суббота, 30 марта 2019 г.

What happened before the Big Bang?

A team of scientists has proposed a powerful new test for inflation, the theory that the universe dramatically expanded in size in a fleeting fraction of a second right after the Big Bang. Their goal is to give insight into a long-standing question: what was the universe like before the Big Bang?











What happened before the Big Bang?
An artist’s illustration showing the patterns of signals generated by primordial standard clocks
in different theories of the primordial universe. Top: Big Bounce. Bottom: Inflation
[Credit: CfA/Zhong-Zhi Xianyu, Xingang Chen, Avi Loeb]

Although cosmic inflation is well known for resolving some important mysteries about the structure and evolution of the universe, other very different theories can also explain these mysteries. In some of these theories, the state of the universe preceding the Big Bang – the so-called primordial universe – was contracting instead of expanding, and the Big Bang was thus a part of a Big Bounce.


To help decide between inflation and these other ideas, the issue of falsifiability – that is, whether a theory can be tested to potentially show it is false – has inevitably arisen. Some researchers, including Avi Loeb of the Center for Astrophysics | Harvard & Smithsonian (CfA) in Cambridge, Mass., have raised concerns about inflation, suggesting that its seemingly endless adaptability makes it all but impossible to properly test.


“Falsifiability should be a hallmark of any scientific theory. The current situation for inflation is that it’s such a flexible idea, it cannot be falsified experimentally,” Loeb said. “No matter what value people measure for some observable attribute, there are always some models of inflation that can explain it.”


Now, a team of scientists led by the CfA’s Xingang Chen, along with Loeb, and Zhong-Zhi Xianyu of the Physics Department of Harvard University, have applied an idea they call a “primordial standard clock” to the non-inflationary theories, and laid out a method that may be used to falsify inflation experimentally. The study will appear in Physical Review Letters as an Editors’ Suggestion.


In an effort to find some characteristic that can separate inflation from other theories, the team began by identifying the defining property of the various theories – the evolution of the size of the primordial universe.


“For example, during inflation, the size of the universe grows exponentially,” Xianyu said. “In some alternative theories, the size of the universe contracts. Some do it very slowly, while others do it very fast.


“The attributes people have proposed so far to measure usually have trouble distinguishing between the different theories because they are not directly related to the evolution of the size of the primordial universe,” he continued. “So, we wanted to find what the observable attributes are that can be directly linked to that defining property.”


The signals generated by the primordial standard clock can serve such a purpose. That clock is any type of heavy elementary particle in the primordial universe. Such particles should exist in any theory and their positions should oscillate at some regular frequency, much like the ticking of a clock’s pendulum.


The primordial universe was not entirely uniform. There were tiny irregularities in density on minuscule scales that became the seeds of the large-scale structure observed in today’s universe. This is the primary source of information physicists rely on to learn about what happened before the Big Bang. The ticks of the standard clock generated signals that were imprinted into the structure of those irregularities. Standard clocks in different theories of the primordial universe predict different patterns of signals, because the evolutionary histories of the universe are different.


“If we imagine all of the information we learned so far about what happened before the Big Bang is in a roll of film frames, then the standard clock tells us how these frames should be played,” Chen explained. “Without any clock information, we don’t know if the film should be played forward or backward, fast or slow, just like we are not sure if the primordial universe was inflating or contracting, and how fast it did so. This is where the problem lies. The standard clock put time stamps on each of these frames when the film was shot before the Big Bang, and tells us how to play the film.”


The team calculated how these standard clock signals should look in non-inflationary theories, and suggested how they should be searched for in astrophysical observations. “If a pattern of signals representing a contracting universe were found, it would falsify the entire inflationary theory,” Xianyu said.


The success of this idea lies with experimentation. “These signals will be very subtle to detect,” Chen said, “and so we may have to search in many different places. The cosmic microwave background radiation is one such place, and the distribution of galaxies is another. We have already started to search for these signals and there are some interesting candidates already, but we need more data.”


Many future galaxy surveys, such as US-lead LSST, European’s Euclid and the newly approved project by NASA, SphereX, are expected to provide high quality data that can be used toward the goal.


The preprint of this paper is available in: https://arxiv.org/abs/1809.02603. A related previous work can be found in: https://arxiv.org/abs/1509.03930.


Source: Harvard-Smithsonian Center for Astrophysics [March 26, 2019]



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In hunt for life, astronomers identify most promising stars

NASA’s new Transiting Exoplanet Survey Satellite (TESS) is designed to ferret out habitable exoplanets, but with hundreds of thousands of sunlike and smaller stars in its camera views, which of those stars could host planets like our own?











In hunt for life, astronomers identify most promising stars
Artists’ concept of the Transiting Exoplanet Survey Satellite against a background of stars and orbiting planets
in the Milky Way [Credit: European Space Agency, European Southern Observatory
and NASA’s Goddard Space Flight Center]

TESS will observe 400,000 stars across the whole sky to catch a glimpse of a planet transiting across the face of its star, one of the primary methods by which exoplanets are identified.


A team of astronomers from Cornell University, Lehigh University and Vanderbilt University has identified the most promising targets for this search in the new “TESS Habitable Zone Star Catalog,” published in Astrophysical Journal Letters. Lead author is Lisa Kaltenegger, professor of astronomy at Cornell, director of Cornell’s Carl Sagan Institute and a member of the TESS science team.


The catalog identifies 1,822 stars for which TESS is sensitive enough to spot Earth-like planets just a bit larger than Earth that receive radiation from their star equivalent to what Earth receives from our sun. For 408 stars, TESS can glimpse a planet just as small as Earth, with similar irradiation, in one transit alone.


“Life could exist on all sorts of worlds, but the kind we know can support life is our own, so it makes sense to first look for Earth-like planets,” Kaltenegger said. “This catalog is important for TESS because anyone working with the data wants to know around which stars we can find the closest Earth-analogs.”


Kaltenegger leads a program on TESS that is observing the catalog’s 1,822 stars in detail, looking for planets. “I have 408 new favorite stars,” said Kaltenegger. “It is amazing that I don’t have to pick just one; I now get to search hundreds of stars.”


Confirming an exoplanet has been observed and figuring out the distance between it and its star requires detecting two transits across the star. The 1,822 stars the researchers have identified in the catalog are ones from which TESS could detect two planetary transits during its mission. Those orbital periods place them squarely in the habitable zone of their star.



The habitable zone is the area around a star at which water can be liquid on a rocky planet’s surface, therefore considered ideal for sustaining life. As the researchers note, planets outside the habitable zone could certainly harbor life, but it would be extremely difficult to detect any signs of life on such frozen planets without flying there.


The catalog also identifies a subset of 227 stars for which TESS can not only probe for planets that receive the same irradiation as Earth, but for which TESS can also probe out farther, covering the full extent of the habitable zone all the way to cooler Mars-like orbits. This will allow astronomers to probe the diversity of potentially habitable worlds around hundreds of cool stars during the TESS mission’s lifetime.


The stars selected for the catalog are bright, cool dwarfs, with temperatures roughly between 2,700 and 5,000 degrees Kelvin. The stars in the catalog are selected due to their brightness; the closest are only approximately 6 light-years from Earth.


“We don’t know how many planets TESS will find around the hundreds of stars in our catalog or whether they will be habitable,” Kaltenegger said, “but the odds are in our favor. Some studies indicate that there are many rocky planets in the habitable zone of cool stars, like the ones in our catalog. We’re excited to see what worlds we’ll find.”


A total of 137 stars in the catalog are within the continuous viewing zone of NASA’s James Webb Space Telescope, now under construction. Webb will be able to observe them to characterize planetary atmospheres and search for signs of life in their atmospheres.


Planets TESS identifies may also make excellent targets for observations by ground-based extremely large telescopes currently being built, the researchers note, as the brightness of their host stars would make them easier to characterize.


In addition to Kaltenegger, Joshua Pepper of Lehigh University and Keivan Stassun and Ryan Oelkers of Vanderbilt University contributed to the catalog, which draws from one originally developed at Vanderbilt that contains hundreds of millions of stars.


“This is a remarkable time in human history and a huge leap for our understanding of our place in the universe,” said Stassun, a member of the TESS science team.


Author: Linda B. Glaser | Source: Cornell University [March 26, 2019]



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Widespread losses of pollinating insects in Britain

Many insect pollinator species are disappearing from areas of Great Britain, a new study has found. The research, led by the Centre for Ecology & Hydrology, measured the presence of 353 wild bee and hoverfly species across the country, from 1980 to 2013. It showed one third of species experienced declines in terms of areas in which they were found, while one tenth increased. For the remainder of species, their distribution was either stable or the trend was inconclusive.











Widespread losses of pollinating insects in Britain
Panurgus banksianus (Large Shaggy Bee) is found in coastal regions in Southern England and Wales.
The study shows that the distribution of this species declined by 54 per cent between 1980 – 2013
[Credit: Steven Falk]

A positive but unexpected finding of the study was the increase in key bee species responsible for pollinating flowering crops, such as oil-seed rape. This could be in response to the large increases of mass-flowering crops grown during the study period and government-subsidised schemes that encourage farmers to plant more of the wildflowers they feed on.


The research, published in the journal Nature Communications, also showed that on average, the geographic range of bee and hoverfly species declined by a quarter. This is equivalent to a net loss of 11 species from each 1km square.


Overall losses were more notable for pollinator species found in northern Britain. This may be a result of climate change, with species that prefer cooler temperatures reducing their geographical spread in response to less climatically suitable landscapes.


Dr Gary Powney of the Centre for Ecology & Hydrology, who led the research, says: “We used cutting-edge statistical methods to analyse a vast number of species observations, revealing widespread differences in distribution change across pollinating insects. There is no one single cause for these differences, but habitat loss is a likely key driver of the declines.


“While the increase in key crop pollinators is good news, they are still a relatively small group of species. Therefore, with species having declined overall, it would be risky to rely on this group to support the long-term food security for our country. If anything happens to them in the future there will be fewer other species to ‘step up’ and fulfil the essential role of crop pollination.


He adds: “Non-crop pollinators are also vital for a healthy countryside rich in biodiversity; not only because of their crucial role in pollinating wildflowers, but as a key food resource for other wildlife.


“Wildflowers and pollinators rely on each other for survival. Losses in either are a major cause for concern when we consider the health and beauty of our natural environment.”


Dr Claire Carvell of the Centre for Ecology & Hydrology, a co-author of the study, points out there are multiple environmental pressures leading to changing patterns of occurrence in bees and hoverflies across the country.


She says: “There is an urgent need for more robust data on the patterns and causes of pollinator declines. While this analysis sends us a warning, the findings support previous studies suggesting that conservation actions, such as wildlife-friendly farming and gardening, can have a lasting, positive impact on wild pollinators in rural and urban landscapes. However, these need further refining to benefit a wider range of species.”


Dr Carvell adds: “In addition to recording species sightings, more standardised monitoring of pollinator numbers is required at a national level and a new UK Pollinator Monitoring Scheme has been set up to do just this.”


Over 700,000 records were analysed for this study. Most were collected by expert naturalists in the Bees, Wasps and Ants Recording Society (BWARS) and the UK Hoverfly Recording Scheme, in more than 19,000 1km by 1km squares across Great Britain. It’s thought to be the first study of its kind, since there have been no previous large-scale, long-term, species-specific estimates of distribution change for pollinating insects in Britain.


Mike Edwards of BWARS said: “All important studies of animal population trends, such as this latest research, rely entirely on the wildlife recorders who go out and record sightings of different species in their area. Therefore, we would encourage more people to take part in wildlife recording, so we can increase our understanding of how wildlife is responding to environmental change.”


Source: Centre for Ecology & Hydrology [March 26, 2019]



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Genetic tagging may help conserve the world’s wildlife

Tracking animals using DNA signatures are ideally suited to answer the pressing questions required to conserve the world’s wildlife, providing benefits over invasive methods such as ear tags and collars, according to a new study by University of Alberta biologists.











Genetic tagging may help conserve the world's wildlife
Hair samples like this one can be collected to track animals using their DNA signatures,
an approach providing benefits over traditional invasive methods such as ear tags
and collars, according to a new study by UAlberta biologists
[Credit: Clayton Lamb]

Genetic tagging, or the identification and tracking of individual animals using DNA, is a non-invasive method of conducting research that uses samples from shed hair, feathers, feces, or saliva.


“This method provides a toolkit that can answer many of the pressing questions in ecology and conservation and provides a ‘one-stop-shop’ for getting these answers,” explained Clayton Lamb, PhD candidate and Vanier scholar in the Department of Biological Sciences and lead author on the study. “Other methods would generally need to be combined to acquire similar insight. Genetic tagging approaches are complementary to traditional approaches and add a powerful tool to the ecologists’ toolkit.”


In addition to being non-invasive–in fact, there’s no need to handle individual animals at all–there are many benefits to using genetic tagging over other methods. Genetic tagging can cover more ground and is scalable, allowing scientists to examine overall population density or the composition of a single community. It also provides the ability to recognize individual animals with great precision, allowing scientists to research animals that are otherwise difficult to study.


Access to DNA sequencing technology has grown increasingly affordable since the 2000s, thereby increasing access and usability for ecologists and biologists around the globe. And it’s a good thing too, as our world continues to change.


“As human pressures on the globe increase, scientists are tasked with identifying drivers of decline and mobilizing this evidence to promote mitigation,” said Lamb. “Genetic tagging offers a powerful approach to parameterize such relationships across massive spatial extents, for difficult to sample species, and in a cost-effective and socially-acceptable manner.”


The study is published in Ecological Applications.


Author: Katie Willis | Source: University of Alberta [March 26, 2019]



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Future of elephants living in captivity hangs in the balance

Scientists at the University of Sheffield and University of Turku are looking at ways to boost captive populations of Asian elephants without relying on taking them from the wild.











Future of elephants living in captivity hangs in the balance
Scientists at the University of Sheffield and University of Turku are looking at ways to boost captive populations
of Asian elephants without relying on taking them from the wild [Credit: University of Sheffield]

Almost a third of Asian elephants are in captivity in countries like India, Myanmar and Thailand, mainly being used in the timber industry to drag logs or for tourism.


Sustaining wild populations is the conservation priority but, with so many individuals in captivity, maintaining sustainable captive populations with high welfare standards is also important for the future of the species.


The sustainability of these elephant populations has always relied on the capture of their wild counterparts, but now they are a protected species their future is uncertain.


In a joint research study, the University of Sheffield and the University of Turku, in Finland, working alongside The Myanma Timber Enterprise (MTE), investigated how trends in elephant capture from the wild influenced birth, death and population growth in 3,500 working elephants over 54 years.


Using birth and death rates from years where wild-capture was reduced the scientists assessed the outlook for captive elephants and found that the population is vulnerable to decline.


The research, published in Proceedings of the Royal Society B, suggests that immediate population declines may be reduced if survival in juvenile elephants is improved.


This could involve improving welfare standards during the training period, as the elephants are separated from their mothers and trained for work around the age of four, which can be stressful for them, and identifying pregnant females earlier and improving their welfare so they can provide for and bond with their calf.


John Jackson, PhD researcher from the University of Sheffield’s Department of Animal and Plant Sciences and lead author of the paper, said: “Our model suggests we may see declines in captive elephants for up to 50 years so we must now work to ensure that the captive population is sustainable. With so many Asian elephants in captivity, we must safeguard both captive and wild elephant populations and the people living and working alongside them for the future of the species.


“One hopeful result is that we may see improvements in population growth if we are able to improve the survival of young elephants by just 10 per cent. This shows we can really make a difference by improving welfare for these vulnerable individuals in captivity.”


He added: “Many of us have the opportunity to visit captive elephants used in tourism, particularly in Southeast Asia. We all have our part to play to ensure that the welfare of captive elephants is improved and this may have a positive effect on Asian elephants globally.”


Professor Virpi Lummaa, from the University of Turku, who led the research, said: “The dependence of captive elephant populations on capture from the wild in the past is truly alarming. The problem with elephants is that they take so long to grow and reproduce and have very complex social lives, making them vulnerable to population declines when disturbed.”


The University of Sheffield’s Department of Animal and Plant Sciences is a leading department for whole organism biology, with the UK’s highest concentration of animal and plant researchers.


It is among the top five animal and plant research centres in the country for research excellence, according to the last Research Excellence Framework in 2014.


Animal and plant scientists at Sheffield study in locations from the Polar Regions to the tropics, at scales from within cells up to entire ecosystems. Their research aims both to understand the fundamental processes that drive biological systems and to solve pressing environmental problems.


Source: University of Sheffield [March 26, 2019]



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Bringing endangered species back from the brink

A technique to produce eggs from ovarian tissue in the lab may offer hope for critically endangered species like the Northern White Rhino that have passed what is currently considered the point of no return.











Bringing endangered species back from the brink
Credit: Shutterstock

A research team at the University of Oxford has begun work to find a new way of saving the Northern White Rhino by using tissue taken from animal ovaries to produce potentially large numbers of eggs in a laboratory setting.


Led by Dr Suzannah Williams, researchers working on the Rhino Fertility Project will refine the method that she has successfully demonstrated in mice. Rhino tissue is scarce and precious – however, ovarian tissue has been obtained by Dr Williams from a euthanased Southern White Rhino which provides the foundation for the work. The research is being funded by Mr Andre Hoffmann, via Fondation Hoffmann.


The desperate plight of the Northern White Rhino has highlighted the precarious situation of many endangered species around the world. Previous breeding programmes had been successful in raising their numbers but the animals were destroyed by poachers. The world’s last remaining male died in 2018 leaving just two female rhinos, Najin and her daughter Fatu, neither of which are capable of producing offspring naturally.


Although sperm has been saved by conservationists from male Northern White Rhinos, any successfully fertilised eggs would have to be raised in a surrogate mother – most likely a Southern White Rhino, one of their closest living relatives.


Dr Suzannah Williams of Oxford’s Nuffield Department of Women’s & Reproductive Health, said: ‘With the death of the last male, Sudan, the Northern White Rhino has passed the point where it can be saved naturally and is a shade away from extinction. This will add yet another species to the list of those wiped out by humans.


‘What is exciting about this research is that it could enable us to pull critically endangered species back from the brink by utilising ovarian tissue from old or injured animals to produce offspring.


‘Once genetic variation within a population has been lost, it is lost forever. This makes it important for us to be able to maintain as many breeding individuals as possible in any conservation programme, to maximise genetic diversity of future populations. This will be a huge buffer against disease and ill health in the long-term, and give the new herds better genetic ability to adapt to changing environments in the future.’


Dr Suzannah Williams added: ‘Some researchers are exploring the possibility of using the remaining Northern White Rhino sperm to cross-breed with Southern White Rhinos to create a hybrid population, but I think we should focus on preserving the Northern White Rhino as the unique species it is, and this project enables us to move directly towards this goal.


‘If successful, this technique would be a powerful tool in the global effort to conserve endangered species.’


Source: University of Oxford [March 26, 2019]



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Speciation: Birds of a feather…

Carrion crows and hooded crows are almost indistinguishable genetically, and hybrid offspring are fertile. Ludwig-Maximilians-Universitaet (LMU) in Munich biologists now show that the two forms have remained distinct largely owing to the dominant role of plumage color in mate choice.











Speciation: Birds of a feather...
Carrion crows and hooded crows [Credit: binah01/stock.adobe.com]

Crows have divided Europe between them. Western Europe is the realm of the soot-black carrion crow, while the eastern half of the continent is home to the hooded crow with its grayish black plumage. The boundary between the two populations – or more precisely, the hybrid zone where the two meet – is only 20-50 km wide, and in Germany it essentially follows the course of the River Elbe.


This is the only stretch of territory in which both of these species are found and sucessfully mate with each other. The plumage of the fertile offspring of these pairings is intermediate in color between those of their parents. The sharp demarcation between the two populations, however, clearly indicates that gene flow across the hybrid zone is restricted, which implies that hybrids are at a selective disadvantage.


“Defining speciation as the buildup of reproductive isolation, carrion crows and hooded crows are in the process of speciation,” says LMU evolutionary biologist Jochen Wolf. He and his research team have now analyzed the genetic basis for the division of European crows into two populations.


Indeed, the results of the study demonstrate that the old saying “birds of a feather flock together” really does apply in this instance: The only genes that differ significantly between the two variants are those involved in determining the color of the plumage. This suggests that each form preferentially mates with partners of the same color as themselves. The new findings appear in the journal Nature Ecology and Evolution.


Europe’s crows once formed a single population. This is thought to have been broken up repeatedly during the last glacial maxima over the last tens to hundreds of thousand years ago, during which the crows retreated from Central Europe to milder refuges in Spain and the Balkans. At the end of the last Ice Age, they returned to their old haunts. But they had changed during the period of their isolation.


“Most probably, a mutation had arisen in the easterly population, which endowed its carriers with a lighter colored, gray plumage,” says Wolf. Then carrion and hooded crows came into contact once again and formed a narrow hybrid zone. However, the genetic mechanisms responsible for maintaining the distinction between the two populations have remained unclear.


In order to identify these mechanisms, Wolf and his colleagues first sequenced the genomes of both carrion crows and hooded crows. “We found that the genomes of both forms are almost identical, and that the few genetic loci that differentiate gray from black crows are likely to be involved in determining the color of their plumage,” Wolf says.


“We have now carried out a more detailed analysis and determined the degree of genetic mixing between the two populations. Using a technique known as admixture mapping we pinned down the genetic basis of their divergence.” To do so, his team examined the variant loci in the genomes of more than 400 birds – from within the hybrid zone and from the regions in which one or other of the two forms is endemic.


In this way, it was possible to identify the genes responsible for the difference in coloration between hooded and carrion crows. “The distinction can largely be explained by variation in just two genetic factors. In addition, we showed that these two loci interact with each other,” Wolf explains. In other words, these two factors together determine the color of the plumage.


Further analyses confirmed that the rest of the genome can be freely exchanged between the two populations – and is common to carrion crows in Western Europe and the hooded crows in the eastern half of the continent.


“Only two major effect genes which together encode the feather color differ sharply on either side of the hybrid zone – the gray alleles are not found to the west of the zone and the black allele is absent in the eastern region,” says Wolf. “That’s a very strong indication that there is rigorous selection on the basis of color.”


According to the authors of the study, these findings convincingly show that the hybrid zone along the Elbe represents an example of early-stage speciation followed upon secondary contact between the two emerging species. The classical biological definition of species – which is based on the concept of reproductive isolation, i.e. on the premise that the hybrid offspring of crosses between ‘true’ species are sterile – obviously does not apply in this case.


Nevertheless, gene flow is locally restricted in the genome, because each form preferentially mates with individuals of the same color. This in turn means that hybrids with an intermediate color are less likely to reproduce. But the two populations are not yet fully isolated genetically from each other, since hybridization still occurs.


“We are now using a mathematical model to work out the level of hybridization in the hybrid zone as it now stands,” says Wolf. “The initial indications suggest that it is very low, on the order of a few percentage points.”


Source: Ludwig Maximilian University of Munich [March 26, 2019]



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Seeds inherit memories from their mother

Seeds remain in a dormant state – a temporary blockage of their germination – as long as environmental conditions are not ideal for germination. The depth of this sleep, which is influenced by various factors, is inherited from their mother, as researchers from the University of Geneva (UNIGE), Switzerland, had previously shown.











Seeds inherit memories from their mother
This is a seed of Arabidopsis thaliana at the beginning of germination
[Credit: © UNIGE/Sylvain Loubery]

Today, they reveal in the journal eLife how this maternal imprint is transmitted through small fragments of so-called ‘interfering’ RNAs, which inactivate certain genes. The biologists also reveal that a similar mechanism enables to transmit another imprint, that of the temperatures present during the development of the seed. The lower this temperature was, the higher the seed’s dormancy level will be. This mechanism allows the seed to optimize the timing of its germination. The information is then erased in the germinated embryo, so that the next generation can store new data on its environment.
Dormancy is implemented during seed development in the mother plant. This property allows the seeds to germinate during the appropriate season, to prevent all the offspring of a plant from developing in the same place and competing for limited resources, and to promote plant dispersal. Seeds also lose their dormancy at variable times. “Subspecies of the same plant can have different levels of dormancy depending on the latitudes at which they are produced, and we wanted to understand why”, explains Luis Lopez-Molina, Professor at the Department of Botany and Plant Biology of the UNIGE Faculty of Science.


The paternal gene is silenced


Like all organisms with sexual reproduction, the seed receives two versions of each gene, a maternal and a paternal allele, which may have different levels of expression. The UNIGE biologists had shown in 2016 that the dormancy levels of Arabidopsis thaliana, a model organism used in laboratories, are inherited from the mother. Indeed, in the seed, the level of expression of a dormancy regulating gene called allantoinase (ALN) is the same as that of the maternal allele. This implies that it is the maternal allele of ALN that is mainly expressed, to the detriment of the paternal allele.


In the current study, the researchers show that this maternal imprint is transmitted by an epigenetic mechanism, which influences the expression of certain genes without altering their sequence. The paternal allele of ALN is ‘silenced’ by biochemical modifications called methylations, which are carried out in the promoter region of the gene in order to inactivate it.


“These methylations are themselves the result of a process in which different enzymatic and factor complexes are involved, as well as small fragments of so-called ‘interfering’ RNA. This is a unique example of genomic imprinting, because it is made in the absence of the enzyme usually responsible for methylation”, says Mayumi Iwasaki, researcher in the Geneva group and the first author of the article.


The imprint of past cold prevents the seed from awakening


The environmental conditions present during the seed formation also leave their mark, as its dormancy level increases with decreasing temperatures. “We have discovered that, in this case, both alleles of the ALN gene are strongly repressed in the seed. This is due to a similar epigenetic mechanism, but not all of the actors are the same as those used to silence the paternal allele”, says Luis Lopez-Molina.


This imprint of the cold enables the seed to keep information on past temperatures, in order to include them in the choice of the optimal time of germination. After germination, the ALN gene is reactivated in the embryo. The memory of the cold will then be cleared, allowing the counters to be reset for the next generation.


“Studying how maternal and environmental factors cause dormant seeds to awaken is of crucial importance for agriculture, especially to prevent early germination in an environment subject to climate change”, concludes Mayumi Iwasaki. The ecological stakes are also high, because increasing temperatures could reduce the dormancy of the seed bank and thus modify the distribution of plant species under a given latitude. This would have multiple consequences, both direct and indirect, for native animal and plant species.


Source: University of Geneva [March 26, 2019]



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The big picture about climate change emerges from looking at small bivalvas

Climate change has always left its footprint on land and in the seas where bivalves such as mussels, scallops, oysters have lived for millions of years. Their limited mobility has been to their disadvantage resulting in most of them dying in the on-site whenever major unpleasant changes occurred in their environment…











The big picture about climate change emerges from looking at small bivalvas
More bivalve genera became extinct in periods of time when the temperature changed
rapidly compared to general temperature trends [Credit: Senckenberg]

“The upside of this is that their way of living resulted in a rich fossil record that informs us about the extinction rate of marine invertebrates when faced with climate change. And as these lineages have been around millions upon millions of years, they have certainly experienced a lot of extinctions,” says Dr. Shan Huang, researcher at the German Senckenberg Biodiversity and Climate Research Centre.


Huang worked with her collaborators from the University of Chicago and the University of University of California, San Diego to investigate 1,500 bivalve genera that occurred or still occur in shallow sea (< 200 meter deep) during the Cenozoic which roughly covers the last 66 million years. They compared the temporal dynamics of extinction intensity and the pattern of ocean temperature as well as its change at different time scales.


It turned out, that the extinctions of bivalves in the Cenozoic were mostly related to how fast climatic changed. “We saw two patterns. If the temperature changed rapidly during a geologic time bin (i.e. stages, mostly spanning around 2 million years), more bivalve genera went extinct. In addition, climate change at a larger time scale also played a role. More bivalves went extinct when temperature changed more from one to the next time bin,” explains Huang.


In-detail analyses also show that consequences of climate change were quite different according to what region the bivalve species inhabited. Climate changes during the last 66 million years hit the bivalve genera nearer the poles the hardest. This has resulted in today’s situation where the number of bivalve (and many other) species in high latitudes is much lower than those found the tropics.


In sum the study suggests that rapid temperature change may lead to higher extinction rates of biodiversity. Most at risk would be genera which live at higher latitudes. However, there is no perfect analog in the past for today’s oceans which have been impacted heavily by human activity and suffer from pollution and overfishing


“Also the ups and downs of bivalve species richness during the Cenozoic cannot be explained by climate change alone; other forces must have been at work as well. More in-depth comparative paleontological research is needed to make better predictions of how the ongoing climate change will impact bivalve and other marine species with no or little mobility in general,” concludes Huang.


The findings are published in Integrative and Comparative Biology.


Source: Senckenberg Research Institute and Natural History Museum [March 26, 2019]



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In the tree of life, youth has its advantages

It’s a question that has captivated naturalists for centuries: Why have some groups of organisms enjoyed incredibly diversity- like fish, birds, insects – while others have contained only a few species – like humans.











In the tree of life, youth has its advantages
A mother sperm whale and her calf off the coast of Mauritius 
[Credit: Gabriel Barathieu, Wikipedia]

Researchers trying to explain why the Tree of Life is so unbalanced have agreed on a few explanations – a species’ ability to change colour, its body size, and how it interacts with its environment all influence how quickly it can form new species compared to other organisms.


Geological age has also been a major explanation–older groups of organisms have had more time to accumulate more species.


But new research in the Proceedings of the National Academy of Sciences shows the passage of time has a surprising, and consistent impact on evolutionary diversity–and might favour young species.


“If you look at rates of macroevolutionary diversification across 3.8 billion years, it’s younger groups of organisms, on average, that accumulate diversity much more quickly than older groups,” says Matthew Pennell, an evolutionary biologist at the University of British Columbia and senior author on the paper.


“This suggest that there are some time-dependant, hidden general principles governing how life diversifies on Earth – operating underneath all the other factors we typically think determine how quickly species diversify or go extinct.”


The researchers estimated specification and extinction rates across almost 25,000 branches of multicellular organisms, using data from studies of over 100 groups of species and an independent data set of fossil time series. That enabled them to compare rates of diversification broadly over time. For example cichlids (a species of fish) from African rift lakes are diversifying incredibly fast, while whales are an example of a group that appear to be far past their prime in terms of diversity.


“If groups of species were simply reaching equilibrium and slowing down over time, we’d expect a more consistent pattern of slowing within every group we look at,” says Pennell. “But our results aren’t showing that.”


When the researchers looked at individual groups, rates of diversification varied dramatically. What they did find at the macro-level was a strong pattern of faster growth of diversity in younger groups of species.


“This really throws a wrench in how we interpret how life diversified on Earth,” says Pennell.


Evolutionary biologists have tended to look at particular features that have helped particular groups of animals diversify–or not.


“The far less explored, and potentially more interesting question, is why, despite all the complexity involved in the evolution of new species, that process looks so similar across the Tree of Life.”


Source: University of British Columbia [March 26, 2019]



TANN



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Libethenite with Pseudomalachite | #Geology #GeologyPage…


Libethenite with Pseudomalachite | #Geology #GeologyPage #Mineral


Locality: Kolwezi, Katanga (Shaba), DR Congo (Zaire), Africa


Dimensions: 10.3 × 8.5 × 7.0 cm


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Crinoid | #Geology #GeologyPage #Fossil A large 420 million…


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A large 420 million year old Crinoid from Morocco.


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2019 March 30 3D 67P Image Credit: ESA, Rosetta, MPS, OSIRIS -…


2019 March 30


3D 67P
Image Credit: ESA, Rosetta, MPS, OSIRIS – Stereo Anaglyph: Philippe Lamy and The Team


Explanation: Put on your red/cyan glasses and float next to the jagged and double-lobed nucleus of Churyumov-Gerasimenko, also known as Comet 67P. The stereo anaglyph was created by combining two images from the Rosetta spacecraft’s narrow angle OSIRIS camera taken on July 25, 2015 from a distance of 184 kilometers. Numerous jets are emanating from the small solar system world’s active surface near its closest approach to the Sun. The larger lobe is around 4 kilometers in diameter, joined to a smaller, 2.5 kilometer diameter lobe by a narrow neck. Rosetta’s mission to the comet ended in September 2016 when the spacecraft was commanded to a controlled impact with the comet’s surface. Keep those 3D glasses on though. You can check out a new catalog of nearly 1400 stereo anaglyphs created from Rosetta image data on this website.


∞ Source: apod.nasa.gov/apod/ap190330.html


Rocket Lab successfully launches R3D2 satellite for DARPA


Rocket Lab – DARPA / R3D2  Mission 5 patch.


March 29, 2019



Rocket Lab Electron R3D2 mission launch

A Rocket Lab Electron launch vehicle successfully lifted off from Launch Complex 1 on New Zealand’s Mahia Peninsula at 23:27, March 28th UTC (12:27, 29 March NZDT). The mission launched a prototype reflect array antenna to orbit for the Defense Advanced Research Projects Agency (DARPA). 


“Congratulations to our dedicated team for delivering another important and innovative asset to space – on time and on target. The unique requirements of this mission made Electron the perfect launch vehicle to lift R3D2 as a dedicated payload to a highly precise orbit,” said Rocket Lab founder and CEO Peter Beck. “Thank you to our mission partners. We look forward to continuing to provide frequent, reliable and rapidly-acquired launch services for innovative small satellites.”



Electron launches DARPA R3D2 mission

Rocket Lab was selected for the launch because of the company’s proven mission heritage and its ability support rapid acquisition of small satellite launch capabilities. Due to Rocket Lab’s streamlined acquisition practices, DARPA’s R3D2 mission was launched just over 18 months from conception – a significant reduction in traditional government launch acquisition timeframes.


With proven flight heritage from four orbital missions, Rocket Lab is the only fully commercial small satellite launch service provider in operation. The experienced Rocket Lab team has delivered 25 satellites to orbit, including innovative new space technologies that provide vital capabilities such as weather monitoring, Earth observation and Internet of Things connectivity. The R3D2 mission was Rocket Lab’s first of 2019, as the company heads into a busy year of launches booked for lift-off every four weeks. To support the small satellite industry’s highest launch cadence, Rocket Lab is currently producing one Electron launch vehicle every 30 days across its Huntington Beach, California, and Auckland, New Zealand, production facilities.


About the DARPA R3D2 payload:



 
DARPA’s R3D2 (Radio Frequency Risk Reduction Deployment Demonstration) spacecraft intends to space-qualify a prototype reflect array antenna to improve radio communications in small spacecraft. The 150kg spacecraft carried an antenna, made of a tissue-thin Kapton membrane, designed to pack tightly inside the small satellite for stowage during launch, before deploying to its full size of 2.25 meters in diameter in low Earth orbit. The design is intended to provide significant capability, typical of large spacecraft, in a much smaller package. The mission could lay the groundwork for a space-based internet by helping to validate emerging concepts for a resilient sensor and data transport layer in low Earth orbit – a capability that does not exist today.


About Electron:


The R3D2 mission was launched on an Electron launch vehicle, comprised of two fully carbon-composite stages, powered by a total of ten 3D printed and electric pump-fed Rutherford engines, designed and built in house by Rocket Lab at the company’s headquarters in Huntington Beach, California. The R3D2 payload was deployed to a circular orbit by Rocket Lab’s unique Kick Stage, an additional stage designed for precise orbital deployment and equipped with the ability to deorbit itself upon mission completion to leave no orbital debris behind.


Rocket Lab: https://www.rocketlabusa.com/


Defense Advanced Research Projects Agency (DARPA): https://www.darpa.mil/


Images, Video, Text, Credits: Rocket Lab/DARPA/SciNews.


Greetings, Orbiter.chArchive link


NASA Astronauts Complete 215th Spacewalk at Station



ISS – Expedition 59 Mission patch / EVA – Extra Vehicular Activities patch.


March 29, 2019


Expedition 59 Flight Engineers Nick Hague and Christina Koch of NASA concluded their spacewalk at 2:27 p.m. EDT. During the six hour and 45-minute spacewalk, the two NASA astronauts successfully connected three newer, more powerful lithium-ion batteries to replace the previous six nickel-hydrogen batteries that provide power for one channel on one pair of the station’s solar arrays. The new batteries provide an improved and more efficient power capacity for operations.


The astronauts also did work to enable robotic specialists to remove one of the three new lithium ion batteries connected during last Friday’s spacewalk that is not charging properly and replace it with the two older nickel hydrogen batteries. The swap will restore a full power supply to that solar array power channel.




Image above: Spacewalker Nick Hague works to upgrade the International Space Station ‘s power storage capacity during today’s six hour and 45-minute spacewalk. Image Credit: NASA TV.


In addition, the astronauts also completed several tasks to prepare the worksite for future spacewalkers who will complete similar operations to upgrade the batteries for the set of solar arrays at the end of the port side of the station’s backbone structure known as the truss. Hague inspected the worksite interfaces for a portable foot restraint a spacewalker uses to anchor themselves during the battery upgrade work while Koch installed fabric handrails to help future spacewalkers move across the worksite.


This was the second spacewalk for Hague, who now has spent a total of 13 hours and 24 minutes spacewalking. It was the first spacewalk for Koch, who became the 14th female spacewalker.


Anne McClain and David Saint-Jacques of the Canadian Space Agency are scheduled to conduct another spacewalk April 8 to establish a redundant path of power to the Canadian-built robotic arm, known as Canadarm2, and install cables to provide for more expansive wireless communications coverage outside the orbital complex, as well as for enhanced hardwired computer network capability.




Image above: NASA astronaut Nick Hague is contrasted by the blackness of space during his first spacewalk on March 22, 2019. Image Credit: NASA TV.


Experts will discuss the work to be performed on the April 8 spacewalk during a news conference at 2 p.m. EDT Tuesday, April 2, at NASA’s Johnson Space Center in Houston. Live coverage of the briefing and spacewalks will air on NASA Television and the agency’s website. Participants in the briefing are Kenny Todd, International Space Station manager for Operations and Integration, Rick Henfling, spacewalk flight director, and John Mularski, lead spacewalk officer.


Space station crew members have conducted 215 spacewalks in support of assembly and maintenance of the orbiting laboratory. Spacewalkers have now spent a total of 56 days 4 hours and 24 minutes working outside the station.


Related links:


Expedition 59: https://www.nasa.gov/mission_pages/station/expeditions/expedition59/index.html


Space Station Research and Technology: https://www.nasa.gov/mission_pages/station/research/index.html


International Space Station (ISS): https://www.nasa.gov/mission_pages/station/main/index.html


Images (mentioned), Text, Credits: NASA/Mark Garcia.


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SOFIA Captures Cosmic Light Show of Star Formation


NASA & DLR – SOFIA Mission patch.


March 29, 2019


When massive stars — many times larger than our Sun— are born, they shine hot and bright before eventually exploding as supernovas. They release so much energy that they can affect the evolution of galaxies. But, unlike stars like our Sun, astronomers know much less about how these enormous stars form.


“Massive stars like this represent less than one percent of all stars, but they can affect the formation of their stellar siblings,” said Jim De Buizer, Universities Space Research Association senior scientist at the SOFIA Science Center. “Stars like our Sun have much quieter and humbler origins, and because there are so many of them, we understand their birth properties more thoroughly.”


To learn more, researchers used the Stratospheric Observatory for Infrared Astronomy, or SOFIA, to study a giant celestial cloud, called W51. Located almost 17,000 light years away and made mostly of hydrogen, it’s a place where rare, gigantic stars are forming. But they are born deep inside the cloud, invisible to the light our eyes can see. Using SOFIA’s airborne telescope and sensitive infrared camera, the research team peered inside the dense cloud. They captured a cosmic light show sparked by the forming stars, including many that have never been seen before.



Image above: A cosmic light show sparked by the formation of massive stars in the stellar nursery, called W51, glows over on a star field image (white) from the Sloan Digital Sky Survey. The oldest and most evolved massive star is in the upper left of the image, shown at the middle of yellowish bubble. The youngest generations are typically found in areas near the center of this figure, near the brightest ball at the slight left from the middle. Massive stars like these emit so much energy that they play a critical role in the evolution of our galaxy. Image Credits: NASA/SOFIA/Lim and De Buizer et al. and Sloan Digital Sky Survey.


The infrared camera, called Faint Object infraRed CAmera for the SOFIA Telescope, or FORCAST, has sensitive detectors and powerful magnification that let the researchers discover the enormous stars right after their birth. Learning how massive stars form in our Milky Way Galaxy helps scientists understand how these stars form in distant galaxies that are too far away to see in detail.


“This is the best resolution currently available using these wavelengths of infrared light,” said Wanggi Lim, Universities Space Research Association scientist at the SOFIA Science Center. “Not only does this reveal areas that we could not see before, but it’s critical to understanding the physical properties and relative age of the stars and their parental clouds.”


Researchers combined the SOFIA data with data from NASA’s Spitzer Space Telescope and Herschel Space Observatory to analyze the stars. They found that while they are all young, some are more evolved, and others are the youngest, most recently-created stars in the cloud. One may be exceptionally large — estimated to have the equivalent mass of 100 Suns. If future observations confirm it is indeed a single, colossal star, rather than multiple stellar siblings clustered together, it would be one of the most massive forming stars in our galaxy.


These are the first results from a survey that will reveal how young, massive stars are lighting up other parts of our Milky Way Galaxy.



SOFIA Boeing 747SP telescope door opening. Animation Credit: NASA

SOFIA, the Stratospheric Observatory for Infrared Astronomy, is a Boeing 747SP jetliner modified to carry a 106-inch diameter telescope. It is a joint project of NASA and the German Aerospace Center, DLR. NASA’s Ames Research Center in California’s Silicon Valley manages the SOFIA program, science and mission operations in cooperation with the Universities Space Research Association headquartered in Columbia, Maryland, and the German SOFIA Institute (DSI) at the University of Stuttgart. The aircraft is maintained and operated from NASA’s Armstrong Flight Research Center Hangar 703, in Palmdale, California.


Related links:


– Spitzer Space Telescope: https://www.nasa.gov/mission_pages/spitzer/main/index.html


– Herschel Space Observatory: https://www.nasa.gov/mission_pages/herschel/index.html


– SOFIA: http://www.nasa.gov/mission_pages/SOFIA/index.html


Image (mentioned), Animation (mentioned), Text, Credits: NASA/Kassandra Bell.


Best regards, Orbiter.chArchive link


Meteor Activity Outlook for March 30-April 5, 2019

This brilliant fireball was captured at 06:14 UT on February 26, 2019, from Vilaflor, Santa Cruz de Tenerife, Canary Islands. © hermastro.

Meteor activity picks up a bit during April as the Lyrids become active during the month. They are active from the 14th through the 30th, with a pronounced maximum on the 23rd. Sporadic rates during April are steady as seen from both hemispheres with southern observers enjoying more activity that can be seen from the mid-northern hemisphere. The eta Aquariids will become active the second half of the month, adding a few swift meteors to the late morning scene.


During this period the moon will reach its new phase on Friday April 5th. This weekend and for most of the week, the waning crescent moon will rise during the early morning hours but will not interfere with meteor observing as long as you keep the moon out of your field of view. Hourly meteor rates for evening observers this week is near 3 as seen from mid-northern latitudes (45N) and 4 as seen from tropical southern locations (25S). For morning observers the estimated total hourly rates should be near 8 as seen from mid-northern latitudes and 10 from the southern tropics. The actual rates will also depend on factors such as personal light and motion perception, local weather conditions, alertness and experience in watching meteor activity. Morning rates are slightly reduced during this period due to moonlight. Note that the hourly rates listed below are estimates as viewed from dark sky sites away from urban light sources. Observers viewing from urban areas will see less activity as only the brighter meteors will be visible from such locations.


The radiant (the area of the sky where meteors appear to shoot from) positions and rates listed below are exact for Saturday night/Sunday morning March 30/31 . These positions do not change greatly day to day so the listed coordinates may be used during this entire period. Most star atlases (available at science stores and planetariums) will provide maps with grid lines of the celestial coordinates so that you may find out exactly where these positions are located in the sky. A planisphere or computer planetarium program is also useful in showing the sky at any time of night on any date of the year. Activity from each radiant is best seen when it is positioned highest in the sky, either due north or south along the meridian, depending on your latitude. It must be remembered that meteor activity is rarely seen at the radiant position. Rather they shoot outwards from the radiant so it is best to center your field of view so that the radiant lies near the edge and not the center. Viewing there will allow you to easily trace the path of each meteor back to the radiant (if it is a shower member) or in another direction if it is a sporadic. Meteor activity is not seen from radiants that are located far below the horizon. The positions below are listed in a west to east manner in order of right ascension (celestial longitude). The positions listed first are located further west therefore are accessible earlier in the night while those listed further down the list rise later in the night.






Radiant Positions at 20:00 Local Daylight Saving Time







Radiant Positions at 1:00 Local Daylight Saving Time







Radiant Positions at 6:00 Local Daylight Saving Time





These sources of meteoric activity are expected to be active this week.


The center of the large Anthelion (ANT) radiant is currently located at 13:32 (203) -09. This position lies in central Virgo, 2 degrees northeast of the 1st magnitude star known as Spica (alpha Virginis). Due to the large size of this radiant, Anthelion activity may also appear from eastern Libra, and northeastern Corvus as well as Virgo. This radiant is best placed near 0200 Local Daylight Saving Time (LDT), when it lies on the meridian and is located highest in the sky. Rates at this time should be near 2 per hour no matter your location. With an entry velocity of 30 km/sec., the average Anthelion meteor would be of slow velocity.


The April lambda Ophiuchids (ALO) were first detected by Damir Šegon and the Croatian Meteor Network team based on studying SonotaCo and CMN observations (SonotaCo 2007-2011, CMN 2007-2010). This source is currently listed among the “working ” showers of the International Astronomical Union. A recent article by Masahiro Koseki in WGN  (IMO Journal) suggests that this source and other working showers may be strong enough to be observed by visual means. The exact stream duration is not available but this source should be active for a least a week centered on the April 6th maximum. The radiant position at maximum is 16:20 (245) +01. This area of the sky is located southeastern Serpens Caput, 2 degrees southwest of the 4th magnitude star known as Marfik (lambda Ophiuchi). This radiant is best placed near 0500 LDT, when it lies on the meridian and is located highest in the sky. Rates at this time should be near 1 per hour no matter your location. With an entry velocity of 56 km/sec., the average meteor from this source would be of fast velocity.


The Zeta Cygnids (ZCY) were first detected by Zdenek Sekanina and mentioned in his article on a study of radio streams. These meteors are active from April 3-10 with maximum activity occurring on the 6th. At maximum the radiant is located at 20:08 (302) +40. This area of the sky is located in central Cygnus just 2 degrees west of the 2nd magnitude star known as Sadr (gamma Cygni). Note that this position is nowhere close to the star zeta Cygni which lies on the east side of the constellation. This usually occurs when activity is suspected from a radiant and further studies indicate a radiant in another position. Rather than correcting the name the original name is kept so that the association of earlier observations and that of newer data remains intact. This may confuse new observers but luckily this does not occur often among the lists of radiants. This radiant is best placed during the last hour before dawn when it lies highest above the horizon in a dark sky. Rates at maximum should be near 1 per hour just before dawn as seen from mid-northern latitudes. Unfortunately these meteors are not well seen from south of the equator. With an entry velocity of 40 km/sec., the average meteor from this source would be of medium velocity.


As seen from the mid-northern hemisphere (45N) one would expect to see approximately 4 sporadic meteors per hour during the last hour before dawn as seen from rural observing sites. Evening rates would be near 2 per hour. As seen from the tropical southern latitudes (25S), morning rates would be near 7 per hour as seen from rural observing sites and 3 per hour during the evening hours. Locations between these two extremes would see activity between the listed figures. Morning rates are slightly reduced due to moonlight.


The list below offers the information from above in a condensed form. Rates and positions are exact for Saturday night/Sunday morning except where noted in the shower descriptions.


















































SHOWER DATE OF MAXIMUM ACTIVITY CELESTIAL POSITION ENTRY VELOCITY CULMINATION HOURLY RATE CLASS
RA (RA in Deg.) DEC Km/Sec Local Daylight Saving Time North-South
Anthelion (ANT) 12:36 (189) -04 30 02:00 2 – 2 II
April lambda Ophiuchids (ALO) Apr 06 16:20 (245) +01 56 05:00 1 – 1 IV
Zeta Cygnids (ZCY) Apr 06 20:04 (302) +40 40 09:00 1 -<1 IV

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2019 March 29 M104: The Sombrero Galaxy Image Data: NASA, ESA,…


2019 March 29


M104: The Sombrero Galaxy
Image Data: NASA, ESA, Hubble Legacy Archive;
Processing & Copyright: Rogelio Bernal Andreo (DeepSkyColors.com)


Explanation: The striking spiral galaxy M104 is famous for its nearly edge-on profile featuring a broad ring of obscuring dust lanes. Seen in silhouette against an extensive central bulge of stars, the swath of cosmic dust lends a broad brimmed hat-like appearance to the galaxy suggesting a more popular moniker, The Sombrero Galaxy. Hubble Space Telescope data have been used to to create this sharp view of the well-known galaxy. The processing results in a natural color appearance and preserves details often lost in overwhelming glare of M104’s bright central bulge when viewed with smaller ground-based telescopes. Also known as NGC 4594, the Sombrero galaxy can be seen across the spectrum and is host to a central supermassive black hole. About 50,000 light-years across and 28 million light-years away, M104 is one of the largest galaxies at the southern edge of the Virgo Galaxy Cluster.


∞ Source: apod.nasa.gov/apod/ap190329.html


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