Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

ORNL team discovers new way to spin up pulsars

09.01.2007
A team of scientists using Oak Ridge National Laboratory supercomputers has discovered the first plausible explanation for a pulsar's spin that fits the observations made by astronomers.

Anthony Mezzacappa of the Department of Energy lab's Physics Division and John Blondin of North Carolina State University explain their results in the Jan. 4 issue of the journal Nature. According to three-dimensional simulations they performed at the Leadership Computing Facility, located at ORNL, the spin of a pulsar is determined not by the spin of the original star, but by the shock wave created when the star's massive iron core collapses.

That shock wave is inherently unstable, a discovery the team made in 2002, and eventually becomes cigar-shaped instead of spherical. The instability creates two rotating flows—one in one direction directly below the shock wave and another, inner flow, that travels in the opposite direction and spins up the core.

"The stuff that's falling in toward the center, if it hits this shock wave that is not a sphere any more but a cigar-shaped surface, will be deflected," Mezzacappa said. "When you do this in 3-D, you find that you wind up with not only one flow, but two counterrotating flows."

The asymmetrical flows establish a "sloshing" motion that, in the complex 3-D models, accounts for the pulsars observed spin velocities from once every 15 to 300 milliseconds, which is much slower than previous models predicted.

Previously, astronomers did not have a workable explanation for how the pulsar gets its spin. The assumption to this point has been that the spin of the leftover collapsed core comes from the spin of the original star. Being much smaller, the pulsar would then spin much faster than the original star, just as a figure skater spins faster by pulling his or her arms in.

The problem with that approach is that it would explain only the fastest observed pulsars. The ORNL-NCSU team, on the other hand, predicts spin periods that are in the observed range between 15 and 300 milliseconds.

The work was funded under the DOE Office of Science's Scientific Discovery through Advanced Computing, or SciDAC, program.

"Our discovery came at a critical time," Mezzacappa noted. "It came at a time when there was no description in the literature of how neutron stars are spun up and, therefore, how pulsars are born, that are consistent with observation. It was a crisis, if you will. Now our simulations come along and provide a way around that conundrum."

The discovery is an outgrowth of the team's use of three-dimensional simulations and the advances in high-performance computing that made the simulations possible. The simulations performed for the Nature paper used the Cray X1E system at ORNL, known as Phoenix. That system boasts a peak performance of more than 18 teraflops and is currently the fastest vector computer in the United States. Later simulations done by the team made use of the center's Jaguar system, a Cray XT3 with a peak performance of more than 50 teraflops.

The team used the VH1 code, developed by Blondin when he was a postdoctoral research associate at the University of Virginia, and moving the simulation data was problematic. Mezzacappa noted that researchers are able now to perform visualizations remotely, without having to move the data off site, but at the time of their early three-dimensional simulations this capability was not in place.

He stressed also that the team is looking forward to further advances in high-performance computing that will be coming to ORNL. For example, the team's simulations have not incorporated the influence of nearly massless, radiation-like particles known as neutrinos and the star's magnetic field.

The real prize, though, for his and other teams is a complete explanation of how the collapse of a star's core leads to the explosion that ejects most of its layers. So far, that explanation has proved elusive.

"In a nutshell, this rapid advance in supercomputing technology will give us the tools to solve this problem and to make these important predictions and to understand these events and their role in our universe. This is a very, very exciting and very satisfying thing," Mezzacappa said.

Oak Ridge National Laboratory is managed by UT-Battelle for the Department of Energy.

Mike Bradley | EurekAlert!
Further information:
http://www.ornl.gov

More articles from Physics and Astronomy:

nachricht When fluid flows almost as fast as light -- with quantum rotation
22.06.2018 | The Henryk Niewodniczanski Institute of Nuclear Physics Polish Academy of Sciences

nachricht Thermal Radiation from Tiny Particles
22.06.2018 | Universität Greifswald

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Temperature-controlled fiber-optic light source with liquid core

In a recent publication in the renowned journal Optica, scientists of Leibniz-Institute of Photonic Technology (Leibniz IPHT) in Jena showed that they can accurately control the optical properties of liquid-core fiber lasers and therefore their spectral band width by temperature and pressure tuning.

Already last year, the researchers provided experimental proof of a new dynamic of hybrid solitons– temporally and spectrally stationary light waves resulting...

Im Focus: Overdosing on Calcium

Nano crystals impact stem cell fate during bone formation

Scientists from the University of Freiburg and the University of Basel identified a master regulator for bone regeneration. Prasad Shastri, Professor of...

Im Focus: AchemAsia 2019 will take place in Shanghai

Moving into its fourth decade, AchemAsia is setting out for new horizons: The International Expo and Innovation Forum for Sustainable Chemical Production will take place from 21-23 May 2019 in Shanghai, China. With an updated event profile, the eleventh edition focusses on topics that are especially relevant for the Chinese process industry, putting a strong emphasis on sustainability and innovation.

Founded in 1989 as a spin-off of ACHEMA to cater to the needs of China’s then developing industry, AchemAsia has since grown into a platform where the latest...

Im Focus: First real-time test of Li-Fi utilization for the industrial Internet of Things

The BMBF-funded OWICELLS project was successfully completed with a final presentation at the BMW plant in Munich. The presentation demonstrated a Li-Fi communication with a mobile robot, while the robot carried out usual production processes (welding, moving and testing parts) in a 5x5m² production cell. The robust, optical wireless transmission is based on spatial diversity; in other words, data is sent and received simultaneously by several LEDs and several photodiodes. The system can transmit data at more than 100 Mbit/s and five milliseconds latency.

Modern production technologies in the automobile industry must become more flexible in order to fulfil individual customer requirements.

Im Focus: Sharp images with flexible fibers

An international team of scientists has discovered a new way to transfer image information through multimodal fibers with almost no distortion - even if the fiber is bent. The results of the study, to which scientist from the Leibniz-Institute of Photonic Technology Jena (Leibniz IPHT) contributed, were published on 6thJune in the highly-cited journal Physical Review Letters.

Endoscopes allow doctors to see into a patient’s body like through a keyhole. Typically, the images are transmitted via a bundle of several hundreds of optical...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Munich conference on asteroid detection, tracking and defense

13.06.2018 | Event News

2nd International Baltic Earth Conference in Denmark: “The Baltic Sea region in Transition”

08.06.2018 | Event News

ISEKI_Food 2018: Conference with Holistic View of Food Production

05.06.2018 | Event News

 
Latest News

Graphene assembled film shows higher thermal conductivity than graphite film

22.06.2018 | Materials Sciences

Fast rising bedrock below West Antarctica reveals an extremely fluid Earth mantle

22.06.2018 | Earth Sciences

Zebrafish's near 360 degree UV-vision knocks stripes off Google Street View

22.06.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>