A new Renaissance Computing Institute (RENCI) animation created from a mathematical model shows a black hole moving supersonically through an interstellar gas cloud. This phenomenon often occurs in multiple star systems, where a companion star provides the gas cloud. The gravity of the black hole pulls the gas inward. Early on in the process, a wake forms behind the black hole, much like the wake behind a motorboat. Unlike a motorboat wake, it begins to move back and forth after a while until it whips all the way around the black hole, forming an accretion disk of gas falling into the hole.

What has mystified scientists since 1988 is the seemingly erratic rotation of accretion disks in the computer-generated models. In some cases the model shows the disk rotating for a time in one direction, then suddenly switching directions. The disk’s spin may remain stable for a time and then abruptly reverse direction again. The reversal may repeat several times.

Astrophysicists refer to this accretion disk about face as “flip-flop instability” and have debated its possible causes for years. Some suggest the phenomenon doesn’t actually occur but is a flaw in the model itself. Yet flip-flop instability has shown up in numerous different studies, leading some scientists to suggest it is the cause of stellar flares and bursts of energy that haven’t otherwise been explained.

North Carolina State University researchers John Blondin and T. Chris Pope generated the data used to construct this visualization. Their computer simulations exploit the power of high-performance computers available through the National Science Foundation’s TeraGrid to explore flip-flop instability at an unprecedented level of detail and scientific sophistication. In a paper published June 30 in the Astrophysical Journal, they conclude that the flip-flop instability is real and not an anomaly of computer models.

In the animation, created by Steve Chall of the RENCI’s North Carolina State Engagement Center, the gas cloud swirls around the black hole at the center, creating an accretion disk around the black hole. At first, the disk spins counterclockwise and then very rapidly reverses to a clockwise direction. The background colors in the animation represent pressure, from green for low through blue, violet, red and finally pale yellow for the highest pressure. Spheres emitted from 10 equally spaced sources upstream from the black hole (far right) show the velocities of representative particles in the gas cloud. Pale yellow spheres exhibit the least velocity, through red, violet and up to blue for the fastest-moving particles.

Credits: Numerical simulation: Dr. John Blondin and T. Chris Pope, department of physics, North Carolina State University. Visualization: Steve Chall, Renaissance Computing Institute NC State. This research was supported in part by a grant from the National Science Foundation, by an NC State Undergraduate Research Award to T. Chris Pope, and by computing resources at the Texas Advanced Computing Center.

Blondin’s image of the beginnings of a supernova shockwave in the core of a star was simulated using computational resources at Oak Ridge National Laboratory, a US Department of Energy (DOE) lab, and visualized by Steve Chall and Theresa-Marie Rhyne at RENCI at NC State. The conference attracts members of the global computer-aided engineering, medical imaging, and scientific visualization communities. CEI, based in Apex, NC, develops cutting-edge visualization and animation software for customers worldwide. The Blondin/RENCI image was created using CEI’s EnSight software.

Supernovas are dying stars that explode, causing a sudden burst of radiation that can briefly outshine an entire galaxy before fading after several weeks or months. Astrophysicists theorize that as the iron core of a star cools and runs short on fuel, a shockwave of energy ripples back through the star and it explodes. Observation has backed up the theory, but so far no scientist has been able to create a complete simulation of a star’s death because of the massive computational power needed.

Blondin’s simulations and visualizations give researchers a better understanding of the dynamics of a supernova and also push the limits of supercomputing processing and data processing. Originally funded by the DOE’s Terascale Supernova Initiative, which involved NC State and seven other universities, the work aims to answer the question “How does a supernova explode?” and illustrates how supernova shockwaves move through the universe.

The visualization was also picked by CEI as the November image for the company’s 2009 calendar. http://www.ensight.com/2009-calendar-contest-winners.html

More information:
NC State astrophysics: http://wonka.physics.ncsu.edu/
CEI: http://www.ensight.com/
RENCI visualization: Visualization

RENCI…Catalyst for Innovation
The Renaissance Computing Institute brings together teams of talented researchers, engineers, technologists and leaders in government, business, the arts and humanities to attack major research questions and community issues in ways that accelerate discovery and drive innovation. RENCI has nationally significant expertise and capabilities in high performance computing, visualization, collaborative tools, networking, device prototyping, and data systems as well as engagement sites across the state. Founded in 2004 as a major collaborative venture of Duke University, North Carolina State University, the University of North Carolina at Chapel Hill and the state of North Carolina, RENCI is a statewide virtual organization. For more, see www.renci.org.

RALEIGH, March 2, 2007—The Renaissance Computing Institute (RENCI) at North Carolina State University will open its doors to the Triangle research community on Friday, March 23, for an open house that will showcase RENCI technologies and collaborations with NC State researchers.

The open house runs from noon – 3 p.m. at the newly opened RENCI at NC State facility, Suite 1500 in the Partners I Building on the Centennial Campus. Remarks by NC State Chancellor James Oblinger, UNC-Chapel Hill Chancellor James Moeser and RENCI Director Dan Reed will begin at 1 pm.

Featured will be visualization work created by the research teams of John Blondin, NC State physics professor, and Christopher Healey, an associate professor in NC State’s computer science department. In addition, NC State’s Institute for Transportation Research and Education will demonstrate a traffic simulation of the use of roundabouts as part of the Hillsborough Street traffic flow improvement effort.  The open house also will offer a sampling of RENCI’s work throughout North Carolina and collaborations with its state and national partners. Included will be weather models that combine atmospheric, hydrological and storm surge data and high-resolution animations of the Milky Way.

Founded in 2004 as a major collaboration of Duke University, NC State, the University of North Carolina at Chapel Hill, and the state of North Carolina, RENCI brings together researchers from all disciplines to addresses our state’s most challenging multidisciplinary problems. By applying technological expertise and world-class computing, networking, visualization and data resources to these issues, RENCI strives to create a collaborative 21st-century problem-solving environment that will spur economic growth and lead to the next generation of transformative discoveries.

Public health issues are among those addressed by RENCI. The institute has partnered with the Triangle biomedical research community to create software, web portals and wireless devices that impact public health and assist researchers studying the genetic causes of disease.

With the opening of RENCI at NC State in January, faculty and staff on the NC State campus now have access to RENCI resources, staff, and collaborators and have the opportunity to contribute to these ongoing research projects. Members of the NC State community also will take the lead on new multidisciplinary research efforts that utilize RENCI’s visualization, computing and data resources and leverage the campus’ expertise in agriculture, environmental sciences, physics, engineering, computer science and other fields.

“We are creating a statewide virtual organization that leverages the expertise of our three founding universities as well as campuses across North Carolina,” said Reed. “The creation of RENCI at NC State is an important milestone because it will help us develop collaborations with faculty at one of North Carolina’s most important research universities. We look forward to some exciting projects that benefit RENCI, NC State, and the state of North Carolina.”

One of the highlights of the open house will be a 14 x 8-foot visualization wall, featuring visualizations created by RENCI, its partners, and NC State faculty, staff and students. Also on display will be state-of-the art video collaboration and editing facilities, including the Access Grid multicast system. Refreshments will be available and musical entertainment will be featured.

“The RENCI at NCSU facility is a key part of our efforts to support successful research and the discovery process with high-end visualization techniques and high-performance computing methods,” NC State Vice Chancellor of Research and Graduate Studies John Gilligan said.