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collision
A Prograde-Retrograde Galaxy Collision
Chris Mihos (Case Western Reserve University)
Video: 620 kB, MPEG
When galaxies collide, a number of factors affect the outcome. This movie shows two large spiral galaxies colliding under a particular set of initial conditions: one galaxy is rotating clockwise, the other counterclockwise. The simulation follows the first 100 million years of the collision. The complexity of these calculations requires a powerful supercomputer and many hours (and sometimes days) to run.
Collisions create star formation
The blue material represents stars in these galaxies, while the yellow material represents clouds of hydrogen gas that could form new stars during the collision. Before the collision, both stars and gas are evenly distributed throughout each galaxy, but as the galaxies crash into each other, the stars spread out into a much larger volume. Conversely, the gas gathers into tight knots and thin threads. This behavior suggests that, because of the collision, new stars will form in massive, concentrated starbursts.
The directions of the galaxies' spin affects how the stellar and gaseous matter move; different combinations of spins, collision speeds, and angles will produce markedly different results.
Charles Liu
Stellar Encounters
Joshua E. Barnes (University of Hawaii)
Video: 1 MB, MPEG
Close encounters between stars are very rare. Only a few of the billions of stars in a typical galaxy will ever collide. Nonetheless, encounters between stars can play an interesting role in the formation of exotic star systems. This supercomputer simulation shows what might happen if a small star crashes into a larger one.
When stars collide
The movie shows one star crashing into another star twice its mass. Stars are not solid objects, but are composed of gas that surrounds a small, dense core. When stars collide, their cores spiral into each other, while their gaseous envelopes swirl about. The friction caused by all this motion releases a tremendous amount of heat and energy. This is shown in the movie by the colors in the stars: red regions have high energy while blue regions have low energy.
Gordon Myers
Binary Neutron Star Collision
David Bock (NCSA Visualization and Virtual Environments Group)
Video: 2 MB, MPEG
Neutron stars are the cinders left over from a supernova explosion. At the instant of their creation, half a million Earth masses of matter are crushed into a ball just ten miles across; one teaspoonful of neutron star material weighs five billion tons. In rare instances, two neutron stars can orbit around each other in a binary system, releasing energy in the form of gravitational radiation. After millions of years, they spiral toward each other, moving faster and faster until they produce a crash so violent that the resulting explosion can be seen billions of light years away.
What happens during the collision?
This movie shows the results of a supercomputer simulation of what might happen when two neutron stars in a binary system collide. By the time they hit each other, they're traveling at nearly the speed of light, and orbit each other a thousand times a second. According to the calculations, the two neutron stars merge together in less than a hundredth of a second and release more energy during that time than our Sun would in ten billion years!
Gordon Myers
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