Star models

Star models

To get a close-up look at the Universe's stellar attractions, astrophysicists at Saint Mary's University are using a super computer to get the whole picture
May 1, 2005

Who hasn't stared up into the starry sky on a lazy summer evening and pondered the riddle of existence?

Observing the stars from a distance may be good enough for most people. But for astrophysicists it’s not enough. They want a front-row seat. They want to learn how the stars were first formed, what they’re made of, what’s inside them, and how they work. Although it takes traditional stargazing into a completely different orbit, armed with answers to these questions, astrophysicists can speculate on the past and future of the Universe.

This desire to understand the Universe is what drives the research at the Institute for Computational Astrophysics (ICA) at Saint Mary's University in Halifax, Nova Scotia. The ICA is one of only a few institutes in the world that focuses on high performance computer code development and applications to investigate the starry skies and conduct research in astrophysics “I'd like to reach out and manipulate the galaxy in the same way that a chemist experiments in his lab”, says David Clarke, Professor of Astrophysics at Saint Mary’s University. “But I can't. So instead, I try to model astrophysical objects with a computer and perform my experiments on the model instead.”

As long as they have computers with enough power to solve all the equations, astrophysicists can mathematically simulate the various known and hypothetical conditions of a given situation and observe the results. “Modeling of stars was one of the first cases where computers not only provided much more realism, but also the ability to solve the relevant equations,” says Robert Deupree, Director of the ICA.

The physical processes that determine the structure of a star's atmosphere, and the shape of its light spectrum, are so complex that they can only be studied by computer modeling. By creating computer models of the atmospheres of stars, researchers can use these models to simulate the spectrum of light from stars. Comparing simulated spectra to observed spectra of real stars helps researchers determine the chemical composition of various structures in our own and in other galaxies. Knowledge of the chemical composition of the Universe throughout space and time is necessary to determine the origins and evolution of galaxies, the nature of the first stars that ever formed, and the origin of the chemical elements.

High-performance computers, or supercomputers, differ from everyday personal computers. In short, they harness the power of numerous processors to perform simultaneously vast calculations. Without the power of these computers, the work of the computational astrophysicists at the ICA would not be possible.


The mere existence and growth of the Institute for Computational Astrophysics (ICA), with its focus on computational astrophysics, is contributing to the evolution of astronomy.

Traditionally, astrophysicists have studied and explained the heavenly bodies by observation and theory. In the last 25 years, however, computational astrophysicists have turned their eyes from the sky to the computer screen, modeling and simulating the objects in the cosmos. As a result, with the ever-increasing power and data retention of these machines, they have added experimentation to observation and theory as the third prong of their scientific investigation.

The ICA computational astrophysicists have created most of the software that they use. David Clarke co-developed the ZEUS-3D software, which enables 3-D modeling of astrophysical jets, fluids, and discs. It has become a permanent fixture in the research world and other astrophysicists have used it extensively. Clarke is now developing an even more powerful version of it.

Over the coming years, the relationship between computation and observation will become even closer. With simulations and models from the ICA research, future astrophysicists will be better equipped to further study a wide variety of astrophysical problems that remain unsolved.

As research advances, so does the need for high-performance computers (researchers believe computational power and storage capacity doubles every two years). Therefore, the work at the ICA continues to raise the bar of demands on these computers, and consequently its own need for bigger and better access.


Saint Mary's University has come a long way since 1999 when it made a modest entry into the world of computational astrophysics.

In the beginning, three faculty members in the Department of Astronomy and Physics—David Clarke, David Guenther, and Malcolm Butler—shared with other faculty members and students in other departments what was then considered a high-performance computer. Today, Saint Mary's belongs to ACEnet—the Atlantic Computational Excellence Network. ACEnet is the most recent of six major regional computing collaborations in Canada. ACEnet will have a combination of clusters and SMP (Shared Memory Platform) machines. State-of-the-art video conferencing at all the member institutions will play an integral role in how ACEnet communicates, and the state-of-the-art visualization centre at Saint Mary's University will be only one of ten such installations in the world.

“This is a big step for the ICA, Saint Mary’s, and for other universities in Atlantic Canada”, says Robert Deupree. “It takes our high-performance computing to a new level and places our capability second to none in Canada.”

ACEnet is led by Memorial University of Newfoundland. Other members include St. Francis Xavier University, University of New Brunswick, Mount Allison University, Dalhousie University, and University of Prince Edward Island.