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  • richardmitnick 11:35 am on January 23, 2020 Permalink | Reply
    Tags: , , , , , , , San Diego Supercomputer Center, ,   

    From Science Node: “How does a planet form?” 

    Science Node bloc
    From Science Node

    15 Jan, 2020
    Jan Zverina

    New simulations of terrestrial planet formation raise questions about the ingredients of life.

    Courtesy NASA/JPL-Caltech


    Most of us are taught in grade school how planets come to be: dust particles clump together and over millions of years continue to collide until one is formed. This lengthy and complicated process was recently modeled using a novel approach with the help of the Comet [below] supercomputer at the San Diego Supercomputer Center.

    SDSC Triton HP supercomputer

    SDSC Gordon-Simons supercomputer

    SDSC Dell Comet supercomputer

    Accumulations of dust, like this disk around a young star, may eventually become planets. A new study models this complicated process. Courtesy NASA/JPL-Caltech.

    The modeling enabled scientists at the Southwest Research Institute (SwRI) to implement a new software package, which in turn allowed them to create a simulation of planet formation that provides a new baseline for future studies of this mysterious field.

    “Specifically, we modeled the formation of terrestrial planets such as Mercury, Venus, Earth, and Mars,” said Kevin Walsh, SwRI researcher and lead author of the paper published in the Icarus Journal.

    “The problem of planet formation is to start with a huge amount of very small dust that interacts on super-short timescales (seconds or less), and the Comet-enabled simulations finish with the final big collisions between planets that continue for 100 million years or more.”

    What’s out there? And who?

    As Earthlings, these models give us insight into the key physics and timescales involved in our own solar system, according to the researchers. They also allow us to better understand how common planets such as ours could be in other solar systems. This may also mean that environments similar to Earth may exist.

    “One big consideration is these models traced the material in the solar system that we know is rich with water, and seeing what important mechanisms can bring those to Earth and where they would have done so.”

    Two large rocky bodies collide. New simulation models give insight into key physics and timescales involved in the formation of our own solar system. Courtesy Gemini Observatory/AURA.

    Studying the formation and evolution of the solar system—events that happened over four billion years ago–helps shed light on the distribution of different material throughout the solar system, explained Walsh.

    “While some of these tracers of solar system history are slight differences in the molecular makeup of different rocks, other differences can be vast and include the distribution of water-rich asteroids. Knowing the history and compositions of these smaller bodies could one day help as more distant and ambitious space travel may require harvesting some of their materials for fuel.”

    How did Comet (the supercomputer) help?

    The number, sizes, and times of the physics of planet formation makes it impossible to model in a single code or simulation. As the researchers learned more about the formation process, they realized that where one starts these final models (i.e. how many asteroids or proto-planets and their locations in a solar system) is very important, and that past models to produce those initial conditions were most likely flawed.

    Simulation of formation of terrestrial planets. Top row shows how eccentric each particle’s orbit is at the four times of 1, 2, 10 and 20 million years (where “eccentric” relates to the orbit’s elongation, where 0 is circular and 1 is a straight line). Black circles are particles that have grown to reach the mass of the Earth’s Moon. Bottom row shows the radius of each particle as a function of its distance from the Sun at the same four times. The black particles are again those that are as massive as the Moon, and the coloring of the particles relates to the mass (and radius). These glimpses show how the smaller particles are quickly gobbled up by the growing planets and that the planets stir and re-shape the orbits of the smaller bodies shown by their increases in eccentricity. Courtesy Kevin Walsh, Southwest Research Institute.

    “In this work we finally deployed a new piece of software that can model a much larger swath of this problem and start with the solar system full of 50 to 100-kilometer asteroids and build them all the way to planets and consider the complications of the gas disk around the sun and the effects of collisions blasting apart some of the material,” said Walsh.

    “We needed a supercomputer such as Comet to be able to crunch the huge amount of calculations required to complete the models and the power of this supercomputer allows us to dream up even bigger problems to attack in the future.”

    See the full article here .

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Science Node is an international weekly online publication that covers distributed computing and the research it enables.

    “We report on all aspects of distributed computing technology, such as grids and clouds. We also regularly feature articles on distributed computing-enabled research in a large variety of disciplines, including physics, biology, sociology, earth sciences, archaeology, medicine, disaster management, crime, and art. (Note that we do not cover stories that are purely about commercial technology.)

    In its current incarnation, Science Node is also an online destination where you can host a profile and blog, and find and disseminate announcements and information about events, deadlines, and jobs. In the near future it will also be a place where you can network with colleagues.

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  • richardmitnick 7:04 pm on February 22, 2019 Permalink | Reply
    Tags: "Supercomputing Neutron Star Structures and Mergers", , Bridges at Pittsburgh Supercomputer Center, , San Diego Supercomputer Center, , Stampede2 at the Texas Advanced Computing Center (TACC), , ,   

    From insideHPC: “Supercomputing Neutron Star Structures and Mergers” 

    From insideHPC

    This image of an eccentric binary neutron star system’s close encounter is an example of the large surface gravity wave excitations, which are similar to ocean waves found in very deep water. Credit: William East, Perimeter Institute for Theoretical Physics

    Perimeter Institute in Waterloo, Canada

    Over at XSEDE, Kimberly Mann Bruch & Jan Zverina from the San Diego Supercomputer Center write that researchers are using supercomputers to create detailed simulations of neutron star structures and mergers to better understand gravitational waves, which were detected for the first time in 2015.

    SDSC Dell Comet* supercomputer

    During a supernova, a single massive star explodes – some die and form black holes while others survive, depending on the star’s mass. Some of these supernova survivors are stars whose centers collapse and their protons and electrons form into a neutron star, which has an average gravitational pull that is two billion times the gravity on Earth.

    Researchers from the U.S., Canada, and Brazil have been focusing on the construction of a gravitational wave model for the detection of eccentric binary neutron stars. Using Comet* at the San Diego Supercomputer Center (SDSC) and Stampede2 at the Texas Advanced Computing Center (TACC), the scientists performed simulations of oscillating binary neutron stars to develop a novel model to predict the timing of various pericenter passages, which are the points of closest approach for revolving space objects.

    Texas Advanced Computer Center

    TACC DELL EMC Stampede2 supercomputer

    Their study, Evolution of Highly Eccentric Binary Neutron Stars Including Tidal Effects was published in Physical Review D. Frans Pretorius, a physics professor at Princeton University, is the Principal Investigator on the allocated project.

    “Our study’s findings provide insight into binary neutron stars and their role in detecting gravitational waves,” according to co-author Huan Yang, with the Perimeter Institute for Theoretical Physics in Waterloo, Ontario, Canada. “We can see that the oscillation of the stars significantly alters the trajectory and it is important to mention the evolution of the modes. For this case, during some of the later close encounters, the frequency of the orbit is larger when this evolution is tracked – compared to when it is not – as energy and angular momentum are taken out of the neutron star oscillations and put back into orbit.”

    In other words, probing gravitational waves from eccentric binary neutron stars provides a unique opportunity to observe neutron star oscillations. Through these measurements, researchers can infer the internal structure of neutron stars.

    “This is analogous to the example of ‘hearing the shape on a drum,’ where the shape of a drumhead can be determined by measuring frequencies of its modes,” said Yang. “By ‘hearing’ the modes of neutron stars with gravitational waves, the star’s size and internal structure will be similarly determined, or at least constrained.”

    “In particular, our dynamical space-time simulations solve the equations of Einstein’s theory of general relativity coupled to perfect fluids,” said co-author Vasileios Paschalidis, with the University of Arizona’s Theoretical Astrophysics Program. “Neutron star matter can be described as a perfect fluid, therefore the simulations contain the necessary physics to understand how neutron stars oscillate due to tidal interactions after every pericenter passage, and how the orbit changes due to the excited neutron star oscillations. Such simulations are computationally very expensive and can be performed only in high-performance computing centers.”

    “XSEDE resources significantly accelerated our scientific output,” noted Paschalidis, whose group has been using XSEDE for well over a decade, when they were students or post-doctoral researchers. “If I were to put a number on it, I would say that using XSEDE accelerated our research by a factor of three or more, compared to using local resources alone.”

    Neutron Star Mergers Form the Cauldron that Brews Gravitational Waves

    Merging neutron stars. Image Credit: Mark Garlick, University of Warwick.

    The merger of two neutron stars produces a hot (up to one trillion degrees Kelvin), rapidly rotating massive neutron star. This remnant is expected to collapse to form a black hole within a timescale that could be as short as one millisecond, or as long as many hours, depending on the sum of the masses of the two neutron stars.

    Featured in a recent issue of the Monthly Notices of the Royal Astronomical Society, Princeton University Computational and Theoretical Astrophysicist David Radice and his colleagues presented results from their simulations of the formation of neutron star merger remnants surviving for at least one tenth of a second. Radice turned to XSEDE for access to Comet, Stampede2, and Bridges, which is based at the Pittsburgh Supercomputing Center (PSC).

    Pittsburgh Supercomputer Center

    Bridges supercomputer at PSC

    It has been long thought that this type of merger product would be driven toward solid-body rotation by turbulent angular momentum transport, which acts as an effective viscosity. However, Radice and his collaborators discovered that the evolution of these objects is actually more complex.

    The massive neutron star shown in this three-dimensional rendition of a Comet-enabled simulation shows the emergence of a wind driven by neutrino radiation. The star is surrounded by debris expelled during and shortly after the merger. Credit: David Radice, Princeton University

    “We found that long-lived neutron star merger remnants are born with so much angular momentum that they are unable to reach solid body rotation,” said Radice. “Instead, they are viscously unstable. We expect that this instability will result in the launching of massive neutron rich winds. These winds, in turn, will be extremely bright in the UV/optical/infrared bands. The observation of such transients, in combination with gravitational-wave events or short gamma-ray bursts, would be ‘smoking gun’ evidence for the formation of long-lived neutron star merger remnants.”

    If detected, the bright transients predicted in this study could allow astronomers to measure the threshold mass below which neutron star mergers do not result in rapid black hole formation. This insight would be key in the quest to understand the properties of matter at extreme densities found in the hearts of neutron stars.

    Radice’s research used 35 high-resolution, general-relativistic neutron star merger simulations, which calculated the geometry of space-time as predicted by Einstein’s equations and simulated the neutron star matter using sophisticated microphysical models. On average, one of these simulations required about 300,000 CPU-hours.

    “My research would not be possible without XSEDE,” said Radice, who has used XSEDE resources since 2013, and for this study collaborated with Lars Koesterke at TACC to run his code efficiently on Stampede2. Specifically, this work was conducted in the context of an XSEDE Extended Collaborative Support Services (ECSS) project, which will be of benefit to future research.”

    “The cost can be up to a factor of three times higher for the selected models that were run at even higher resolution and depending on the detail level in the microphysics,” added Radice. “Because of the unique requirements of this study, which included a large number of intermediate-size simulations and few larger calculations, a key enabler was the availability of a combination of capability and capacity supercomputers including Comet and Bridges.”

    See the full article here .


    Please help promote STEM in your local schools.

    Stem Education Coalition

    Founded on December 28, 2006, insideHPC is a blog that distills news and events in the world of HPC and presents them in bite-sized nuggets of helpfulness as a resource for supercomputing professionals. As one reader said, we’re sifting through all the news so you don’t have to!

    If you would like to contact me with suggestions, comments, corrections, errors or new company announcements, please send me an email at rich@insidehpc.com. Or you can send me mail at:

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  • richardmitnick 2:47 pm on December 27, 2016 Permalink | Reply
    Tags: Antarctic Circumpolar Current, , San Diego Supercomputer Center   

    From Eos: “Notorious Ocean Current Is Far Stronger Than Previously Thought” 

    Eos news bloc


    Emily Underwood

    The Antarctic Circumpolar Current is the only ocean current to circle the planet and the largest wind-driven current on Earth. It’s also 30% more powerful than scientists realized.

    An ocean circulation model shows the Antarctic Circumpolar Current swirling around Antarctica, with slow-moving water in blue and warmer colors indicating faster speeds (red represents speeds above 1 mile per hour). But how much water is really flowing through the current? Recent fieldwork provides unexpected results. Credit: M. Mazloff, MIT; Source: San Diego Supercomputer Center, UC San Diego

    SDSC’s GORDON supercomputer

    Notorious among sailors for its strength and the rough seas it creates, the Antarctic Circumpolar Current (ACC) is the largest wind-driven current on Earth and the only ocean current to travel all the way around the planet. Now, researchers have found that the current transports 30% more water than previously thought. The revised estimate is an important update for scientists studying how the world’s oceans will respond to a warming climate.

    The ACC transports massive amounts of water between the Atlantic, Indian, and Pacific oceans in an eastward loop. Just how much water has long been uncertain, however, because of the difficulty and expense of accurately measuring its flow.

    A working day aboard research vessel and ice breaker N. B. Palmer. All hands concentrate as a current- and pressure-recording inverted echo sounder (CPIES) is deployed off the working deck into the Antarctic Circumpolar Current to begin its 4-year measurement mission at the seafloor in Drake Passage. Credit: T. Chereskin

    For the new study, Donohue et al. installed gauges along the bottom of Drake Passage, spanning an 800-kilometer passage between Cape Horn and the South Shetland Islands of Antarctica. Housed in glass spheres and spaced between 30 and 60 kilometers apart along a line near the seafloor, the gauges included pressure sensors, floating current meters attached by 50-meter tethers, and instruments that measure acoustic travel time from the seafloor to the sea surface.

    The classic estimate used for the ACC’s transport is 134 sverdrups (Sv). One sverdrup is equivalent to 1 million cubic meters per second. Using 4 years of data collection from 2007 to 2011, the researchers found that the transport rate was 30% higher than historical estimates, around 173.3 Sv. Although it’s possible that stronger winds in the Southern Ocean over the past few decades may have caused the increase, satellite-based studies showing that transport has remained fairly steady during this time suggest that improved measurement tools, not increased wind, are responsible for the discrepancy. (Geophysical Research Letters, doi:10.1002/2016GL070319, 2016)

    See the full article here .

    Please help promote STEM in your local schools.

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    Stem Education Coalition

    Eos is the leading source for trustworthy news and perspectives about the Earth and space sciences and their impact. Its namesake is Eos, the Greek goddess of the dawn, who represents the light shed on understanding our planet and its environment in space by the Earth and space sciences.

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