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 100 000 stars each. We plan to complete a 500-frame movie by the end of the run.

• Simulate evolution of stars, galaxies and solar systems • http://research.amnh.org/~summers/mihos/ mihos.html