By Chris Worman and Andrey Mirtchovski

Why Galaxies? Interest in scientific computation and simulation Visually appealing results To learn how to model gravity based systems

Galaxy Collision A galaxy is modeled as a grouping of stars around a massive body Only stars with a velocity that is less than the escape velocity will remain in the galaxy:

Velocity If the velocity of a star is too low then it will be sucked into the center of the galaxy The direction of the velocity should also be tangential to the desired orbit

Gravity If a body A of mass m is at a distance of r from a body B of mass M then Where G is the gravitational constant

Gravity This implies that the acceleration in the i-th component c i is given by

2D Results Initially the simulation was implemented in two dimensions The following slides depict a collision between two galaxies The galaxy on the top of the screen is the more massive of the two There are 10,000 stars per galaxy

Challenges in 3D Implementation Computationally expensive –O(n^2) or O(n*log(n)) minimum –Scientific simulations run on 256+ processor machines Memory requirements –Based on design and number of galaxies memory requirements can grow up to gigabytes Visualization – creating a visually appealing galaxy

Galaxy Collision Realism Very close to real-life galaxy collisions Compare a two-galaxy collision with images taken from Hubble Space Telescope

3D Results Due to the extreme computation requirements for the 3D version, real-time galaxy collision is limited to about 500 stars per galaxy The following slides depict a 3D galaxy collision with 1000 stars per galaxy

Expandability Both 2D and 3D models could be extended to more than 2 galaxies. Number of stars per galaxy can vary Galaxy masses vary Simulation of different celestial objects (quasars, black holes, etc)

Conclusion Java3D is a viable tool for creating scientific simulations and visualizations Performance losses from using Java3D are relatively big compared with pure OpenGL Development time is significantly less, due to higher level abstraction of Java3D’s API NASA officials have already contacted us… (which leads us to ‘Future Plans’)

Future Plans Over the next 5 years we plan to run a 3D simulation of 2 galaxies with stars each. We plan to complete a 500-frame movie by the end of the run. Simulate evolution of stars, galaxies and solar systems mihos.html