New Study Upends A Theory Of How Earth’s Mantle Flows

A new study carried out on the floor of Pacific Ocean provides the most detailed view yet of how the Earth’s mantle flows beneath the ocean’s tectonic plates. The findings, published in the journal Nature, appear to upend a common belief that the strongest deformation in the mantle is controlled by large-scale movement of the plate tectonics. Instead, the highest resolution imaging yet reveals smaller-scale processes at work that have more powerful effects.

earth's mantle

By developing a better picture of the underlying engine of plate tectonics, scientists hope to gain a better understanding of the mechanisms that drive plate movement and influence related process, including those involving earthquakes and volcanoes.

When we look out at the earth, we see its rigid crust, a relatively thin layer of rock that makes up the continents and the ocean floor. The crust sits on tectonic plates that move slowly over time in a layer called the lithosphere. At the bottom of the plates, some 80 to 100 kilometers below the surface, the asthenosphere begins. Earth’s interior flows more easily in the asthenosphere, and convection here is believed to help drive plate tectonics, but how exactly that happens and what the boundary between the lithosphere and asthenosphere looks like isn’t clear.

To take a closer look at these processes, a team led by scientists from Columbia University’s Lamont-Doherty Earth Observatory installed an array of seismometers on the floor of the Pacific Ocean, near the center of the Pacific Plate. By recording seismic waves generated by earthquakes, they were able to look deep inside the earth and create images of the mantle’s flow, similar to the way a doctor images a broken bone.

Seismic waves move faster through flowing rock because the pressure deforms the crystals of olivine, a mineral common in the mantle, and stretches them in the same direction. By looking for faster seismic wave movement, scientists can map where the mantle is flowing today and where it has flowed in the past.

Three basic forces are believed to drive oceanic plate movement: plates are “pushed” away from mid-ocean ridges as new sea floor forms; plates are “pulled” as the oldest parts of the plate dive back into the earth at subduction zones; and convection within the asthenosphere helps ferry the plates along. If the dominant flow in the asthenosphere resulted solely from “ridge push” or “plate pull,” then the crystals just below the plate should align with the plate’s movement. The study finds, however, that the direction of the crystals doesn’t correlate with the apparent plate motion at any depth in the asthenosphere. Instead, the alignment of the crystals is strongest near the top of the lithosphere where new sea floor forms, weakest near the base of the plate, and then peaks in strength again about 250 kilometers below the surface, deep in the asthenosphere.

“If the main flow were the mantle being sheared by the plate above it, where the plate is just dragging everything with it, we would predict a fast direction that’s different than what we see,” said coauthor James Gaherty, a geophysicist at Lamont-Doherty. “Our data suggest that there are two other processes in the mantle that are stronger: one, the asthenosphere is clearly flowing on its own, but it’s deeper and smaller scale; and, two, seafloor spreading at the ridge produces a very strong lithospheric fabric that cannot be ignored.” Shearing probably does happen at the plate boundary, Gaherty said, but it is substantially weaker.

Donald Forsyth, a marine geophysicist at Brown University who was not involved in the new study, said, “These new results will force reconsideration of prevailing models of flow in the oceanic mantle.”

Looking at the entire upper mantle, the scientists found that the most powerful process causing rocks to flow happens in the upper part of the lithosphere as new sea floor is created at a mid-ocean ridge. As molten rock rises, only a fraction of the flowing rock squeezes up to the ridge. On either side, the pressure bends the excess rock 90 degrees so it pushes into the lithosphere parallel to the bottom of the crust. The flow solidifies as it cools, creating a record of sea floor spreading over millions of years.

This “corner flow” process was known, but the study brings it into greater focus, showing that it deforms the rock crystals to a depth of at least 50 kilometers into the lithosphere.

In the asthenosphere, the patterns suggest two potential flow scenarios, both providing evidence of convection channels that bottom out about 250 to 300 kilometers below the earth’s surface. In one scenario, differences in pressure drive the flow like squeezing toothpaste from a tube, causing rocks to flow east-to-west or west-to-east within the channel. The pressure difference could be caused by hot, partially molten rock piled up beneath mid-ocean ridges or beneath the cooling plates diving into the earth at subduction zones, the authors write. Another possible scenario is that small-scale convection is taking place within the channel as chunks of mantle cool and sink. High-resolution gravity measurements show changes over relatively small distances that could reflect small-scale convection.

“The fact that we observe smaller-scale processes that dominate upper-mantle deformation, that’s a big step forward. But it still leaves uncertain what those flow processes are. We need a wider set of observations from other regions,” Gaherty said.

The study is part of the NoMelt project, which was designed to explore the lithosphere-asthenosphere boundary at the center of an oceanic plate, far from the influence of melting at the ridge. The scientists believe the findings here are representative of the Pacific Basin and likely ocean basins around the world.

NoMelt is unique because of its location. Most studies use land-based seismometers at edge of the ocean that tend to highlight the motion of the plates over the asthenosphere because of its large scale and miss the smaller-scale processes. NoMelt’s ocean bottom seismometer array, with the assistance of Lamont’s seismic research ship the Marcus G. Langseth, recorded data from earthquakes and other seismic sources from the middle of the plate over the span of a year.

A New Look At The Galaxy-Shaping Power Of Black Holes

Data from a now-defunct X-ray satellite is providing new insights into the complex tug-of-war between galaxies, the hot plasma that surrounds them, and the giant black holes that lurk in their centers.

black hole

Launched from Japan on February 17, 2016, the Japanese space agency (JAXA) Hitomi X-ray Observatory functioned for just over a month before contact was lost and the craft disintegrated. But the data obtained during those few weeks was enough to paint a startling new picture of the dynamic forces at work within galaxies.

New research, published in the journal Nature today, reveals data that shows just how important the giant black holes in galactic centers are to the evolution of the galaxies as a whole.

“We think that supermassive black holes act like thermostats,” said Brian McNamara, University Research Chair in Astrophysics at the University of Waterloo. “They regulate the growth of galaxies.”

Champagne bubbles of plasma

During its brief life, the Hitomi satellite collected X-ray data from the core of the Perseus cluster, an enormous gravitationally-bound grouping of hundreds of galaxies. Located some 240 million light years from earth, the Perseus cluster is one of the largest known structures in the universe. The cluster includes not only the ordinary matter that makes up the galaxies, but an “atmosphere” of hot plasma with a temperature of tens of millions of degrees, as well as a halo of invisible dark matter.

Earlier studies, going back to the 1960s, have shown that each of the galaxies in the cluster — and indeed most galaxies — likely contains a supermassive black hole in its centre, an object 100 million to more than ten billion times as massive as our sun.

“These giant black holes are among the universe’s most efficient energy generators, a hundred times more efficient than a nuclear reactor,” said McNamara from Waterloo’s Department of Physics and Astronomy in the Faculty of Science. “Matter falling into the black hole is ripped apart, releasing vast amounts of energy in the form of high speed particles and thermal energy.”

This heat is released from just outside the black hole’s event horizon, the boundary of no return. The remaining matter gets absorbed into the black hole, adding to its mass. The released energy heats up the surrounding gas, creating bubbles of hot plasma that ripple through the cluster, just as bubbles of air rise up in a glass of champagne.

The research is shedding light on the crucial role that this hot plasma plays in galactic evolution. Researchers are now tackling the foremost issue in the formation of structure in the universe and asking: why doesn’t most of the gas cool down, and form stars and galaxies? The answer seems to be that bubbles created by blasts of energy from the black holes keep temperatures too high for such structures to form.

“Any time a little bit of gas falls into the black hole, it releases an enormous amount of energy,” said McNamara. “It creates these bubbles, and the bubbles keep the plasma hot. That’s what prevents galaxies from becoming even bigger than they are now.”

Because plasma is invisible to the eye, and to optical telescopes, it wasn’t until the advent of X-ray astronomy that the full picture began to emerge. In visible light, the Perseus cluster appears to contain many individual galaxies, separated by seemingly-empty space. In an X-ray image, however, the individual galaxies are invisible, and the plasma atmosphere, centred on the cluster’s largest galaxy, known as NGC 1275, dominates the scene.

Although the black hole at the heart of NGC 1275 has only one-thousandth of the mass of its host galaxy, and has a much smaller volume, it seems to have a huge influence on how the galaxy and how the surrounding hot plasma atmosphere evolve.

“It’s as though the galaxy somehow knows about this black hole sitting at the centre,” said McNamara. “It’s like nature’s thermostat, that keeps these galaxies from growing. If the galaxy tries to grow too fast, matter falls into the black hole, releasing an enormous amount of energy, which drives out the matter and prevents it from forming new stars.”

McNamara notes that the actual event horizon of the black hole is about the same size as our solar system, making it as small compared to its host galaxy as a grape is to the Earth. “What’s going on in this tiny region is affecting a vast volume of space,” he said.

Thanks to the black hole’s regulatory effect, the gas that would have formed new stars instead remains a hot plasma — whose properties Hitomi was designed to measure.

Doomed satellite missions

Hitomi employed an X-ray spectrometer which measures the Doppler shifts in emissions from the plasma; those shifts can then be used to calculate the speed at which different parts of the plasma are moving. At the heart of the spectrometer is a microcalorimeter; cooled to just one-twentieth of a degree above absolute zero, the device records the precise energy of each incoming X-ray photon.

Getting an X-ray satellite equipped with a microcalorimeter into space has proved daunting: McNamara was deeply involved with NASA’s Chandra X-ray Observatory, launched in 1999, that was initially set to include a microcalorimeter, but the project was scaled back due to budget constraints, and the calorimeter was dropped. Another mission with the Japanese space agency known as ASTRO-E was equipped with a microcalorimeter; it was set for launch in 2000, but the rocket exploded shortly after liftoff. A third effort, Japan’s Suzaku satellite, launched in 2005, but a leak in the cooling system destroyed the calorimeter. Hitomi launched and deployed perfectly, but a series of problems with the attitude control system caused the satellite to spin out of control and break up.

The data from Hitomi, limited as it is, is enough to make astronomers re-think the role of plasma in galactic evolution, according to McNamara. “The plasma can be thought of forming an enormous atmosphere that envelopes whole clusters of galaxies. These hot atmospheres represent the failure of the past — the failure of the universe to create bigger galaxies,” he said. “But it’s also the hope for the future. This is the raw material for the future growth of galaxies — which is everything: stars, planets, people. It’s the raw material that in the next several billion years is going to make the next generation of suns and solar systems. And how rapidly that happens is governed by the black hole.”

The observations give researchers, for the first time, a direct measurement of the turbulent speed of the hot plasma. “This measurement tells us how the enormous energy released by supermassive black holes regulates the growth of the galaxy and the black hole itself,” said McNamara.

Chemical Trail On Saturn’s Moon Titan May Be Key To Prebiotic Conditions

NASA’s Cassini and Huygens missions have provided a wealth of data about chemical elements found on Saturn’s moon Titan, and Cornell scientists have uncovered a chemical trail that suggests prebiotic conditions may exist there.

mars

Titan, Saturn’s largest moon, features terrain with Earthlike attributes such as lakes, rivers and seas, although filled with liquid methane and ethane instead of water. Its dense atmosphere — a yellow haze — brims with nitrogen and methane. When sunlight hits this toxic atmosphere, the reaction produces hydrogen cyanide — a possible prebiotic chemical key.

“This paper is a starting point, as we are looking for prebiotic chemistry in conditions other than Earth’s,” said Martin Rahm, postdoctoral researcher in chemistry and lead author of the new study, “Polymorphism and Electronic Structure of Polyimine and Its Potential Significance for Prebiotic Chemistry on Titan,” published in the Proceedings of the National Academy of Sciences, July 4.

To grasp the blueprint of early planetary life, Rahm said we must think outside of green-blue, Earth-based biology: “We are used to our own conditions here on Earth. Our scientific experience is at room temperature and ambient conditions. Titan is a completely different beast.” Although Earth and Titan both have flowing liquids, Titan’s temperatures are very low, and there is no liquid water. “So if we think in biological terms, we’re probably going to be at a dead end,” he said.

Hydrogen cyanide is an organic chemical that can react with itself or with other molecules — forming long chains, or polymers, one of which is called polyimine. The chemical is flexible, which helps mobility under very cold conditions, and it can absorb the sun’s energy and become a possible catalyst for life.

“Polyimine can exist as different structures, and they may be able to accomplish remarkable things at low temperatures, especially under Titan’s conditions,” said Rahm, who works in the lab of Roald Hoffmann, winner of the 1981 Nobel Prize in chemistry and Cornell’s Frank H.T. Rhodes Professor of Humane Letters Emeritus. Rahm and the paper’s other scientists consulted with Hoffmann on this work.

“We need to continue to examine this, to understand how the chemistry evolves over time. We see this as a preparation for further exploration,” said Rahm. “If future observations could show there is prebiotic chemistry in a place like Titan, it would be a major breakthrough. This paper is indicating that prerequisites for processes leading to a different kind of life could exist on Titan, but this only the first step.”

Warming Pulses In Ancient Climate Record Link Volcanoes, Asteroid Impact And Dinosaur-Killing Mass Extinction

A new reconstruction of Antarctic ocean temperatures around the time the dinosaurs disappeared 66 million years ago supports the idea that one of the planet’s biggest mass extinctions was due to the combined effects of volcanic eruptions and an asteroid impact.

asteroid

Two University of Michigan researchers and a Florida colleague found two abrupt warming spikes in ocean temperatures that coincide with two previously documented extinction pulses near the end of the Cretaceous Period. The first extinction pulse has been tied to massive volcanic eruptions in India, the second to the impact of an asteroid or comet on Mexico’s Yucatan Peninsula.

Both events were accompanied by warming episodes the U-M-led team found by analyzing the chemical composition of fossil shells using a recently developed technique called the carbonate clumped isotope paleothermometer.

The new technique, which avoids some of the pitfalls of previous methods, showed that Antarctic ocean temperatures jumped about 14 degrees Fahrenheit during the first of the two warming events, likely the result of massive amounts of heat-trapping carbon dioxide gas released from India’s Deccan Traps volcanic region. The second warming spike was smaller and occurred about 150,000 years later, around the time of the Chicxulub impact in the Yucatan.

“This new temperature record provides a direct link between the volcanism and impact events and the extinction pulses — that link being climate change,” said Sierra Petersen, a postdoctoral researcher in the U-M Department of Earth and Environmental Sciences.

“We find that the end-Cretaceous mass extinction was caused by a combination of the volcanism and meteorite impact, delivering a theoretical ‘one-two punch,'” said Petersen, first author of a paper scheduled for online publication July 5 in the journal Nature Communications.

The cause of the Cretaceous-Paleogene (KPg) mass extinction, which wiped out the non-avian dinosaurs and roughly three-quarters of the planet’s plant and animal species about 66 million years ago, has been debated for decades. Many scientists believe the extinction was caused by an asteroid impact; some think regional volcanism was to blame, and others suspect it was due to a combination of the two.

Recently, there’s been growing support for the so-called press-pulse mechanism. The “press” of gradual climatic change due to Deccan Traps volcanism was followed by the instantaneous, catastrophic “pulse” of the impact. Together, these events were responsible for the KPg extinction, according to the theory.

The new record of ancient Antarctic ocean temperatures provides strong support for the press-pulse extinction mechanism, Petersen said. Pre-impact climate warming due to volcanism “may have increased ecosystem stress, making the ecosystem more vulnerable to collapse when the meteorite hit,” concluded Petersen and co-authors Kyger Lohmann of U-M and Andrea Dutton of the University of Florida.

To create their new temperature record, which spans 3.5 million years at the end of the Cretaceous and the start of the Paleogene Period, the researchers analyzed the isotopic composition of 29 remarkably well-preserved shells of clam-like bivalves collected on Antarctica’s Seymour Island.

These mollusks lived 65.5-to-69 million years ago in a shallow coastal delta near the northern tip of the Antarctic Peninsula. At the time, the continent was likely covered by coniferous forest, unlike the giant ice sheet that is there today.

As the 2-to-5-inch-long bivalves grew, their shells incorporated atoms of the elements oxygen and carbon of slightly different masses, or isotopes, in ratios that reveal the temperature of the surrounding seawater.

The isotopic analysis showed that seawater temperatures in the Antarctic in the Late Cretaceous averaged about 46 degrees Fahrenheit, punctuated by two abrupt warming spikes.

“A previous study found that the end-Cretaceous extinction at this location occurred in two closely timed pulses,” Petersen said. “These two extinction pulses coincide with the two warming spikes we identified in our new temperature record, which each line up with one of the two ‘causal events.'”

Unlike previous methods, the clumped isotope paleothermometer technique does not rely on assumptions about the isotopic composition of seawater. Those assumptions thwarted previous attempts to link temperature change and ancient extinctions on Seymour Island.

Lush Venus? Searing Earth? It Could Have Happened

If conditions had been just a little different an eon ago, there might be plentiful life on Venus and none on Earth.

The idea isn’t so far-fetched, according to a hypothesis by Rice University scientists and their colleagues who published their thoughts on life-sustaining planets, the planets’ histories and the possibility of finding more in Astrobiology this month.

earth

The researchers maintain that minor evolutionary changes could have altered the fates of both Earth and Venus in ways that scientists may soon be able to model through observation of other solar systems, particularly ones in the process of forming, according to Rice Earth scientist Adrian Lenardic.

The paper, he said, includes “a little bit about the philosophy of science as well as the science itself, and about how we might search in the future. It’s a bit of a different spin because we haven’t actually ­­­­done the work, in terms of searching for signs of life outside our solar system, yet. It’s about how we go about doing the work.”

Lenardic and his colleagues suggested that habitable planets may lie outside the “Goldilocks zone” in extra-solar systems, and that planets farther from or closer to their suns than Earth may harbor the conditions necessary for life.

The Goldilocks zone has long been defined as the band of space around a star that is not too warm, not too cold, rocky and with the right conditions for maintaining surface water and a breathable atmosphere. But that description, which to date scientists have only been able to calibrate using observations from our own solar system, may be too limiting, Lenardic said.

“For a long time we’ve been living, effectively, in one experiment, our solar system,” he said, channeling his mentor, the late William Kaula. Kaula is considered the father of space geodetics, a system by which all the properties in a planetary system can be quantified. “Although the paper is about planets, in one way it’s about old issues that scientists have: the balance between chance and necessity, laws and contingencies, strict determinism and probability.

“But in another way, it asks whether, if you could run the experiment again, would it turn out like this solar system or not? For a long time, it was a purely philosophical question. Now that we’re observing solar systems and other planets around other stars, we can ask that as a scientific question.

“If we find a planet (in another solar system) sitting where Venus is that actually has signs of life, we’ll know that what we see in our solar system is not universal,” he said.

In expanding the notion of habitable zones, the researchers determined that life on Earth itself isn’t necessarily a given based on the Goldilocks concept. A nudge this way or that in the conditions that existed early in the planet’s formation may have made it inhospitable.

By extension, a similarly small variation could have changed the fortunes of Venus, Earth’s closest neighbor, preventing it from becoming a burning desert with an atmosphere poisonous to terrestrials.

The paper also questions the idea that plate tectonics is a critical reason Earth harbors life. “There’s debate about this, but the Earth in its earliest lifetimes, let’s say 2-3 billion years ago, would have looked for all intents and purposes like an alien planet,” Lenardic said. “We know the atmosphere was completely different, with no oxygen. There’s a debate that plate tectonics might not have been operative.

“Yet there’s no argument there was life then, even in this different a setting. The Earth itself could have transitioned between planetary states as it evolved. So we have to ask ourselves as we look at other planets, should we rule out an early Earth-like situation even if there’s no sign of oxygen and potentially a tectonic mode distinctly different from the one that operates on our planet at present?

“Habitability is an evolutionary variable,” he said. “Understanding how life and a planet co-evolve is something we need to think about.”

Lenardic is kicking his ideas into action, spending time this summer at conferences with the engineers designing future space telescopes. The right instruments will greatly enhance the ability to find, characterize and build a database of distant solar systems and their planets, and perhaps even find signs of life.

“There are things that are on the horizon that, when I was a student, it was crazy to even think about,” he said. “Our paper is in many ways about imagining, within the laws of physics, chemistry and biology, how things could be over a range of planets, not just the ones we currently have access to. Given that we will have access to more observations, it seems to me we should not limit our imagination as it leads to alternate hypothesis.”

###

Rice graduate student Matt Weller, now a postdoctoral fellow at the Lunar and Planetary Institute, is a co-author of the paper. Additional co-authors are John Crowley, a geodetic engineer at the Canadian Geodetic Survey of Natural Resources Canada and an adjunct professor in the Department of Earth and Environmental Sciences at the University of Ottawa, and Mark Jellinek, a professor of volcanology, geodynamics, planetary science and geological fluid mechanics at the University of British Columbia.

The National Science Foundation supported the research.

Alma Finds A Swirling, Cool Jet That Reveals A Growing, Supermassive Black Hole

A Chalmers-led team of astronomers have used the Alma telescope to make the surprising discovery of a jet of cool, dense gas in the centre of a galaxy located 70 million light years from Earth. The jet, with its unusual, swirling structure, gives new clues to a long-standing astronomical mystery — how supermassive black holes grow.

galaxy NGC 1377

A team of astronomers led by Susanne Aalto, professor of radio astronomy at Chalmers, has used the Alma telescope (Atacama Large Millimeter/submillimeter Array) to observe a remarkable structure in the centre of the galaxy NGC 1377, located 70 million light years from Earth in the constellation Eridanus (the River). The results are presented in a paper published in the June 2016 issue of the journal Astronomy and Astrophysics.

“We were curious about this galaxy because of its bright, dust-enshrouded centre. What we weren’t expecting was this: a long, narrow jet streaming out from the galaxy nucleus,” says Susanne Aalto.

The observations with Alma reveal a jet which is 500 light years long and less than 60 light years across, travelling at speeds of at least 800,000 kilometres per hour (500,000 miles per hour).

Most galaxies have a supermassive black hole in their centres; these black holes can have masses of between a few million to a billion solar masses. How they grew to be so massive is a long-standing mystery for scientists.

A black hole’s presence can be seen indirectly by telescopes when matter is falling into it — a process which astronomers call “accretion.” Jets of fast-moving material are typical signatures that a black hole is growing by accreting matter. The jet in NGC 1377 reveals the presence of a supermassive black hole. But it has even more to tell us, explains Francesco Costagliola (Chalmers), co-author on the paper.

“The jets we usually see emerging from galaxy nuclei are very narrow tubes of hot plasma. This jet is very different. Instead it’s extremely cool, and its light comes from dense gas composed of molecules,” he says.

The jet has ejected molecular gas equivalent to two million times the mass of the Sun over a period of only around half a million years — a very short time in the life of a galaxy. During this short and dramatic phase in the galaxy’s evolution, its central, supermassive black hole must have grown fast.

“Black holes that cause powerful narrow jets can grow slowly by accreting hot plasma. The black hole in NGC1377, on the other hand, is on a diet of cold gas and dust, and can therefore grow — at least for now — at a much faster rate,” explains team member Jay Gallagher (University of Wisconsin-Madison).

The motion of the gas in the jet also surprised the astronomers. The measurements with Alma are consistent with a jet that is precessing — swirling outwards like water from a garden sprinkler.

“The jet’s unusual swirling could be due to an uneven flow of gas towards the central black hole. Another possibility is that the galaxy’s centre contains two supermassive black holes in orbit around each other,” says Sebastien Muller, Chalmers, also a member of the team.

The discovery of the remarkable cool, swirling jet from the centre of this galaxy would have been impossible without Alma, concludes Susanne Aalto.

“Alma’s unique ability to detect and measure cold gas is revolutionising our understanding of galaxies and their central black holes. In NGC 1377 we’re witnessing a transient stage in a galaxy’s evolution which will help us understand the most rapid and important growth phases of supermassive black holes, and the life cycle of galaxies in the universe,” she says.

Breaking News: Three New Findings Hint to Purpose of Concern

I suggest the purpose of these three studies released yesterday, appear to imply interest in the action of venturing  funnels of charged particles, often referred to as Active Galactic Nuclei or (AGN), heading into our solar systems path. Such an event could cause serious damage to Earth’s ozone layer, which protects us from harmful radiation.

CREATOR: gd-jpeg v1.0 (using IJG JPEG v62), default quality

There is good reason to be concerned of a stream of charged particles produced by a gamma ray burst, supernova, quasar or galactic center black hole AGN. Why? Because it has happened before in near history and no doubt some number of times over vast history. The last event occurred in the year 774-775 A.D.

In this 2012 discovery, scientist Fusa Miyake announced the detection of high levels of the isotope Carbon-14 and Beryllium-10 in tree rings formed in 775 AD, suggesting that a burst of radiation struck the Earth in the year 774 or 775. Carbon-14 and Beryllium-10 form when radiation from space collides with nitrogen atoms, which then decay to these heavier forms of carbon and beryllium.

gamma-ray-tree-rings

Lead researcher Dr Ralph Neuhӓuser at Astrophysics Institute of the University of Jena in Germany said: “If the gamma ray burst had been much closer to the Earth it would have caused significant harm to the biosphere. But even thousands of light years away, a similar event today could cause havoc with the sensitive electronic systems that advanced societies have come to depend on. The challenge now is to establish how rare such Carbon-14 spikes are i.e. how often such radiation bursts hit the Earth. In the last 3000 years, the maximum age of trees alive today, only one such event appears to have taken place.”

New study published July 1st 2016 – Scientists from Moscow Institute of Physics and Technology (MIPT), the Institute for Theoretical and Experimental Physics, and the National Research University Higher School of Economics have devised a method of distinguishing black holes from compact massive objects that are externally indistinguishable from one another. The method involves studying the energy spectrum of particles moving in the vicinity — in one case it will be continuous and in the other it will be discrete. The findings have been published in Physical Review D.

schwarzshild_radius_m

Black holes, which were predicted by Einstein’s theory of general relativity, have an event horizon — a boundary beyond which nothing, even light, can return to the outside world. The radius of this boundary is called the Schwarzschild radius, in physical terms it is the radius of an object for which the escape velocity is greater than the speed of light, which means that nothing is able to overcome its gravity.

Astrophysicists have not yet been able to “see” a black hole directly, but there are many objects that are “suspected” of being black holes. Most scientists are sure that in the center of our galaxy there is a supermassive black hole; there are binary systems where one of the components is most likely a black hole. However, some astrophysicists believe that there may be compact massive objects that fall very slightly short of black hole status; their range is only a little larger than the Schwarzschild radius. It may be the case that some of the “suspects” are in fact objects such as these. From the outside, however, they are not distinguishable from black holes.

_radiation_black_hole

“We examined the scalar quantum field around a black hole and a compact object and found that around the collapsing object – it is a black hole; explains FedorPopov, of Moscow Institute of Physics and Technology (MIPT), there are no bound states, but around the compact object there are.”

Second article published July 1st 2016 – Some galaxies pump out vast amounts of energy from a very small volume of space, typically not much bigger than our own solar system. The cores of these galaxies, so called Active Galactic Nuclei or AGNs, are often hundreds of millions or even billions of light years away, so are difficult to study in any detail. Natural gravitational ‘microlenses’ can provide a way to probe these objects, and now a team of astronomers have seen hints of the extreme AGN brightness changes that hint at their presence.

synchrontron_emission_m

The energy output of an AGN is often equivalent to that of a whole galaxy of stars. This is an output so intense that most astronomers believe only gas falling in towards a supermassive black hole – an object with many millions of times the mass of the Sun – can generate it. As the gas spirals towards the black hole it speeds up and forms a disc, which heats up and releases energy before the gas meets its demise.

A research team from the University of Edinburgh, explain if a planet or star in an intervening galaxy passes directly between the Earth and a more distant AGN, over a few years or so they act as a lens, focusing and intensifying the signal coming from near the black hole. This type of lensing, due to a single star, is termed microlensing. As the lensing object travels across the AGN, emitting regions are amplified to an extent that depends on their size, providing astronomers with valuable clues.

_Monochromatic_Emission_m

There are expected to be fewer than 100 active AGN microlensing events on the sky at any one time, but only some will be at or near their peak brightness. The big hope for the future is the Large Synoptic Survey Telescope (LSST), a project the UK recently joined. From 2019 on, it will survey half the sky every few days, so has the potential to watch the characteristic changes in the appearance of the AGNs as the lensing events take place.

Third study published July 1st 2016 – A study of gravitationally lensed images of four mini-jets of material ejected from a central supermassive black hole has revealed the structure of these distant galaxies in unprecedented detail. This has enabled astronomers to trace particle emissions to a very small region at the heart of the quasars, and helped to solve a 50-year-old puzzle about their source. The results will be presented by Dr Neal Jackson at the National Astronomy Meeting in Nottingham on Friday, 1st July.

gravitational_lensing_m

“In radio-loud quasars, the intense radio emission clearly comes from vast jets of material blasted out from the region around a central black hole. By contrast, the radio emission from radio-quiet quasars is extremely feeble and difficult to see, so it has been hard to identify its source,” explained Jackson of the Jodrell Bank Center for Astrophysics in Manchester. “To study most radio-quiet quasars, we will have to wait until future extremely large telescopes, like the Square Kilometer Array, come online. However, if we find radio-quiet quasars which are lensed by galaxies in front of them, we can use the increased brightness to be able to study them with today’s radio telescopes.”

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