Jul 29, 2017
Now researchers at Queen Mary University of London (QMUL), UK, have discovered an important part of the mechanism involved in how chromosomes are pulled apart during cell division, so that one complete set goes into each of the new cells.
"During cell division, a mother cell divides into two daughter cells, and during this process the DNA in the mother cell, wrapped up in the form of chromosomes, is divided into two equal sets. To achieve this, rope-like structures called microtubules capture the chromosomes at a special site called the kinetochore, and pull the DNA apart," said Dr Viji Draviam, senior lecturer in structural cell and molecular biology from QMUL's School of Biological and Chemical Sciences.
"We have identified two proteins -- tiny molecular machines -- that enable the correct attachment between the chromosomes and microtubules. When these proteins don't function properly, the cells can lose or gain a chromosome. This finding gives us a glimpse of an important step in the process of cell division."
The study, which is published today (Friday 26 July 2017) in the journal Nature Communications, helps to explain the condition known as aneuploidy -- when cells end up with the wrong number of chromosomes.
Using high resolution microscopes to video the inner workings of live human cells, Dr Draviam and her colleagues at the University of Cambridge (UK) and the European Molecular Biology Laboratory in Heidelberg (Germany), discovered that two proteins -- Aurora-B kinase and BubR1-bound PP2A phosphatase -- act in opposition to each other, adding or removing phosphate groups respectively, to correctly control the attachment of microtubules to the chromosomes.
Co-author Duccio Conti, who is Dr Draviam's PhD student, said: "We found that a balance between Aurora-B kinase and BubR1-bound phosphatase is important to maintain correct chromosome numbers in human cells."
Understanding the underlying molecular mechanisms of cell division could help in treating a range of diseases and disorders.
"Aggressive cancers often display irregular number of chromosomes. Normal human cells usually have 23 pairs of chromosomes; however, cancer cells can have 50 or more chromosomes. To specifically diagnose the underlying reason for aneuploidy and also to specifically target or treat aneuploidy, one has to understand what causes aneuploidy in the first place," added Dr Draviam.
Some people are born with mutations that predispose them to aneuploidy. One such condition is mosaic variegated aneuploidy (MVA) in which patients lack a small part of the BubR1 protein. It is a very rare condition, but those affected can suffer from microcephaly (smaller than normal head), restricted growth, problems with the brain and nervous system, developmental delay, mental disability and seizures, as well as having an increased risk of cancer.
Dr Draviam said: "It will be useful to see what are the levels of AuroraB kinase in MVA patients who lack portions of the BubR1 gene in their DNA. To counteract the loss of BubR1 in these patients, perhaps Aurora-B could be reduced. Also we are curious to know whether chromosomes are captured normally in patients lacking BubR1-bound phosphatase. This may reveal novel ways to tackle additional changes in chromosome numbers seen in patients who suffer from BubR1 mutations.
"In fertility treatments, it will be useful to study the levels of these two proteins at the kinetochore in order to select healthy eggs to implant in women's wombs to give them the best chance of achieving a successful pregnancy."
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The brain and the neurons (nerve cells) in the rest of our body are connected in the spine. Here, motor neurons, which control muscle movement, and sensory neurons, which relay sensory information such as pain, temperature and touch, connect with the spinal cord.
Where the neurons connect with the cord, motor neurons bundle together to form a structure called the motor root, while sensory neurons form a sensory root. In patients with traumatic injuries, these roots can be torn, causing areas of the body to lose neural control.
Surgeons can implant motor roots at the area from which they are torn, and they will usually successfully reconnect, as motor neurons can regrow out of the spinal cord and into the motor root. However, this does not apply to the more troublesome sensory root, which surgeons couldn't reconnect properly until recently. "Doctors previously considered this type of spinal cord injury impossible to repair," says Nicholas James, a researcher at King's College London. "These torn root injuries can cause serious disability and excruciating pain."
Happily, Thomas Carlstedt, also at King's College London, recently helped to develop a new surgical technique to reconnect the sensory root. It involves cutting the original sensory nerve cells out of the root and implanting the remaining root directly into a deeper structure in the spinal cord. This area is called the dorsal horn, and it contains secondary sensory neurons that don't normally directly connect to sensory roots. When the team tried the technique in patients, certain spinal reflexes returned, indicating that the implanted neuron had integrated with the spine to form a functional neural circuit.
In a new study recently published in Frontiers in Neurology, James, Carlstedt and other collaborators set out to understand how the implanted sensory root was connecting with the spinal cord in the dorsal horn. By understanding the mechanism, they hope to develop new treatments for patients with other types of spinal injuries.
The scientists used a rat model of spinal injury to study the process at a cellular level. During surgery, they produced a similar spinal injury in the rats and then reattached the sensory root using the new technique. At 12-16 weeks after surgery, the researchers assessed the spinal repair by passing electricity along the neurons to see if they formed a complete neural circuit. They then sacrificed the rats and analyzed the neural tissue under a microscope.
The electrical tests showed that the neural circuit was complete, and that the root had successfully integrated with the spinal cord. When they examined the tissue, they found that small neural offshoots had grown from structures called dendrites (branched projections at the end of neurons) in the dorsal horn. These thin offshoots had extended all the way into the implanted sensory root to create a functional neural circuit.
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Jul 28, 2017
The answer to this daunting biological riddle is central to understanding how the three-dimensional organization of DNA in the nucleus influences our biology, from how our genome orchestrates our cellular activity to how genes are passed from parents to children.
Now, scientists at the Salk Institute and the University of California, San Diego, have for the first time provided an unprecedented view of the 3D structure of human chromatin -- the combination of DNA and proteins -- in the nucleus of living human cells.
In the tour de force study, described in Science on July 27, 2017, the Salk researchers identified a novel DNA dye that, when paired with advanced microscopy in a combined technology called ChromEMT, allows highly detailed visualization of chromatin structure in cells in the resting and mitotic (dividing) stages. By revealing nuclear chromatin structure in living cells, the work may help rewrite the textbook model of DNA organization and even change how we approach treatments for disease.
"One of the most intractable challenges in biology is to discover the higher-order structure of DNA in the nucleus and how is this linked to its functions in the genome," says Salk Associate Professor Clodagh O'Shea, a Howard Hughes Medical Institute Faculty Scholar and senior author of the paper. "It is of eminent importance, for this is the biologically relevant structure of DNA that determines both gene function and activity."
Ever since Francis Crick and James Watson determined the primary structure of DNA to be a double helix, scientists have wondered how DNA is further organized to allow its entire length to pack into the nucleus such that the cell's copying machinery can access it at different points in the cell's cycle of activity. X-rays and microscopy showed that the primary level of chromatin organization involves 147 bases of DNA spooling around proteins to form particles approximately 11 nanometers (nm) in diameter called nucleosomes. These nucleosome "beads on a string" are then thought to fold into discrete fibers of increasing diameter (30, 120, 320 nm etc.), until they form chromosomes. The problem is, no one has seen chromatin in these discrete intermediate sizes in cells that have not been broken apart and had their DNA harshly processed, so the textbook model of chromatin's hierarchical higher-order organization in intact cells has remained unverified.
To overcome the problem of visualizing chromatin in an intact nucleus, O'Shea's team screened a number of candidate dyes, eventually finding one that could be precisely manipulated with light to undergo a complex series of chemical reactions that would essentially "paint" the surface of DNA with a metal so that its local structure and 3D polymer organization could be imaged in a living cell. The team partnered with University of California, San Diego, professor and microscopy expert Mark Ellisman, one of the paper's coauthors, to exploit an advanced form of electron microscopy that tilts samples in an electron beam enabling their 3D structure to be reconstructed. O'Shea's team called the technique, which combines their chromatin dye with electron-microscope tomography, ChromEMT.
The team used ChromEMT to image and measure chromatin in resting human cells and during cell division (mitosis) when DNA is compacted into its most dense form -- the 23 pairs of mitotic chromosomes that are the iconic image of the human genome. Surprisingly, they did not see any of the higher-order structures of the textbook model anywhere.
"The textbook model is a cartoon illustration for a reason," says Horng Ou, a Salk research associate and the paper's first author. "Chromatin that has been extracted from the nucleus and subjected to processing in vitro -- in test tubes -- may not look like chromatin in an intact cell, so it is tremendously important to be able to see it in vivo."
What O'Shea's team saw, in both resting and dividing cells, was chromatin whose "beads on a string" did not form any higher-order structure like the theorized 30 or 120 or 320 nanometers. Instead, it formed a semi-flexible chain, which they painstakingly measured as varying continuously along its length between just 5 and 24 nanometers, bending and flexing to achieve different levels of compaction. This suggests that it is chromatin's packing density, and not some higher-order structure, that determines which areas of the genome are active and which are suppressed.
With their 3D microscopy reconstructions, the team was able to move through a 250 nm x 1000 nm x 1000 nm volume of chromatin's twists and turns, and envision how a large molecule like RNA polymerase, which transcribes (copies) DNA, might be directed by chromatin's variable packing density, like a video game aircraft flying through a series of canyons, to a particular spot in the genome. Besides potentially upending the textbook model of DNA organization, the team's results suggest that controlling access to chromatin could be a useful approach to preventing, diagnosing and treating diseases such as cancer.
"We show that chromatin does not need to form discrete higher-order structures to fit in the nucleus," adds O'Shea. "It's the packing density that could change and limit the accessibility of chromatin, providing a local and global structural basis through which different combinations of DNA sequences, nucleosome variations and modifications could be integrated in the nucleus to exquisitely fine-tune the functional activity and accessibility of our genomes."
Read more at Science Daily
The conditions on Titan, however, are not conducive to the formation of life as we know it; it’s simply too cold. At ten times the distance from the Earth to the sun, Titan is so cold that liquid methane rains onto its solid icy surface, forming rivers, lakes, and seas.
These pools of hydrocarbons, however, create a unique environment that may help molecules of vinyl cyanide (C2H3CN) link together to form membranes, features resembling the lipid-based cell membranes of living organisms on Earth.
Astronomers using archival data from the Atacama Large Millimeter/submillimeter Array (ALMA), which was collected over a series of observations from February to May 2014, have found compelling evidence that molecules of vinyl cyanide are indeed present on Titan and in significant quantities.
“The presence of vinyl cyanide in an environment with liquid methane suggests the intriguing possibility of chemical processes that are analogous to those important for life on Earth,” said Maureen Palmer, a researcher at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and lead author on a paper published in Science Advances.
Previous studies by NASA’s Cassini spacecraft, as well as laboratory simulations of Titan’s atmosphere, inferred the likely presence of vinyl cyanide on Titan, but it took ALMA to make a definitive detection.
By reviewing the archival data, Palmer and her colleagues found three distinct signals – spikes in the millimeter-wavelength spectrum – that correspond to vinyl cyanide. These telltale signatures originated at least 200 kilometers above the surface of Titan.
Titan’s atmosphere is a veritable chemical factory, harnessing the light of the sun and the energy from fast-moving particles that orbit around Saturn to convert simple organic molecules into larger, more complex chemicals.
“As our knowledge of Titan’s chemistry grows, it becomes increasingly apparent that complex molecules arise naturally in environments similar to those found on the early Earth, but there are important differences,” said Martin Cordiner, also with NASA’s Goddard Space Flight Center and a co-author on the paper.
For example, Titan is much colder than Earth at any period in its history. Titan averages about 95 kelvins (-290 degrees Fahrenheit), so water at its surface remains frozen. Geologic evidence also suggests that the early Earth had high concentrations of carbon dioxide (CO2); Titan does not. Earth’s rocky surface was also frenetically active, with extensive volcanism and routine asteroid impacts, which would have affected the evolution of our atmosphere. In comparison, Titan’s icy crust appears quite docile.
“We are continuing to use ALMA to make further observations of Titan’s atmosphere,” concluded Conor Nixon, also with NASA’s Goddard Space Flight Center and a co-author on the paper. “We are looking for new and more complex organic chemicals as well as studying this moon’s atmospheric circulation patterns. In the future, higher-resolution studies will shed more light on this intriguing world and hopefully give us new insights into Titan’s potential for prebiotic chemistry.”
Read more at Science Daily
Jungles near the equator, piney northern forests, and other flora are absorbing 17 percent more carbon dioxide than 30 years ago, resulting in land plants acting as “sinks” for around 30 percent of the carbon in the atmosphere, said the study published July 24 in the journal Nature Communications. The oceans absorb another 25 percent.
It’s no surprise that plants would gobble up excess carbon dioxide in the atmosphere. Under natural conditions, humans and other oxygen-inhaling creatures breathe it out while plants breathe it in and exhale oxygen. But the buildup of greenhouse gases in recent decades have given plants even more to gobble up.
“All that carbon that instead of being respired back into the atmosphere stays with the plants until it goes back in the soil when the plant falls and decomposes,” said study coauthor Pep Canadell, a Canberra-based scientist at the Commonwealth Scientific and Industrial Research Organization and executive director of the Global Carbon Project.
Canadell and his colleagues tracked carbon and water levels in forests around the world using atmospheric readings, satellite pictures of Earth and poles around 200 feet tall that put data recorders at the top of forest canopies around the world. They observed thicker forests and more woody encroachments on grasslands, he said. Carbon composes around 50 percent of plants, so more of it was helping the planet’s vegetation grow hardier.
“It’s really transforming, to some extent, the structure of the land’s surface,” said Canadell. “It’s becoming rougher. It's becoming denser. Forests are thickening. Plants are becoming more stems-per-hectare, or they are just getting bigger. From the carbon perspective, we are increasing the global carbon stocks on land.”
The findings don’t predict a glut of water as a result of less thirsty plants, unfortunately. Instead, they suggest that even though plants are using less water individually, they often wind up drinking more water collectively over time as they flourish.
“There are more plants in the landscape because you now have more water to go around,” he said, explaining that this indirect effect of camel-like plants could spell big trouble for arid areas already struggling with droughts and other symptoms of climate change. “Where water is not plentiful, this can be a deal breaker.”
Climate change scientists had already factored plants storing carbon dioxide into their projections, so the findings also don’t mean plants would compensate for a new gas-guzzling car, either.
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Scientists don't know the sun's size as precisely as the details of the Earth and moon, making it a sticking point for perplexed eclipse modelers.
Xavier Jubier creates detailed models of solar and lunar eclipses that work with Google Maps to show precisely where the shadow of the sun will fall on the Earth, and what the eclipse will look like at each point. He came to realize there was something off about the sun's measurements as he matched his eclipse simulations with actual photos. The photos helped him identify exactly where an observer had been for historical eclipses — but those precise eclipse shapes only made sense if he scaled up the sun's radius by a few hundred kilometers.
"For me, something was wrong somewhere, but that's all I could say," Jubier told Space.com.
Scientists' knowledge of the Earth's and moon's contours weren't exact enough to highlight this discrepancy until about 10 years ago — the same time that modern eclipse simulations became possible through computer power and precision mapping. So it was around then that Jubier began to realize something was amiss.
"How can you not know this?" Wright recalls thinking. "You just hold a ruler up to the sky, and you say it's this big."
But as it turns out, it's not that simple, Wright told Space.com.
Where did it come from?
Historically, researchers have used the value 696,000 kilometers as the radius of the sun's photosphere — the body of the sun whose wavelengths are visible to the naked eye on Earth. The value was first published in 1891 by the German astronomer Arthur Auwers, Wright said, and it was taken as a standard value for quite some time. In 2015, the International Astronomical Union defined a "unit" based on the sun's radius as a similar 695,700 km, based on a 2008 study, so researchers can use that value to compare the sizes of other stars in the universe.
But efforts to measure the sun's radius have never been accurate enough to match our knowledge of the moon's and the Earth's contours, the researchers said. Scientists have tried measuring it through transits of Mercury and Venus — when those planets cross the face of the sun — and through images taken from sun-observing satellites like the Solar Dynamics Observatory. Each pixel on SDO images covers about 90 miles (150 km), Wright said, which means there's a limit to how precisely the size of the photosphere can be measured with this method. In addition, orbiting solar telescopes like SDO generally collect wavelengths of light emitted deeper inside or further outside the sun, rather than its visible photosphere.
"It's harder than you think just to put a ruler on these images and figure out how big the sun is — [SDO] doesn't have enough precision to nail this down," Wright said. "Similarly, with the Mercury and Venus transits, it turns out [a measurement based on those is] not quite as precise as you'd like it to be."
Different papers trying to pin down the sun's radius, using planet transits, space-based sensors as well as ground observations, have produced results that differ by as many as 930 miles (1,500 km), and can't seem to be reconciled with one another, Wright said. And for eclipse modelers, it's a critical and irritating problem.
Eclipse viewers might find the uncertainty of interest, as well, as they plot out where they'll be in the path of totality. A slightly larger sun means the period of total blackout can be a few seconds shorter in the center of the path, and the path itself would warp, as well.
"For most people, yes, it doesn't really matter; it won't change everything," Jubier said. "But the closer you get to the edge of the [eclipse] path, the more risk you take." If the sun is indeed bigger, the path is narrower than projections made with the usual value would suggest. So those chasing the effects on the eclipse's edge could be in trouble if they're not using a large enough value for their calculations.
Few people do eclipse predictions, Jubier added, and the precise value isn't necessary to a lot of researchers. Because of that, definitions can vary and it's hard to compare different values to one another, including the original 1891 value. It can be hard to tell for a given study what assumptions went into their answer for the sun's diameter, and so they can't be adapted easily to match each other or the eclipse. Any discrepancies in eclipse measurements can be attributed to not fully understanding the values, Jubier added.
"It is definitely still an area of ongoing research, and something that the field itself is interested in getting a better handle on," C. Alex Young, a solar astrophysicist at NASA's Goddard Space Flight Center in Maryland, told Space.com. "Probably a little esoteric for many people, and I would say that the calculation is not as important for a lot of areas, for example in solar physics, in terms of the accuracy needed. But especially the eclipse community is very interested in the accuracy."
Michael Kentrianakis, an avid eclipse chaser and a member of the American Astronomical Society's Solar Eclipse Task Force, learned about the confusion over the sun's size from his colleague Luca Quaglia, a physicist and eclipse researcher.
"The straw that broke the camel's back," Kentrianakis said, came during an expedition to Argentina in February, where he positioned himself outside what should have been the edge of an annular eclipse — where the moon is circled by a bright "ring of fire." A larger sun would make the "ring of fire" effect visible to a wider area.
"Technically, I should have been outside of annularity, [but the unfiltered photographs show] we were still in the path of annularity, and we have this beautiful chromosphere circling around at the edge," Kentrianakis said. That experience fully convinced him the sun was larger than generally thought.
This upcoming eclipse — which will very likely be the most-watched total solar eclipse in history, NASA officials have said — will provide a chance for others inside and outside the path of totality to help verify its size.
While researchers would ordinarily use the radius of the sun to compute exactly when the moon will cover and uncover the sun for a given location, called contact times, the opposite strategy is required here, Quaglia told Space.com. "If we can measure contact times accurately, everything else being the same, the only thing that can change is the solar radius. We can actually compute the solar radius that way," he said.
Kentrianakis, Jubier, Quaglia and others want to pin it down by positioning researchers inside and outside where totality should be, armed with the equipment for what's called a "flash spectrum" photograph. The process uses a textured grating over a camera, which splits incoming light into component wavelengths — making it easy to determine precisely when the entire photosphere has been covered by the moon, revealing a more limited set of wavelengths emitted by the chromosphere. Combined with accurate timestamps, that process would provide strong evidence for the sun's size. (Such a process has been used before, but on a limited scale, Quaglia said.)
Such measurements would also provide another benefit, Jubier said — investigating what some think is a thin layer in between the photosphere and chromosphere called the mesosphere. That thin layer can be visible for a moment after the photosphere is blotted out during an eclipse, which means observers may make measurements that confuse the mesosphere for more of the photosphere. A flash spectrum can help distinguish between the two, although it must be a high enough resolution so the signals from each can be clearly separated.
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Jul 27, 2017
“We cannot say exactly when life began on Earth, but we can now say with much more certainty that it existed 3.7 billion years ago,” lead author Tue Hassenkam said. “We can also say for sure that the microbes were living in a marine environment, since the biological remains must have precipitated onto the bottom of an early ocean.”
Hassenkam, an associate professor at the University of Copenhagen’s Nano-Science Center, along with senior author Minik Rosing of the University of Copenhagen and several colleagues utilized a groundbreaking high-tech method to study the Greenland rock. Hassenkam likened the effort to a blind man feeling the pavement in front of him with a stick. In this case, the "stick” was a very sharp laser needle emitted via a process called Atomic Force Microscopy (AFM).
“AFM can feel down rows of single atoms,” Hassenkam explained. “By varying the wavelength of laser light, we could ‘feel’ how the surface responded. The response depends on the chemical bonds in the surface at that spot.”
The researchers later determined that hydrogen is so small — it is the lightest chemical element — that it must have seeped through the rocks. Its absence actually provides evidence that the samples were not contaminated by more recent biological material.
What they did find, by way of the other elements, were “remains of early life trapped inside inclusions inside garnet crystals that grew in a sedimentary rock, and included parts of the sediment as inclusions,” Rosing said. “The materials inside the inclusions were part of the sediment, which formed more than 3.7 billion years ago.”
That age has previously been confirmed by a barrage of dating methods, with measurements of the decay of uranium-to-lead providing the most definitive, precise information.
The researchers believe that the identified life-associated chemical elements within the rock are the remains of single-celled organisms, possibly bacteria. These elements are “still tightly bound to each other within the scale of single-celled organisms inside the garnets,” Rosing said.
Earlier studies speculated that remains of early life could be found in the Isua Greenstone Belt. The new research not only confirms such prior speculations, but also pinpoints what these remains consist of with greater clarity.
“The rocks have recently been scoured by the Greenland Ice Sheet and have little or no vegetation,” Hassenkam said, indicating that this lack of other natural materials allowed the rocks to better preserve and show their earlier, ancient inclusions.
“We did something similar to what is portrayed in the movie ‘Jurassic Park,’” said Rosing, “but with the difference being that our time capsules were not amber, but garnet, and our samples were 50 times older and, instead of mosquitoes, we had single-celled organisms.”
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Gamma-ray bursts are some of the most luminous explosions astronomers can observe, but they are quick and fleeting and therefore mysterious, because no one knows for sure what the sources of GRBs are. They could be caused by massive supernovae, or they could be from a dying star collapsing to become a black hole.
GRB 160625B was one of the brightest bursts in recent years, and in about 40 seconds it released as much energy as the sun will emit over its entire lifetime, which happened by chance to be directed in a tight beam of gamma rays toward Earth.
Two NASA satellites that monitor the sky for such phenomena, the Fermi Gamma-ray Space Telescope and the Swift Gamma-Ray Burst Mission, detected the GRB event. These telescopes slewed quickly to the location of the burst to make observations and also immediately relayed the GRB’s position to several automated ground-based telescopes, which then began their observations.
Thanks to this quick reaction, said Nathanial Butler from Arizona State University in a statement, “we were able to measure this one's development and decay almost from the initial blast.”
A team of 31 astronomers combined their findings in a new paper published in Nature, providing strong evidence that this particular GRB came from a young black hole.
“Gamma-ray bursts are catastrophic events, related to the explosion of massive stars 50 times the size of our sun,” Eleonora Troja, an assistant research scientist from the University of Maryland and lead author of the paper, remarked in a statement. “If you ranked all the explosions in the universe based on their power, gamma-ray bursts would be right behind the Big Bang.”
At least once a day, gamma-ray bursts are detected as brief but intense flashes of gamma radiation, the most energetic form of light. They come from all different directions in the sky, and they last from tens of milliseconds to about a minute, making it hard to observe them in detail.
Gamma rays are invisible to the human eye, but gamma-ray telescopes — if they are fast enough — can catch at least part of the burst, or what’s called the afterglow of light that lingers from the blast. Additionally, there are sometimes additional wavelengths of light emitted, and astronomers can garner other details, especially if there is an optical component associated with the GRB.
In June 2016, the first telescope to begin observations of GRB 160625B was the MASTER-IRC telescope at the Teide Observatory in the Canary Islands, which observed it within a minute of the satellite notification. It made optical light observations while the initial phase was still active, gathering data on the amount of polarized optical light relative to the total light produced.
Another telescope, the RATIR camera (Reionization and Transients InfraRed camera), a 1.5-meter (60-inch) optical and infrared telescope in Baja California, had to wait eight and a half hours to make observations until the right area of the sky came into view.
“This means the gamma-ray burst itself had ended, and we were observing what's called the afterglow,” Butler said. “This is the fading explosion as the radiation shocks up the interstellar medium around the star that exploded.”
RATIR continued its observations over the weeks that followed the June 2016 event. They revealed that the outburst jetted out in a beam that was roughly two degrees wide, which is about four times the size of the moon. The fact that Earth found itself within the beam was entirely random.
Based on all the observations from both ground-based and space telescopes, and the long-lasting afterglow, the researchers concluded this GRB most likely originated from collimated jets of particles spewing from a young black hole.
Researchers in this field have typically theorized that a black hole's energy emission jets are dominated either by its magnetic field or by matter. The new data suggests that both factors are key. The black hole's magnetic field dominates the jets at the outset, and matter becomes dominant as the magnetic field dissipates.
“We find evidence for both models, suggesting that gamma-ray burst jets have a dual, hybrid nature,” Troja said. “The jets start off magnetic, but as the jets grow, the magnetic field degrades and loses dominance. Matter takes over and dominates the jets, although sometimes a weaker vestige of the magnetic field might survive.”
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Astrophysicists who were analyzing galaxy formation recently looked at how intergalactic gas and dust is transported over time and across great distances. They found that up to half of the matter in our Milky Way galaxy likely comes from other galaxies far, far away.
“Given how much of the matter out of which we formed may have come from other galaxies, we could consider ourselves space travelers or extragalactic immigrants,” Daniel Anglés-Alcázar, an astrophysics postdoctoral fellow from Northwestern University who led the study, said in a statement. “It is likely that much of the Milky Way’s matter was in other galaxies before it was kicked out by a powerful wind, traveled across intergalactic space and eventually found its new home in the Milky Way.”
This is a “first-of-its-kind analysis,” the team said, with the findings opening a new line of research into understanding galaxy formation. The study appears in the Monthly Notices of the Royal Astronomical Society.
Anglés-Alcázar and his fellow researchers used a supercomputer simulation based on the FIRE (Feedback in Realistic Environments) project, which is co-led by Northwestern physics and astronomy professor Claude-André Faucher-Giguère. FIRE uses numerical simulations that can produce realistic 3D models of galaxies. Anglés-Alcázar developed state-of-the-art algorithms to follow how a galaxy forms over time, from just after the Big Bang to the present day.
The findings on galactic evolution were unexpected, and the researchers coined a new term to explain the phenomenon: intergalactic transfer.
The simulations showed that supernova explosions within galaxies eject enormous amounts of gas, which causes atoms to be transported from one galaxy to another via powerful galactic winds. Even though galaxies are far apart from each other, the galactic winds propagate material at several hundred kilometers per second, and over several billion years this process infused new material into galaxies, sparking star formation.
“We show that in situ star formation fueled by fresh accretion dominates the early growth of galaxies of all masses, while the re-accretion of gas previously ejected in galactic winds often dominates the gas supply for a large portion of every galaxy’s evolution,” the team wrote. “Externally processed material contributes increasingly to the growth of central galaxies at lower redshifts.”
By tracking in detail the complex flows of matter in the simulations, the research team found that gas flows from smaller galaxies to larger galaxies, such as the Milky Way, where the gas forms stars. Additionally, even stars formed in one galaxy could be transferred to another. This transfer of mass through galactic winds can account for up to 50 percent of matter in the larger galaxies, the researchers said.
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A newfound Late Cretaceous carnivorous dinosaur, however, is a doppelganger for living cassowaries, which are the third-tallest and second-heaviest modern birds, smaller only than the emu and ostrich. Cassowaries have the ability to kill animals, including humans, by charging and kicking them.
The new dinosaur, described in an article in the journal Scientific Reports, was — like cassowaries, emus, and ostriches — covered with feathers, yet it could not fly. Lead author Junchang Lu and colleagues think it is possible that today’s flightless birds never did have ancestors that took to the skies. Feathers can serve functions other than enabling flight, such as by providing insulation and enabling forms of visual communication.
The dinosaur’s most distinctive feature had nothing to do with feathers, though, but did inspired its name: Corythoraptor jacobsi. Corythoraptor refers to a “raptor bearing a cassowary-like crest” on its head. The crest, technically known as a casque, was like a horn helmet covered with keratinous skin. Keratin is a fibrous protein that forms the main structural constituent of hair, claws, and other tough tissues.
Like horns on deer and antelope, the dinosaur’s casque might have helped choosy individuals to select their mates by using the size, shape, and other features of the head structure as visual fitness cues.
Cassowaries use their casques for similar reasons, although scientists continue to debate other possible functions. Some suggest the head feature is great for cutting through underbrush, while others think it might amplify the big bird’s deep sounds.
Cassowary calls are so creepy sounding that they have been included in horror film soundtracks. It is possible that dinosaurs like Corythoraptor produced similar vocalizations.
The researchers suspect that Corythoraptor craved meat.
“They might have eaten lizards, small dinosaurs, and other small animals,” Lu explained.
Lu and his team now believe that Ganzhou “was home to the world’s greatest known dinosaur diversity.”
Numerous other dinosaurs of all shapes and sizes have been discovered at this location over the years. Banji long, for example, once lived there and was a small and scrappy carnivore with a parrot-like face. It and many other dinosaurs once flourished where high-speed trains now zip through Ganzhou.
The past could also meet the present in terms of Corythoraptor’s lineage. The researchers cannot confirm that the dinosaur was directly related to today’s cassowaries, but the similarities between these birds and the dinosaur are numerous: head casques, long necks, chubby feathered bodies, muscular legs, an appetite for meat and more.
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New genetic research, published in the journal PLOS Biology, reveals how tardigrades achieve such resurrections after drying to a crisp. The authors now even believe that alien life forms could possess this remarkable ability.
“If life exists on other planets, and it is water-based, then those organisms that live out of water will evolve to resist extreme events, including the threat of drying out,” said co-author Mark Blaxter of the University of Edinburgh’s Institute of Evolutionary Biology.
He added that the ability to undergo anhydrobiosis — the desiccated, dormant state — “has evolved multiple times on Earth, so I am sure it will have evolved on other living planets.”
Blaxter and his colleagues took a clever approach to unravel the scientific secrets behind anhydrobiosis in tardigrades.
The researchers then looked at a particular set of genes, the so-called HOX genes, which establish the nose-to-tail pattern in embryos. There are usually about ten different HOX genes in animals, but tardigrades are missing five. Nematodes (roundworms) lack these same five genes.
“This could be because they share a common ancestor with tardigrades, and the loss happened in this ancestor,” Blaxter said. “Alternatively, it could be that the loss is associated with both groups becoming miniaturized, and these ‘middle’ HOX genes are the ones that are the easiest to lose.”
He added that the shared genetic loss could also simply be due to independent evolution. Because of these remaining questions, scientists continue to debate whether or not tardigrades are more closely related to nematodes or to arthropods — insects, spiders, and crustaceans.
Arakawa explained that all cells contain around 60–80 percent water when they are active, including human cells.
The key proteins that they identified are highly soluble. They dissolve in water that, due to surface tension, clings to and surrounds intracellular molecules within tardigrades. Like a microscopic protective coating, they prevent the cells from denaturing when the animal otherwise desiccates.
Arakawa added that tardigrades also possess additional genes that protect their DNA from damage. Because these small animals lack stress-sensing pathways, their cells do not usually die out when damaged. Instead, the identified proteins try to make repairs, and are often successful in doing so.
Due to these abilities, scientific consensus holds that tardigrades could be Earth’s last survivors. Such resilience is unexpected in a tiny creature that seems to exist in the slow lane.
“Tardigrades are slow walkers, and are not really aggressive animals,” Arakawa explained. “Therefore, they tend to lose competitions for food, or can become prey in a diversified ecosystem. But tardigrades fled to their own niche, where only tardigrades can survive, so paradoxically, tardigrades presumably acquired their extreme survival abilities due to their ecological incompetence.”
Arakawa and his colleagues can envision a day when enzymes, vaccines, human organs, tissues, and cells could be preserved in a state of anhydrobiosis instead of by liquid-nitrogen-based freezing.
“Some people have suggested that tardigrades could somehow travel through space to seed other planets with Earth-derived life,” Baxter said. “That obviously didn’t happen on Earth, as only some tardigrades are able to do anhydrobiosis, and tardigrades are derived from other, more ancient forms.”
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Jul 26, 2017
The research team, led by Sabrina Sholts, a curator in the Department of Anthropology at the Smithsonian's National Museum of Natural History, and Sebastian Wärmländer at Stockholm University, used digital 3-D models to scrutinize the angles and contours on the surfaces of North American projectile points. In doing so, they discovered a turning point at which the techniques used to produce the points became more variable. That variability suggests that individual toolmakers, who may have had fewer opportunities than their predecessors to learn from others, began working out how to make the tools on their own. The findings were reported July 12 in the journal PLOS ONE.
"Our study really allows stone tools to speak in a new way," said Joseph Gingerich, a research associate at the museum and assistant professor of anthropology at Ohio University. "By being able to document subtle changes in stone tool technology, we can better understand how social interactions among artisans changed in North America over 12,000 years ago."
The earliest well-documented group of people in North America, known as Clovis, is recognized by distinctive pointed stone projectiles that appear about 13,500 years ago. These culture-defining tools, called Clovis points, are sharp-edged and symmetrical, with a groove near the base -- called a flute -- where a spear shaft may have fit. Anthropologists consider them to be a very sophisticated technology.
The highly mobile hunter-gatherers of the Clovis culture spread quickly across North America, and Clovis points have been found all over the continent. In 2012, Sholts and colleagues analyzed 50 authentic and replicate Clovis points, examining how their surfaces had been shaped as flakes of stone were chipped away to craft the tool. Using an approach Sholts and Wärmländer originally developed for studying bones, the researchers laser scanned each point to create a three-dimensional model and then analyzed its contours, measuring and comparing subtle surface features that cannot be discerned by eye. "It's a way to capture all the individual actions to reduce the core, which reflect the technique used to shape it," Sholts said.
The analysis revealed remarkable consistency among the ancient artifacts compared to almost perfect copies made by a modern knapper, an artisan that crafts stone tools using ancient techniques. The team concluded that the manufacturing technique used by the Clovis people was so uniform that it must have been passed on directly from one knapper to another.
According to the archaeological record, Clovis technology was used for several hundred years. A variety of other styles emerged later, though they never spread across the continent like Clovis points did. To learn more about the groups that manufactured these later styles, the authors of the new study analyzed the surface features of 100 projectile points from collections at several museums, including the Smithsonian collection, which is curated by anthropologist Dennis Stanford.
The new study included Clovis points and samples of four later styles of fluted points, which had been recovered from sites in the eastern United States. The team analyzed the points' surface contours as they had done in the earlier study and also introduced a new method of analyzing digital models to assess the objects' three-dimensional asymmetry.
Using another new technique developed by Wärmländer and co-author Stefan Schlager of the University of Freiburg, the team determined that the overall three-dimensional shapes of the points did not vary significantly. However, they did find increased variability in the surface contours among some of the later styles of points, indicating that those tools had not been produced using a consistent technique.
The increase in variability among the later points suggests a decrease in social learning and possibly a reduction in overall interactions among North American populations beginning around 12,500 years ago, the researchers say. This is consistent with anthropologists' current thinking about how people were living during this time. "There seems to be evidence of increased experimentation during this period, due to groups moving away from each other and pushing into new environments," Sholts said.
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|Reconstruction of Pyrrhula crassa (left) and skull (right).|
Until hundreds of years ago, a species of bullfinch, a small songbird with a very short and robust beak, lived on Graciosa Island in the Azores archipelago. The arrival of humans to this island, however, depleted its population and it ended up going extinct, as was the case with numerous bird species on other islands, such as the Canaries and Madeira.
Now, an international team of scientists, backed by a project led by Josep Antoni Alcover, from the Mediterranean Institute for Advanced Studies (IMEDEA, CSIC-UIB), has discovered the bones of this bullfinch, called Pyrrhula crassa, in a cave located in a 12,000-year-old volcano in the southeast of the island.
"It is the first extinct passerine bird described in the archipelago, and it won't be the last," states Alcover, co-author of the study published in Zootaxa which focused on the analysis of beak morphology in order to determine the new species.
Despite there being few known remains of this bird, they are sufficiently distinctive for the scientists to have succeeded in establishing that they belong to a new extinct species of bullfinch.
The new bird, being the largest of its genus according to the size of the skull remains found, recalls due to its flying ability the existing bullfinch from the other Azores island (São Miguel) which is 'vulnerable' to extinction because of the expansion of agriculture and the disappearance of laurel forests.
"Its short and wide beak was not just considerably bigger, but also relatively higher than that of the common bullfinch or that from São Miguel, with a very robust configuration reminiscent to an extent of the beak of a small parrot," asserts the researcher.
Invasions wiped out the birds
These islands were colonized during the 13th century by the Portuguese, although they could have been visited by Vikings over one thousand years ago. Just as has happened on many other islands, such as the Canaries or Madeira, different bird species have disappeared throughout the last millennium due to the arrival of humans along with various invasive species.
Human colonization led to the destruction and burning of the islands' habitats in which humans started settling, and they impacted on the birds which were part of the indigenous fauna. P. crassa was no exception, finding itself affected until its extinction.
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Long ago, about 300,000 years after the beginning of the universe (the Big Bang), the universe was dark. There were no stars or galaxies, and the universe was filled with neutral hydrogen gas. In the next half billion years or so the first galaxies and stars appeared. Their energetic radiation ionized their surroundings, illuminating and transforming the universe.
This dramatic transformation, known as re-ionization, occurred sometime in the interval between 300 million years and one billion years after the Big Bang. Astronomers are trying to pinpoint this milestone more precisely and the galaxies found in this study help in this determination.
"Before re-ionization, these galaxies were very hard to see, because their light is scattered by gas between galaxies, like a car's headlights in fog," says Malhotra. "As enough galaxies turn on and 'burn off the fog' they become easier to see. By doing so, they help provide a diagnostic to see how much of the 'fog' remains at any time in the early universe."
The Dark Energy Camera
To detect these galaxies, Malhotra and Rhoads have been using the Dark Energy Camera (DECam), one of the new powerful instruments in the astronomy field. DECam is installed at the National Optical Astronomy Observatory (NOAO)'s 4-meter Blanco Telescope, located at the Cerro Tololo Inter-American Observatory (CTIO), in northern Chile, at an altitude of 7,200 feet.
"Several years ago, we carried out a similar study using a 64-megapixel camera that covers the same amount of sky as the full moon," says Rhoads. "DECam, by comparison, is a 570-megapixel camera and covers 15 times the area of the full moon in a single image."
DECam was recently made even more powerful when it was equipped with a special narrowband filter, designed at ASU's School of Earth and Space Exploration (SESE), primarily by Rhoads and Zheng (who was a SESE postdoctoral fellow and is currently at the Shanghai Astronomical Observatory in China), with assistance from Alistair Walker of NOAO.
"We spent several months refining the design of the filter profile, optimizing the design to get maximum sensitivity in our search" says Zheng, the lead author of this study.
Touching the Cosmic Dawn
The galaxy search using the ASU-designed filter and DECam is part of the ongoing "Lyman Alpha Galaxies in the Epoch of Reionization" project (LAGER). It is the largest uniformly selected sample that goes far enough back in the history of the universe to reach cosmic dawn.
"The combination of large survey size and sensitivity of this survey enables us to study galaxies that are common but faint, as well as those that are bright but rare, at this early stage in the universe," says Malhotra.
Junxian Wang, a co-author on this study and the lead of the Chinese LAGER team, adds that "our findings in this survey imply that a large fraction of the first galaxies that ionized and illuminated the universe formed early, less than 800 million years after the Big Bang."
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New research not only supports Darwin’s views, but also identifies a universal “language” of arousal emitted and understood by amphibians, reptiles, birds, and mammals. The findings, published in the journal Proceedings of the Royal Society B, suggest that we are at least somewhat like the famous fictional character Doctor Dolittle, who could decipher animal communications with ease.
“Our study shows that humans are naturally able to recognize emotional arousal across all classes of vocalizing animals,” said lead author Piera Filippi, a postdoctoral researcher at the University of Aix-Marseille and the Max Planck Institute for Psycholinguistics. “This outcome may find an important application in animal welfare, suggesting that humans may rely on their intuition to assess when animals are stressed.”
Prior research additionally suggests that animals understand human emotional vocal expressions. Pet owners are often more attuned to this, given the reactions that dogs, cats, horses, birds, rodents, and more have to a range of owner outbursts, from angry scolding to happy praise.
For the latest study, Filippi, senior author Onur Gunturkun, and their team went beyond investigating such a familiar collection of animal pets. They instead gathered 180 recordings of vocalizations from nine different and very diverse species: hourglass treefrog, black-capped chickadee, common raven, American alligator, African bush elephant, giant panda, domestic pig, and Barbary macaque. People who spoke English, Mandarin, and German were then recruited to evaluate the levels of arousal communicated in each animal recording.
The human listeners, no matter their native language, aced the tests. This indicates that human ability to assess vocal expressions of arousal — whether emitted due to sexual bliss, infant distress, or terror over a predator — is biologically rooted and somehow cemented in our DNA.
The scientists further conducted an acoustic analysis of the recordings. Pairing this data with the findings concerning the human listeners, the researchers discovered that people use multiple acoustic parameters to infer levels of arousal in vocalizations. Mainly, however, humans rely on fundamental frequency cues and the forcefulness of the sounds.
The primary explanation for the ability, seemingly shared across much of the animal kingdom, has to do with the body-sound connection.
“Across vocalizing animals, higher levels of emotional intensity may induce the contraction of muscles that are required for vocal production,” Filippi explained. “This modification alters the quality of the sounds produced, often resulting in changes related to the perceived frequency of the sound.”
The researchers believe their study’s findings could extend to marine species with audible forms of communication. We therefore should be able to identify a dolphin’s levels of arousal, for example, just by hearing its vocalizations, and vice versa.
It may be that skills for vocal expression in marine and terrestrial species evolved from a common ancestor. This underlying connection, as well as the shared basic universal “language,” are tied to critical life-and-death concerns.
“The ability to recognize emotional content across diverse species may have favored the perception of heightened levels of threat or danger in the surrounding environment,” Filippi said. “This may have increased survival opportunities.”
Infant distress calls appear to be the most easily understood, from baby alligators calling for their mothers to young giant pandas squeaking, growling, barking, and huffing. The researchers suspect that this primal ability to decipher baby speak is “particularly salient to caregivers.”
Some animals can even manipulate humans via their infant-resembling cries. Earlier research, for example, found that cats can purr in the same frequency range of a crying baby when soliciting food from their owners.
It remains unclear if insects share the ability of other animals in deciphering the arousal levels of various species’ communications. Filippi explained that insects produce sounds that differ in the level of emotional intensity through stridulation, which refers to vibration resulting from rubbing two body structures against each other. Since the sound-production mechanism is different from that of most other animals, insects may not be included in the universal “language” that connects other creatures.
Another identified disconnect exists between how humans mentally process speech versus nonverbal emotional communications like screams of pain, pleasure, and fear. “Spoken language can be highly emotional,” Filippi said. “However, the fine-tuned articulatory movements involved in speech production may constrain the perception of emotional intensity encoded in the signal.”
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The latest study was a meta-analysis of English-language studies on sperm count and concentration that was published this week in the journal Human Reproduction Update. Led by researchers from the Hebrew University-Hadassah Braun School of Public Health and Community Medicine and the Icahn School of Medicine at Mount Sinai, the work analyzed 185 studies on sperm count and quality that were published between 1973 and 2011.
The findings, the researchers say, are unnerving.
After combing through the material, the researchers found a large decrease in sperm quality among men from North America, Europe, Australia, and New Zealand. The drop was particularly notable among men who had never had kids and were unaware of their fertility status. In these men, they found a 52.5 percent drop in sperm concentration, and a 59.3 percent decrease in total sperm count.
They did not find the same decrease in men from non-Western countries, although the authors acknowledged that this could potentially be due to a lack of data.
Birth and fertility rates in the United States have continually gone down since around 2007. According to data from the World Bank, the current US birth rate is about 12.4 babies per population of 1,000 people, down from 14.8 in 1973 (the year that researchers began looking at the data).
In addition, low sperm count has more consequences than fertility and childbirth. The researchers pointed out in their meta-analysis that “poor sperm count is associated with overall morbidity and mortality.” In other words, men who have low sperm count tend to have other health problems as well.
It is important to note that there is so far no conclusive evidence about why the sperm count has dropped. The authors speculate it is due to environmental and lifestyle causes, including pesticides, smoking, and obesity. Their assessment didn’t establish any causal links, however.
“If we will not change the ways that we are living and the environment and the chemicals that we are exposed to, I am very worried about what will happen in the future," Levine told the BBC, warning ominously that “it may be the extinction of the human species.”
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Jul 25, 2017
Attributing scientific progress to eureka moments is popular because it is easy to understand, argues Milan Cirkovic, a senior research associate at the Astronomical Observatory of Belgrade and an assistant physics professor at the University of Novi Sad in Serbia and Montenegro. But, he writes in the journal Space Policy, "It puts too big an emphasis on the 'origin myths' and the role of great personalities, key moments, events, and circumstances in any historical process.”
Cirkovic said in an email that the community involved in the search for extraterrestrial intelligence (SETI) should instead be prepared for a process that would take a very long time. It may take decades as the SETI community looks at all the reasons aliens might not be the source of a mysterious signal.
"I have only tried to point out that both history of science and logic and common sense suggest — on a descriptive level — that contact will be a protracted affair, probably not recognizable as such over timescales of years or decades," Cirkovic said. He was careful not to say how contact might proceed, but that it would take a long time and repeated observations.
Think about the protracted debate concerning "Tabby's star," which is showing strange brightening and dimming. Some say it's due to a possible "alien megastructure," while others are pointing to various natural processes, such as exocomets.
"More structure is obviously necessary, as far as signals are concerned," Cirkovic said. "The example often quoted (first due to Nikola Tesla, who was somewhat forgotten as a SETI pioneer) is the presence of prime numbers 2, 3, 5, 7, 11, ... etc. in the signal."
Prime numbers are a non-natural process that are considered by SETI scholars an indication of possible life.
"However," Cirkovic added, "this is the classic understanding of the first contact which I actually intend to undermine in the present paper. I argue — after some of the SETI ‘founding fathers,’ notably Nikolai Kardashev — that we are more likely to detect an anomalous astrophysical phenomenon, which would be a signpost of massive engineering effort by extraterrestrial intelligence.”
He added that in recent years the SETI community has said it expects contact to come through detecting one of these engineering signatures rather than through a radio signal. Cirkovic and some other experts call this "Dysonian SETI", after a 2011 paper that Cirkovic co-authored and was led by Robert Bradbury of the Astronomical Observatory of Belgrade.
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Previous research had suggested that huge "rogue" or "unbound" worlds, which have no discernible host star, are extremely common in the Milky Way, perhaps outnumbering stars by a factor of 2 to 1. But that's probably not the case, according to the new study.
"We found that Jupiter-mass [rogue] planets are at least 10 times less frequent than previously thought," study lead author Przemek Mróz, a researcher at the Warsaw University Observatory in Poland, told Space.com via email.
Astronomers think most rogue planets were likely booted out of their native solar systems by interactions with neighboring planets. Scientists generally hunt for these lonely worlds using a technique called gravitational microlensing, which involves watching for a foreground object to pass in front of a distant star. When this happens, the closer body's gravity bends and magnifies the star's light, in ways that can reveal clues about the foreground object's mass and other characteristics.
A 2011 study, based on 474 microlensing events detected by a telescope in New Zealand, estimated that gas-giant rogue worlds are nearly twice as common as main-sequence ("normal") stars in the Milky Way. (The number of stars in our galaxy is a matter of debate, with estimates ranging from 100 billion to 1 trillion.)
In the new study, Mróz and his team analyzed a much bigger data set — more than 2,600 microlensing events that were detected between 2010 and 2015 by the Optical Gravitational Lensing Experiment (OGLE). This survey, which is run by researchers at the University of Warsaw, depends primarily on observations made at the Las Campanas Observatory in Chile.
The researchers determined that the Milky Way likely hosts a maximum of one Jupiter-like rogue for every four main-sequence stars — still a lot, to be sure, but not nearly as many as the previous study had suggested.
The new results make sense on a number of levels, Mróz said.
"Our new microlensing observations are in agreement with theoretical expectations on the frequency of free-floating Jupiters and with infrared surveys for planetary-mass objects in star-forming regions," he said.
Intriguingly, the OGLE survey also spotted a few extremely brief microlensing events, which Mróz said were likely caused by much smaller worlds — ones about the size of Earth, or just a bit bigger.
"Because our sensitivity to such short events was very low, free-floating Earths should be very common, perhaps more frequent than stars, but we are unable to provide a precise number owing to [the] small number of detections," he told Space.com.
Increasing the number of ground-based microlensing detections would give astronomers a somewhat better understanding of the population of small rogue planets, Mróz said. But big gains may have to wait for future space observatories, such as Europe's Euclid mission and NASA's Wide-Field Infrared Survey Telescope (WFIRST).
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