Indian astrophysicists have discovered relic radio signals that are emanating from the edge of a distant low-mass galaxy cluster named Abell 16971.
Stemming from a merger of two galaxy clusters, such radio signals provide a unique opportunity to study matter and galaxy cluster physics that cannot be explored in laboratories.
Since the Big Bang, galaxy cluster mergers are the most energetic events in the universe. Behaving like particle accelerators, such mergers release tremendous energy and accelerate electrons close to the speed of light, eventually generating tsunami-like shock waves. These waves then reach the edge of clusters and emit relic radio signals.
Relics are common in massive merging clusters. But only a few relics have been detected in low-mass clusters.
While scanning the Northern Sky with the LOFAR Two-metre Sky Survey (LoTSS), an array of radio telescopes, the scientists from the Savitribai Phule Pune University and the National centre for radio Astrophysics of Tata Institute of Fundamental Research, both in Pune, India, accidentally discovered Abell 1697. They observed that the cluster is moving away from us. The cluster is home to 84 galaxies.
Radio and optical images reveal that the radio emission from the cluster is purely diffuse in nature. Survey provides reasonable evidence that the structure is a peripheral relic. The diffuse radio emission has very low surface brightness.
Analysis indicates that the radio emission is a radio phoenix, a special type of relic radio signal generated by fossil electrons from the past events of radio galaxies.
References
1. Paul, S. et al. Radio-relic and the diffuse emission trail discovered in a low mass galaxy cluster Abell 1697. Astron. Astrophys. 633, A9 (2020) Source: https://www.natureasia.com/
An artist’s depiction of an ice-covered planet in a distant solar system resembles what the early Earth might have looked like if a mysterious mix of greenhouse gases had not warmed the climate, Credit: ESA
A UC Riverside-led astrobiology team discovered that methane, a potent greenhouse gas, was not the climate savior once imagined for the mysterious middle chapter of Earth history For at least a billion years of the distant past, planet Earth should have been frozen over but wasn’t. Scientists thought they knew why, but a new modeling study from the Alternative Earths team of the NASA Astrobiology Institute has fired the lead actor in that long-accepted scenario. Humans worry about greenhouse gases, but between 1.8 billion and 800 million years ago, microscopic ocean dwellers really needed them. The sun was 10 to 15 percent dimmer than it is today—too weak to warm the planet on its own. Earth required a potent mix of heat-trapping gases to keep the oceans liquid and livable. For decades, atmospheric scientists cast methane in the leading role. The thinking was that methane, with 34 times the heat-trapping capacity of carbon dioxide, could have reigned supreme for most of the first 3.5 billion years of Earth history, when oxygen was absent initially and little more than a whiff later on. (Nowadays oxygen is one-fifth of the air we breathe, and it destroys methane in a matter of years.) “A proper accounting of biogeochemical cycles in the oceans reveals that methane has a much more powerful foe than oxygen,” said Stephanie Olson, a graduate student at the University of California, Riverside, a member of the Alternative Earths team and lead author of the new study published September 26 in the Proceedings of the National Academy of Sciences. “You can’t get significant methane out of the ocean once there is sulfate.” Sulfate wasn’t a factor until oxygen appeared in the atmosphere and triggered oxidative weathering of rocks on land. The breakdown of minerals such as pyrite produces sulfate, which then flows down rivers to the oceans. Less oxygen means less sulfate, but even 1 percent of the modern abundance is sufficient to kill methane, Olson said. Stephanie Olson and Tim Lyons next to an image of visualizations of sulfate concentrations (top) and methane destruction (bottom) from their biogeochemical model of Earth’s ocean and atmosphere roughly one billion years ago.
Credit: UC Riverside
Olson and her Alternative Earths coauthors, Chris Reinhard, an assistant professor of earth and atmospheric sciences at Georgia Tech University, and Timothy Lyons, a distinguished professor of biogeochemistry at UC Riverside, assert that during the billion years they assessed, sulfate in the ocean limited atmospheric methane to only 1 to 10 parts per million—a tiny fraction of the copious 300 parts per million touted by some previous models. The fatal flaw of those past climate models and their predictions for atmospheric composition, Olson said, is that they ignore what happens in the oceans, where most methane originates as specialized bacteria decompose organic matter. Seawater sulfate is a problem for methane in two ways: Sulfate destroys methane directly, which limits how much of the gas can escape the oceans and accumulate in the atmosphere. Sulfate also limits the production of methane. Life can extract more energy by reducing sulfate than it can by making methane, so sulfate consumption dominates over methane production in nearly all marine environments. The numerical model used in this study calculated sulfate reduction, methane production, and a broad array of other biogeochemical cycles in the ocean for the billion years between 1.8 billion and 800 million years ago. This model, which divides the ocean into nearly 15,000 three-dimensional regions and calculates the cycles for each region, is by far the highest resolution model ever applied to the ancient Earth. By comparison, other biogeochemical models divide the entire ocean into a two-dimensional grid of no more than five regions. “There really aren’t any comparable models,” says Reinhard, who was lead author on a related paper in Proceedings of the National Academy of Sciences that described the fate of oxygen during the same model runs that revealed sulfate’s deadly relationship with methane. Reinhard notes that oxygen dealt methane an additional blow, based on independent evidence published recently by the Alternative Earths team in the journals Science and Geology. These papers describe geochemical signatures in the rock record that track extremely low oxygen levels in the atmosphere, perhaps much less than 1 percent of modern values, up until about 800 million years ago, when they spiked dramatically. Less oxygen seems like a good thing for methane, since they are incompatible gases, but with oxygen at such extremely low levels, another problem arises. “Free oxygen [O2] in the atmosphere is required to form a protective layer of ozone [O3], which can shield methane from photochemical destruction,” Reinhard said. When the researchers ran their model with the lower oxygen estimates, the ozone shield never formed, leaving the modest puffs of methane that escaped the oceans at the mercy of destructive photochemistry. With methane demoted, scientists face a serious new challenge to determine the greenhouse cocktail that explains our planet’s climate and life story, including a billion years devoid of glaciers, Lyons said. Knowing the right combination other warming agents, such as water vapor, nitrous oxide, and carbon dioxide, will also help us assess habitability of the hundreds of billions of other Earth-like planets estimated to reside in our galaxy. “If we detect methane on an exoplanet, it is one of our best candidates as a biosignature, and methane dominates many conversations in the search for life on Mars,” Lyons said. “Yet methane almost certainly would not have been detected by an alien civilization looking at our planet a billion years ago—despite the likelihood of its biological production over most of Earth history.”
Contacts and sources: Sean Nealon, University of California Riverside
Using laboratory techniques to mimic the conditions found deep inside the Earth, a team of Carnegie scientists led by Ho-Kwang "Dave" Mao has identified a form of iron oxide that they believe could explain seismic and geothermal signatures in the deep mantle. Their work is published in Nature. Iron and oxygen are two of the most geochemically important elements on Earth. The core is rich in iron and the atmosphere is rich in oxygen, and between them is the entire range of pressures and temperatures on the planet. An artwork depicting the decomposition of FeOOH in lower mantle conditions. The cycle starts from α-FeOOH (blue dot on the top) to its high-pressure form (brown dot), to FeO2 (center crystal) and hydrogen (cyan bubbles), and finally produce other minerals (bubbles on the left side). "Interactions between oxygen and iron dictate Earth's formation, differentiation--or the separation of the core and mantle--and the evolution of our atmosphere, so naturally we were curious to probe how such reactions would change under the high-pressure conditions of the deep Earth," said Mao. The research team--Qingyang Hu, Duck Young Kim, Wenge Yang, Liuxiang Yang, Yue Meng, Li Zhang, & Ho-Kwang Mao--put ordinary rust, or FeOOH, under about 900,000 times normal atmospheric pressure and at about 3200 degrees Fahrenheit and were able to synthesize a form of iron oxide, FeO2, that structurally resembles pyrite, also known as fool's gold. The reaction gave off hydrogen in the form of H2. FeOOH is found in iron ore deposits that exist in bogs, so it could easily move into the deep Earth at plate tectonic boundaries, as could samples of ferric oxide, Fe2O3, which along with water will also form the pyrite-like iron oxide under deep lower mantle conditions. Why does this interest the researchers? For one thing, this type of reaction could have started in Earth's infancy, and understanding it could inform theories of our own planet's evolution, as well as its current geochemistry. Furthermore, the H2 released in this reaction would work its way upward, possibly reacting with other materials on its way. Meanwhile, the iron oxide would settle planet's depths and form reservoirs of oxygen there, particularly if one of these patches of iron oxide moved upward along the pressure gradient to the middle part of the mantle and separated into iron and O2. "Pools of free oxygen under these conditions could create many reactions and chemical phases, which might be responsible for seismic and geochemical signatures of the deep Earth," Mao explained. "Our experiments mimicking mantle conditions demonstrate that more research is needed on this pyrite-like phase of iron oxide." Hu added. The research team believes their findings could even offer an alternate explanation for the Great Oxygenation Event that changed Earth's atmosphere between 2 and 2.5 billion years ago. The rise of bacteria performing photosynthesis, which releases oxygen as a byproduct, is often considered the source of the rapid increase in atmospheric oxygen, which had previously been scarce. But releases of oxygen from upwelling of deep mantle FeO2 patches could provide an abiotic explanation for the phenomenon, they say. Contacts and sources: The Carnegie Institution for Science. Source: http://www.ineffableisland.com/
NASA's Hubble Space Telescope has detected hydrogen and helium, but no water vapour, in the atmosphere of 55 Cancri e – the first time the atmosphere of a "super-Earth" has been analysed successfully. For the first time, astronomers were able to analyse the atmosphere of an exoplanet in the class known as super-Earths. Using data gathered with the NASA/ESA Hubble Space Telescope and new analysis techniques, the exoplanet 55 Cancri e is revealed to have a dry atmosphere without any indications of water vapour. The results, to be published in the Astrophysical Journal, indicate that the atmosphere consists mainly of hydrogen and helium. The international team, led by scientists from University College London (UCL), took measurements of the nearby exoplanet 55 Cancri e, a super-Earth with a mass of eight Earths. It is located in the planetary system of 55 Cancri, a star about 40 light-years from Earth. Using observations made by the Wide Field Camera 3 (WFC3) on board the NASA/ESA Hubble Space Telescope, the scientists were able to analyse the atmosphere in detail. The results were only made possible by exploiting a newly-developed processing technique. "This is a very exciting result,
because it's the first time that we have been able to find the spectral fingerprints that show the gases present in the atmosphere of a super-Earth," explains Angelos Tsiaras, a PhD student at UCL, who developed the analysing technique, along with his colleagues Ingo Waldmann and Marco Rocchetto. "The observations of 55 Cancri e's atmosphere suggest that the planet has managed to cling on to a significant amount of hydrogen and helium from the nebula from which it originally formed." Super-Earths like 55 Cancri e are thought to be the most common type of planet in our galaxy. They acquired the name 'super-Earth' because they have a mass larger than that of the Earth, but are still much smaller than the gas giants in the Solar System. The WFC3 instrument on Hubble has already been used to probe the atmospheres of two other super-Earths, but no spectral features were found in those previous studies. 55 Cancri e, however, is an unusual super-Earth, as it orbits very close to its parent star. A year on the exoplanet lasts for only 18 hours and temperatures on the surface are thought to reach around 2000 degrees Celsius. Because the planet orbits its bright parent star at such a small distance, the team was able to use their new technique to extract key information about the planet, during its transits in front of the host star. Observations were made by scanning the WFC3 very quickly across the star to create a number of spectra. By combining these observations and processing them through analytic software, the researchers were able to retrieve the spectrum of 55 Cancri e embedded in the light of its parent star. "This result gives a first insight into the atmosphere of a super-Earth. We now have clues as to what the planet is currently like and how it might have formed and evolved, and this has important implications for 55 Cancri e and other super-Earths," said Giovanna Tinetti, also from UCL. Intriguingly, the data also contain hints of the presence of hydrogen cyanide, a marker for carbon-rich atmospheres. "Such an amount of hydrogen cyanide would indicate an atmosphere with a very high ratio of carbon to oxygen," said Olivia Venot, KU Leuven, who developed an atmospheric chemical model of 55 Cancri e that supported the analysis of the observations. "If the presence of hydrogen cyanide and other molecules is confirmed in a few years time by the next generation of infrared telescopes, it would support the theory that this planet is indeed carbon rich and a very exotic place," concludes Jonathan Tennyson, UCL. "Although hydrogen cyanide, or prussic acid, is highly poisonous, so it is perhaps not a planet I would like to live on!"Source: http://www.futuretimeline.net/
Washington: It's a known fact that oxygen is crucial for the existence of animals on Earth, but did you know that an increase in oxygen level did not apparently lead to the evolution of the first animals. A new research conducted by the University of Southern Denmark showed that 1.4 billion years ago there was enough oxygen for animals and yet over 800 million years went by before the first animals appeared on Earth. Animals evolved by about 600 million years ago, which was late in Earth's history. The late evolution of animals and the fact that oxygen is central for animal respiration, has led to the widely promoted idea that animal evolution corresponded with a late a rise in atmospheric oxygen concentrations. Researchers Emma Hammarlund and Don Canfield said that their study indicates that sufficient oxygen in itself does not seem to be enough for animals to rise. Their analyses revealed that a deep ocean 1.4 billion years ago contained at least 4 per cent of modern oxygen concentrations. The study is published in the journal Proceedings of National Academy of Sciences. — ANI. Source: http://www.tribuneindia.com
