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Primeur weekly 2011-09-19

Exascale supercomputing

New IBM Blue Gene/Q supercomputer for Rensselaer ...

Fujitsu Laboratories develops compact silicon photonics light source for high-bandwidth CPU interconnects ...

The future accelerated: multi-core goes mainstream, computing pushed to extremes ...

The Cloud

Cordys selected by Fujitsu as strategic platform to offer Cloud services globally ...

EMC's new Center of Excellence and Cloud Data Center powers company's Cloud computing vision ...

Two new publications provide a Cloud computing standards roadmap and reference architecture ...

Hitachi Data Systems announces acquisition of BlueArc ...

HP unveils expanded Enterprise Security Solutions for the instant-on enterprise ...

Desktop Grids

TheSkyNet launched ...

IBM and University of Antioquia co-operate to seek drug for Leishmaniasis treatment ...

EuroFlash

Barcelona Supercomouting Center triples its calculation capacity ...

ADVA Optical Networking introduces industry's first 100G Metro solution ...

Registration open for the e-IRG open workshop in Poznań 12-13 October 2011 ...

Cracow Grid Workshop 2011 to issue Call for Papers ...

USFlash

Appro to deliver 800TFLOPs supercomputer to Japan's University of Tsukuba ...

NEC bundles TotalView as standard debugger for LX series HPC cluster solutions ...

WellPoint and IBM announce agreement to put Watson to work in health care ...

UC San Diego's HPWREN aids in recent supernova discovery ...

How the Milky Way got its spiral ...

Oracle sets new world-record result on SAP Sales and Distribution-Parallel standard application benchmark ...

$13-million NSF centre to explore new ways to manipulate light at the nanoscale ...

Oracle Utilities Customer Care and Billing with Oracle Exadata Database Machine demonstrates extreme performance for utility bill processing ...

Ferro-electrics could pave way for ultra-low power computing ...

Oracle introduces Pillar Axiom Release 5 Storage System Software ...

Broadcom to acquire NetLogic Microsystems Inc., an expert in network communications processors ...

SDSC and SDSU receive NSF grant to expand computer science curriculum ...

Intel announces new SATA solid-state drive for the data centre ...

SDSC researcher co-authors new book on managing event data ...

Syncfusion Sponsoring High Performance Computing for Wall Street Conference ...

Oracle releases Oracle Solaris 10 8/11 ...

How the Milky Way got its spiral

19 Sep 2011 Pittsburgh - The signature spiral arms of the Milky Way galaxy were likely formed by an epic collision between the Milky Way and the Sagittarius Dwarf galaxy, according to a University of Pittsburgh researcher and his collaborators, published in the prestigious British journalNature. Supercomputer simulations by Christopher W. Purcell, postdoctoral research associate in the Department of Physics and Astronomy in Pitt's School of Arts and Sciences, and colleagues report their findings in a paper titled "The Sagittarius Impact as an Architect of Spirality and Outer Rings in the Milky Way".

This paper is the first to identify Sagittarius as the architect of spiral structure in our Milky Way. "It presents a new and somewhat unexpected way of thinking about why the galaxy we live in looks the way it does", stated Christopher W. Purcell.

"Cosmologically speaking, it demonstrates the idea that relatively small impacts like this can have a dramatic impact on the structure of galaxies throughout the universe", he added. This idea had been assumed theoretically, but never demonstrated.

Christopher W. Purcell's collaborators include University of California High-Performance AstroComputing Center (UC-HIPACC)-affiliates James S. Bullock, Erik J. Tollerud, and Miguel Rocha, all at the University of California at Irvine. The fifth co-author is Sukanya Chakrabarti at Florida Atlantic University.

In the field of cosmology, supercomputer simulations are the only laboratories for scientific experimentation. With supercomputers, astronomers can recreate a small-scale simulation or model of distant, violent events that occurred over billions of years, and observe that model in sped-up time, in order to make predictions that can be tested by actual observations of the universe.

Christopher W. Purcell's findings are based on supercomputer simulations he conducted for his PhD at the University of California, Irvine, and in the lab of Pitt professor of physics and astronomy Andrew Zentner.

Interestingly, Christopher W. Purcell's simulations revealed that even more important than the stars of the Sagittarius Dwarf was its halo of invisible "dark matter" - equal in mass to all the stars in the Milky Way.

Visible matter makes up less than five percent of the universe, while nearly a quarter of the universe is made of transparent dark matter. Its existence is felt only through its gravitational influence. It is now known that every galaxy, including the Sagittarius Dwarf (precollision) and our own Milky Way, resides at the centre of a giant halo of dark matter several times larger in radius and many times greater in mass.

"When all the dark matter smacked into the Milky Way, 80 to 90 percent of it was stripped off", Christopher W. Purcell stated. That first impact - more than two billion years ago - produced instabilities that were quickly amplified, eventually forming the spiral arms and ring structures in the outskirts of our own galaxy.

In his dissertation, Christopher W. Purcell focused on the question: What effects have the repeated collisions with the Sagittarius Dwarf had on the Milky Way?

Throughout the past few decades, conventional wisdom has been that the Milky Way was relatively unperturbed for the past several million years. Whatever spiral structure exists, these arms, were just a result of the Milky Way disc evolving in isolation.

Since the Sagittarius Dwarf was discovered, astronomers have tried to match up debris from that galaxy to what they saw in the universe. In 2003, infrared telescopes and supercomputers that traced the orbital motions of its stars has revealed that the Sagittarius Dwarf had actually collided with the Milky Way twice - once 1.9 billion years ago and again 0.9 billion years ago.

"But what those collisions did to the Milky Way hadn't been simulated at all", stated Christopher W. Purcell. "Ours was the first ever to try to do that."

Researchers found that the collision set up instabilities - fluctuations in density of stars - in the flat disk of the rotating Milky Way. Our galaxy rotates faster toward its centre than toward its edges, so those instabilities were stretched and sheared, leading to the formation of spiral arms.

The simulations also revealed that the impact gave rise to ring-like structures found at the edges of our galaxy.

The second impact affected the Milky Way less, giving rise to only milder, less dense spiral-creating waves, because the Sagittarius Dwarf had by then lost most of its dark matter mass.

Without the dark matter to hold the dwarf galaxy together, its visible stars began to be pulled apart by the Milky Way's huge gravitational field and tidal forces.

"The dominant cosmology in astrophysics is one that's very violent on small scales. Galaxies like the Milky Way are constantly being bombarded by these small dwarf galaxies. It had not been appreciated prior to our work just how dramatic those impacts could be on the stellar disc itself", stated Christopher W. Purcell. "We expected to find some more subtle signatures of an impact like this - a flare in the outer disc, like bell-bottom jeans. We expected to see some mild morphological changes to the Milky Way. But we did not expect to see a spiral structure begin to emerge as a result of these impacts. That was something we didn't foresee."

Indeed, Christopher W. Purcell and collaborators delayed publication for several months while they made sure they understood why they were seeing these results. "We had to convince ourselves that we weren't crazy", he joked.

Today, long streamers of stars from the dismembered dwarf galaxy arch over and around the Milky Way, and "right now, billions and billions of dark matter particles from the Sagittarius Dwarf are raining down onto the Earth", stated Christopher W. Purcell. "Meantime, the Sun itself is revolving around the centre of the Milky Way Galaxy, in a complex and still-evolving system of multiple spiral arms."

We're just a few million years short of a third impact, Christopher W. Purcell said. But how can the researchers tell?

"We can tell when we look toward the centre of the Milky Way", stated Christopher W. Purcell. "Immediately on the opposite side of us, we can see this blob of stars crashing into the southern face of the disc from beneath. We can measure the velocities of these stars. We know that the dwarf galaxy is just about to smash the disc - in only another 10 million years."
Source: University of Pittsburgh

Back to Table of contents

Primeur weekly 2011-09-19

Exascale supercomputing

New IBM Blue Gene/Q supercomputer for Rensselaer ...

Fujitsu Laboratories develops compact silicon photonics light source for high-bandwidth CPU interconnects ...

The future accelerated: multi-core goes mainstream, computing pushed to extremes ...

The Cloud

Cordys selected by Fujitsu as strategic platform to offer Cloud services globally ...

EMC's new Center of Excellence and Cloud Data Center powers company's Cloud computing vision ...

Two new publications provide a Cloud computing standards roadmap and reference architecture ...

Hitachi Data Systems announces acquisition of BlueArc ...

HP unveils expanded Enterprise Security Solutions for the instant-on enterprise ...

Desktop Grids

TheSkyNet launched ...

IBM and University of Antioquia co-operate to seek drug for Leishmaniasis treatment ...

EuroFlash

Barcelona Supercomouting Center triples its calculation capacity ...

ADVA Optical Networking introduces industry's first 100G Metro solution ...

Registration open for the e-IRG open workshop in Poznań 12-13 October 2011 ...

Cracow Grid Workshop 2011 to issue Call for Papers ...

USFlash

Appro to deliver 800TFLOPs supercomputer to Japan's University of Tsukuba ...

NEC bundles TotalView as standard debugger for LX series HPC cluster solutions ...

WellPoint and IBM announce agreement to put Watson to work in health care ...

UC San Diego's HPWREN aids in recent supernova discovery ...

How the Milky Way got its spiral ...

Oracle sets new world-record result on SAP Sales and Distribution-Parallel standard application benchmark ...

$13-million NSF centre to explore new ways to manipulate light at the nanoscale ...

Oracle Utilities Customer Care and Billing with Oracle Exadata Database Machine demonstrates extreme performance for utility bill processing ...

Ferro-electrics could pave way for ultra-low power computing ...

Oracle introduces Pillar Axiom Release 5 Storage System Software ...

Broadcom to acquire NetLogic Microsystems Inc., an expert in network communications processors ...

SDSC and SDSU receive NSF grant to expand computer science curriculum ...

Intel announces new SATA solid-state drive for the data centre ...

SDSC researcher co-authors new book on managing event data ...

Syncfusion Sponsoring High Performance Computing for Wall Street Conference ...

Oracle releases Oracle Solaris 10 8/11 ...