Tagged: ScienceNews Toggle Comment Threads | Keyboard Shortcuts

  • richardmitnick 11:13 am on February 8, 2018 Permalink | Reply
    Tags: , , ScienceNews, , Wikipedia has become a science reference source even though scientists don’t cite it   

    From ScienceNews: “Wikipedia has become a science reference source even though scientists don’t cite it” 


    ScienceNews

    February 5, 2018
    Bethany Brookshire

    Phrases from Wikipedia pages on hot scientific fields end up in published papers, a study finds.

    1
    SCIENCE IN ACTION The section of a Wikipedia page on the synthesis of hydrastine was part of a project that showed how Wikipedia topics might end up in scientific studies. Farknot Architect/shutterstock; Wikimedia Commons

    Wikipedia: The settler of dinnertime disputes and the savior of those who cheat on trivia night. Quick, what country has the Nile’s headwaters? What year did Gershwin write “Rhapsody in Blue”? Wikipedia has the answer to all your burning trivia questions — including ones about science.

    With hundreds of thousands of scientific entries, Wikipedia offers a quick reference for the molecular formula of Zoloft, who the inventor of the 3-D printer is and the fact that the theory of plate tectonics is only about 100 years old. The website is a gold mine for science fans, science bloggers and scientists alike. But even though scientists use Wikipedia, they don’t tend to admit it. The site rarely ends up in a paper’s citations as the source of, say, the history of the gut-brain axis or the chemical formula for polyvinyl chloride.

    But scientists are browsing Wikipedia just like everyone else. A recent analysis found that Wikipedia stays up-to-date on the latest research — and vocabulary from those Wikipedia articles finds its way into scientific papers. The results don’t just reveal the Wiki-habits of the ivory tower. They also show that the free, widely available information source is playing a role in research progress, especially in poorer countries.

    Teachers in middle school, high school and college drill it in to their students: Wikipedia is not a citable source. Anyone can edit Wikipedia [not true any longer], and articles can change from day to day — sometimes by as little as a comma, other times being completely rewritten overnight. “[Wikipedia] has a reputation for being untrustworthy,” says Thomas Shafee, a biochemist at La Trobe University in Melbourne, Australia.

    But those same teachers — even the college professors — who warn students away from Wikipedia are using the site themselves. “Academics use Wikipedia all the time because we’re human. It’s something everyone is doing,” says Doug Hanley, a macroeconomist at the University of Pittsburgh.

    And the site’s unreliable reputation may be unwarranted. Wikipedia is not any less consistent than Encyclopedia Britannica, a 2005 Nature study showed (a conclusion that the encyclopedia itself vehemently objected to). Citing it as a source, however, is still a bridge too far. “It’s not respected like academic resources,” Shafee notes.

    Academic science may not respect Wikipedia, but Wikipedia certainly loves science. Of the roughly 5.5 million articles, half a million to a million of them touch on scientific topics. And constant additions from hundreds of thousands of editors mean that entries can be very up to date on the latest scientific literature.

    How recently published findings affect Wikipedia is easy to track. They’re cited on Wikipedia, after all. But does the relationship go the other way? Do scientific posts on Wikipedia worm their way into the academic literature, even though they are never cited? Hanley and his colleague Neil Thompson, an innovation scholar at MIT, decided to approach the question on two fronts.

    First, they determined the 1.1 million most common scientific words in published articles from the scientific publishing giant Elsevier. Then, Hanley and Thompson examined how often those same words were added to or deleted from Wikipedia over time, and cited in the research literature. The researchers focused on two fields, chemistry and econometrics — a new area that develops statistical tests for economics.

    There was a clear connection between the language in scientific papers and the language on Wikipedia. “Some new topic comes up and it gets exciting, it will generate a new Wikipedia page,” Thompson notes. The language on that new page was then connected to later scientific work. After a new entry was published, Hanley and Thompson showed, later scientific papers contained more language similar to the Wikipedia article than to papers in the field published before the new Wikipedia entry. There was a definite association between the language in the Wikipedia article and future scientific papers.

    But was Wikipedia itself the source of that language? This part of the study can’t answer that. It only observes words increasing together in two different spaces. It can’t prove that scientists were reading Wikipedia and using it in their work.

    So the researchers created new Wikipedia articles from scratch to find out if the language in them affected the scientific literature in return. Hanley and Thompson had graduate students in chemistry and in econometrics write up new Wikipedia articles on topics that weren’t yet on the site. The students wrote 43 chemistry articles and 45 econometrics articles. Then, half of the articles in each set got published to Wikipedia in January 2015, and the other half were held back as controls. The researchers gave the articles three months to percolate through the internet. Then they examined the next six months’ worth of published scientific papers in those fields for specific language used in the published Wikipedia entries, and compared it to the language in the entries that never got published.

    In chemistry, at least, the new topics proved popular. Both the published and control Wikipedia page entries had been selected from graduate level topics in chemistry that weren’t yet covered on Wikipedia. They included entries such as the synthesis of hydrastine (the precursor to a drug that stops bleeding). People were interested enough to view the new articles on average 4,400 times per month.

    The articles’ words trickled into to the scientific literature. In the six months after publishing, the entries influenced about 1 in 300 words in the newly published papers in that chemical discipline. And scientific papers on a topic covered in Wikipedia became slightly more like the Wikipedia article over time. For example, if chemists wrote about the synthesis of hydrastine — one of the new Wikipedia articles — published scientific papers more often used phrases like “Passarini reaction,” a term used in the Wikipedia entry. But if an article never went on to Wikipedia, the scientific papers published on the topic didn’t become any more similar to the never-published article (which could have happened if the topics were merely getting more popular). Hanley and Thompson published a preprint of their work to the Social Science Research Network on September 26.

    Unfortunately, there was no number of Wikipedia articles that could make econometrics happen. “We wanted something on the edge of a discipline,” Thompson says. But it was a little too edgy. The new Wikipedia entries in that field got one-thirtieth of the views that chemistry articles did. Thompson and Hanley couldn’t get enough data from the articles to make any conclusions at all. Better luck next time, econometrics.

    The relationship between Wikipedia entries and the scientific literature wasn’t the same in all regions. When Hanley and Thompson broke the published scientific papers down by the gross domestic product of their countries of origin, they found that Wikipedia articles had a stronger effect on the vocabulary in scientific papers published by scientists in countries with weaker economies. “If you think about it, if you’re a relatively rich country, you have access at your institution to a whole list of journals and the underlying scientific literature,” Hanley notes. Institutions in poorer countries, however, may not be able to afford expensive journal subscriptions, so scientists in those countries may rely more heavily on publicly available sources like Wikipedia.

    The Wikipedia study is “excellent research design and very solid analysis,” says Heather Ford, who studies digital politics at the University of Leeds in England. “As far as I know, this is the first paper that attributes a strong link between what is on Wikipedia and the development of science.” But, she says, this is only within chemistry. The influence may be different in different fields.

    “It’s addressing a question long in people’s minds but difficult to pin down and prove,” says Shafee. It’s a link, but tracking language, he explains, isn’t the same as finding out how ideas and concepts were moving from Wikipedia into the ivory tower. “It’s a real cliché to say more research is needed, but I think in this case it’s probably true.”

    Hanley and Thompson would be the first to agree. “I think about this as a first step,” Hanley says. “It’s showing that Wikipedia is not just a passive resource, it also has an effect on the frontiers of knowledge.”

    It’s a good reason for scientists get in and edit entries within their expertise, Thompson notes. “This is a big resource for science and I think we need to recognize that,” Thompson says. “There’s value in making sure the science on Wikipedia is as good and complete as possible.” Good scientific entries might not just settle arguments. They might also help science advance. After all, scientists are watching, even if they won’t admit it.

    See the full article here .

    Science News is edited for an educated readership of professionals, scientists and other science enthusiasts. Written by a staff of experienced science journalists, it treats science as news, reporting accurately and placing findings in perspective. Science News and its writers have won many awards for their work; here’s a list of many of them.

    Published since 1922, the biweekly print publication reaches about 90,000 dedicated subscribers and is available via the Science News app on Android, Apple and Kindle Fire devices. Updated continuously online, the Science News website attracted over 12 million unique online viewers in 2016.

    Science News is published by the Society for Science & the Public, a nonprofit 501(c) (3) organization dedicated to the public engagement in scientific research and education.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

     
  • richardmitnick 10:54 am on February 8, 2018 Permalink | Reply
    Tags: , , ScienceNews, Skyrmions open a door to next-level data storage   

    From ScienceNews: “Skyrmions open a door to next-level data storage “ 


    ScienceNews

    February 7, 2018
    Emily Conover

    Knots in magnetic materials could one day make for faster, sturdier, tinier electronics.

    1
    MAGNETIC KNOTS A skyrmion is a swirl (red) among the atoms of a magnetic material. Here, cones point in the direction of each atom’s magnetization. Skyrmions come in several types; this one, a Néel skyrmion, is found in thin materials. Ella Maru Studio.

    Like sailors and spelunkers, physicists know the power of a sturdy knot.

    Some physicists have tied their hopes for a new generation of data storage to minuscule knotlike structures called skyrmions, which can form in magnetic materials. Incredibly tiny and tough to undo, magnetic skyrmions could help feed humankind’s hunger for ever-smaller electronics.

    On traditional hard drives, the magnetic regions that store data are about 10 times as large as the smallest skyrmions. Ranging from a nanometer to hundreds of nanometers in diameter, skyrmions “are probably the smallest magnetic systems … that can be imagined or that can be realized in nature,” says physicist Vincent Cros of Unité Mixte de Physique CNRS/Thales in Palaiseau, France.

    What’s more, skyrmions can easily move through a material, pushed along by an electric current. The magnetic knots’ nimble nature suggests that skyrmions storing data in a computer could be shuttled to a sensor that would read off the information as the skyrmions pass by. In contrast, traditional hard drives read and write data by moving a mechanical arm to the appropriate region on a spinning platter (SN: 10/19/13, p. 28). Those moving parts tend to be fragile, and the task slows down data recall. Scientists hope that skyrmions could one day make for more durable, faster, tinier gadgets.

    One thing, however, has held skyrmions back: Until recently, they could be created and controlled only in the frigid cold. When solid-state physicist Christian Pfleiderer and colleagues first reported the detection of magnetic skyrmions, in Science in 2009, the knots were impractical to work with, requiring very low temperatures of about 30 kelvins (–243° Celsius). Those are “conditions where you’d say, ‘This is of no use for anybody,’ ” says Pfleiderer of the Technical University of Munich.

    Skyrmions have finally come out of the cold, though they are finicky and difficult to control. Now, scientists are on the cusp of working out the kinks to create thawed-out skyrmions with all the desired characteristics. At the same time, researchers are chasing after new kinds of skyrmions, which may be an even better fit for data storage. The skyrmion field, Pfleiderer says, has “started to develop its own life.”

    2
    A grid of skyrmions (blue circled by white) is revealed in an ultrathin film of palladium and iron, in this image from a scanning tunneling microscope (left) and illustrated inset of a single skyrmion (right). K. von Bergmann.

    Memories in magnets

    In a magnetic material, such as iron, each atom acts like a tiny bar magnet with its own north and south poles. This magnetization arises from spin, a quantum property of the atom’s electrons. In a ferromagnet, a standard magnet like the one holding up the grocery list on your refrigerator, the atoms’ magnetic poles point in the same direction (SN Online: 5/14/12).

    Skyrmions, which dwell within such magnetic habitats, are composed of groups of atoms with their magnetic poles oriented in whorls. Those spirals of magnetization disrupt the otherwise orderly alignment of atoms in the magnet, like a cowlick in freshly combed hair. Within a skyrmion, the direction of the atoms’ poles twists until the magnetization in the center points in the opposite direction of the magnetization outside. That twisting is difficult to undo, like a strong knot (SN Online: 10/31/08). So skyrmions won’t spontaneously disappear — a plus for long-term data storage.

    Using knots of various kinds to store information has a long history. Ancient Incas used khipu, a system of knotted cord, to keep records or send messages (SN Online: 5/8/17). In a more modern example, Pfleiderer says, “if you don’t want to forget something then you put a knot in your handkerchief.” Skyrmions could continue that tradition.


    GIVE IT A WHIRL Skyrmions move across magnetic material by sliding from atom to atom. Here, each atom is indicated by a cone that points in the direction of its magnetization. As the swirl travels, atoms stay in place, but their magnetic poles rotate. Skyrmions may be a future option for fast, sturdy, small data storage.

    On the right track

    Skyrmions are a type of “quasiparticle,” a disturbance within a material that behaves like a single particle, despite being a collective of many individual particles. Although skyrmions are made up of atoms, which remain stationary within the material, skyrmions can move around like a true particle, by sliding from one group of atoms to another. “The magnetism just twists around, and thus the skyrmion travels,” says condensed matter physicist Kirsten von Bergmann of the University of Hamburg.

    In fact, skyrmions were first proposed in the context of particles. British physicist Tony Skyrme, who lends his name to the knots, suggested about 60 years ago that particles such as neutrons and protons could be thought of as a kind of knot. In the late 1980s, physicists realized the math that supported Skyrme’s idea could also represent knots in the magnetization of solid materials.

    Such skyrmions could be used in futuristic data storage schemes, researchers later proposed. A chain of skyrmions could encode bits within a computer, with the presence of a skyrmion representing 1 and the absence representing 0.

    In particular, skyrmions might be ideal for what are known as “racetrack” memories, Cros and colleagues proposed in Nature Nanotechnology in 2013. In racetrack devices, information-holding skyrmions would speed along a magnetic nanoribbon, like cars on the Indianapolis Motor Speedway.

    Solid-state physicist Stuart Parkin proposed a first version of the racetrack concept years earlier. In a 2008 paper in Science, Parkin and colleagues demonstrated the beginnings of a racetrack memory based not on skyrmions, but on magnetic features called domain walls, which separate regions with different directions of magnetization in a material. Those domain walls could be pushed along the track using electric currents to a sensor that would read out the data encoded within. To maximize the available space, the racetrack could loop straight up and back down (like a wild Mario Kart ride), allowing for 3-D memory that could pack in more data than a flat chip.

    “When I first proposed [racetrack memories] many years ago, I think people were very skeptical,” says Parkin, now at the Max Planck Institute of Microstructure Physics in Halle, Germany. Today, the idea — with and without skyrmions — has caught on. Racetrack memories are being tested in laboratories, though the technology is not yet available in computers.

    To make such a system work with skyrmions, scientists need to make the knots easier to wrangle at room temperature. For skyrmion-based racetrack memories to compete with current technologies, skyrmions must be small and move quickly and easily through a material. And they should be easy to create and destroy, using something simple like an electric current. Those are lofty demands: A step forward on one requirement sometimes leads to a step backward on the others. But scientists are drawing closer to reining in the magnetic marvels.

    Heating up

    Those first magnetic skyrmions found by Pfleiderer and colleagues appeared spontaneously in crystals with asymmetric structures that induce a twist between neighboring atoms. Only certain materials have that skyrmion-friendly asymmetric structure, limiting the possibilities for studying the quasiparticles or coaxing them to form under warmer conditions.

    Soon, physicists developed a way to artificially create an asymmetric structure by depositing material in thin layers. Interactions between atoms in different layers can induce a twist in the atoms’ orientations. “Now, we can suddenly use ordinary magnetic materials, combine them in a clever way with other materials, and make them work at room temperature,” says materials scientist Axel Hoffmann of Argonne National Laboratory in Illinois.

    Scientists produced such thin film skyrmions for the first time in a one-atom-thick layer of iron on top of iridium, but temperatures were still very low. Reported in Nature Physics in 2011, those thin film skyrmions required a chilly 11 kelvins (–262° C). That’s because the thin film of iron loses its magnetic properties above a certain temperature, says von Bergmann, who coauthored the study, along with nanoscientist Roland Wiesendanger of the University of Hamburg and colleagues. But thicker films can stay magnetic at higher temperatures. And so, “one important step was to increase the amount of magnetic material,” von Bergmann says.

    To go thicker, scientists began stacking sheets of various magnetic and nonmagnetic materials, like a club sandwich with repeating layers of meat, cheese and bread. Stacking multiple layers of iridium, platinum and cobalt, Cros and colleagues created the first room-temperature skyrmions smaller than 100 nanometers, the researchers reported in May 2016 in Nature Nanotechnology.

    By adjusting the types of materials, the number of layers and their thicknesses, scientists can fashion designer skyrmions with desirable properties. When condensed matter physicist Christos Panagopoulos of Nanyang Technological University in Singapore and colleagues fiddled with the composition of layers of iridium, iron, cobalt and platinum, a variety of skyrmions swirled into existence. The resulting knots came in different sizes, and some were more stable than others, the researchers reported in Nature Materials in September 2017.

    Although scientists now know how to make room-temperature skyrmions, the heat-tolerant swirls, tens to hundreds of nanometers in diameter, tend to be too big to be very useful. “If we want to compete with current state-of-the-art technology, we have to go for skyrmionic objects [that] are much smaller in size than 100 nanometers,” Wiesendanger says. The aim is to bring warmed-up skyrmions down to a few nanometers.

    As some try to shrink room-temp skyrmions down, others are bringing them up to speed, to make for fast reading and writing of data. In a study reported in Nature Materials in 2016, skyrmions at room temperature reached top speeds of 100 meters per second (about 220 miles per hour). Fittingly, that’s right around the fastest speed NASCAR drivers achieve. The result showed that a skyrmion racetrack might actually work, says study coauthor Mathias Kläui, a condensed matter physicist at Johannes Gutenberg University Mainz in Germany. “Fundamentally, it’s feasible at room temperature.” But to compete against domain walls, which can reach speeds of over 700 m/s, skyrmions still need to hit the gas.

    __________________________________________

    Bloch skyrmion
    The first type of skyrmion detected, called a Bloch skyrmion, appears in asymmetric crystals. The magnetic poles tilt around the circle.

    4

    Néel skyrmion
    In a Néel skyrmion, the magnetic poles tilt outward instead of around the circle as they do in a Bloch skyrmion.

    5

    Antiskyrmion
    Newly discovered antiskyrmions are like a cross between Néel and Bloch skyrmions, and may have some advantages for memory devices, such as tolerating a range of temperatures.

    6
    __________________________________________

    Despite progress, there are a few more challenges to work out. One possible issue: A skyrmion’s swirling pattern makes it behave like a rotating object. “When you have a rotating object moving, it may not want to move in a straight line,” Hoffmann says. “If you’re a bad golf player, you know this.” Skyrmions don’t move in the same direction as an electric current, but at an angle to it. On the racetrack, skyrmions might hit a wall instead of staying in their lanes. Now, researchers are seeking new kinds of skyrmions that stay on track.

    A new twist

    Just as there’s more than one way to tie a knot, there are several different types of skyrmions, formed with various shapes of magnetic twists. The two best known types are Bloch and Néel. Bloch skyrmions are found in the thick, asymmetric crystals in which skyrmions were first detected, and Néel skyrmions tend to show up in thin films.

    “The type of skyrmions you get is related to the crystal structure of the materials,” says physical chemist Claudia Felser of the Max Planck Institute for Chemical Physics of Solids in Dresden, Germany. Felser studies Heusler compounds, materials that have unusual properties particularly useful for manipulating magnetism. Felser, Parkin and colleagues detected a new kind of skyrmion, an antiskyrmion, in a thin layer of such a material. They reported the find in August 2017 in Nature.

    Antiskyrmions might avoid some of the pitfalls that their relatives face, Parkin says. “Potentially, they can move in straight lines with currents, rather than moving to the side.” Such straight-shooting skyrmions may be better suited for racetrack schemes. And the observed antiskyrmions are stable at a wide range of temperatures, including room temperature. Antiskyrmions also might be able to shrink down smaller than other kinds of skyrmions.

    Physicists are now on the hunt for skyrmions within a different realm: antiferromagnetic materials. Unlike in ferromagnetic materials — in which atoms all align their poles — in antiferromagnets, atoms’ poles point in alternating directions. If one atom points up, its neighbor points down. Like antiskyrmions, antiferromagnetic skyrmions wouldn’t zip off at an angle to an electric current, so they should be easier to control. Antiferromagnetic skyrmions might also move faster, Kläui says.

    Materials scientists still need to find an antiferromagnetic material with the necessary properties to form skyrmions, Kläui says. “I would expect that this would be realized in the next couple of years.”

    Finding the knots’ niche

    Once skyrmions behave as desired, creating a racetrack memory with them is an obvious next step. “It is a technology that combines the best of multiple worlds,” Kläui says — stability, easily accessible data and low energy requirements. But Kläui and others acknowledge the hurdles ahead for skyrmion racetrack memories. It will be difficult, these researchers say, to beat traditional magnetic hard drives — not to mention the flash memories available in newer computers — on storage density, speed and cost simultaneously.

    “The racetrack idea, I’m skeptical about,” Hoffmann says. Instead, skyrmions might be useful in devices meant for performing calculations. Because only a small electric current is required to move skyrmions around, such devices might be used to create energy-efficient computer processors.

    Another idea is to use skyrmions for biologically inspired computers, which attempt to mimic the human brain (SN: 9/6/14, p. 10). Brains consume about as much power as a lightbulb, yet can perform calculations that computers still can’t match, thanks to large interconnected networks of nerve cells. Skyrmions could help scientists achieve this kind of computation in the lab, without sapping much power.

    5
    IN THEORY If found, antiferromagnetic skyrmions would move in a straight line when pushed by electric current. They would arise in materials with atoms that have alternating magnetic poles. X. Zhang, Y. Zhou, M. Ezawa/Scientific Reports 2016, Adapted by E. Otwell

    A single skyrmion could behave like a nerve cell, or neuron, electrical engineer Sai Li of Beihang University in Beijing and colleagues suggest. In the human body, a neuron can add up signals from its neighbors, gradually building up a voltage across its membrane. When that voltage reaches a certain threshold, ions begin shifting across the membrane in waves, generating an electric pulse. Skyrmions could imitate this behavior: An electric current would push a skyrmion along a track, with the distance traveled acting as an analog for the neuron’s increasing voltage. A skyrmion reaching a detector at the end would be equivalent to a firing neuron, the researchers proposed in July 2017 in Nanotechnology.

    By combining a large number of neuron-imitating skyrmions, the thinking goes, scientists could create a computer that operates something like a brain.

    Additional ideas for how to use the magnetic whirls keep cropping up. “It’s still a growing field,” von Bergmann says. “There are several new ideas ahead.”

    Whether or not skyrmions end up in future gadgets, the swirls are part of a burgeoning electronics ecosystem. Ever since electricity was discovered, researchers have focused on the motion of electric charges. But physicists are now fashioning a new parallel system called spintronics — of which skyrmions are a part — based on the motion of electron spin, that property that makes atoms magnetic (SN Online: 9/26/17). By studying skyrmions, researchers are expanding their understanding of how spins move through materials.

    Like a kindergartner fumbling with shoelaces, studying how to tie spins up in knots is a learning process.

    See the full article here .

    Science News is edited for an educated readership of professionals, scientists and other science enthusiasts. Written by a staff of experienced science journalists, it treats science as news, reporting accurately and placing findings in perspective. Science News and its writers have won many awards for their work; here’s a list of many of them.

    Published since 1922, the biweekly print publication reaches about 90,000 dedicated subscribers and is available via the Science News app on Android, Apple and Kindle Fire devices. Updated continuously online, the Science News website attracted over 12 million unique online viewers in 2016.

    Science News is published by the Society for Science & the Public, a nonprofit 501(c) (3) organization dedicated to the public engagement in scientific research and education.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

     
  • richardmitnick 1:49 pm on February 1, 2018 Permalink | Reply
    Tags: , , ScienceNews, Universes with no weak force might still have stars and life   

    From ScienceNews: “Universes with no weak force might still have stars and life” 


    ScienceNews

    January 30, 2018
    Lisa Grossman

    An alternate cosmos could do without one of the fundamental forces, physicists say.

    1
    MANY WORLDS Alternate universes with different laws of physics could still host galaxies, stars and planets, a new study suggests. Juergen Faelchle/Shutterstock

    Not all fundamental forces are created equal. An alternate universe that lacks the weak nuclear force — one of the four fundamental forces that govern all matter in our universe — could still form galaxies, stars, planets and perhaps life, according to calculations published online January 18 at arXiv.org.

    Scientists have long thought that our universe wouldn’t exist, or at least wouldn’t support life, without certain physical laws. For instance, if gravity were much stronger than it is, most matter would collapse into black holes; if it were weaker, the universe wouldn’t form structures such as galaxies or planets. The strong nuclear force holds atomic nuclei together, and the electromagnetic force carries light across the universe.

    “Those three forces, gravity, strong and electromagnetic, are part of the deal,” says theoretical physicist Fred Adams of the University of Michigan in Ann Arbor. But the weak nuclear force — responsible for making neutrons decay into protons, electrons and neutrinos — might not be so essential (SN: 4/29/17, p. 22). “That’s the only one you can get rid of entirely without messing everything up,” he says.

    A previous study [Physical Review D] had argued that a universe lacking the weak force could exist. Some physicists think our universe is just one in an infinite multiverse, where many different cosmoses exist side-by-side, possibly governed by different physical rules. We live in this one simply because we couldn’t live anywhere else (SN Online: 10/10/14), some scientists say.

    “People talk about universes like they’re very fine-tuned; if you changed things just a little bit, life would die,” Adams says. But “the universe and stars have a lot more pathways to success.”

    In the new research, he and his colleagues simulated how matter was created in the Big Bang and then condensed into stars, but without the effects of the weak nuclear force. In our universe, one consequence of neutron decay is that most of the universe is made of hydrogen, which consists of a single proton and electron. Stars, in their hot cores, fuse protons into helium and heavier elements and then scatter them into space, helping to create everything from planets to physicists. But with no weak force, a universe would be filled with neutrons that didn’t decay — a dead end for building heavier elements.

    The only way such a universe could create complex matter would be to have started out with fewer neutrons and more free protons than our universe did. That way, neutrons and protons could link up and make deuterium, also called heavy hydrogen. So Adams and his colleagues tweaked the simulated universe’s initial neutron and proton content, too.

    Stars fueled with deuterium would still shine, the simulations showed, but the objects would look different. Burning deuterium is more efficient than burning hydrogen, so these stars would be a little hotter, larger and redder than our stars. But the stars could still create all the elements of the periodic table up to iron, and stellar winds could carry those elements out into space.

    Any planets that formed would have water made with deuterium instead of hydrogen, which is toxic to life in our universe. “But if life had to evolve with deuterated water … it might be OK,” Adams says.

    Adams and his colleagues are some of the first to explore the consequences of a “weakless” universe seriously by tweaking the numbers, says Martin Rees of the University of Cambridge, who was not involved in either study.

    The paper does not help figure out if the multiverse is real, though. “We hope that eventually we’ll know,” Rees says, but “I’m not holding my breath.”

    See the full article here .

    Science News is edited for an educated readership of professionals, scientists and other science enthusiasts. Written by a staff of experienced science journalists, it treats science as news, reporting accurately and placing findings in perspective. Science News and its writers have won many awards for their work; here’s a list of many of them.

    Published since 1922, the biweekly print publication reaches about 90,000 dedicated subscribers and is available via the Science News app on Android, Apple and Kindle Fire devices. Updated continuously online, the Science News website attracted over 12 million unique online viewers in 2016.

    Science News is published by the Society for Science & the Public, a nonprofit 501(c) (3) organization dedicated to the public engagement in scientific research and education.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

     
  • richardmitnick 7:36 am on January 30, 2018 Permalink | Reply
    Tags: Asteroid bombardment, , , , , , Life may have been possible in Earth’s earliest, most hellish eon, ScienceNews,   

    From ScienceNews: “Life may have been possible in Earth’s earliest, most hellish eon” 


    ScienceNews

    January 26, 2018
    Carolyn Gramling

    New analyses suggest heat caused by asteroid bombardment didn’t sterilize the planet.

    1
    FIERY MYTH Scientists have long thought that Earth was a sterile hellscape during its earliest eon (illustrated), due to asteroid bombardment. But the heat from those impacts wasn’t too much for life to exist, new research indicates. SwRI/Dan Durda

    Maybe Earth’s early years weren’t so hellish after all.

    Asteroid strikes repeatedly bombarded the planet during its first eon, but the heat released by those hits wasn’t as sterilizing as once thought, new research suggests. Simulations indicate that after the first few hundred million years of bombardment, the heat from the impacts had dissipated enough that 10 to 75 percent of the top kilometer of the subsurface was habitable for mesophiles — microbes that live in temperatures of 20° to 50° Celsius. If so, the planet may have been habitable much earlier than previously believed.

    Earth’s earliest eon, the Hadean, spans the period from about 4.6 billion years ago, when the planet was born, to 4 billion years ago. The name, for the Greek god of the underworld, reflects the original conception of the age: dark and hellish and inhospitable to life. But little direct evidence of Hadean asteroid impacts still exists, limiting scientists’ understanding of how those collisions affected the planet’s habitability.

    “There has been an assumption that the Hadean was mostly an uninteresting slag heap until the sky stopped falling and life could take hold,” says Stephen Mojzsis, a geologist at the University of Colorado Boulder. That’s not to say that all of the Hadean was pleasant; the first 150 million years of Earth’s history, which included the giant whack that formed the moon, were pretty dramatic. But after that, things settled down considerably, says Mojzsis, who was not an author of the new study.

    For example, scientists have found signs of liquid water and even faint hints of possible life in zircon crystals dating back 4.1 billion years (SN: 11/28/15, p. 16). Other researchers have contested the idea that Earth was continually bombarded by asteroids through much of the Hadean, or that a last barrage of asteroids shelled the planet 3.9 billion years ago in what has been called the Late Heavy Bombardment, killing any incipient life (SN Online: 9/12/16).

    2
    QUIET INTERVAL A new study suggests that the planet was mostly peaceful after the first 150 million years of its existence (illustrated). Rather than repeatedly sterilizing the planet, the intense heat from asteroid impacts dissipated relatively rapidly, the researchers suggest. As a result, habitable zones in the subsurface of the planet grew larger over the next billion years. SwRI/Dan Durda

    In the new study, geophysicist Robert Grimm and planetary scientist Simone Marchi, both of the Southwest Research Institute in Boulder, Colo., estimated how hot it would have been just a few kilometers beneath the planet’s surface during the Hadean. The scientists used an estimated rate of asteroid bombardment, as well as how much heat the projectiles would have added to the subsurface and how much that heat would have dissipated over time to simulate how hot it got — and whether microbial life could have withstood those conditions. The research built on earlier work, including Marchi’s 2014 finding that asteroid impacts became smaller and less frequent with time (SN: 8/23/14, p. 13).

    Asteroid impacts did heat the subsurface, according to the simulations, but even the heaviest bombardment scenarios were not intense enough to sterilize the planet, the researchers report March 1 in Earth and Planetary Science Letters. And if the rate of bombardment did decrease as the eon progressed, the heat the asteroids delivered to Earth’s subsurface would also have had time to dissipate. As a result, that habitable zone would have increased over time.

    A Late Heavy Bombardment, if it occurred, would have been tougher for the microbes, because the heat wouldn’t have had time to dissipate with such a rapid barrage. But that just would have meant the habitable zone didn’t increase, the team reports; mesophiles could still have inhabited at least 20 percent of the top kilometer of subsurface.

    Mojzsis says he’s come to similar conclusions in his own work. “For a long time people said, with absolutely no data, that there could be no biosphere before 3.9 billion years ago,” he says. But “after the solar system settled down, the biosphere could have started on Earth 4.4 billion years ago.”

    That’s not to say that there was definitely life, Grimm notes. Although the heat from impacts may not have been a limiting factor for life, asteroid bombardment introduced numerous other challenges, affecting the climate, surface or even convection of the mantle. Still, the picture of Earth’s earliest days is undergoing a sea change. As Grimm says, “An average day in the Hadean did not spell doom.”

    See the full article here .

    Science News is edited for an educated readership of professionals, scientists and other science enthusiasts. Written by a staff of experienced science journalists, it treats science as news, reporting accurately and placing findings in perspective. Science News and its writers have won many awards for their work; here’s a list of many of them.

    Published since 1922, the biweekly print publication reaches about 90,000 dedicated subscribers and is available via the Science News app on Android, Apple and Kindle Fire devices. Updated continuously online, the Science News website attracted over 12 million unique online viewers in 2016.

    Science News is published by the Society for Science & the Public, a nonprofit 501(c) (3) organization dedicated to the public engagement in scientific research and education.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

     
    • stewarthoughblog 9:31 pm on January 30, 2018 Permalink | Reply

      Any proposition that the Hadean was not so Hadeanish is interesting science given what has been postulated previously, but it is not geochemically relevant to the intractable issues of any and all naturalistic stories about the origin of life. If no prospect for the origin of life is plausible even in the intelligently designed lab conditions of the labs being used to try to produce even simple biochemical processes and assembly formation, then any change in the Hadean conditions is a moot point.

      Like

  • richardmitnick 6:56 am on January 30, 2018 Permalink | Reply
    Tags: , , , , , , ScienceNews   

    From SciNews: “Clumps of dark matter could be lurking undetected in our galaxy” 


    ScienceNews

    January 26, 2018
    Emily Conover

    A hypothetical ‘dark’ force could allow clouds of invisible particles to collapse into small structures.

    1
    ESO/ L. Calçada (CC BY 4.0)

    Clumps of dark matter may be sailing through the Milky Way and other galaxies.

    Typically thought to form featureless blobs surrounding entire galaxies, dark matter could also collapse into smaller clumps — similar to normal matter condensing into stars and planets — a new study proposes. Thousands of collapsed dark clumps could constitute 10 percent of the Milky Way’s dark matter, researchers from Rutgers University in Piscataway, N.J., report in a paper accepted in Physical Review Letters.

    Dark matter is necessary to explain the motions of stars in galaxies. Without an extra source of mass, astronomers can’t explain why stars move at the speeds they do. Such observations suggest that a spherical “halo” of invisible, unidentified massive particles surrounds each galaxy.

    But the halo might be only part of the story. “We don’t really know what dark matter at smaller scales is doing,” says theoretical physicist Matthew Buckley, who coauthored the study with physicist Anthony DiFranzo. More complex structures might be hiding within the halo.

    To collapse, dark matter would need a way to lose energy, slowing particles as gravity pulls them into the center of the clump, so they can glom on to one another rather than zipping right through. In normal matter, this energy loss occurs via electromagnetic interactions. But the most commonly proposed type of dark matter particles, weakly interacting massive particles, or WIMPs, have no such way to lose energy.

    Buckley and DiFranzo imagined what might happen if an analogous “dark electromagnetism” allowed dark matter particles to interact and radiate energy. The researchers considered how dark matter would behave if it were like a pared-down version of normal matter, composed of two types of charged particles — a dark proton and a dark electron. Those particles could interact — forming dark atoms, for example — and radiate energy in the form of dark photons, a dark matter analog to particles of light.

    The researchers found that small clouds of such dark matter could collapse, but larger clouds, the mass of the Milky Way, for example, couldn’t — they have too much energy to get rid of. This finding means that the Milky Way could harbor a vast halo, with a sprinkling of dark matter clumps within. By picking particular masses for the hypothetical particles, the researchers were able to calculate the number and sizes of clumps that could be floating through the Milky Way. Varying the choice of masses led to different levels of clumpiness.

    In Buckley and DiFranzo’s scenario, the dark matter can’t squish down to the size of a star. Before the clumps get that small, they reach a point where they can’t lose any more energy. So a single clump might be hundreds of light-years across.

    The result, says theoretical astrophysicist Dan Hooper of Fermilab in Batavia, Ill., is “interesting and novel … but it also leaves a lot of open questions.” Without knowing more about dark matter, it’s hard to predict what kind of clumps it might actually form.

    Scientists have looked for the gravitational effects of unidentified, star-sized objects, which could be made either of normal matter or dark matter, known as massive compact halo objects, or MACHOs. But such objects turned out to be too rare to make up a significant fraction of dark matter. On the other hand, says Hooper, “what if these things collapse to solar system‒sized objects?” Such larger clumps haven’t have been ruled out yet.

    By looking for the effects of unexplained gravitational tugs on stars, scientists may be able to determine whether galaxies are littered with dark matter clumps. “Because we didn’t think these things were a possibility, I don’t think people have looked,” Buckley says. “It was a blind spot.”

    Up until now, most scientists have focused on WIMPs. But after decades of searching in sophisticated detectors, there’s no sign of the particles (SN: 11/12/16, p. 14). As a result, says theoretical physicist Hai-Bo Yu of the University of California, Riverside, “there’s a movement in the community.” Scientists are now exploring new ideas for what dark matter might be.

    See the full article here .

    Science News is edited for an educated readership of professionals, scientists and other science enthusiasts. Written by a staff of experienced science journalists, it treats science as news, reporting accurately and placing findings in perspective. Science News and its writers have won many awards for their work; here’s a list of many of them.

    Published since 1922, the biweekly print publication reaches about 90,000 dedicated subscribers and is available via the Science News app on Android, Apple and Kindle Fire devices. Updated continuously online, the Science News website attracted over 12 million unique online viewers in 2016.

    Science News is published by the Society for Science & the Public, a nonprofit 501(c) (3) organization dedicated to the public engagement in scientific research and education.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

     
  • richardmitnick 9:28 am on January 18, 2018 Permalink | Reply
    Tags: , , , , , , Λ Cosmological Constant, ScienceNews, Speed of universe’s expansion remains elusive, Type 1a supernovas as “standard candles”? Maybe not   

    From ScienceNews: “Speed of universe’s expansion remains elusive” 

    ScienceNews

    January 16, 2018
    Tom Siegfried

    1
    In August of 2011, researchers discovered SN 2011fe, a type 1a supernova 21 million light-years away in galaxy M101 (images show the galaxy before and after the supernova, with the supernova circled at right). Studies using type 1a supernovas as “standard candles” to measure how fast the universe expands (the Hubble constant) produce a result in conflict with other data used to infer the cosmic growth rate. NASA, Swift, Peter Brown, Univ. of Utah

    NASA Neil Gehrels Swift Observatory

    Unless you are a recent arrival from another universe, you’ve no doubt heard that this one is expanding. It’s getting bigger all the time. What’s more, its growth rate is accelerating. Every day, the universe expands a little bit faster than it did the day before.

    Those day-to-day differences are negligible, though, for astronomers trying to measure the universe’s expansion rate. They want to know how fast it is expanding “today,” meaning the current epoch of cosmic history. That rate is important for understanding how the universe works, knowing what its ultimate fate will be and even what it is made of. After all, the prime mission of the Hubble Space Telescope when it was launched in 1990 was to help determine that expansion rate (known, not coincidentally, as the Hubble constant, named for the astronomer Edwin Hubble).

    Since then evidence from Hubble (the telescope) and other research projects has established a reasonably precise answer for the Hubble constant: 73, in the units commonly used for this purpose. (It means that two independent astronomical bodies separated by 3.26 million light-years will appear to be moving away from each other at 73 kilometers per second.) Sure, there’s a margin of error, but not much. The latest analysis from one team, led by Nobel laureate Adam Riess, puts the Hubble constant in the range of 72–75, as reported in a paper posted online January 3 ApJ. Considering that as late as the 1980s astronomers argued about whether the Hubble constant was closer to 40 or 90, that’s quite an improvement in precision.

    But there’s a snag in this success. Current knowledge of the universe suggests a way to predict what the Hubble constant ought to be. And that prediction gives a probable range of only 66–68. The two methods don’t match.

    “This is very surprising, I think, and very interesting,” Riess, of the Space Telescope Science Institute in Baltimore, said in a talk January 9 at a meeting of the American Astronomical Society.

    It’s surprising because astrophysicists and cosmologists thought they had pretty much figured the universe out. It’s made up of a little bit of ordinary matter, a lot of some exotic “dark matter” of unknown identity, and even more of a mysterious energy permeating the vacuum of space, exerting gravitational repulsion. Remember that acceleration of the expansion rate? It implies the existence of such energy. Because nobody knows what it is, people call it “dark energy,” while suspecting that its real name is lambda, the Greek letter that stands for “cosmological constant.” (It’s called a constant because any part of space should possess the same amount of vacuum energy.) Dark energy contributes something like 70 percent of the total mass-energy content of the universe, various lines of evidence indicate.

    If all that’s right, then it’s not all that hard to infer how fast the universe should be expanding today. You just take the recipe of matter, dark matter and dark energy and add some ghostly subatomic particles known as neutrinos. Then you carefully measure the temperature of deep space, where the only heat is the faint glow remaining from the Big Bang. That glow, the cosmic microwave background radiation, varies slightly in temperature from point to point. From the size of those variations, you can calculate how far the radiation from the Big Bang has been traveling to reach our telescopes. Combine that with the universe’s mass-energy recipe, and you can calculate how fast the universe is expanding. (You can, in fact, do this calculation at home with the proper mathematical utensils.)

    An international team’s project using cosmic microwave background [CMB]data inferred a Hubble constant of 67, substantially less than the 73 or 74 based on actually measuring the expansion (by analyzing how the light from distant supernova explosions has dimmed over time).

    CMB per ESA/Planck

    When this discrepancy first showed up a few years ago, many experts believed it was just a mirage that would fade with more precise measurement. But it hasn’t.

    “This starts to get pretty serious,” Riess said at the astronomy meeting. “In both cases these are very mature measurements. This is not the first time around for either of these projects.”

    One commonly proposed explanation contends that the supernova studies are measuring the local value of the Hubble constant. Perhaps we live in a bubble, with much less matter than average, skewing expansion measurements. In that case, the cosmic microwave background data might provide a better picture of the “global” expansion rate for the whole universe. But supernovas observed by the Hubble telescope extend far enough out to refute that possibility, Riess said.

    “Even if you thought we lived in a void…, you still are basically stuck with the same problem.”

    Consequently it seems most likely that something is wrong with the matter-energy recipe for the universe (technically, the cosmological standard model) used in making the expansion rate prediction. Maybe the vacuum energy driving cosmic acceleration is not a cosmological constant after all, but some other sort of field filling space. Such a field could vary in strength over time and throw off the calculations based on a constant vacuum energy. But Riess pointed out that the evidence is growing stronger and stronger that the vacuum energy is just the cosmological constant. “I would say there we have less and less wiggle room.”

    Another possibility, appealing to many theorists, is the existence of a new particle, perhaps a fourth neutrino or some other relativistic (moving very rapidly) particle zipping around in the early universe.

    “Relativistic particles — theorists have no trouble inventing new ones, ones that don’t violate anything else,” Riess said. “Many of them are quite giddy about the prospect of some evidence for that. So that would not be a long reach.”

    Other assumptions built into the current cosmological standard model might also need to be revised. Dark matter, for example, is presumed to be very aloof from other forms of matter and energy. But if it interacted with radiation in the early universe, it could have an effect similar to that of relativistic particles, changing how the energy in the early universe is divided up among its components. Such a change in energy balance would alter how much the universe expands at early times, corrupting the calibrations needed to infer the current expansion rate.

    It’s not the first time that determining the Hubble constant has provoked controversy. Edwin Hubble himself initially (in the 1930s) vastly overestimated the expansion rate. Using his rate, calculations indicated that the universe was much younger than the Earth, an obvious contradiction. Even by the 1990s, some Hubble constant estimates suggested an age for the universe of under 10 billion years, whereas many stars appeared to be several billion years older than that.

    Hubble’s original error could be traced to lack of astronomical knowledge. His early overestimates turned out to be signals of a previously unknown distinction between different generations of stars, some younger and some older, Riess pointed out. That threw off distance estimates to some stars that Hubble used to estimate the expansion rate. Similarly, in the 1990s the expansion rate implied too young a universe because dark energy was not then known to exist and therefore was not taken into account when calculating the universe’s age.

    So the current discrepancy, Riess suggested, might also be a signal of some astronomical unknown, whether a new particle, new interactions of matter and radiation, or a phenomenon even more surprising — something that would really astound a visitor from another universe.

    See the full article here .

    Science News is edited for an educated readership of professionals, scientists and other science enthusiasts. Written by a staff of experienced science journalists, it treats science as news, reporting accurately and placing findings in perspective. Science News and its writers have won many awards for their work; here’s a list of many of them.

    Published since 1922, the biweekly print publication reaches about 90,000 dedicated subscribers and is available via the Science News app on Android, Apple and Kindle Fire devices. Updated continuously online, the Science News website attracted over 12 million unique online viewers in 2016.

    Science News is published by the Society for Science & the Public, a nonprofit 501(c) (3) organization dedicated to the public engagement in scientific research and education.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

     
  • richardmitnick 1:28 pm on January 9, 2018 Permalink | Reply
    Tags: , , , , ScienceNews, White dwarf’s inner makeup is mapped for the first time,   

    From ScienceNews: “White dwarf’s inner makeup is mapped for the first time” 

    ScienceNews

    January 8, 2018
    Lisa Grossman

    The stellar corpse is richer in oxygen than expected, challenging long-standing theories about stellar evolution.

    1
    WHAT LIES WITHIN The inner structure of a white dwarf star (shown in this artist’s impression) has been mapped for the first time — and it’s more oxygen-rich than expected. Stéphane Charpinet.

    Astronomers have probed the inner life of a dead star. Tiny changes in a white dwarf’s brightness reveal that the stellar corpse has more oxygen in its core than expected, researchers report online January 8 in Nature. The finding could challenge theories of how stars live and die, and may have implications for measuring the expansion of the universe.

    As a star ages, it sheds most of its gas into space until all that remains is a dense core of carbon and oxygen, the ashes of a lifetime of burning helium (SN: 4/30/16, p. 12). That core, plus a thin shellacking of helium, is called a white dwarf.

    But the proportion of those elements relative to one another was uncertain. “From theory, we have a rough idea of how it’s supposed to be, but we have no way to measure it directly,” says astrophysicist Noemi Giammichele, now at the Institute of Research in Astrophysics and Planetology in Toulouse, France.

    Luckily, some white dwarfs encode their inner nature on their surface. These stars change their brightness in response to internal vibrations. Astrophysicists can infer a star’s internal structure from the vibrations, similar to how geologists learn about Earth’s interior by measuring seismic waves during an earthquake.

    Giammichele and her colleagues used data from NASA’s Kepler space telescope, which watched stars unblinkingly to track periodic changes in their brightness. Kepler’s chief aim was to find exoplanets, the worlds orbiting distant stars (SN Online: 10/31/17). But it also monitored white dwarf KIC 08626021, located 1,375 light-years away in the constellation Cygnus, for 23 months. The observations provided the highest-precision data ever on tiny changes in a white dwarf’s brightness and, indirectly, its vibrations.

    Next, Giammichele borrowed a computer simulation technique from her former life as an aeronautical engineer to figure out how the changes in vibrations related to the makeup of the core. The team ran millions of simulations, looking for one that reproduced the exact light changes that Kepler observed. One simulation fit the data perfectly, showing that the white dwarf had the expected carbon and oxygen core with a thin shell of helium.

    But the details were surprising. The core was about 86 percent oxygen, 15 percent greater than physicists had previously calculated. That suggests that something about the processes that convert helium to carbon and oxygen or mix elements in the star’s core during its active lifetime must boost the amount of oxygen.

    Four other white dwarfs show a similar trend, says study coauthor Gilles Fontaine, an astrophysicist at the University of Montreal. “We certainly will go ahead and analyze many more.” If other white dwarfs turn out to be similar, the results will send theorists who study stellar evolution back to the drawing board, he says.

    White dwarfs are also thought to be the precursors of type 1a supernovas. These catastrophic stellar explosions were once thought to have the same intrinsic brightness, meaning they appeared brighter or dimmer depending only on their distance from Earth. Measuring their actual distances led to the discovery that the universe is expanding at an accelerating rate (SN: 8/6/16, p. 10), which physicists explain by invoking a mysterious substance called dark energy.

    More recent observations suggest that these so-called standard candles may not be so standard after all. If the white dwarfs that help create supernovas have varying oxygen contents, that may help explain some of the differences, Fontaine says.

    Accounting for that difference may someday help reveal details of what dark energy is made of, says astrophysicist Alexei Filippenko of the University of California, Berkeley. But those implications are a long way off. “Just how much bearing it will have on cosmology remains to be seen,” he says.

    See the full article here .

    Science News is edited for an educated readership of professionals, scientists and other science enthusiasts. Written by a staff of experienced science journalists, it treats science as news, reporting accurately and placing findings in perspective. Science News and its writers have won many awards for their work; here’s a list of many of them.

    Published since 1922, the biweekly print publication reaches about 90,000 dedicated subscribers and is available via the Science News app on Android, Apple and Kindle Fire devices. Updated continuously online, the Science News website attracted over 12 million unique online viewers in 2016.

    Science News is published by the Society for Science & the Public, a nonprofit 501(c) (3) organization dedicated to the public engagement in scientific research and education.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

     
  • richardmitnick 2:36 pm on January 1, 2018 Permalink | Reply
    Tags: , , , , Megamaser, , ScienceNews, UGC 6093   

    From ScienceNews: “Hubble Space Telescope Spots Megamaser Galaxy: UGC 6093” 

    ScienceNews bloc

    ScienceNews

    Jan 1, 2018
    No writer credit

    1
    This image, captured by Hubble’s Wide Field Camera 3, shows the megamaser galaxy UGC 6093. Image credit: NASA / ESA / Hubble.

    NASA/ESA Hubble Telescope

    Wide Field Camera 3 (WFC3) being tested.

    UGC 6093, also known as LEDA 33198 and SDSS J110047.95+104341.3, lies in the constellation Leo at a distance of 500 million light-years.

    This galaxy is classified as a barred spiral galaxy — it has beautiful arms that swirl outwards from a bar slicing through the galaxy’s center.

    It is also classified as an active galaxy, which means that it hosts an active galactic nucleus, or AGN: a compact region at a galaxy’s center within which material is dragged towards a supermassive black hole.

    As this black hole devours the surrounding matter it emits intense radiation, causing it to shine brightly.

    But UGC 6093 is more exotic still.

    The entire galaxy essentially acts as an astronomical laser that beams out microwave emission rather than visible light (hence the ‘m’ replacing the ‘l’).

    This type of object is dubbed a megamaser.

    Megamasers such as UGC 6093 are intensely bright, around 100 million times brighter than the masers found in galaxies like our Milky Way Galaxy.

    This new image of UGC 6093 is made up of observations from Hubble’s Wide Field Camera 3 (WFC3) in the infrared and optical parts of the spectrum.

    Four filters were used to sample various wavelengths.

    The color results from assigning different hues to each monochromatic image associated with an individual filter.

    See the full article here .

    If there is a NASA article on this I will cover it.

    Science News is edited for an educated readership of professionals, scientists and other science enthusiasts. Written by a staff of experienced science journalists, it treats science as news, reporting accurately and placing findings in perspective. Science News and its writers have won many awards for their work; here’s a list of many of them.

    Published since 1922, the biweekly print publication reaches about 90,000 dedicated subscribers and is available via the Science News app on Android, Apple and Kindle Fire devices. Updated continuously online, the Science News website attracted over 12 million unique online viewers in 2016.

    Science News is published by the Society for Science & the Public, a nonprofit 501(c) (3) organization dedicated to the public engagement in scientific research and education.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

     
  • richardmitnick 8:50 am on November 30, 2017 Permalink | Reply
    Tags: , , , , Here’s what really happened to Hanny’s Voorwerp, How the activity of supermassive black holes varies on superhuman time scales, ScienceNews   

    From ScienceNews: “Here’s what really happened to Hanny’s Voorwerp” 

    ScienceNews bloc

    ScienceNews

    November 27, 2017
    Lisa Grossman

    Astronomers can finally explain a gas cloud’s strange glow.

    1
    GLOWING GAS Hanny’s Voorwerp, the greenish smudge at the bottom of this image, is glowing thanks to photons from a feasting black hole in the galaxy above. NASA, ESA, W. Keel (Univ. Alabama), et al., Galaxy Zoo Team.

    The weird glowing blob of gas known as Hanny’s Voorwerp was a 10-year-old mystery. Now, Lia Sartori of ETH Zürich and colleagues have come to a two-pronged solution.

    Hanny van Arkel, then a teacher in the Netherlands, discovered the strange bluish-green voorwerp, Dutch for “object,” in 2008 as she was categorizing pictures of galaxies as part of the Galaxy Zoo citizen science project.

    Further observations showed that the voorwerp was a glowing cloud of gas that stretched some 100,000 light-years from the core of a massive nearby galaxy called IC 2497. The glow came from radiation emitted by an actively feeding black hole in the galaxy.

    To excite the voorwerp’s glow, the black hole should have had the brightness of about 2.5 trillion suns; its radio emission, however, suggested the black hole emitted the equivalent of a relatively paltry 25,000 suns. Either the black hole was obscured by dust, or it stopped eating around 100,000 years ago, causing its brightness to plunge.

    Sartori and colleagues made the first direct measurement of the black hole’s intrinsic brightness using NASA’s NuSTAR telescope, which observed IC 2497 in high-energy X-rays that cut through the dust.

    NASA NuSTAR X-ray telescope

    They found that, yes, the black hole is obscured by dust, and yes, it is dimmer than expected. The team reported on arXiv.org on November 20 that IC 2497’s heart is as bright as 50 billion to 100 billion suns, meaning it dropped in brightness by a factor of 50 in the past 100,000 years — a less dramatic drop than previously thought.

    “Both hypotheses that we thought before are true,” Sartori says.

    Sartori plans to analyze NuSTAR observations of other voorwerpjes to see if their galaxies’ black holes are also in the process of shutting down — or even booting up.

    “If you look at these clouds, you get information on how the black hole was in the past,” she says. “So we have a way to study how the activity of supermassive black holes varies on superhuman time scales.”

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

     
  • richardmitnick 8:04 am on November 27, 2017 Permalink | Reply
    Tags: , , , , , , , ScienceNews, Simulating the universe using Einstein’s theory of gravity may solve cosmic puzzles   

    From ScienceNews: “Simulating the universe using Einstein’s theory of gravity may solve cosmic puzzles” 

    ScienceNews bloc

    ScienceNews

    November 25, 2017
    Emily Conover

    Until recently, simulations of the universe haven’t given its lumps their due.

    1
    UNEVEN TERRAIN Universe simulations that consider general relativity (one shown) may shift knowledge of the cosmos. James Mertens

    If the universe were a soup, it would be more of a chunky minestrone than a silky-smooth tomato bisque.

    Sprinkled with matter that clumps together due to the insatiable pull of gravity, the universe is a network of dense galaxy clusters and filaments — the hearty beans and vegetables of the cosmic stew. Meanwhile, relatively desolate pockets of the cosmos, known as voids, make up a thin, watery broth in between.

    Until recently, simulations of the cosmos’s history haven’t given the lumps their due. The physics of those lumps is described by general relativity, Albert Einstein’s theory of gravity. But that theory’s equations are devilishly complicated to solve. To simulate how the universe’s clumps grow and change, scientists have fallen back on approximations, such as the simpler but less accurate theory of gravity devised by Isaac Newton.

    Relying on such approximations, some physicists suggest, could be mucking with measurements, resulting in a not-quite-right inventory of the cosmos’s contents. A rogue band of physicists suggests that a proper accounting of the universe’s clumps could explain one of the deepest mysteries in physics: Why is the universe expanding at an increasingly rapid rate?

    The accepted explanation for that accelerating expansion is an invisible pressure called dark energy. In the standard theory of the universe, dark energy makes up about 70 percent of the universe’s “stuff” — its matter and energy. Yet scientists still aren’t sure what dark energy is, and finding its source is one of the most vexing problems of cosmology.

    Perhaps, the dark energy doubters suggest, the speeding up of the expansion has nothing to do with dark energy. Instead, the universe’s clumpiness may be mimicking the presence of such an ethereal phenomenon.

    Most physicists, however, feel that proper accounting for the clumps won’t have such a drastic impact. Robert Wald of the University of Chicago, an expert in general relativity, says that lumpiness is “never going to contribute anything that looks like dark energy.” So far, observations of the universe have been remarkably consistent with predictions based on simulations that rely on approximations.

    _____________________________________________________________________________

    Growing a lumpy universe

    The universe has gradually grown lumpier throughout its history. During inflation, rapid expansion magnified tiny quantum fluctuations into minute density variations. Over time, additional matter glommed on to dense spots due to the stronger gravitational pull from the extra mass. After 380,000 years, those blips were imprinted as hot and cold spots in the cosmic microwave background, the oldest light in the universe. Lumps continued growing for billions of years, forming stars, planets, galaxies and galaxy clusters.

    1

    _____________________________________________________________________________

    As observations become more detailed, though, even slight inaccuracies in simulations could become troublesome. Already, astronomers are charting wide swaths of the sky in great detail, and planning more extensive surveys. To translate telescope images of starry skies into estimates of properties such as the amount of matter in the universe, scientists need accurate simulations of the cosmos’s history. If the detailed physics of clumps is important, then simulations could go slightly astray, sending estimates off-kilter. Some scientists already suggest that the lumpiness is behind a puzzling mismatch of two estimates of how fast the universe is expanding.

    Researchers are attempting to clear up the debate by conquering the complexities of general relativity and simulating the cosmos in its full, lumpy glory. “That is really the new frontier,” says cosmologist Sabino Matarrese of the University of Padua in Italy, “something that until a few years ago was considered to be science fiction.” In the past, he says, scientists didn’t have the tools to complete such simulations. Now researchers are sorting out the implications of the first published results of the new simulations. So far, dark energy hasn’t been explained away, but some simulations suggest that certain especially sensitive measurements of how light is bent by matter in the universe might be off by as much as 10 percent.

    Soon, simulations may finally answer the question: How much do lumps matter? The idea that cosmologists might have been missing a simple answer to a central problem of cosmology incessantly nags some skeptics. For them, results of the improved simulations can’t come soon enough. “It haunts me. I can’t let it go,” says cosmologist Rocky Kolb of the University of Chicago.

    Smooth universe

    By observing light from different eras in the history of the cosmos, cosmologists can compute the properties of the universe, such as its age and expansion rate. But to do this, researchers need a model, or framework, that describes the universe’s contents and how those ingredients evolve over time. Using this framework, cosmologists can perform computer simulations of the universe to make predictions that can be compared with actual observations.

    2
    COSMIC WEB Clumps and filaments of matter thread through a simulated universe 2 billion light years across. This simulation incorporates some aspects of Einstein’s theory of general relativity, allowing for detailed results while avoiding the difficulties of the full-fledged theory.

    After Einstein introduced his theory in 1915, physicists set about figuring out how to use it to explain the universe. It wasn’t easy, thanks to general relativity’s unwieldy, difficult-to-solve suite of equations. Meanwhile, observations made in the 1920s indicated that the universe wasn’t static as previously expected; it was expanding. Eventually, researchers converged on a solution to Einstein’s equations known as the Friedmann-Lemaître-Robertson-Walker metric. Named after its discoverers, the FLRW metric describes a simplified universe that is homogeneous and isotropic, meaning that it appears identical at every point in the universe and in every direction. In this idealized cosmos, matter would be evenly distributed, no clumps. Such a smooth universe would expand or contract over time.

    A smooth-universe approximation is sensible, because when we look at the big picture, averaging over the structures of galaxy clusters and voids, the universe is remarkably uniform. It’s similar to the way that a single spoonful of minestrone soup might be mostly broth or mostly beans, but from bowl to bowl, the overall bean-to-broth ratios match.

    In 1998, cosmologists revealed that not only was the universe expanding, but its expansion was also accelerating (SN: 2/2/08, p. 74). Observations of distant exploding stars, or supernovas, indicated that the space between us and them was expanding at an increasing clip. But gravity should slow the expansion of a universe evenly filled with matter. To account for the observed acceleration, scientists needed another ingredient, one that would speed up the expansion. So they added dark energy to their smooth-universe framework.

    Now, many cosmologists follow a basic recipe to simulate the universe — treating the cosmos as if it has been run through an imaginary blender to smooth out its lumps, adding dark energy and calculating the expansion via general relativity. On top of the expanding slurry, scientists add clumps and track their growth using approximations, such as Newtonian gravity, which simplifies the calculations.

    In most situations, Newtonian gravity and general relativity are near-twins. Throw a ball while standing on the surface of the Earth, and it doesn’t matter whether you use general relativity or Newtonian mechanics to calculate where the ball will land — you’ll get the same answer. But there are subtle differences. In Newtonian gravity, matter directly attracts other matter. In general relativity, gravity is the result of matter and energy warping spacetime, creating curves that alter the motion of objects (SN: 10/17/15, p. 16). The two theories diverge in extreme gravitational environments. In general relativity, for example, hulking black holes produce inescapable pits that reel in light and matter (SN: 5/31/14, p. 16). The question, then, is whether the difference between the two theories has any impact in lumpy-universe simulations.

    Most cosmologists are comfortable with the status quo simulations because observations of the heavens seem to fit neatly together like interlocking jigsaw puzzle pieces. Predictions based on the standard framework agree remarkably well with observations of the cosmic microwave background — ancient light released when the universe was just 380,000 years old (SN: 3/21/15, p. 7). And measurements of cosmological parameters — the fraction of dark energy and matter, for example — are generally consistent, whether they are made using the light from galaxies or the cosmic microwave background [CMB].

    CMB per ESA/Planck


    ESA/Planck

    3
    An image from the Two-Micron All Sky Survey of 1.6 million galaxies in infrared light reveals how matter clumps into galaxy clusters and filaments. Future large-scale surveys may require improved simulations that use general relativity to track the evolution of lumps over time. T.H. Jarrett, J. Carpenter & R. Hurt, obtained as part of 2MASS, a joint project of Univ. of Massachusetts and the Infrared Processing and Analysis Center/Caltech, funded by NASA and NSF.


    Caltech 2MASS Telescopes, a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center (IPAC) at Caltech, at the Whipple Observatory on Mt. Hopkins south of Tucson, AZ, and at the Cerro Tololo Inter-American Observatory near La Serena, Chile.

    Dethroning dark energy

    Some cosmologists hope to explain the universe’s accelerating expansion by fully accounting for the universe’s lumpiness, with no need for the mysterious dark energy.

    These researchers argue that clumps of matter can alter how the universe expands, when the clumps’ influence is tallied up over wide swaths of the cosmos. That’s because, in general relativity, the expansion of each local region of space depends on how much matter is within. Voids expand faster than average; dense regions expand more slowly. Because the universe is mostly made up of voids, this effect could produce an overall expansion and potentially an acceleration. Known as backreaction, this idea has lingered in obscure corners of physics departments for decades, despite many claims that backreaction’s effect is small or nonexistent.

    Backreaction continues to appeal to some researchers because they don’t have to invent new laws of physics to explain the acceleration of the universe. “If there is an alternative which is based only upon traditional physics, why throw that away completely?” Matarrese asks.

    Most cosmologists, however, think explaining away dark energy just based on the universe’s lumps is unlikely. Previous calculations have indicated any effect would be too small to account for dark energy, and would produce an acceleration that changes in time in a way that disagrees with observations.

    “My personal view is that it’s a much smaller effect,” says astrophysicist Hayley Macpherson of Monash University in Melbourne, Australia. “That’s just basically a gut feeling.” Theories that include dark energy explain the universe extremely well, she points out. How could that be if the whole approach is flawed?

    New simulations by Macpherson and others that model how lumps evolve in general relativity may be able to gauge the importance of backreaction once and for all. “Up until now, it’s just been too hard,” says cosmologist Tom Giblin of Kenyon College in Gambier, Ohio.

    To perform the simulations, researchers needed to get their hands on supercomputers capable of grinding through the equations of general relativity as the simulated universe evolves over time. Because general relativity is so complex, such simulations are much more challenging than those that use approximations, such as Newtonian gravity. But, a seemingly distinct topic helped lay some of the groundwork: gravitational waves, or ripples in the fabric of spacetime.

    4
    SPECKLED SPACETIME A lumpy universe, recently simulated using general relativity, shows clumps of matter (pink and yellow) that beget stars and galaxies. H. Macpherson, Paul Lasky, Daniel Price.

    The Advanced Laser Interferometer Gravitational-Wave Observatory, LIGO, searches for the tremors of cosmic dustups such as colliding black holes (SN: 10/28/17, p. 8).


    VIRGO Gravitational Wave interferometer, near Pisa, Italy

    Caltech/MIT Advanced aLigo Hanford, WA, USA installation


    Caltech/MIT Advanced aLigo detector installation Livingston, LA, USA

    Cornell SXS, the Simulating eXtreme Spacetimes (SXS) project

    Gravitational waves. Credit: MPI for Gravitational Physics/W.Benger-Zib

    ESA/eLISA the future of gravitational wave research

    1
    Skymap showing how adding Virgo to LIGO helps in reducing the size of the source-likely region in the sky. (Credit: Giuseppe Greco (Virgo Urbino group)

    In preparation for this search, physicists honed their general relativity skills on simulations of the spacetime storm kicked up by black holes, predicting what LIGO might see and building up the computational machinery to solve the equations of general relativity. Now, cosmologists have adapted those techniques and unleashed them on entire, lumpy universes.

    The first lumpy universe simulations to use full general relativity were unveiled in the June 2016 Physical Review Letters. Giblin and colleagues reported their results simultaneously with Eloisa Bentivegna of the University of Catania in Italy and Marco Bruni of the University of Portsmouth in England.

    So far, the simulations have not been able to account for the universe’s acceleration. “Nearly everybody is convinced [the effect] is too small to explain away the need for dark energy,” says cosmologist Martin Kunz of the University of Geneva. Kunz and colleagues reached the same conclusion in their lumpy-universe simulations, which have one foot in general relativity and one in Newtonian gravity. They reported their first results in Nature Physics in March 2016.

    Backreaction aficionados still aren’t dissuaded. “Before saying the effect is too small to be relevant, I would, frankly, wait a little bit more,” Matarrese says. And the new simulations have potential caveats. For example, some simulated universes behave like an old arcade game — if you walk to one edge of the universe, you cross back over to the other side, like Pac-Man exiting the right side of the screen and reappearing on the left. That geometry would suppress the effects of backreaction in the simulation, says Thomas Buchert of the University of Lyon in France. “This is a good beginning,” he says, but there is more work to do on the simulations. “We are in infancy.”

    Different assumptions in a simulation can lead to disparate results, Bentivegna says. As a result, she doesn’t think that her lumpy, general-relativistic simulations have fully closed the door on efforts to dethrone dark energy. For example, tricks of light might be making it seem like the universe’s expansion is accelerating, when in fact it isn’t.

    When astronomers observe far-away sources like supernovas, the light has to travel past all of the lumps of matter between the source and Earth. That journey could make it look like there’s an acceleration when none exists. “It’s an optical illusion,” Bentivegna says. She and colleagues see such an effect in a simulation reported in March in the Journal of Cosmology and Astroparticle Physics. But, she notes, this work simulated an unusual universe, in which matter sits on a grid — not a particularly realistic scenario.

    For most other simulations, the effect of optical illusions remains small. That leaves many cosmologists, including Giblin, even more skeptical of the possibility of explaining away dark energy: “I feel a little like a downer,” he admits.

    6
    Lumps (gray) within this simulated universe change the path light takes (yellow lines), potentially affecting observations. Matter bends space, slightly altering the light’s trajectory from that in a smooth universe. James Mertens.

    Surveying the skies

    Subtle effects of lumps could still be important. In Hans Christian Andersen’s The Princess and the Pea, the princess felt a tiny pea beneath an impossibly tall stack of mattresses. Likewise, cosmologists’ surveys are now so sensitive that even if the universe’s lumps have a small impact, estimates could be thrown out of whack.

    The Dark Energy Survey, for example, has charted 26 million galaxies using the Victor M. Blanco Telescope in Chile, measuring how the light from those galaxies is distorted by the intervening matter on the journey to Earth.

    Dark Energy Survey


    Dark Energy Camera [DECam], built at FNAL


    NOAO/CTIO Victor M Blanco 4m Telescope which houses the DECam at Cerro Tololo, Chile, housing DECam at an altitude of 7200 feet

    In a set of papers posted online August 4 at arXiv.org, scientists with the Dark Energy Survey reported new measurements of the universe’s properties, including the amount of matter (both dark and normal) and how clumpy that matter is (SN: 9/2/17, p. 32). The results are consistent with those from the cosmic microwave background [CMB] — light emitted billions of years earlier.

    To make the comparison, cosmologists took the measurements from the cosmic microwave background, early in the universe, and used simulations to extrapolate to what galaxies should look like later in the universe’s history. It’s like taking a baby’s photograph, precisely computing the number and size of wrinkles that should emerge as the child ages and finding that your picture agrees with a snapshot taken decades later. The matching results so far confirm cosmologists’ standard picture of the universe — dark energy and all.

    “So far, it has not yet been important for the measurements that we’ve made to actually include general relativity in those simulations,” says Risa Wechsler, a cosmologist at Stanford University and a founding member of the Dark Energy Survey. But, she says, for future measurements, “these effects could become more important.” Cosmologists are edging closer to Princess and the Pea territory.

    Those future surveys include the Dark Energy Spectroscopic Instrument, DESI, set to kick off in 2019 at Kitt Peak National Observatory near Tucson; the European Space Agency’s Euclid satellite, launching in 2021; and the Large Synoptic Survey Telescope in Chile, which is set to begin collecting data in 2023.

    LBNL/DESI spectroscopic instrument on the Mayall 4-meter telescope at Kitt Peak National Observatory, Altitude 2,120 m (6,960 ft)

    LBNL/DESI spectroscopic instrument on the Mayall 4-meter telescope at Kitt Peak National Observatory starting in 2018

    NOAO/Mayall 4 m telescope at Kitt Peak, Arizona, USA, Altitude 2,120 m (6,960 ft)

    ESA/Euclid spacecraft

    LSST


    LSST Camera, built at SLAC



    LSST telescope, currently under construction at Cerro Pachón Chile, a 2,682-meter-high mountain in Coquimbo Region, in northern Chile, alongside the existing Gemini South and Southern Astrophysical Research Telescopes.

    If cosmologists keep relying on simulations that don’t use general relativity to account for lumps, certain kinds of measurements of weak lensing — the bending of light due to matter acting like a lens — could be off by up to 10 percent, Giblin and colleagues reported at arXiv.org in July. “There is something that we’ve been ignoring by making approximations,” he says.

    That 10 percent could screw up all kinds of estimates, from how dark energy changes over the universe’s history to how fast the universe is currently expanding, to the calculations of the masses of ethereal particles known as neutrinos. “You have to be extremely certain that you don’t get some subtle effect that gets you the wrong answers,” Geneva’s Kunz says, “otherwise the particle physicists are going to be very angry with the cosmologists.”

    Some estimates may already be showing problem signs, such as the conflicting estimates of the cosmic expansion rate (SN: 8/6/16, p. 10). Using the cosmic microwave background, cosmologists find a slower expansion rate than they do from measurements of supernovas. If this discrepancy is real, it could indicate that dark energy changes over time. But before jumping to that conclusion, there are other possible causes to rule out, including the universe’s lumps.

    Until the issue of lumps is smoothed out, scientists won’t know how much lumpiness matters to the cosmos at large. “I think it’s rather likely that it will turn out to be an important effect,” Kolb says. Whether it explains away dark energy is less certain. “I want to know the answer so I can get on with my life.”

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

     
c
Compose new post
j
Next post/Next comment
k
Previous post/Previous comment
r
Reply
e
Edit
o
Show/Hide comments
t
Go to top
l
Go to login
h
Show/Hide help
shift + esc
Cancel
%d bloggers like this: