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  • richardmitnick 12:04 pm on July 26, 2019 Permalink | Reply
    Tags: "Small but mighty: A mini plasma-powered satellite under construction may launch a new era in space exploration", A fleet of CubeSats, , Princeton University   

    From Princeton University and PPPL: “Small but mighty: A mini plasma-powered satellite under construction may launch a new era in space exploration” 

    Princeton University
    From Princeton University

    PPPL

    July 26, 2019
    John Greenwald, Princeton Plasma Physics Laboratory

    A tiny satellite under construction at the U.S. Department of Energy’s Princeton Plasma Physics Laboratory (PPPL) could open new horizons in space exploration. Princeton University students are building the device, a cubic satellite or “CubeSat,” as a testbed for a miniaturized rocket thruster with unique capabilities being developed at PPPL.

    1
    The CubeSat’s thruster, whose development is led by PPPL physicist Yevgeny Raitses, holds the promise of increased flexibility for the tiny satellites, more than a thousand of which have been launched by universities, research centers and commercial interests around the world. The proposed propulsion device — powered by plasma — could raise and lower the orbits of CubeSats circling the Earth, a capability not broadly available to small spacecraft today, and would hold the potential for exploration of deep space.

    “Essentially, we will be able to use these miniature thrusters for many missions,” Raitses said.

    A fleet of CubeSats

    One example: A fleet made up of hundreds of such micropowered CubeSats could capture in fine detail the reconnection process in the magnetosphere, the magnetic field that surrounds the Earth, said physicist Masaaki Yamada. Yamada is the principal investigator of the PPPL Magnetic Reconnection Experiment, which studies magnetic reconnection — the separation and explosive snapping together of magnetic field lines in plasma that triggers auroras, solar flares and geomagnetic storms that can disrupt cell phone service and power grids on Earth.

    Key advantage

    The miniaturized engine scales down a cylindrical thruster with a high volume-to-surface geometry developed at the PPPL Hall Thruster Experiment, which Raitses leads and launched with PPPL physicist Nat Fisch in 1999. The experiment investigates the use of plasma — the state of matter composed of free-floating electrons and atomic nuclei, or ions — for space propulsion.

    A key advantage of the miniaturized cylindrical Hall thruster will be its ability to produce a higher density of rocket thrust than existing plasma thrusters used for most CubeSats now orbiting Earth. The miniaturized thruster can achieve both increased density and a high specific impulse — the technical term for how efficiently a rocket burns fuel — that will be many times greater than that produced by chemical rockets and cold-gas thrusters typically used on small satellites.

    High specific-impulse thrusters use much less fuel and can lengthen satellite missions, making them more cost-effective. Equally important is the fact that a high specific impulse can produce a large enough increase in a satellite’s momentum to enable the spacecraft to change orbits — a feature not available on currently orbiting CubeSats. Finally, high thrust density will enable satellites to accomplish complex fuel-optimized orbits in a reasonable time.

    These capabilities provide many benefits. For example, a CubeSat might descend to lower orbit to track hurricanes or monitor shoreline changes and return to a higher orbit where the drag force on a satellite is weaker, requiring less fuel for propulsion.

    The foot-long CubeSat, which Princeton has dubbed a “TigerSat,” consists of three 4-inch aluminum cubes stacked vertically together. Sensors, batteries, radio equipment and other instruments will fill the CubeSat, with a miniaturized thruster roughly equal in diameter to two U.S. quarters housed at either end. A thruster will fire to change orbits when the satellite passes the Earth’s equator.

    Mechanical and aerospace engineering students

    Building the CubeSat are some 10 Princeton graduate and undergraduate students in the Department of Mechanical and Aerospace Engineering, with Daniel Marlow, the Evans Crawford 1911 Professor of Physics, serving as faculty advisor. Undergraduates include Andrew Redd (Class of 2020), who leads design and construction of the CubeSat, and Seth Freeman (Class of 2022), who is working full-time on the project over the summer. Working on thruster development is Jacob Simmonds, a third-year graduate engineering student, whose thesis advisors are Raitses and Yamada. “This project began as a prototype of Yamada’s CubeSat and has evolved into its own project as a testbed for the plasma thruster,” Simmonds said.

    Also under construction at PPPL is a test facility designed to simulate key aspects of the CubeSat’s operation. Undergraduates working on their own time are building the satellite and this facility. “To the extent that students and their advisors have identified well-defined questions associated with the TigerSat project, they can get independent work credit,” Marlow said. “Also, some problem sets in the introductory physics course for undergraduates that I teach have questions related to the TigerSat flight plan.”

    Simmonds, while working on the thruster, is drafting a proposal for NASA’s Cubic Satellite Launch Initiative that is due in November. Projects selected by the Initiative, which promotes public-private technology partnerships and low-cost technology development, have launch costs covered on commercial and NASA vehicles. Plans call for a TigerSat launch in the fall of 2021.

    Value of collaboration

    For Raitses, this project demonstrates the value of Princeton engineering students collaborating with PPPL and of University faculty cooperating with the Laboratory. “This is something that is mutually beneficial,” he said, “and something that we want to encourage.”

    Support for the thruster work comes from Laboratory Directed Research and Development funds made available through the DOE Office of Science. Basic science aspects of the novel thruster based on low-temperature magnetized plasma is supported by the Air Force Office of Scientific Research. Princeton University supports construction of the CubeSat and the test facility.

    PPPL, on Princeton University’s Forrestal Campus in Plainsboro, N.J., is devoted to creating new knowledge about the physics of plasmas — ultra-hot, charged gases — and to developing practical solutions for the creation of fusion energy. The Laboratory is managed by the University for the U.S. Department of Energy’s Office of Science, which is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, visit http://www.energy.gov/science.

    See the full article here .

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    Princeton Plasma Physics Laboratory is a U.S. Department of Energy national laboratory managed by Princeton University. PPPL, on Princeton University’s Forrestal Campus in Plainsboro, N.J., is devoted to creating new knowledge about the physics of plasmas — ultra-hot, charged gases — and to developing practical solutions for the creation of fusion energy. Results of PPPL research have ranged from a portable nuclear materials detector for anti-terrorist use to universally employed computer codes for analyzing and predicting the outcome of fusion experiments. The Laboratory is managed by the University for the U.S. Department of Energy’s Office of Science, which is the largest single supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit science.http://www.energy.gov.


    PPPL campus


    Princeton University campus

    About Princeton: Overview

    Princeton University is a vibrant community of scholarship and learning that stands in the nation’s service and in the service of all nations. Chartered in 1746, Princeton is the fourth-oldest college in the United States. Princeton is an independent, coeducational, nondenominational institution that provides undergraduate and graduate instruction in the humanities, social sciences, natural sciences and engineering.

    As a world-renowned research university, Princeton seeks to achieve the highest levels of distinction in the discovery and transmission of knowledge and understanding. At the same time, Princeton is distinctive among research universities in its commitment to undergraduate teaching.

    Today, more than 1,100 faculty members instruct approximately 5,200 undergraduate students and 2,600 graduate students. The University’s generous financial aid program ensures that talented students from all economic backgrounds can afford a Princeton education.

    Princeton Shield

     
  • richardmitnick 4:37 pm on July 24, 2019 Permalink | Reply
    Tags: , Portable scanners, Princeton University   

    From Princeton University: “Innovative tiny laser has potential uses in drug quality control, medical diagnosis, airplane safety” 

    Princeton University
    From Princeton University

    July 24, 2019
    Molly Sharlach

    In a major step toward developing portable scanners that can rapidly measure molecules on the pharmaceutical production line or classify tissue in patients’ skin, a Princeton-led team of researchers have created an imaging system that uses lasers small and efficient enough to fit on a microchip.

    The team demonstrated the system’s resolution by using it to image a U.S. quarter. Fine details like the eagle’s wing feathers, as small as one-fifth of a millimeter wide, were clearly visible.

    The system emits and detects electromagnetic radiation at terahertz frequencies — higher than radio waves but lower than the long-wave infrared light used for thermal imaging. Imaging using terahertz radiation has long been a goal for engineers, but the difficulty of creating practical systems that work in this frequency range has stymied most applications and resulted in what engineers call the “terahertz gap.”

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    Laser-generated images. A new imaging technology rapidly measures the chemical compositions of solids. A conventional image of a sample pill is shown at left; at right, looking at the same surface with terahertz frequencies reveals various ingredients as different colors. Such images would aid quality control and development in pharmaceutical manufacturing, as well as medical diagnosis. Images courtesy of the researchers

    “Here, we have a revolutionary technology that doesn’t have any moving parts and uses direct emission of terahertz radiation from semiconductor chips,” said Gerard Wysocki, an associate professor of electrical engineering at Princeton University and one of the leaders of the research team.

    Terahertz radiation can penetrate substances such as fabrics and plastics, is non-ionizing and therefore safe for medical use, and can be used to view materials difficult to image at other frequencies. It could potentially be used as a diagnostic tool for skin cancer, for example, even as its ability to image metal could be applied to test airplane wings for damage after being struck by an object in flight.

    The new system, described in a paper published in the June issue of the journal Optica, can quickly probe the identity and arrangement of molecules or expose structural damage to materials.

    The device uses stable beams of radiation at precise frequencies. The setup is called a frequency comb because it contains multiple “teeth” that each emit a different, well-defined frequency of radiation. The radiation interacts with molecules in the sample material. A dual-comb structure allows the instrument to efficiently measure the reflected radiation. Unique patterns, or spectral signatures, in the reflected radiation allow researchers to identify the molecular makeup of the sample.

    While current terahertz imaging technologies are expensive to produce and cumbersome to operate, the new system is based on a semiconductor design that costs less and can generate many images per second. This speed could make it useful for real-time quality control of pharmaceutical tablets on a production line and other fast-paced uses.

    “Imagine that every 100 microseconds a tablet is passing by, and you can check if it has a consistent structure and there’s enough of every ingredient you expect,” said Wysocki.

    2
    Gerard Wysocki (left), an associate professor of electrical engineering, and Jonas Westberg, an associate research scholar, helped create a new terahertz imaging system that represents a major step toward developing portable scanners that can rapidly measure molecules in pharmaceuticals or classify tissue in patients’ skin. Photo by David Kelly Crow

    As a proof of concept, the researchers created a tablet with three zones containing common inert ingredients in pharmaceuticals — forms of glucose, lactose and histidine. The terahertz imaging system identified each ingredient and revealed the boundaries between them, as well as a few spots where one chemical had spilled over into a different zone. This type of “hot spot” represents a frequent problem in pharmaceutical production that occurs when the active ingredient is not properly mixed into a tablet.

    While the technology makes the industrial and medical use of terahertz imaging more feasible than before, it still requires cooling to a low temperature, a major hurdle for practical applications. Many researchers are now working on lasers that will potentially operate at room temperature. The Princeton team said its dual-comb hyperspectral imaging technique will work well with these new room-temperature laser sources, which could then open many more uses.

    In addition to Wysocki, the paper’s Princeton authors are former visiting graduate student Lukasz Sterczewski (currently a postdoctoral scholar at NASA’s Jet Propulsion Laboratory) and associate research scholar Jonas Westberg. Other co-authors are Yang Yang, David Burghoff and Qing Hu of the Massachusetts Institute of Technology; and John Reno of Sandia National Laboratories.

    Terahertz hyperspectral imaging with dual chip-scale combs by Lukasz A. Sterczewski, Jonas Westberg, Yang Yang, David Burghoff, John Reno, Qing Hu and Gerard Wysocki was published in the June issue of the journal Optica (Vol. 6, Issue 6, pp. 766-771, DOI: 10.1364/OPTICA.6.000766). Support for the research was provided in part by the Defense Advanced Research Projects Agency and the U.S. Department of Energy.

    See the full article here .

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    Princeton University Campus

    About Princeton: Overview

    Princeton University is a vibrant community of scholarship and learning that stands in the nation’s service and in the service of all nations. Chartered in 1746, Princeton is the fourth-oldest college in the United States. Princeton is an independent, coeducational, nondenominational institution that provides undergraduate and graduate instruction in the humanities, social sciences, natural sciences and engineering.

    As a world-renowned research university, Princeton seeks to achieve the highest levels of distinction in the discovery and transmission of knowledge and understanding. At the same time, Princeton is distinctive among research universities in its commitment to undergraduate teaching.

    Today, more than 1,100 faculty members instruct approximately 5,200 undergraduate students and 2,600 graduate students. The University’s generous financial aid program ensures that talented students from all economic backgrounds can afford a Princeton education.

    Princeton Shield

     
  • richardmitnick 2:35 pm on July 10, 2019 Permalink | Reply
    Tags: , , , , , , , Princeton University   

    From Princeton University: “Princeton scientists spot two supermassive black holes on collision course with each other” 

    Princeton University
    From Princeton University

    1
    Titanic Twosome: A Princeton-led team of astrophysicists has spotted a pair of supermassive black holes, roughly 2.5 billion light-years away, that are on a collision course (inset). The duo can be used to estimate how many detectable supermassive black hole mergers are in the present-day universe and to predict when the historic first detection of the background “hum” of gravitational waves will be made.
    Image courtesy of Andy Goulding et al./Astrophysical Journal Letters 2019

    July 10, 2019

    Each black hole’s mass is more than 800 million times that of our sun. As the two gradually draw closer together in a death spiral, they will begin sending gravitational waves rippling through space-time.


    Two Black Holes Merge into One.
    LIGO Lab Caltech : MIT
    Published on Feb 11, 2016
    A computer simulation shows the collision of two black holes, a tremendously powerful event detected for the first time ever by the Laser Interferometer Gravitational-Wave Observatory, or LIGO. LIGO detected gravitational waves, or ripples in space and time generated as the black holes spiraled in toward each other, collided, and merged. This simulation shows how the merger would appear to our eyes if we could somehow travel in a spaceship for a closer look. It was created by solving equations from Albert Einstein’s general theory of relativity using the LIGO data.

    Cornell SXS, the Simulating eXtreme Spacetimes (SXS) project

    The two merging black holes are each roughly 30 times the mass of the sun, with one slightly larger than the other. Time has been slowed down by a factor of about 100. The event took place 1.3 billion years ago.

    The stars appear warped due to the incredibly strong gravity of the black holes. The black holes warp space and time, and this causes light from the stars to curve around the black holes in a process called gravitational lensing. The ring around the black holes, known as an Einstein ring, arises from the light of all the stars in a small region behind the holes, where gravitational lensing has smeared their images into a ring.

    The gravitational waves themselves would not be seen by a human near the black holes and so do not show in this video, with one important exception. The gravitational waves that are traveling outward toward the small region behind the black holes disturb that region’s stellar images in the Einstein ring, causing them to slosh around, even long after the collision. The gravitational waves traveling in other directions cause weaker, and shorter-lived sloshing, everywhere outside the ring.

    Those cosmic ripples will join the as-yet-undetected background noise of gravitational waves from other supermassive black holes. Even before the destined collision, the gravitational waves emanating from the supermassive black hole pair will dwarf those previously detected from the mergers of much smaller black holes and neutron stars.

    “Collisions between enormous galaxies create some of the most extreme environments we know of, and should theoretically culminate in the meeting of two supermassive black holes, so it was incredibly exciting to find such an immensely energetic pair of black holes so close together in our Hubble Space Telescope images,” said Andy Goulding, an associate research scholar in astrophysical sciences at Princeton who is the lead author on a paper appearing July 10 in Astrophysical Journal Letters.

    “Supermassive black hole binaries produce the loudest gravitational waves in the universe,” said co-discoverer and co-author Chiara Mingarelli, an associate research scientist at the Flatiron Institute’s Center for Computational Astrophysics in New York City. Gravitational waves from supermassive black hole pairs “are a million times louder than those detected by LIGO.

    .”

    “When these supermassive black holes merge, they will create a black hole hundreds of times larger than the one at the center of our own galaxy,” said Princeton graduate student Kris Pardo, a co-author on the paper.

    The two supermassive black holes are especially interesting because they are around 2.5 billion light-years away from Earth. Since looking at distant objects in astronomy is like looking back in time, the pair belong to a universe 2.5 billion years younger than our own. Coincidentally, that’s roughly the same amount of time the astronomers estimate the black holes will take to begin producing powerful gravitational waves.

    In the present-day universe, the black holes are already emitting these gravitational waves, but even at light speed the waves won’t reach us for billions of years. The duo is still useful, though. Their discovery can help scientists estimate how many nearby supermassive black holes are emitting gravitational waves that we could detect right now.

    Detecting the gravitational wave background would help answer some of the biggest unknowns in astronomy, such as how often galaxies merge and whether supermassive black hole pairs merge at all, or if they become stuck in a near-endless waltz around each other.

    “It’s a major embarrassment for astronomy that we don’t know if supermassive black holes merge,” said Jenny Greene, a professor of astrophysical sciences at Princeton and a co-author on the paper. “For everyone in black hole physics, observationally this is a long-standing puzzle that we need to solve.”

    Supermassive black holes can contain millions or even billions of suns’ worth of mass. Nearly all galaxies, including our own Milky Way, contain at least one of these behemoths at their core.

    SGR A* , the supermassive black hole at the center of the Milky Way. NASA’s Chandra X-Ray Observatory


    SGR A and SGR A* from Penn State and NASA/Chandra

    When galaxies merge, their supermassive black holes meet up and begin orbiting one another. Over time, this orbit tightens as gas and stars pass between the black holes and steal energy.

    Once the supermassive black holes get too close, though, this energy theft all but stops. Some theories suggest that they stall at around 1 parsec apart (roughly 3.2 light-years). This slowdown lasts nearly indefinitely and is known as the “final parsec problem.” In this scenario, only very rare groups of three or more supermassive black holes result in mergers.

    Astronomers can’t just look for stalled pairs, because long before the black holes are a parsec apart, they’re too close to distinguish as two separate objects. Moreover, they don’t produce strong gravitational waves until they overcome the final parsec hurdle and get closer together. (Observed as they were 2.5 billion years ago, the newfound supermassive black holes appear about 430 parsecs apart.)

    If the final parsec problem turns out not to be a problem, then astronomers expect that the universe is filled with the clamor of gravitational waves from supermassive black hole pairs in the process of merging. “This noise is called the gravitational wave background, and it’s a bit like a chaotic chorus of crickets chirping in the night,” Goulding said. “You can’t discern one cricket from another, but the volume of the noise helps you estimate how many crickets are out there.”

    If two supermassive black holes do collide and combine, it will send a thundering “chirp” that will dwarf the background chorus – but it’s no small task to “hear” it.

    The telltale gravitational waves generated by merging supermassive black holes are outside the frequencies currently observable by experiments such as LIGO and Virgo, which have detected the mergers of much smaller black holes and neutron stars. Scientists hunting for the larger gravitational waves from supermassive black hole collisions rely on arrays of special stars called pulsars that act like metronomes, sending out radio waves in a steady rhythm. If a passing gravitational wave stretches or compresses the space between Earth and the pulsar, the rhythm will be thrown off slightly.

    Detecting the gravitational wave background using one of these pulsar timing arrays takes patience and plenty of monitored stars. A single pulsar’s rhythm might be disrupted by only a few hundred nanoseconds over a decade. The louder the background noise, the larger the timing disruptions and the quicker the detection will be made.

    Goulding, Greene and the other observational astronomers on the team detected the two titans with the Hubble Space Telescope. Although supermassive black holes aren’t directly visible through an optical telescope like Hubble, they are surrounded by bright clumps of luminous stars and warm gas drawn in by the powerful gravitational tug.

    Stars around SGR A* including S0-2 Andrea Ghez Keck/UCLA Galactic Center Group.

    For its time in history, the galaxy harboring the newfound supermassive black hole pair “is basically the most luminous galaxy in the universe,” Goulding said. What’s more, the galaxy’s core is shooting out two unusually colossal plumes of gas. When they pointed Hubble at it to uncover the origins of its spectacular gas clouds, the researchers discovered that the system contained not one but two massive black holes.

    The observational astronomers then teamed up with gravitational wave physicists Mingarelli and Pardo to interpret the finding in the context of the gravitational wave background. The discovery provides an anchor point for estimating how many merging supermassive black holes are within detection distance of Earth. Previous estimates relied on computer models of how often galaxies merge, rather than actual observations of supermassive black hole pairs.

    Based on the data, Pardo and Mingarelli predicted that in an optimistic scenario, there are about 112 nearby supermassive black holes emitting gravitational waves. The first detection of the gravitational wave background from supermassive black hole mergers should therefore come within the next five years or so. If such a detection isn’t made, that would be evidence that the final parsec problem may be insurmountable. The team is currently looking at other galaxies similar to the one harboring the newfound supermassive black hole binary. Finding additional pairs will help them further hone their predictions.

    “This is the first example of a close pair of such massive black holes that we’ve found, but there may well be additional binary black holes remaining to be discovered,” said co-author Professor Michael Strauss, the associate chair of Princeton’s Department of Astrophysical Sciences. “The more we can learn about the population of merging black holes, the better we will understand the process of galaxy formation and the nature of the gravitational wave background.”

    See the full article here .

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    Princeton University Campus

    About Princeton: Overview

    Princeton University is a vibrant community of scholarship and learning that stands in the nation’s service and in the service of all nations. Chartered in 1746, Princeton is the fourth-oldest college in the United States. Princeton is an independent, coeducational, nondenominational institution that provides undergraduate and graduate instruction in the humanities, social sciences, natural sciences and engineering.

    As a world-renowned research university, Princeton seeks to achieve the highest levels of distinction in the discovery and transmission of knowledge and understanding. At the same time, Princeton is distinctive among research universities in its commitment to undergraduate teaching.

    Today, more than 1,100 faculty members instruct approximately 5,200 undergraduate students and 2,600 graduate students. The University’s generous financial aid program ensures that talented students from all economic backgrounds can afford a Princeton education.

    Princeton Shield

     
  • richardmitnick 11:50 am on May 8, 2019 Permalink | Reply
    Tags: "Five projects will explore sustainability using the Princeton campus as a laboratory", Adding renewables to the electrical grid, Building better compost, Building without waste, Farming on campus lands, Field-testing solar-powered smart windows, Princeton University   

    From Princeton University: “Five projects will explore sustainability using the Princeton campus as a laboratory” 

    Princeton University
    From Princeton University

    May 8, 2019
    Catherine Zandonella, Office of the Dean for Research

    1
    In 2012, the University completed a restoration of meandering and stepped form for a portion of the stream along Washington Road to mitigate erosion and flood risks and improve the riparian habitat. Photo by Christopher Lillja, Facilities Organization.

    Research projects that explore energy-saving technologies, sustainable farming and resource reuse have been selected to receive Dean for Research Innovation Funds for the Campus as a Lab.

    The five projects will be conducted with the University’s grounds as the laboratory or testbed for the exploration of technologies or practices that enhance sustainability and environmental responsibility. The campus serves as a real-world setting where ideas and theories can be tried on a relatively small scale, with the goal of scaling up successful projects beyond campus.

    Princeton aims to engage the entire University community in creating a more sustainable campus and world through its new Sustainability Action Plan, announced on Earth Day, April 22. The campus as a lab projects are one aspect of this broad endeavor.

    A faculty-led committee chose the winning proposals based on quality, originality and potential impact on the campus or in the field of study. All projects involve either graduate students or postdoctoral researchers, or undergraduate students.

    Funding for the Dean for Research Innovation Funds for the Campus as a Lab comes from the Princeton Environmental Institute, Office of the Dean for Research, Andlinger Center for Energy and the Environment, High Meadows Foundation Sustainability Fund, and Facilities. The funding program is administered by the Office of the Dean for Research in collaboration with the Office of Sustainability.

    Adding renewables to the electrical grid

    2
    Minjie Chen and Darren Hammell. Photos by David Kelly Crow and Princeton Power Systems.

    To meet the challenge of including renewable energy sources such as wind and solar to the electrical grid — the network of power stations and lines that deliver electricity to homes and businesses — a team of researchers will build a prototype grid to allow experimentation on ways to coordinate electricity from renewable and non-renewable sources. Solar and wind energy production fluctuates widely depending on weather and time of day. An electric grid with a large percentage of renewable integration may become highly unstable if not coordinated correctly.

    The research team, led by Minjie Chen, assistant professor of electrical engineering and the Andlinger Center for Energy and the Environment, and Darren Hammell, the Gerhard R. Andlinger Visiting Fellow in Energy and the Environment, will test ways to incorporate solar, wind, battery and other sources of power by building a testing environment called the Andlinger Distributed Energy and Power Testbed (ADEPT). The testbed will be highly programmable to allow the team to explore various configurations of power supplies as well as spikes in power usage, such as the greater demand posed from charging electric vehicles. The project will also explore innovations in how to meet spikes in user demand, such as programming the grid to autonomously cluster into “micro-grids” to defend against cyberattacks or natural hazards, and using smart technologies to enhance grid stability.

    Building without waste

    3
    Erin Besler and Stefana Parascho. Photos by Andy Scott and Andreas Thoma.

    Reducing and reusing leftover construction materials — typically scraps of metal, wood and concrete —is the focus of a new initiative to improve the ecological footprint of architecture. The project, led by Erin Besler and Stefana Parascho, two assistant professors in the School of Architecture, has two parts: new design tools to cut down the ordering of excess materials and innovative robotic assembly methods to reuse existing materials.

    To reduce construction leftovers, the team will build an intuitive-to-use design tool that improves architectural planning. For existing leftovers, which often come in irregular shapes that can be a challenge to reuse, a team made up of faculty, graduate students and Facilities staff members will use computational approaches and robotics to design structures incorporating the materials. The project offers a way for architects, contractors and builders to develop more sustainable approaches to planning and constructing buildings. For the broader public, the project offers the opportunity to experience cast-off materials in architectural designs and structures.

    Selected projects involving undergraduate research:

    Field-testing solar-powered smart windows

    4
    Lynn Loo. Photo by David Kelly Crow.

    A new smart-window technology that uses solar power to darken or lighten window glass — which saves energy by reducing the need for heating and cooling indoor spaces — will be tested this summer on buildings around campus. The technology involves coating windows with a film of flexible, transparent solar cells that convert sunlight into electrical energy to drive the change in transparency. Developed in the laboratory of Lynn Loo, director of the Andlinger Center for Energy and the Environment and the Theodora D. ’78 and William H. Walton III ’74 Professor in Engineering, these organic photovoltaic cells could power smart windows without the need for an external electrical power supply, allowing this technology to address retrofits and upgrades of existing windows.

    To determine how these solar-powered smart windows perform in real-world situations, undergraduate Matthew Marquardt, Class of 2020, will install and evaluate them in campus buildings. In collaboration with engineers at Andluca Technologies, a startup founded by members of the Loo group, Marquardt will design hardware to monitor and control the solar cells via the internet of things, integrate the solar cells with smart windows, and develop software to optimize the energy savings and benefit to occupants.

    Building better compost

    5
    Xinning Zhang. Photo by Chris Fascenelli, Office of Communications.

    A team of researchers will work with Princeton’s on-campus composting facility to explore conditions for creating high-quality compost that is high in nutrients and low in greenhouse gas emissions. The facility, known as the Sustainable Composting Research at Princeton (S.C.R.A.P.) Lab, houses a biodigester that converts campus food scraps into nutrient-rich plant food, helping to divert food waste from landfills and reduce reliance on chemical fertilizers. The biodigester consists of a large barrel that rotates to mix air with food waste and a carbon source — such as wood chips or cardboard — to aerobically decompose the materials into compost in just five days.

    The team, which will include an undergraduate researcher and be led by Xinning Zhang, assistant professor of geosciences and the Princeton Environmental Institute, will test various proportions of food waste, carbon inputs and air as well as operating conditions to identify conditions that create compost with superior levels of nutrients while reducing the natural emission of greenhouse gases due to biodegradation of compostable materials. The team will also explore the use of waste cardboard from the campus to replace wood chips.

    Farming on campus lands

    6
    Daniel Rubenstein and Gina Talt. Photos by Igor Heifetz and Denise Applewhite, Office of Communications.

    A new study will explore how to improve Princeton’s land stewardship practices in ways that encourage sustainability while improving agricultural yield. Princeton University enables local farmers to raise crops on large portions of its land, but in recent years farmers have reported finding it hard to make a profit due to crop consumption by deer. Additionally, years of growing monoculture crops with herbicides and fertilizers have led to nutrient-deficient soils and a system reliant on fossil-fuel-based inputs to suppress weeds.

    The project — led by Daniel Rubenstein, the Class of 1877 Professor of Zoology, a professor in the Department of Ecology and Evolutionary Biology, and director of the Princeton Environmental Institute’s certificate Program in Environmental Studies, along with Gina Talt, food systems project specialist with the Office of Sustainability — will involve undergraduates in examining the cost-effectiveness of fencing the lands to keep out deer while also exploring a variety of soil enriching and anti-weed control methods. The team will grow field corn in one-acre test plots, including fenced and non-fenced areas, to compare how farming practices affect crop growth, soil health and farmland profitability. The sustainable practices to be tested include applying compost made from campus food scraps, planting cover crops during the off-season, and weeding with equipment rather than applying herbicides.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Princeton University Campus

    About Princeton: Overview

    Princeton University is a vibrant community of scholarship and learning that stands in the nation’s service and in the service of all nations. Chartered in 1746, Princeton is the fourth-oldest college in the United States. Princeton is an independent, coeducational, nondenominational institution that provides undergraduate and graduate instruction in the humanities, social sciences, natural sciences and engineering.

    As a world-renowned research university, Princeton seeks to achieve the highest levels of distinction in the discovery and transmission of knowledge and understanding. At the same time, Princeton is distinctive among research universities in its commitment to undergraduate teaching.

    Today, more than 1,100 faculty members instruct approximately 5,200 undergraduate students and 2,600 graduate students. The University’s generous financial aid program ensures that talented students from all economic backgrounds can afford a Princeton education.

    Princeton Shield

     
  • richardmitnick 2:58 pm on March 13, 2019 Permalink | Reply
    Tags: "Astronomers discover 83 supermassive black holes in the early universe", , , , , Princeton University,   

    From Princeton University: “Astronomers discover 83 supermassive black holes in the early universe” 

    Princeton University
    From Princeton University

    March 13, 2019
    Liz Fuller-Wright

    Astronomers from Japan, Taiwan and Princeton University have discovered 83 quasars powered by supermassive black holes in the distant universe, from a time when the universe was less than 10 percent of its present age.

    “It is remarkable that such massive dense objects were able to form so soon after the Big Bang,” said Michael Strauss, a professor of astrophysical sciences at Princeton University who is one of the co-authors of the study. “Understanding how black holes can form in the early universe, and just how common they are, is a challenge for our cosmological models.”

    This finding increases the number of black holes known at that epoch considerably, and reveals, for the first time, how common they are early in the universe’s history. In addition, it provides new insight into the effect of black holes on the physical state of gas in the early universe in its first billion years. The research appears in a series of five papers published in The Astrophysical Journal and the Publications of the Astronomical Observatory of Japan.

    2
    Light from one of the most distant quasars known, powered by a supermassive black hole lying 13.05 billion light-years away from Earth. The image was obtained by the Hyper Suprime-Cam (HSC) mounted on the Subaru Telescope. The other objects in the field are mostly stars in our Milky Way or galaxies along the line of sight. Image courtesy of the National Astronomical Observatory of Japan

    NAOJ Subaru Hyper Suprime-Cam


    NAOJ/Subaru Telescope at Mauna Kea Hawaii, USA,4,207 m (13,802 ft) above sea level

    Supermassive black holes, found at the centers of galaxies, can be millions or even billions of times more massive than the sun. While they are prevalent today, it is unclear when they first formed, and how many existed in the distant early universe. A supermassive black hole becomes visible when gas accretes onto it, causing it to shine as a “quasar.” Previous studies have been sensitive only to the very rare, most luminous quasars, and thus the most massive black holes. The new discoveries probe the population of fainter quasars, powered by black holes with masses comparable to most black holes seen in the present-day universe.

    3
    An artist’s impression of a quasar. A supermassive black hole sits at the center, and the gravitational energy of material accreting onto it is released as light.
    Image courtesy of Yoshiki Matsuoka

    HSC has a gigantic field-of-view — 1.77 degrees across, or seven times the area of the full moon — mounted on one of the largest telescopes in the world. The HSC team is surveying the sky over the course of 300 nights of telescope time, spread over five years.

    The team selected distant quasar candidates from the sensitive HSC survey data. They then carried out an intensive observational campaign to obtain spectra of those candidates, using three telescopes: the Subaru Telescope [above]; the Gran Telescopio Canarias on the island of La Palma in the Canaries, Spain; and the Gemini South Telescope in Chile.


    Gran Telescopio Canarias at the Roque de los Muchachos Observatory on the island of La Palma, in the Canaries, Spain, sited on a volcanic peak 2,267 metres (7,438 ft) above sea level


    Gemini/South telescope, Cerro Tololo Inter-American Observatory (CTIO) campus near La Serena, Chile, at an altitude of 7200 feet

    The team selected distant quasar candidates from the sensitive HSC survey data. They then carried out an intensive observational campaign to obtain spectra of those candidates, using three telescopes: the Subaru Telescope; the Gran Telescopio Canarias on the island of La Palma in the Canaries, Spain; and the Gemini South Telescope in Chile. The survey has revealed 83 previously unknown very distant quasars. Together with 17 quasars already known in the survey region, the researchers found that there is roughly one supermassive black hole per cubic giga-light-year — in other words, if you chunked the universe into imaginary cubes that are a billion light-years on a side, each would hold one supermassive black hole.

    4
    The 100 quasars identified from the HSC data. The top seven rows show the 83 newly discovered quasars while the bottom two rows represent 17 previously known quasars in the survey area. They appear extremely red due to the cosmic expansion and absorption of light in intergalactic space. All the images were obtained by HSC.
    Image courtesy of the National Astronomical Observatory of Japan

    The sample of quasars in this study are about 13 billion light-years away from the Earth; in other words, we are seeing them as they existed 13 billion years ago. As the Big Bang took place 13.8 billion years ago, we are effectively looking back in time, seeing these quasars and supermassive black holes as they appeared only about 800 million years after the creation of the (known) universe.

    5
    If the history of the universe from the Big Bang to the present were laid out on a football field, Earth and our solar system would not appear until our own 33-yard line. Life appeared just inside the 28-yard line and dinosaurs went extinct halfway between the 1-yard line and the goal. All of human history, since hominids first climbed out of trees, takes place within an inch of the goal line. On this timeline, the supermassive black holes discovered by Princeton astrophysicist Michael Strauss and his international team of colleagues would appear back on the universe’s 6-yard line, very shortly after the Big Bang itself.
    Image by Kyle McKernan, Office of Communications

    The survey has revealed 83 previously unknown very distant quasars. Together with 17 quasars already known in the survey region, the researchers found that there is roughly one supermassive black hole per cubic giga-light-year — in other words, if you chunked the universe into imaginary cubes that are a billion light-years on a side, each would hold one supermassive black hole.

    It is widely accepted that the hydrogen in the universe was once neutral, but was “reionized” — split into its component protons and electrons — around the time when the first generation of stars, galaxies and supermassive black holes were born, in the first few hundred million years after the Big Bang. This is a milestone of cosmic history, but astronomers still don’t know what provided the incredible amount of energy required to cause the reionization. A compelling hypothesis suggests that there were many more quasars in the early universe than detected previously, and it is their integrated radiation that reionized the universe.

    “However, the number of quasars we observed shows that this is not the case,” explained Robert Lupton, a 1985 Princeton Ph.D. alumnus who is a senior research scientist in astrophysical sciences. “The number of quasars seen is significantly less than needed to explain the reionization.” Reionization was therefore caused by another energy source, most likely numerous galaxies that started to form in the young universe.

    The present study was made possible by the world-leading survey ability of Subaru and HSC. “The quasars we discovered will be an interesting subject for further follow-up observations with current and future facilities,” said Yoshiki Matsuoka, a former Princeton postdoctoral researcher now at Ehime University in Japan, who led the study. “We will also learn about the formation and early evolution of supermassive black holes, by comparing the measured number density and luminosity distribution with predictions from theoretical models.”

    Based on the results achieved so far, the team is looking forward to finding yet more distant black holes and discovering when the first supermassive black hole appeared in the universe.

    The HSC collaboration includes astronomers from Japan, Taiwan and Princeton University. The HSC instrumentation and software were developed by the National Astronomical Observatory of Japan (NAOJ), the Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU), the University of Tokyo, the High Energy Accelerator Research Organization (KEK), the Academia Sinica Institute for Astronomy and Astrophysics in Taiwan (ASIAA), and Princeton University. Funding was contributed by the FIRST program from Japanese Cabinet Office, the Ministry of Education, Culture, Sports, Science and Technology (MEXT), the Japan Society for the Promotion of Science (JSPS), Japan Science and Technology Agency (JST), the Toray Science Foundation, NAOJ, Kavli IPMU, KEK, ASIAA, and Princeton University.

    The results of the present study are published in the following five papers — the second paper in particular.

    [1] “Discovery of the First Low-luminosity Quasar at z > 7”, by Yoshiki Matsuoka1, Masafusa Onoue2, Nobunari Kashikawa3,4,5, Michael A Strauss6, Kazushi Iwasawa7, Chien-Hsiu Lee8, Masatoshi Imanishi4,5, Tohru Nagao and 40 co-authors, including Princeton astrophysicists James Bosch, James Gunn, Robert Lupton and Paul Price, appeared in the Feb. 6 issue of The Astrophysical Journal Letters, 872 (2019),

    [2] “Subaru High-z Exploration of Low-luminosity Quasars (SHELLQs). V. Quasar Luminosity Function and Contribution to Cosmic Reionization at z = 6,” appeared in the Dec. 20 issue of The Astrophysical Journal, 869 (2018), 150

    [3] “Subaru High-z Exploration of Low-luminosity Quasars (SHELLQs). IV. Discovery of 41 Quasars and Luminous Galaxies at 5.7 ≤ z ≤ 6.9,” was published July 3, 2018 in The Astrophysical Journal Supplement Series, 237 (2018), 5

    [4] “Subaru High-z Exploration of Low-Luminosity Quasars (SHELLQs). II. Discovery of 32 quasars and luminous galaxies at 5.7 < z ≤ 6.8,” was published July 5, 2017 in Publications of the Astronomical Society of Japan, 70 (2018), S35

    [5] “Subaru High-z Exploration of Low-luminosity Quasars (SHELLQs). I. Discovery of 15 Quasars and Bright Galaxies at 5.7 < z < 6.9”, was published Aug. 25, 2016 in The Astrophysical Journal, 828 (2016), 26 .

    See the full article here .

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    About Princeton: Overview

    Princeton University is a vibrant community of scholarship and learning that stands in the nation’s service and in the service of all nations. Chartered in 1746, Princeton is the fourth-oldest college in the United States. Princeton is an independent, coeducational, nondenominational institution that provides undergraduate and graduate instruction in the humanities, social sciences, natural sciences and engineering.

    As a world-renowned research university, Princeton seeks to achieve the highest levels of distinction in the discovery and transmission of knowledge and understanding. At the same time, Princeton is distinctive among research universities in its commitment to undergraduate teaching.

    Today, more than 1,100 faculty members instruct approximately 5,200 undergraduate students and 2,600 graduate students. The University’s generous financial aid program ensures that talented students from all economic backgrounds can afford a Princeton education.

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  • richardmitnick 11:52 am on December 19, 2018 Permalink | Reply
    Tags: AdS/CFT, Beyond Einstein: Physicists find surprising connections in the cosmos, , From tiny bits of string, , Our world when we get down to the level of particles is a quantum world, , Princeton University, Relatability between gravity and subatomic particles provides a sort of Rosetta stone for physics, The idea that fundamental particles are actually tiny bits of vibrating string was taking off and by the mid-1980s “string theory” had lassoed the imaginations of many leading physicists,   

    From Princeton University: “Beyond Einstein: Physicists find surprising connections in the cosmos” 

    Princeton University
    From Princeton University

    Dec. 17, 2018
    Catherine Zandonella

    1
    Gravity, the force that brings baseballs back to Earth and governs the growth of black holes, is mathematically relatable to the peculiar antics of the subatomic particles that make up all the matter around us. Illustration by J.F. Podevin

    Albert Einstein’s desk can still be found on the second floor of Princeton’s physics department. Positioned in front of a floor-to-ceiling blackboard covered with equations, the desk seems to embody the spirit of the frizzy-haired genius as he asks the department’s current occupants, “So, have you solved it yet?”

    Einstein never achieved his goal of a unified theory to explain the natural world in a single, coherent framework. Over the last century, researchers have pieced together links between three of the four known physical forces in a “standard model,” but the fourth force, gravity, has always stood alone.

    No longer. Thanks to insights made by Princeton faculty members and others who trained here, gravity is being brought in from the cold — although in a manner not remotely close to how Einstein had imagined it.

    Though not yet a “theory of everything,” this framework, laid down over 20 years ago and still being filled in, reveals surprising ways in which Einstein’s theory of gravity relates to other areas of physics, giving researchers new tools with which to tackle elusive questions.

    The key insight is that gravity, the force that brings baseballs back to Earth and governs the growth of black holes, is mathematically relatable to the peculiar antics of the subatomic particles that make up all the matter around us.

    This revelation allows scientists to use one branch of physics to understand other seemingly unrelated areas of physics. So far, this concept has been applied to topics ranging from why black holes run a temperature to how a butterfly’s beating wings can cause a storm on the other side of the world.

    This relatability between gravity and subatomic particles provides a sort of Rosetta stone for physics. Ask a question about gravity, and you’ll get an explanation couched in the terms of subatomic particles. And vice versa.

    “This has turned out to be an incredibly rich area,” said Igor Klebanov, Princeton’s Eugene Higgins Professor of Physics, who generated some of the initial inklings in this field in the 1990s. “It lies at the intersection of many fields of physics.”

    From tiny bits of string

    The seeds of this correspondence were sprinkled in the 1970s, when researchers were exploring tiny subatomic particles called quarks. These entities nest like Russian dolls inside protons, which in turn occupy the atoms that make up all matter. At the time, physicists found it odd that no matter how hard you smash two protons together, you cannot release the quarks — they stay confined inside the protons.

    One person working on quark confinement was Alexander Polyakov, Princeton’s Joseph Henry Professor of Physics. It turns out that quarks are “glued together” by other particles, called gluons. For a while, researchers thought gluons could assemble into strings that tie quarks to each other. Polyakov glimpsed a link between the theory of particles and the theory of strings, but the work was, in Polyakov’s words, “hand-wavy” and he didn’t have precise examples.

    Meanwhile, the idea that fundamental particles are actually tiny bits of vibrating string was taking off, and by the mid-1980s, “string theory” had lassoed the imaginations of many leading physicists. The idea is simple: just as a vibrating violin string gives rise to different notes, each string’s vibration foretells a particle’s mass and behavior. The mathematical beauty was irresistible and led to a swell of enthusiasm for string theory as a way to explain not only particles but the universe itself.

    One of Polyakov’s colleagues was Klebanov, who in 1996 was an associate professor at Princeton, having earned his Ph.D. at Princeton a decade earlier. That year, Klebanov, with graduate student Steven Gubser and postdoctoral research associate Amanda Peet, used string theory to make calculations about gluons, and then compared their findings to a string-theory approach to understanding a black hole. They were surprised to find that both approaches yielded a very similar answer. A year later, Klebanov studied absorption rates by black holes and found that this time they agreed exactly.

    That work was limited to the example of gluons and black holes. It took an insight by Juan Maldacena in 1997 to pull the pieces into a more general relationship. At that time, Maldacena, who had earned his Ph.D. at Princeton one year earlier, was an assistant professor at Harvard. He detected a correspondence between a special form of gravity and the theory that describes particles. Seeing the importance of Maldacena’s conjecture, a Princeton team consisting of Gubser, Klebanov and Polyakov followed up with a related paper formulating the idea in more precise terms.

    Another physicist who was immediately taken with the idea was Edward Witten of the Institute for Advanced Study (IAS), an independent research center located about a mile from the University campus. He wrote a paper that further formulated the idea, and the combination of the three papers in late 1997 and early 1998 opened the floodgates.

    “It was a fundamentally new kind of connection,” said Witten, a leader in the field of string theory who had earned his Ph.D. at Princeton in 1976 and is a visiting lecturer with the rank of professor in physics at Princeton. “Twenty years later, we haven’t fully come to grips with it.”

    2

    Two sides of the same coin

    This relationship means that gravity and subatomic particle interactions are like two sides of the same coin. On one side is an extended version of gravity derived from Einstein’s 1915 theory of general relativity. On the other side is the theory that roughly describes the behavior of subatomic particles and their interactions.

    The latter theory includes the catalogue of particles and forces in the “standard model” (see sidebar), a framework to explain matter and its interactions that has survived rigorous testing in numerous experiments, including at the Large Hadron Collider.

    In the standard model, quantum behaviors are baked in. Our world, when we get down to the level of particles, is a quantum world.

    Notably absent from the standard model is gravity. Yet quantum behavior is at the basis of the other three forces, so why should gravity be immune?

    The new framework brings gravity into the discussion. It is not exactly the gravity we know, but a slightly warped version that includes an extra dimension. The universe we know has four dimensions, the three that pinpoint an object in space — the height, width and depth of Einstein’s desk, for example — plus the fourth dimension of time. The gravitational description adds a fifth dimension that causes spacetime to curve into a universe that includes copies of familiar four-dimensional flat space rescaled according to where they are found in the fifth dimension. This strange, curved spacetime is called anti-de Sitter (AdS) space after Einstein’s collaborator, Dutch astronomer Willem de Sitter.

    The breakthrough in the late 1990s was that mathematical calculations of the edge, or boundary, of this anti-de Sitter space can be applied to problems involving quantum behaviors of subatomic particles described by a mathematical relationship called conformal field theory (CFT). This relationship provides the link, which Polyakov had glimpsed earlier, between the theory of particles in four space-time dimensions and string theory in five dimensions. The relationship now goes by several names that relate gravity to particles, but most researchers call it the AdS/CFT (pronounced A-D-S-C-F-T) correspondence.

    3

    Tackling the big questions

    This correspondence, it turns out, has many practical uses. Take black holes, for example. The late physicist Stephen Hawking startled the physics community by discovering that black holes have a temperature that arises because each particle that falls into a black hole has an entangled particle that can escape as heat.

    Using AdS/CFT, Tadashi Takayanagi and Shinsei Ryu, then at the University of California-Santa Barbara, discovered a new way to study
    entanglement in terms of geometry, extending Hawking’s insights in a fashion that experts consider quite remarkable.

    In another example, researchers are using AdS/CFT to pin down chaos theory, which says that a random and insignificant event such as the flapping of a butterfly’s wings could result in massive changes to a large-scale system such as a faraway hurricane. It is difficult to calculate chaos, but black holes — which are some of the most chaotic quantum systems possible — could help. Work by Stephen Shenker and Douglas Stanford at Stanford University, along with Maldacena, demonstrates how, through AdS/CFT, black holes can model quantum chaos.

    One open question Maldacena hopes the AdS/CFT correspondence will answer is the question of what it is like inside a black hole, where an infinitely dense region called a singularity resides. So far, the relationship gives us a picture of the black hole as seen from the outside, said Maldacena, who is now the Carl P. Feinberg Professor at IAS.

    “We hope to understand the singularity inside the black hole,” Maldacena said. “Understanding this would probably lead to interesting lessons for the Big Bang.”

    The relationship between gravity and strings has also shed new light on quark confinement, initially through work by Polyakov and Witten, and later by Klebanov and Matt Strassler, who was then at IAS.

    Those are just a few examples of how the relationship can be used. “It is a tremendously successful idea,” said Gubser, who today is a professor of physics at Princeton. “It compels one’s attention. It ropes you in, it ropes in other fields, and it gives you a vantage point on theoretical physics that is very compelling.”

    The relationship may even unlock the quantum nature of gravity. “It is among our best clues to understand gravity from a quantum perspective,” said Witten. “Since we don’t know what is still missing, I cannot tell you how big a piece of the picture it ultimately will be.”

    Still, the AdS/CFT correspondence, while powerful, relies on a simplified version of spacetime that is not exactly like the real universe. Researchers are working to find ways to make the theory more broadly applicable to the everyday world, including Gubser’s research on modeling the collisions of heavy ions, as well as high-temperature superconductors.

    Also on the to-do list is developing a proof of this correspondence that draws on underlying physical principles. It is unlikely that Einstein would be satisfied without a proof, said Herman Verlinde, Princeton’s Class of 1909 Professor of Physics, the chair of the Department of Physics and an expert in string theory, who shares office space with Einstein’s desk.

    “Sometimes I imagine he is still sitting there,” Verlinde said, “and I wonder what he would think of our progress.”

    See the full article here .

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    About Princeton: Overview

    Princeton University is a vibrant community of scholarship and learning that stands in the nation’s service and in the service of all nations. Chartered in 1746, Princeton is the fourth-oldest college in the United States. Princeton is an independent, coeducational, nondenominational institution that provides undergraduate and graduate instruction in the humanities, social sciences, natural sciences and engineering.

    As a world-renowned research university, Princeton seeks to achieve the highest levels of distinction in the discovery and transmission of knowledge and understanding. At the same time, Princeton is distinctive among research universities in its commitment to undergraduate teaching.

    Today, more than 1,100 faculty members instruct approximately 5,200 undergraduate students and 2,600 graduate students. The University’s generous financial aid program ensures that talented students from all economic backgrounds can afford a Princeton education.

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  • richardmitnick 1:27 pm on October 24, 2018 Permalink | Reply
    Tags: Biermann battery effect, , , , Princeton University,   

    From COSMOS Magazine: “Supercomputer finds clues to violent magnetic events” 

    Cosmos Magazine bloc

    From COSMOS Magazine

    24 October 2018
    Phil Dooley

    1
    An aurora over Iceland, the product of sudden magnetic reconnection. Credit Natthawat/Getty Images

    Researchers are a step closer to understanding the violent magnetic events that cause the storms on the sun’s surface and fling clouds of hot gas out into space, thanks to colossal computer simulations at Princeton University in the US.

    The disruptions in the magnetic field, known as magnetic reconnections, are common in the universe – the same process causes the aurora in high latitude skies – but existing models are unable to explain how they happen so quickly.

    A team led by Jackson Matteucci decided to investigate by building a full three-dimensional simulation of the ejected hot gas, something that required enormous computing power. The results are published in the journal Physical Review Letters.

    The researchers modelled more than 200 million particles using Titan, the biggest supercomputer [no longer true, the writer should have known that] in the US.

    ORNL Cray Titan XK7 Supercomputer, once the fastest in the world.

    They discovered that a three-dimensional interaction called the Biermann battery effect was at the heart of the sudden reconnection process.

    Discovered in the fifties by German astrophysicist Ludwig Biermann, the Biermann battery effect shows how magnetic fields can be generated in charged gases, known as plasma.

    In such plasmas, if a region develops in which there is a temperature gradient at right angles to a density gradient, a magnetic field is created that encircles it.

    Astrophysicists propose that this effect might take place in interstellar plasma clouds, such as nebulae, and generate the cosmic magnetic fields that we see throughout the universe.

    In contrast with the huge scale of cosmic plasma clouds, magnetic reconnection happens at a scale of microns when two magnetic fields collide, says Matteucci.

    He likens the process to collisions between two sizable handfuls of rubber bands. In stable circumstances the magnetic field lines are loops, like the bands. But sometimes turbulence in the plasma pushes these band analogues together so forcefully that they sever and reconnect to different ones, thus forming loops at different orientations.

    Some of the new loops are stretched taut and snap back, providing the energy that ejects material so violently, and causes magnetic storms or glowing auroras.

    The Princeton simulation showed that as the fields collide there is a sudden spike in the temperature in a very localised region, which sets off the Biermann battery effect, suddenly creating a new magnetic field in the midst of the collision. It’s this newly-appearing field that severs the lines and allows them to reconfigure.

    Although Matteucci’s simulations are for tiny plasma clouds generated by lasers hitting foil, he says they could help us understand large-scale processes in the atmosphere.

    “If you do a back of the envelope calculation, you find it could play an important role in reconnection in the magnetosphere, where the solar wind collides with the Earth’s magnetic field,” he says.

    See the full article here .


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  • richardmitnick 3:05 pm on September 12, 2018 Permalink | Reply
    Tags: A novel quantum state of matter that can be manipulated at will with a weak magnetic field, , , , Princeton University, , Scanning tunneling spectromicroscope operating in conjunction with a rotatable vector magnetic field capability, This could indeed be evidence of a new quantum phase of matter   

    From Princeton University: “Princeton scientists discover a ‘tuneable’ novel quantum state of matter” 

    Princeton University
    From Princeton University

    Sept. 12, 2018
    Liz Fuller-Wright, Office of Communications

    Quantum particles can be difficult to characterize, and almost impossible to control if they strongly interact with each other — until now.

    1
    An international team of researchers led by Princeton physicist Zahid Hasan has discovered a novel quantum state of matter that can be manipulated at will with a weak magnetic field, which opens new possibilities for next-generation nano- or quantum technologies. Researchers in Hasan’s lab include (from left): Jia-Xin Yin, Zahid Hasan, Songtian Sonia Zhang, Daniel Multer, Maksim Litskevich and Guoqing Chang. Photo by Nick Barberio, Office of Communications.

    An international team of researchers led by Princeton physicist Zahid Hasan has discovered a quantum state of matter that can be “tuned” at will — and it’s 10 times more tuneable than existing theories can explain. This level of manipulability opens enormous possibilities for next-generation nanotechnologies and quantum computing.

    “We found a new control knob for the quantum topological world,” said Hasan, the Eugene Higgins Professor of Physics. “We expect this is tip of the iceberg. There will be a new subfield of materials or physics grown out of this. … This would be a fantastic playground for nanoscale engineering.”

    Hasan and his colleagues, whose research appears in the current issue of Nature, are calling their discovery a “novel” quantum state of matter because it is not explained by existing theories of material properties.

    Hasan’s interest in operating beyond the edges of known physics is what attracted Jia-Xin Yin, a postdoctoral research associate and one of three co-first-authors on the paper, to his lab. Other researchers had encouraged him to tackle one of the defined questions in modern physics, Yin said.

    “But when I talked to Professor Hasan, he told me something very interesting,” Yin said. “He’s searching for new phases of matter. The question is undefined. What we need to do is search for the question rather than the answer.”

    The classical phases of matter — solids, liquids and gases — arise from interactions between atoms or molecules. In a quantum phase of matter, the interactions take place between electrons, and are much more complex.

    “This could indeed be evidence of a new quantum phase of matter — and that’s, for me, exciting,” said David Hsieh, a professor of physics at the California Institute of Technology and a 2009 Ph.D. graduate of Princeton, who was not involved in this research. “They’ve given a few clues that something interesting may be going on, but a lot of follow-up work needs to be done, not to mention some theoretical backing to see what really is causing what they’re seeing.”

    Hasan has been working in the groundbreaking subfield of topological materials, an area of condensed matter physics, where his team discovered topological quantum magnets a few years ago. In the current research, he and his colleagues “found a strange quantum effect on the new type of topological magnet that we can control at the quantum level,” Hasan said.

    The key was looking not at individual particles but at the ways they interact with each other in the presence of a magnetic field. Some quantum particles, like humans, act differently alone than in a community, Hasan said. “You can study all the details of the fundamentals of the particles, but there’s no way to predict the culture, or the art, or the society, that will emerge when you put them together and they start to interact strongly with each other,” he said.

    To study this quantum “culture,” he and his colleagues arranged atoms on the surface of crystals in many different patterns and watched what happened. They used various materials prepared by collaborating groups in China, Taiwan and Princeton. One particular arrangement, a six-fold honeycomb shape called a “kagome lattice” for its resemblance to a Japanese basket-weaving pattern, led to something startling — but only when examined under a spectromicroscope in the presence of a strong magnetic field, equipment found in Hasan’s Laboratory for Topological Quantum Matter and Advanced Spectroscopy, located in the basement of Princeton’s Jadwin Hall.

    All the known theories of physics predicted that the electrons would adhere to the six-fold underlying pattern, but instead, the electrons hovering above their atoms decided to march to their own drummer — in a straight line, with two-fold symmetry.

    “The electrons decided to reorient themselves,” Hasan said. “They ignored the lattice symmetry. They decided that to hop this way and that way, in one line, is easier than sideways. So this is the new frontier. … Electrons can ignore the lattice and form their own society.”

    This is a very rare effect, noted Caltech’s Hsieh. “I can count on one hand” the number of quantum materials showing this behavior, he said.

    The researchers were shocked to discover this two-fold arrangement, said Songtian Sonia Zhang, a graduate student in Hasan’s lab and another co-first-author on the paper. “We had expected to find something six-fold, as in other topological materials, but we found something completely unexpected,” she said. “We kept investigating — Why is this happening? — and we found more unexpected things. It’s interesting because the theorists didn’t predict it at all. We just found something new.”

    2
    When the researchers turn an external magnetic field in different directions (indicated with arrows), they change the orientation of the linear electron flow above the kagome (six-fold) magnet, as seen in these electron wave interference patterns on the surface of a topological quantum kagome magnet. Each pattern is created by a particular direction of the external magnetic field applied on the sample.
    Image by M. Z. Hasan, Jia-Xin Yin, Songtian Sonia Zhang, Princeton University.

    The decoupling between the electrons and the arrangement of atoms was surprising enough, but then the researchers applied a magnetic field and discovered that they could turn that one line in any direction they chose. Without moving the crystal lattice, Zhang could rotate the line of electrons just by controlling the magnetic field around them.

    “Sonia noticed that when you apply the magnetic field, you can reorient their culture,” Hasan said. “With human beings, you cannot change their culture so easily, but here it looks like she can control how to reorient the electrons’ many-body culture.”

    The researchers can’t yet explain why.

    “It is rare that a magnetic field has such a dramatic effect on electronic properties of a material,” said Subir Sachdev, the Herchel Smith Professor of Physics at Harvard University and chair of the physics department, who was not involved in this study.

    Even more surprising than this decoupling — called anisotropy — is the scale of the effect, which is 100 times more than what theory predicts. Physicists characterize quantum-level magnetism with a term called the “g factor,” which has no units. The g factor of an electron in a vacuum has been precisely calculated as very slightly more than two, but in this novel material, the researchers found an effective g factor of 210, when the electrons strongly interact with each other.

    “Nobody predicted that in topological materials,” said Hasan.

    “There are many things we can calculate based on the existing theory of quantum materials, but this paper is exciting because it’s showing an effect that was not known,” he said. This has implications for nanotechnology research especially in developing sensors. At the scale of quantum technology, efforts to combine topology, magnetism and superconductivity have been stymied by the low effective g factors of the tiny materials.

    “The fact that we found a material with such a large effective g factor, meaning that a modest magnetic field can bring a significant effect in the system — this is highly desirable,” said Hasan. “This gigantic and tunable quantum effect opens up the possibilities for new types of quantum technologies and nanotechnologies.”

    The discovery was made using a two-story, multi-component instrument known as a scanning tunneling spectromicroscope, operating in conjunction with a rotatable vector magnetic field capability, in the sub-basement of Jadwin Hall. The spectromicroscope has a resolution less than half the size of an atom, allowing it to scan individual atoms and detect details of their electrons while measuring the electrons’ energy and spin distribution. The instrument is cooled to near absolute zero and decoupled from the floor and the ceiling to prevent even atom-sized vibrations.

    “We’re going down to 0.4 Kelvin. It’s colder than intergalactic space, which is 2.7 Kelvin,” said Hasan. “And not only that, the tube where the sample is — inside that tube we create a vacuum condition that’s more than a trillion times thinner than Earth’s upper atmosphere. It took about five years to achieve these finely tuned operating conditions of the multi-component instrument necessary for the current experiment,” he said.

    “All of us, when we do physics, we’re looking to find how exactly things are working,” said Zhang. “This discovery gives us more insight into that because it’s so unexpected.”

    By finding a new type of quantum organization, Zhang and her colleagues are making “a direct contribution to advancing the knowledge frontier — and in this case, without any theoretical prediction,” said Hasan. “Our experiments are advancing the knowledge frontier.”

    The team included numerous researchers from Princeton’s Department of Physics, including present and past graduate students Songtian Sonia Zhang, Ilya Belopolski, Tyler Cochran and Suyang Xu; and present and past postdoctoral research associates Jia-Xin Yin, Guoqing Chang, Hao Zheng, Guang Bian and Biao Lian. Other co-authors were Hang Li, Kun Jiang, Bingjing Zhang, Cheng Xiang, Kai Liu, Tay-Rong Chang, Hsin Lin, Zhongyi Lu, Ziqiang Wang, Shuang Jia and Wenhong Wang.

    See the full article here .

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    Princeton University Campus

    About Princeton: Overview

    Princeton University is a vibrant community of scholarship and learning that stands in the nation’s service and in the service of all nations. Chartered in 1746, Princeton is the fourth-oldest college in the United States. Princeton is an independent, coeducational, nondenominational institution that provides undergraduate and graduate instruction in the humanities, social sciences, natural sciences and engineering.

    As a world-renowned research university, Princeton seeks to achieve the highest levels of distinction in the discovery and transmission of knowledge and understanding. At the same time, Princeton is distinctive among research universities in its commitment to undergraduate teaching.

    Today, more than 1,100 faculty members instruct approximately 5,200 undergraduate students and 2,600 graduate students. The University’s generous financial aid program ensures that talented students from all economic backgrounds can afford a Princeton education.

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  • richardmitnick 12:33 pm on July 26, 2018 Permalink | Reply
    Tags: , , , , , Galactic-wind whisperers, OLCF ORNL Cray Titan XK7 Supercomputer, Princeton University,   

    From ASCRDiscovery: “Galactic-wind whisperers” 

    From ASCRDiscovery
    ASCR – Advancing Science Through Computing

    UC Santa Cruz and Princeton University team simulates galactic winds on the DOE’s Titan supercomputer.

    ORNL Cray Titan XK7 Supercomputer

    1
    A high-resolution, 18-billion-cell simulation of galactic winds created by Cholla hydrodynamic code run on DOE’s Titan supercomputer at the Oak Ridge Leadership Computing Facility, an Office of Science user facility. Shown is a calculation of a disk-shaped galaxy (green) where supernova explosions near the center of the galaxy have driven outflowing galactic winds (red, pink, purple). The red to purple transition indicates areas of increasing wind velocity. Image courtesy of Schneider, Robertson and Thompson via arXiv:1803.01005.

    Winds made of gas particles swirl around galaxies at hundreds of kilometers per second. Astronomers suspect the gusts are stirred by nearby exploding stars that exude photons powerful enough to move the gas. Whipped fast enough, this wind can be ejected into intergalactic space.

    Astronomers have known for decades that these colossal gales exist, but they’re still parsing precisely what triggers and drives them. “Galactic winds set the properties of certain components of galaxies like the stars and the gas,” says Brant Robertson, an associate professor of astronomy and astrophysics at the University of California, Santa Cruz (UCSC). “Being able to model galactic winds has implications ranging from understanding how and why galaxies form to measuring things like dark energy and the acceleration of the universe.”

    But getting there has been extraordinarily difficult. Models must simultaneously resolve hydrodynamics, radiative cooling and other physics on the scale of a few parsecs in and around a galactic disk. Because the winds consist of hot and cold components pouring out at high velocities, capturing all the relevant processes with a reasonable spatial resolution requires tens of billions of computational cells that tile the disk’s entire volume.

    Most traditional models would perform the bulk of calculations using a computer’s central processing unit, with bits and pieces farmed out to its graphics processing units (GPUs). Robertson had a hunch, though, that thousands of GPUs operating in parallel could do the heavy lifting – a feat that hadn’t been tried for large-scale astronomy projects. Robertson’s experience running numerical simulations on supercomputers as a Harvard University graduate student helped him overcome challenges associated with getting the GPUs to efficiently communicate with each other.

    Once he’d decided on the GPU-based architecture, Robertson enlisted Evan Schneider, then a graduate student in his University of Arizona lab and now a Hubble Fellow at Princeton University, to work with him on a hydrodynamic code that suited the computational approach. They dubbed it Computational Hydrodynamics on II Architectures, or Cholla – also a cactus indigenous to the Southwest, and the two lowercase Ls represent those in the middle of the word “parallel.”

    “We knew that if we could design an effective GPU-centric code,” Schneider says, “we could really do something completely new and exciting.”

    With Cholla in hand, she and Robertson searched for a computer powerful enough to get the most out of it. They turned to Titan, a Cray XK7 supercomputer housed at the Oak Ridge Leadership Computing Facility (OLCF), a Department of Energy (DOE) Office of Science user facility at DOE’s Oak Ridge National Laboratory.

    Robertson notes that “simulating galactic winds requires exquisite resolution over a large volume to fully understand the system, much better resolution than other cosmological simulations used to model populations of galaxies. You really need a machine like Titan for this kind of project.”

    Cholla had found its match in Titan, a 27-petaflops system containing more than 18,000 GPUs. After testing the code on a smaller GPU cluster at the University of Arizona, Robertson and Schneider benchmarked it on Titan with the support of two small OLCF director’s discretionary awards. “We were definitely hoping that Titan would be the main workhorse for what we were doing,” Schneider says.

    Robertson and Schneider then unleashed Cholla to test a well-known theory for how galactic winds work. They simulated a hot, supernova-driven wind colliding with a cool gas cloud across 300 light years. With Cholla’s remarkable resolution, they zoomed in on various simulated regions to study phases and properties of galactic wind in isolation, letting the team rule out a theory that cold clouds close to the galaxy’s center could be pushed out by hot, fast-moving supernova wind. It turns out the hot wind shreds the cold clouds, turning them into ribbons that would be difficult to push on.

    With time on Titan allocated through DOE’s INCITE program (for Innovative and Novel Computational Impact on Theory and Experiment), Robertson and Schneider recently used Cholla to generate a simulation using nearly a trillion cells to model an entire galaxy spanning more than 30,000 light years – 10 to 20 times bigger than the largest galactic simulation produced so far. Robertson and Schneider expect the calculations will help test another potential explanation for how galactic winds work. They also may reveal additional details about these phenomena and the forces that regulate galaxies that are important for understanding low-mass varieties, dark matter and the universe’s evolution.

    Robertson and Schneider hope that additional DOE machines – including Summit, a 200-petaflops behemoth that ranks as the world’s fastest supercomputer – will soon support Cholla, which is now publicly available on GitHub.

    ORNL IBM AC922 SUMMIT supercomputer. Credit: Carlos Jones, Oak Ridge National Laboratory/U.S. Dept. of Energy

    To support the code’s dissemination, last year Schneider gave a brief how-to session at Los Alamos National Laboratory. More recently, she and Robertson ran a similar session at OLCF. “There are many applications and developments that could be added to Cholla that would be useful for people who are interested in any type of computational fluid dynamics, not just astrophysics,” Robertson says.

    Robertson also is exploring using GPUs for deep-learning approaches to astrophysics. His lab has been working to adapt a deep-learning model that biologists use to identify cancerous cells. Robertson thinks this method can automate galaxy identification, a crucial need for projects like the LSST, or Large Synoptic Survey Telescope.

    LSST


    LSST Camera, built at SLAC



    LSST telescope, currently under construction on the El Peñón peak 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.

    Its DOE-funded camera “will take an image of the whole southern sky every three days. There’s a huge amount of information,” says Robertson, who’s also co-chair of the LSST Galaxies Science Collaboration. “LSST is expected to find on the order of 30 billion galaxies, and it’s impossible to think that humans can look at all those and figure out what they are.”

    Normally, calculations have to be quite intensive to get substantial time on Titan, and Robertson believes the deep-learning project may not pass the bar. “However, because DOE has been supporting GPU-enabled systems, there is the possibility that, in a few years when the LSST data comes in, there may be an appropriate DOE system that could help with the analyses.”

    See the full article here.


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    ASCRDiscovery is a publication of The U.S. Department of Energy

     
  • richardmitnick 5:56 pm on April 25, 2018 Permalink | Reply
    Tags: , Princeton University, , Ultrahigh-pressure laser experiments shed light on cores of ‘super-Earth’ exoplanets   

    From Princeton University: “Ultrahigh-pressure laser experiments shed light on cores of ‘super-Earth’ exoplanets” 

    Princeton University
    Princeton University

    April 25, 2018
    Liz Fuller-Wright

    Using high-powered laser beams, researchers have simulated conditions inside a planet three times as large as Earth.

    Scientists have identified more than 2,000 of these “super-Earths,” exoplanets that are larger than Earth but smaller than Neptune, the next-largest planet in our solar system. By studying how iron and silicon alloys respond to extraordinary pressures, scientists are gaining new insights into the nature of super-Earths and their cores.

    “We now have a technique that allows us to directly access the extreme pressures of the deep interiors of exoplanets and measure important properties,” said Thomas Duffy, a professor of geosciences at Princeton. “Previously, scientists were restricted to either theoretical calculations or long extrapolations of low-pressure data. The ability to perform direct experiments allows us to test theoretical results and provides a much higher degree of confidence in our models for how materials behave under these extreme conditions.”

    1
    Inside the target chamber at the University of Rochester’s Omega Facility, lasers compress iron-silicon samples to the ultrahigh pressures found in the cores of super-Earths.
    Photo courtesy of Laboratory for Laser Energetics

    U Rochester Laboratory for Laser Energetics

    The work, which resulted in the highest-pressure X-ray diffraction data ever recorded, was led by June Wicks when she was an associate research scholar at Princeton, working with Duffy and colleagues at Lawrence Livermore National Laboratory and the University of Rochester. Their results were published today in the journal Science Advances written by by June Wicks, Raymond Smith, Dayne Fratanduono, Federica Coppari, Richard Kraus, Matthew Newman, J. Ryan Rygg, Jon Eggert and Thomas Duffy.

    Because super-Earths have no direct analogues in our own solar system, scientists are eager to learn more about their possible structures and compositions, and thereby gain insights into the types of planetary architectures that may exist in our galaxy. But they face two key limitations: we have no direct measurements of our own planetary core from which to extrapolate, and interior pressures in super-Earths can reach more than 10 times the pressure at the center of the Earth, well beyond the range of conventional experimental techniques.

    The pressures achieved in this study, up to 1,314 gigapascals (GPa) are about three times higher than previous experiments, making them more directly useful for modeling the interior structure of large, rocky exoplanets, Duffy said.

    “Most high-pressure experiments use diamond anvil cells which rarely reach more than 300 GPa,” or 3 million times the pressure at the surface of the Earth, he said. Pressures in Earth’s core reach up to 360 GPa.

    “Our approach is newer, and many people in the community are not as familiar with it yet, but we have shown in this (and past) work that we can routinely reach pressures above 1,000 GPa or more (albeit only for a fraction of a second). Our ability to combine this very high pressure with X-ray diffraction to obtain structural information provides us with a very unique tool — there is no other facility in the world that can do this,” he said.

    The researchers compressed two samples for only a few billionths of a second, just long enough to probe the atomic structure using a pulse of bright X-rays. The resulting diffraction pattern provided information on the density and crystal structure of the iron-silicon alloys, revealing that the crystal structure changed with higher silicon content.

    “The method of simultaneous X-ray diffraction and shock experiments is still in its infancy, so it’s exciting to see a ‘real-world application’ for the Earth’s core and beyond,” said Kanani Lee, an associate professor of geology and geophysics at Yale University who was not involved in this research.

    This new technique constitutes a “very significant” contribution to the field of exoplanet research, said Diana Valencia, a pioneer in the field and an assistant professor of physics at the University of Toronto-Scarborough, who was not involved in this research. “This is a good study because we are not just extrapolating from low pressures and hoping for the best. This is actually giving us that ‘best,’ giving us that data, and it therefore constrains our models better.”

    Wicks and her colleagues directed a short but intense laser beam onto two iron samples: one alloyed with 7 weight-percent silicon, similar to the modeled composition of Earth’s core, and another with 15 weight-percent silicon, a composition that is possible in exoplanetary cores.

    A planet’s core exerts control over its magnetic field, thermal evolution and mass-radius relationship, Duffy said. “We know that the Earth’s core is iron alloyed with about 10 percent of a lighter element, and silicon is one of the best candidates for this light element both for Earth and extrasolar planets.”

    The researchers found that at ultrahigh pressures, the lower-silica alloy organized its crystal structure in a hexagonal close-packed structure, while the higher-silica alloy used body-centered cubic packing. That atomic difference has enormous implications, said Wicks, who is now an assistant professor at Johns Hopkins University.

    “Knowledge of the crystal structure is the most fundamental piece of information about the material making up the interior of a planet, as all other physical and chemical properties follow from the crystal structure,” she said.

    Wicks and her colleagues also measured the density of the iron-silicon alloys over a range of pressures. They found that at the highest pressures, the iron-silicon alloys reach 17 to 18 grams per cubic centimeter — about 2.5 times as dense as on the surface of Earth, and comparable to the density of gold or platinum at Earth’s surface. They also compared their results to similar studies done on pure iron and discovered that the silicon alloys are less dense than unalloyed iron, even under extreme pressures.

    “A pure iron core is not realistic,” said Duffy, “as the process of planetary formation will inevitably lead to the incorporation of significant amounts of lighter elements. Our study is the first to consider these more realistic core compositions.”

    The researchers calculated the density and pressure distribution inside super-Earths, taking into account the presence of silicon in the core for the first time. They found that incorporating silicon increases the modeled size of a planetary core but reduces its central pressure.

    Future research will investigate how other light elements, such as carbon or sulfur, affect the structure and density of iron at ultrahigh pressure conditions. The researchers also hope to measure other key physical properties of iron alloys, to further constrain models of exoplanets’ interiors.

    “For a geologist, the discovery of so many extrasolar planets has opened the door to a new field of exploration,” said Duffy. “We now realize that the varieties of planets that are out there go far beyond the limited examples in our own solar system, and there is a much broader field of pressure, temperature and composition space that must be explored. Understanding the interior structure and composition of these large, rocky bodies is necessary to probe fundamental questions such as the possible existence of plate tectonics, magnetic field generation, their thermal evolution and even whether they are potentially habitable.”

    The research was funded by the National Nuclear Security Administration through the National Laser Users’ Facility Program (contract nos. DE-NA0002154 and DE-NA0002720) and the Laboratory Directed Research and Development Program at Lawrence Livermore National Laboratory (project no. 15-ERD-012).

    See the full article here .

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    Princeton University Campus

    About Princeton: Overview

    Princeton University is a vibrant community of scholarship and learning that stands in the nation’s service and in the service of all nations. Chartered in 1746, Princeton is the fourth-oldest college in the United States. Princeton is an independent, coeducational, nondenominational institution that provides undergraduate and graduate instruction in the humanities, social sciences, natural sciences and engineering.

    As a world-renowned research university, Princeton seeks to achieve the highest levels of distinction in the discovery and transmission of knowledge and understanding. At the same time, Princeton is distinctive among research universities in its commitment to undergraduate teaching.

    Today, more than 1,100 faculty members instruct approximately 5,200 undergraduate students and 2,600 graduate students. The University’s generous financial aid program ensures that talented students from all economic backgrounds can afford a Princeton education.

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