Supermassive black-hole-eating star ejects high-speed flare

Artist’s conception of a star being drawn toward a black hole and destroyed (left), and the black hole later emitting a “jet” of plasma composed of the debris left from the star’s destruction (credit: modified from an original image by Amadeo Bachar)

An international team of astrophysicists has for the first time witnessed a black hole swallowing a star and ejecting a flare of matter moving at nearly the speed of light.

The finding, reported in the journal Science, tracks the star — about the size of our sun — as it shifts from its customary path, slips into the gravitational pull of a supermassive black hole and is sucked in, said Sjoert van Velzen, a Hubble fellow at Johns Hopkins University.

Jet escapes from near the event horizon

“These events are extremely rare,” van Velzen said. “It’s the first time we see everything from the stellar destruction followed by the launch of a conical outflow, also called a jet, and we watched it unfold over several months.”

The astrophysicists had predicted that when a black hole is force-fed a large amount of gas, in this case a whole star, a fast-moving jet of plasma — elementary particles in a magnetic field — can escape from near the black hole rim, or “event horizon.” This study suggests this prediction was correct, the scientists said.

“Previous efforts to find evidence for these jets, including my own, were late to the game,” said van Velzen, who led the analysis and coordinated the efforts of 13 other scientists in the United States, the Netherlands, Great Britain and Australia.

Supermassive black holes, the largest of black holes, are believed to exist at the center of most massive galaxies. This particular one lies at the lighter end of the supermassive black hole spectrum, at only about a million times the mass of our sun, but still packing the force to gobble a star.

Witnessing a star destruction

The first observation of the star being destroyed was made by a team at The Ohio State University, using an optical telescope in Hawaii. That team announced its discovery on Twitter in early December 2014.

After reading about the event, van Velzen contacted an astrophysics team led by Rob Fender at the University of Oxford in Great Britain. That group used radio telescopes to follow up as fast as possible. They were just in time to catch the action.

By the time it was done, the international team had data from satellites and ground-based telescopes that gathered X-ray, radio and optical signals, providing a stunning “multi-wavelength” portrait of this event.

It helped that the galaxy in question is closer to Earth than those studied previously in hopes of tracking a jet emerging after the destruction of a star. This galaxy is about 300 million light years away, while the others were at least three times farther away. One light year is 5.88 trillion miles.

The first step for the international team was to rule out the possibility that the light was from a pre-existing expansive swirling mass called an “accretion disk” that forms when a black hole is sucking in matter from space. That helped to confirm that the sudden increase of light from the galaxy was due to a newly trapped star.

“The destruction of a star by a black hole is beautifully complicated, and far from understood,” van Velzen said. “From our observations, we learn the streams of stellar debris can organize and make a jet rather quickly, which is valuable input for constructing a complete theory of these events.”

Abstract of A radio jet from the optical and X-ray bright stellar tidal disruption flare ASASSN-14li

The tidal disruption of a star by a supermassive black hole leads to a short-lived thermal flare. Despite extensive searches, radio follow-up observations of known thermal stellar tidal disruption flares (TDFs) have not yet produced a conclusive detection. We present a detection of variable radio emission from a thermal TDF, which we interpret as originating from a newly-launched jet. The multi-wavelength properties of the source present a natural analogy with accretion state changes of stellar mass black holes, suggesting all TDFs could be accompanied by a jet. In the rest frame of the TDF, our radio observations are an order of magnitude more sensitive than nearly all previous upper limits, explaining how these jets, if common, could thus far have escaped detection.

Do fish have emotions and consciousness?

Zebrafish (credit: Azul/CC)

Researchers in Spain and the U.K. have made the first observations infish of an increase in body temperature of 2–4 ºC when zebrafish were subjected to a stressful situation (they were confined in a net inside the tank at an uncomforable 27ºC for 15 minutes).*

This phenomenon is called “emotional fever” because it’s related to the emotions that animals feel in the face of an external stimulus, which been linked, controversially, with their consciousness. Until now, emotional fever had been observed in mammals, birds and certain reptiles, but never in fish, which is why fish have been regarded as animals without emotions or consciousness.

Does consciousness require a cerebral cortex?

Scientists differ on the degree to which fish can have consciousness. Some researchers argue that they cannot have consciousness as their brain is simple, lacking a cerebral cortex, and they have little capacity for learning and memory, a very simple behavioral repertoire, and no ability to experience suffering.

Others contest this view, pointing out that, despite the small size of the fish brain, detailed morphological and behavioral analyses have highlighted similarities between some fish brain structures and those seen in other vertebrates, such as the hippocampus (linked to learning and spatial memory) and the amygdala (linked to emotions) of mammals.

The research was published in an open-access paper recently in Proceedings of the Royal Society of London, Biological Sciences. It began three years ago at the Universitat Autònoma de Barcelona. Scientists from Stirling and Bristol universities helped with statistical analysis of the data.

* The researchers divided 72 zebrafish into two groups of 36 and placed them in a large tank with different interconnected compartments with temperatures ranging from 18ºC to 35ºC. The fish in one of these groups — the control group — were left undisturbed in the area where the temperature was at the level they prefer: 28ºC. The other group was subjected to a stressful situation: they were confined in a net inside the tank at 27ºC for 15 minutes. After this period the group was released.

While the control fish mainly stayed in the compartments at around 28ºC, the fish subjected to stress tended to move towards the compartments with a higher temperature, increasing their body temperature by two to four degrees. The researchers point to this as proof that these fish were displaying emotional fever.

Abstract of Fish can show emotional fever: stress-induced hyperthermia in zebrafish

Whether fishes are sentient beings remains an unresolved and controversial question. Among characteristics thought to reflect a low level of sentience in fishes is an inability to show stress-induced hyperthermia (SIH), a transient rise in body temperature shown in response to a variety of stressors. This is a real fever response, so is often referred to as ‘emotional fever’. It has been suggested that the capacity for emotional fever evolved only in amniotes (mammals, birds and reptiles), in association with the evolution of consciousness in these groups. According to this view, lack of emotional fever in fishes reflects a lack of consciousness. We report here on a study in which six zebrafish groups with access to a temperature gradient were either left as undisturbed controls or subjected to a short period of confinement. The results were striking: compared to controls, stressed zebrafish spent significantly more time at higher temperatures, achieving an estimated rise in body temperature of about 2–4°C. Thus, zebrafish clearly have the capacity to show emotional fever. While the link between emotion and consciousness is still debated, this finding removes a key argument for lack of consciousness in fishes.

New inventions track greenhouse gas, remediate oil spills

Camera test at Foljesjon, a lake in a research area west of Vanersborg, Sweden (credit: Linkoping University)

A new camera that can image methane in the air, allowing for precision monitoring of a greenhouse gas, has been developed by a team of researchers from Linköping and Stockholm Universities.

The new camera should help us better understand the rapid but irregular increase of methane in the atmosphere (which has puzzled researchers) and identify the sources and sinks of methane in the landscape. It may also suggest ways to reduce emissions.

”The camera is very sensitive, which means that the methane is both visible and measureable close to ground level, with much higher resolution [less than a square meter and at ambient levels (~1.8 ppmv, or parts per million volume)] than previously. Being able to measure on a small scale is crucial,” says Magnus Gålfalk, Assistant Professor at Tema Environmental Change, Linköping University who led the study.

An image of methane gas from the hyperspectral infrared camera, visualized in purple (credit: Linköping University)

The advanced hyperspectral (across the spectrum) thermal infrared camera weighs 30 kilos and measures 50 x 45 x 25 centimeters. It is optimized to measure the same portion of the solar radiation spectrum that methane absorbs and which makes methane such a powerful greenhouse gas.

The camera can be used to measure emissions from many environments including sewage sludge deposits, combustion processes, animal husbandry, and lakes.

For each pixel in the image (320 x 256 pixels), the camera records a precise spectrum range (in the 7.7 microns thermal IR region), which makes it possible to quantify the methane separately from the other gases.

The camera was developed by a team with expertise in astronomy, biogeochemistry, engineering. and environmental sciences. “We’re working to make it airborne for more large-scale methane mapping,” says principal investigator David Bastviken, professor at Tema Environmental Change, Linköping University.

The research was recently published in Nature Climate Change.

Super-absorbent material to soak up oil spills

Boron nitride material supported by a plant spike, demonstrating its light weight (credit: Weiwei Lei et al./Nature Communications)

In hopes of limiting the disastrous environmental effects of massive oil spills, materials scientists from Drexel University and Deakin University (Australia) have teamed up to manufacture and test a new “boron nitride nanosheet” material that can absorb oils and organic solvents up to 33 times its weight. That could make it possible to quickly mitigate these costly, environmentally damaging accidents.

The material, which literally absorbs oil like a sponge, is now ready to be tested by industry after two years of refinement in the laboratory at Deakin’s Institute for Frontier Materials (IFM).

Deakin Professor Ying (Ian) Chen, PhD, the lead author of the project’s research paper, recently published in Nature Communications, said the material is the most exciting advancement in oil spill remediation technology in decades.

“Oil spills are a global problem and wreak havoc on our aquatic ecosystems, not to mention they cost billions of dollars in damage,” Chen said. “Everyone remembers the Gulf Coast disaster, but here in Australia they are a regular problem, and not just in our waters. Oil spills from trucks and other vehicles can close freeways for an entire day, again amounting to large economic losses,” Chen said.

The nanosheet is made up of flakes just several nanometers (one billionth of a meter) in thickness with tiny holes. This strecture enables the nanosheet to increase its effective surface area to 273 square meters (3000 square feet) per gram.

Researchers from Drexel’s College of Engineering helped to study and functionalize the material, which started as boron nitride powder, commonly called “white graphite.” By forming the powder into atomically thin sheets, the material could be made into a sponge.

“The mechanochemical technique developed meant it was possible to produce high-concentration stable aqueous colloidal solutions of boron nitride sheets, which could then be transformed into the ultralight porous aerogels and membranes for oil clean-up,” said Vadym Mochalin, PhD, a co-author of the paper, who was a research associate professor at Drexel while working on the project, and is now an associate professor at Missouri University of Science and Technology.

The Drexel team used computational modeling to help understand the intimate details of how the material was formed. In the process, the team learned that the boron nitride nanosheets are flame resistant — which means they could also find applications in electrical and heat insulation.

The nanotechnology team at Deakin’s Institute for Frontier Materials has been working on boron nitride nanomaterials for two decades and has been internationally recognized for its work in the development of boron nitride nanotubes and nanosheets. This project is the next step in the IFM’s continued research to discover new uses for the material.

Abstract of Making methane visible

Methane (CH4) is one of the most important greenhouse gases, and an important energy carrier in biogas and natural gas. Its large-scale emission patterns have been unpredictable and the source and sink distributions are poorly constrained. Remote assessment of CH4 with high sensitivity at a m2 spatial resolution would allow detailed mapping of the near-ground distribution and anthropogenic sources in landscapes but has hitherto not been possible. Here we show that CH4 gradients can be imaged on the <m2scale at ambient levels (~1.8 ppm) and filmed using optimized infrared (IR) hyperspectral imaging. Our approach allows both spectroscopic confirmation and quantification for all pixels in an imaged scene simultaneously. It also has the ability to map fluxes for dynamic scenes. This approach to mapping boundary layer CH4 offers a unique potential way to improve knowledge about greenhouse gases in landscapes and a step towards resolving source–sink attribution and scaling issues.

Abstract of Boron nitride colloidal solutions, ultralight aerogels and freestanding membranes through one-step exfoliation and functionalization

Manufacturing of aerogels and membranes from hexagonal boron nitride (h-BN) is much more difficult than from graphene or graphene oxides because of the poor dispersibility of h-BN in water, which limits its exfoliation and preparation of colloidal solutions. Here, a simple, one-step mechano-chemical process to exfoliate and functionalize h-BN into highly water-dispersible, few-layer h-BN containing amino groups is presented. The colloidal solutions of few-layer h-BN can have unprecedentedly high concentrations, up to 30 mg ml−1, and are stable for up to several months. They can be used to produce ultralight aerogels with a density of 1.4 mg cm−3, which is ~1,500 times less than bulk h-BN, and freestanding membranes simply by cryodrying and filtration, respectively. The material shows strong blue light emission under ultraviolet excitation, in both dispersed and dry state.