do Rats 'Dream' Paths to a Brighter Future?

When rats rest, their brains simulate journeys to a desired future such as a tasty treat, finds new University College London (UCL) research funded by the Wellcome Trust and Royal Society.

The researchers monitored brain activity in rats, first as the animals viewed food in a location they could not reach, then as they rested in a separate chamber, and finally as they were allowed to walk to the food. The activity of specialised brain cells involved in navigation suggested that during the rest the rats simulated walking to and from food that they had been unable to reach.

An illustration of a sleeping rat. This was part of a paper published in the open access eLife journal suggesting that rats 'dream' paths to a brighter future. The research at UCL (University College London) found that when rats rest, their brains simulate journeys to a desired future such as a tasty treat.

Credit: Deepmind Ltd.

The study, published in the open access journal eLife, could help to explain why some people with damage to a part of the brain called the hippocampus are unable to imagine the future.

"During exploration, mammals rapidly form a map of the environment in their hippocampus," says senior author Dr Hugo Spiers (UCL Experimental Psychology). "During sleep or rest, the hippocampus replays journeys through this map which may help strengthen the memory. It has been speculated that such replay might form the content of dreams. Whether or not rats experience this brain activity as dreams is still unclear, as we would need to ask them to be sure! Our new results show that during rest the hippocampus also constructs fragments of a future yet to happen. Because the rat and human hippocampus are similar, this may explain why patients with damage to their hippocampus struggle to imagine future events."

In the experiment, animals were individually placed on a straight track with a T-junction ahead. Access to the junction as well as the left and right hand arms beyond it was prevented by a transparent barrier. One of the arms had food at the end, the other side was empty. After observing the food the rats were put in a sleep chamber for an hour. Finally after the barrier was removed, the animals were returned to the track and allowed to run across the junction and on to the arms.

During the rest period, the data showed that place cells that would later provide an internal map of the food arm were active. Cells representing the empty arm were not activated in this way. This indicates that the brain was simulating or preparing future paths leading to a desired goal.

"What's really interesting is that the hippocampus is normally thought of as being important for memory, with place cells storing details about locations you've visited," explains co-lead author Dr Freyja Ólafsdóttir (UCL Biosciences). "What's surprising here is that we see the hippocampus planning for the future, actually rehearsing totally novel journeys that the animals need to take in order to reach the food."

The results suggest that the hippocampus plans routes that have not yet happened as well as recording those that have already happened, but only when there is a motivational cue such as food. This may also imply the ability to imagine future events is not a uniquely human ability.

"What we don't know at the moment is what these neural simulations are actually for," says co-lead author Dr Caswell Barry (UCL Biosciences). "It seems possible this process is a way of evaluating the available options to determine which is the most likely to end in reward, thinking it through if you like. We don't know that for sure though and something we'd like to do in the future is try to establish a link between this apparent planning and what the animals do next."



Contacts and sources: 
Harry Dayantis
University College London
 

Think You Know Your Cat? New Study Suggests Not


Study finds pet owners reluctant to face up to their cats' kill count.

Cats are increasingly earning themselves a reputation as wildlife killers with estimates of animals killed every year by domestic cats in the UK numbering into the millions. This new study on the attitudes of cat owners suggests that proposals to keep cats indoors in order to preserve wildlife would not be well received.

A study finds pet owners are reluctant to face up to their cats' kill count.

Credit: Jenni McDonald / University of Exeter

The researchers studied cats from two UK villages, Mawnan Smith in Cornwall and Thornhill near Stirling. They found that although cat owners were broadly aware of whether their cat was predatory or not, those with a predatory cat had little idea of how many prey items it typically caught.

Regardless of the amount of prey returned by their cats, the majority of cat owners did not agree that cats are harmful to wildlife and were against suggestions that they should keep their cat inside as a control measure. They were however willing to consider neutering which is generally associated with cat welfare.

The results, which are published in Ecology and Evolution, indicate that management options to control cat predation are likely to be unsuccessful unless they focus on cat welfare.

Dr Jenni McDonald from the Centre for Ecology and Conservation at the University of Exeter's Penryn Campus in Cornwall said: "Our study shows that cat owners do not accept that cats are a threat to wildlife, and oppose management strategies with the exception of neutering. There is a clear need to directly address the perceptions and opinions of cat owners.

"If we are to successfully reduce the number of wildlife deaths caused by domestic cats, the study suggests that we should use cat welfare as a method of encouraging cat owners to get involved."

Co-author Professor Matthew Evans, Professor of Ecology at Queen Mary University of London, said: "In this paper we examined how aware cat owners were of the predatory behaviour of their pet. Owners proved to be remarkably unaware of the predatory behaviour of their cat, they also did not agree with any measures that might limit the impact that cats have on local wildlife.

This study illustrates how difficult it would be to change the behaviour of cat owners if they are both unaware of how many animals are killed by their pet and resistant to control measures. This presents conservationists who might be attempting to reduce cat predation with serious difficulties, as owners disassociate themselves from any conservation impacts of their cat and take the view that cat predation is a natural part of the ecosystem."

A total of 58 households, with 86 cats, took part in the study. Owners' views regarding their cats' predatory behaviour was assessed by comparing predictions of the number of prey their cat returns with the actual numbers bought home. A questionnaire was given to 45 owners at Mawnan Smith to determine whether the predatory behaviour of cats influences the attitudes of their owners.

In the UK, 23% of households share a population of over ten million domestic cats.

Previous studies have shown that although the majority of cats only return a small amount of prey, one or two items per month, it is the cumulative effect of high densities of cats that is likely to have an overall negative effect on the environment.



Contacts and sources:
Jo Bowler
University of Exeter

Citation: Reconciling actual and perceived rates of predation by domestic cats by Jennifer L. McDonald, Mairead Maclean, Matthew R. Evans and Dave J. Hodgson is published in Ecology and Evolution.

2 Billion Year Old Mystery Solved

Planets tend to cool as they get older, but Saturn is hotter than astrophysicists say it should be without some additional energy source.

The unexplained heat has caused a two-billion-year discrepancy for computer models estimating Saturn's age. "Models that correctly predict Jupiter to be 4.5 billion years old find Saturn to be only 2.5 billion years old," says Thomas Mattsson, manager of Sandia's high-energy-density physics theory group.

Experiments at the Z machine at Sandia National Laboratories have provided data that may explain why Saturn is 2 billion years younger than Jupiter in some simulations.
Credit: NASA

Experiments at Sandia's Z machine may have helped solve that problem when they verified an 80-year-old proposition that molecular hydrogen, normally an insulator, becomes metallic if squeezed by enough pressure. Physicists Eugene Wigner and Hilliard Huntington predicted in 1935 that a pressured lattice of hydrogen molecules would break up into individual hydrogen atoms, releasing free-floating electrons that could carry a current.

Jupiter 
Credit: NASA

"That long-ago prediction would explain Saturn's temperature because, when hydrogen metallizes and mixes with helium in a dense liquid, it can release helium rain," said Sandia researcher Mike Desjarlais. Helium rain is an energy source that can alter the evolution of a planet.

"Essentially, helium rain would keep Saturn warmer than calculations of planetary age alone would predict," said Marcus Knudson. Knudson and Desjarlais are the lead authors of a June 26 Science article, "Direct observation of an abrupt insulator-to-metal transition in dense liquid deuterium."

This proposed density-driven hydrogen transition had never been observed experimentally until Sandia's recent experiments.

The tests ran on Sandia's Z machine, the world's most powerful pulsed-power machine, which sends a huge but precisely tuned sub-microsecond pulse of electricity at a target. The correspondingly strong magnetic field surrounding the pulse was used to shocklessly squeeze deuterium -- a heavier variant of hydrogen -- at relatively low temperatures. Previous experiments elsewhere used gas guns to shock the gas. This increased its pressure but at the same time raised its temperature beyond the range of interest for the density-driven phase transition.

"We started at 20 degrees Kelvin, where hydrogen is a liquid, and sent a few hundred kilobar shock -- a tiny flyer plate pushed by Z's magnetic field into the hydrogen -- to warm the liquid," said Knudson. "Then we used Z's magnetic field to further compress the hydrogen shocklessly, which kept it right above the liquid-solid line at about 1,000 degrees K."

Said Desjarlais, "When the liquid was compressed to over 12 times its starting density, we saw the signs that it became atomic rather than molecular. The transition, at three megabars of pressure, gives theorists a solid figure to use in their calculations and helps identify the best theoretical framework for modeling these extreme conditions."

The results need to be plugged into astrophysical models to see whether the now-confirmed transition to atomic hydrogen significantly decreases the age gap between the two huge planets.

"The Sandia work shows that dense hydrogen can be metallic, which in turn changes the coexistence of hydrogen and helium in the planet," says Mattsson. "The mechanism of helium rain that has been proposed is therefore very plausible, given our results, but the scientific discussion will continue over the next few years in establishing a new consensus."

Interestingly, the determination that a metallic phase was reached was made optically. "There's too much electrical noise in Z to make an electrical test, though we plan to directly measure current down the road," Knudson said.

Optical tests rely on the transition from zero reflectivity (insulators) to the reflectivity achieved by metals.

"The only way you get reflectivity is when a material is metallic," Knudson said. Reflectivity was tested across the visible spectrum -- from 450 to 750 nanometers. "The experiment itself produced light," he said. "We collected it, put it through a spectrometer to disperse it and passed it into a camera to observe it."

When the hydrogen insulator reached enough pressure to become metallized, the researchers observed 45 percent reflectivity, an excellent agreement with theoretical calculations, said Desjarlais.

"This is a very nice merging of theory and experiment," he said. "We threw all our computational tools -- which are significant -- at providing verification and interpretation of the complex experimental observations at Z."

The work was done in collaboration with professor Ronald Redmer's research group at University of Rostock in Germany and is a part of the Z Fundamental Science Program at Sandia. The multidisciplinary team included researchers with expertise in innovative experimental design, diagnostics and pulse-shaping capabilities, matched with theoretical analysis using methods based on quantum mechanics.

Other authors besides Knudson, Desjarlais and Mattsson include Redmer and Andreas Becker at University of Rostock and Ray Lemke, Kyle Cochrane, Mark Savage, and Dave Bliss at Sandia.

The Z machine is a National High Energy Density Science Facility supported by the National Nuclear Security Administration.



Contacts and sources:
Neal Singer
Sandia National Laboraty 

Hubble View of a Nitrogen-Rich Nebula

This NASA/ESA Hubble Space Telescope image shows a planetary nebula named NGC 6153, located about 4,000 light-years away in the southern constellation of Scorpius (The Scorpion). The faint blue haze across the frame shows what remains of a star like the sun after it has depleted most of its fuel. When this happens, the outer layers of the star are ejected, and get excited and ionized by the energetic ultraviolet light emitted by the bright hot core of the star, forming the nebula.
Image credit: ESA/Hubble & NASA, Acknowledgement: Matej Novak

NGC 6153 is a planetary nebula that is elliptical in shape, with an extremely rich network of loops and filaments, shown clearly in this Hubble image. However, this is not what makes this planetary nebula so interesting for astronomers.

Measurements show that NGC 6153 contains large amounts of neon, argon, oxygen, carbon and chlorine — up to three times more than can be found in the solar system. The nebula contains a whopping five times more nitrogen than our sun! Although it may be that the star developed higher levels of these elements as it grew and evolved, it is more likely that the star originally formed from a cloud of material that already contained a lot more of these elements.


Contacts and sources: 
Ashley Morrow
NASA Goddard Space Flight Center
Text credit: European Space Agency

Earth's Rotation Is Slowing Says NASA, What They Plan To Do About It - Video

The day will officially be a bit longer than usual on Tuesday, June 30, 2015, because an extra second, or "leap" second, will be added.

Credit: NASA

"Earth's rotation is gradually slowing down a bit, so leap seconds are a way to account for that," said Daniel MacMillan of NASA's Goddard Space Flight Center in Greenbelt, Md.

Originally developed to study distant astronomical objects called quasars, the technique called Very Long Baseline Interferometry provides information about the relative locations of observing stations and about Earth’s rotation and orientation in space.

Credits: NASA Goddard Space Flight Center

Strictly speaking, a day lasts 86,400 seconds. That is the case, according to the time standard that people use in their daily lives -- Coordinated Universal Time, or UTC. UTC is "atomic time" -- the duration of one second is based on extremely predictable electromagnetic transitions in atoms of cesium. These transitions are so reliable that the cesium clock is accurate to one second in 1,400,000 years.

However, the mean solar day -- the average length of a day, based on how long it takes Earth to rotate -- is about 86,400.002 seconds long. That's because Earth's rotation is gradually slowing down a bit, due to a kind of braking force caused by the gravitational tug of war between Earth, the moon and the sun. Scientists estimate that the mean solar day hasn't been 86,400 seconds long since the year 1820 or so.

This difference of 2 milliseconds, or two thousandths of a second -- far less than the blink of an eye -- hardly seems noticeable at first. But if this small discrepancy were repeated every day for an entire year, it would add up to almost a second. In reality, that's not quite what happens. Although Earth's rotation is slowing down on average, the length of each individual day varies in an unpredictable way.

The length of day is influenced by many factors, mainly the atmosphere over periods less than a year. Our seasonal and daily weather variations can affect the length of day by a few milliseconds over a year. Other contributors to this variation include dynamics of the Earth's inner core (over long time periods), variations in the atmosphere and oceans, groundwater, and ice storage (over time periods of months to decades), and oceanic and atmospheric tides. Atmospheric variations due to El Niño can cause Earth's rotation to slow down, increasing the length of day by as much as 1 millisecond, or a thousandth of a second.

Scientists monitor how long it takes Earth to complete a full rotation using an extremely precise technique called Very Long Baseline Interferometry (VLBI). These measurements are conducted by a worldwide network of stations, with Goddard providing essential coordination of VLBI, as well as analyzing and archiving the data collected.

The time standard called Universal Time 1, or UT1, is based on VLBI measurements of Earth's rotation. UT1 isn't as uniform as the cesium clock, so UT1 and UTC tend to drift apart. Leap seconds are added, when needed, to keep the two time standards within 0.9 seconds of each other. The decision to add leap seconds is made by a unit within the International Earth Rotation and Reference Systems Service.

Typically, a leap second is inserted either on June 30 or December 31. Normally, the clock would move from 23:59:59 to 00:00:00 the next day. But with the leap second on June 30, UTC will move from 23:59:59 to 23:59:60, and then to 00:00:00 on July 1. In practice, many systems are instead turned off for one second.

Previous leap seconds have created challenges for some computer systems and generated some calls to abandon them altogether. One reason is that the need to add a leap second cannot be anticipated far in advance.

"In the short term, leap seconds are not as predictable as everyone would like," said Chopo Ma, a geophysicist at Goddard and a member of the directing board of the International Earth Rotation and Reference Systems Service. "The modeling of the Earth predicts that more and more leap seconds will be called for in the long-term, but we can't say that one will be needed every year."

From 1972, when leap seconds were first implemented, through 1999, leap seconds were added at a rate averaging close to one per year. Since then, leap seconds have become less frequent. This June's leap second will be only the fourth to be added since 2000. (Before 1972, adjustments were made in a different way.)

Scientists don't know exactly why fewer leap seconds have been needed lately. Sometimes, sudden geological events, such as earthquakes and volcanic eruptions, can affect Earth's rotation in the short-term, but the big picture is more complex.

VLBI tracks these short- and long-term variations by using global networks of stations to observe astronomical objects called quasars. The quasars serve as reference points that are essentially motionless because they are located billions of light years from Earth. Because the observing stations are spread out across the globe, the signal from a quasar will take longer to reach some stations than others. Scientists can use the small differences in arrival time to determine detailed information about the exact positions of the observing stations, Earth's rotation rate, and our planet's orientation in space.

Current VLBI measurements are accurate to at least 3 microseconds, or 3 millionths of a second. A new system is being developed by NASA's Space Geodesy Project in coordination with international partners. Through advances in hardware, the participation of more stations, and a different distribution of stations around the globe, future VLBI UT1 measurements are expected to have a precision better than 0.5 microseconds, or 0.5 millionths of a second.

"The next-generation system is designed to meet the needs of the most demanding scientific applications now and in the near future," says Goddard's Stephen Merkowitz, the Space Geodesy Project manager.

NASA manages many activities of the International VLBI Service for Geodesy and Astrometry including day-to-day and long-term operations, coordination and performance of the global network of VLBI antennas, and coordination of data analysis. NASA also directly supports the operation of six global VLBI stations.

Proposals have been made to abolish the leap second. No decision about this is expected until late 2015 at the earliest, by the International Telecommunication Union, a specialized agency of the United Nations that addresses issues in information and communication technologies.



Contacts and sources: 
Elizabeth Zubritsky
NASA Goddard Space Flight Center

For more information about NASA's Space Geodesy Project, including VLBI, visit: http://space-geodesy.nasa.gov/.