When black
holes are perturbed, they vibrate somewhat like a ringing bell. Now astronomers
have narrowed down the rotational speed at which that vibration should stop.
As is
typical, they did it out by running a simulation. But instead of a
supercomputer, they used a batch of Sony Playstation 3 gaming consoles wired
together.
The so-called
PS3 Gravity Grid, a network of 16 Playstation 3 consoles grouped together
in a cluster capable of running simulations that rival a dedicated
supercomputer at a much lower cost.
"You can
get a supercomputer's
capability with relatively little money," said Lior Burko of the University
of Alabama, Huntsville, who led the black hole study, in an interview.
Rather than
renting computer time on a supercomputer that could cost $5,000 per simulation,
Burko and his colleagues used the PS3 Gravity Grid built by Gaurav Khanna, a
physics professor at the University of Massachusetts, Dartmouth.
The cluster
can be built for around $6,000, and allows simulations to be repeated at no
extra cost. The system is tailored to simulations that require massive amounts
of computations, but relatively little RAM memory.
Burko and
Khanna used the PS3 Gravity Grid to run simulations that resolved an ongoing
dispute over the speed at which spinning black holes stop vibrating just
after forming or being perturbed by an outside object. One theory held that
the black holes go silent at relatively fast speeds, while another theory
contended they went quiet at slower speeds.
According
to the new simulations, the gravity wave vibrations from a
spinning black hole that's been perturbed would settle out according to the
faster of the two theories, though the actual speed will vary, Burko said.
"It depends
on the mass of the black hole," he added. "Let's say you're in a spaceship
orbiting the black hole and the black hole is perturbed. Then you need to wait
a shorter time for the vibrations to settle to a certain amplitude."
The
phenomena, Burko said, can be compared to a ringing bell.
"A
bell rings, but eventually it gets quiet. The energy that goes out with the
sound waves is energy that the bell is losing," Burko described in a statement.
"A black hole does exactly that in gravitational waves instead of sound waves.
A black hole that is wobbling is emitting gravitational waves. When those
vibrations die down you get a quiet black hole."
Gravitational
waves are predicted by Einstein's theory of general relativity to emanate
from neutron stars and black holes, but astronomers have not yet detected any
directly.
The
research is detailed in the Jan. 7 issue of the science journal Classical
and Quantum Gravity.
While the
PS3 Gravity Grid may not be useful for all types of research, for those
requiring little RAM but massive computations it can prove a cost-cutting tool,
said Khanna, who built a smaller cluster before stringing together the
16-machine grid.
"Science
budgets have been significantly dropping over the last decade," said
Khanna, who describes how to build a PS3 computer cluster on his Web site.
"Here's a way that people can do science projects less expensively."
advertisement
