An image from Toomre and Brown's visualization of the magnetic field of the solar convection zone. Here, the sunspot is magnified for better visibility, and is not to scale relative to the sun. © 2009, American Museum of Natural History

"Journey to the Stars" is currently showing at the American Museum of Natural History's Hayden Planetarium in New York City, US

The stars are writ large in all their majesty in "Journey to the Stars," a planetarium show that uses grid-generated simulations to take audiences deep under the surface of the sun.

With Whoopi Goldberg as a guide, viewers embark on a journey through the lifespan of stars and the origin of life. Visualizations of the universe, projected onto the 87-foot seven-million-pixel dome of the Hayden Planetarium in New York City, explain how stars first formed and then exploded to produce the chemical elements that make life possible.

The 25-minute journey culminates in a flight to the center of the sun. This was the most difficult sequence to accurately depict; the producers wanted to take viewers below the sun's surface, through its convective layer, and down to its core to reveal the underlying mechanisms that create its powerful magnetic field.

To do this, they contacted Juri Toomre, researcher at the University of Colorado at Boulder, and his doctoral student Benjamin Brown, who have spent the past two years using TeraGrid supercomputers to build complex computer models of the sun.

Toomre and Brown modeled the sun's convection zone based on a sphere of hydrogen and helium plasma. Based on that model, the properties of hydrogen and helium, and how they react to the sun' heat, they were then able to produce convective motions.

To create a computer simulation of their model, Toomre and Brown needed a great deal of computational power. To fill that need, they turned to the Ranger supercomputer at the Texas Advanced Computing Center, and visualization software developed at the National Center for Atmospheric Research.

The resulting simulation allows planetarium visitors to take a peek at the sun's convective zone, but to show viewers the magnetic processes occurring deep within the sun, the producers turned to NCAR scientist Matthias Rempel.

Rempel and his research team recently created the most detailed model of an entire sunspot ever produced. Sunspots - dark spots on the sun's surface - are actually concentrations of strong magnetic fields that occasionally erupt above the sun's surface. These provide clues to the sun's internal magnetic field.

"Numerical simulations allow us to look several thousand kilometers into the sun and see how the surface structure we observe is related to convective motions that happen far below the visible surface," explained Rempel.

To create the simulation used in the show, Rempel and his team first designed a three-dimensional virtual domain to replicate a region on the sun 31,000 miles in length and height and about 5,100 miles in depth. The domain was large enough to fit an entire sunspot, which has a typical size of 12,000 to 19,000 miles, and provided enough resolution to view substructure on the scale of 20- to 30- miles.

The researchers then used TACC's Ranger supercomputer to solve complex solar equations for each of 268 million points spaced 20- to 30- miles apart within the virtual domain. This involved processing approximately a terabyte of data and took several days to run on 512 processors.

"Models of this kind require a lot of computing power, and only in recent years have computers reached the size that this becomes possible," Rempel said.

Likewise, the detailed scientific simulations allowed the producers of "Journey to the Stars" to showcase the sun more realistically than ever before.

"Shows like this are one of the most amazing ways to share our research with the public," Brown said. "The supercomputing simulations projected across the planetarium dome are stunning, and the show does a tremendous job in sharing the excitement and joy of the science that we do."

-Amelia Williamson, iSGTW