Andrew Yee[_1_]
May 2nd 08, 10:29 PM
News Office
University of Chicago
Chicago, Illinois
MEDIA CONTACT
Steve Koppes, 773-702-8366
May 1, 2008
Argonne supercomputer to simulate extreme physics of exploding stars
Robert Fisher and Cal Jordan are among a team of scientists who will expend
22 million computational hours during the next year on one of the world's
most powerful supercomputers, simulating an event that takes less than five
seconds.
Fisher and Jordan require such resources in their field of extreme science.
Their work at the University of Chicago's Center for Astrophysical
Thermonuclear Flashes explores how the laws of nature unfold in natural
phenomena at unimaginably extreme temperatures and pressures. The Blue
Gene/P supercomputer at Argonne National Laboratory will serve as one of
their primary tools for studying exploding stars.
"The Argonne Blue Gene/P supercomputer is one of the largest and fastest
supercomputers in the world," said Fisher, a Flash Center Research
Scientist. "It has massive computational resources that are not available on
smaller platforms elsewhere." Desktop computers typically contain only one
or two processors; Blue Gene/P has more than 160,000 processors. What a
desktop computer could accomplish in a thousand years, the Blue Gene/P
supercomputer can perform in three days. "It's a different scale of
computation. It's computation at the cutting edge of science," Fisher said.
Access to Blue Gene/P, housed at the Argonne Advanced Leadership Computing
Facility, was made possible by a time allocation from the U.S. Department of
Energy's Innovative and Novel Computational Impact on Theory and Experiment
program. The Flash Center was founded in 1997 with a grant from the National
Nuclear Security Administration's Office of Advanced Simulation and
Computing. The NNSA's Academic Strategic Alliance Program has sustained the
Flash Center with funding and computing resources throughout its history.
The support stems from the DOE's interest in the physics that take place at
extremes of concentrated energy, including exploding stars called
supernovas. The Flash Center will devote its computer allocation to studying
Type Ia supernovas, in which temperatures reach billions of degrees.
A better understanding of Type Ia supernovas is critical to solving the
mystery of dark energy, one of the grandest challenges facing today's
cosmologists. Dark energy is somehow causing the universe to expand at an
accelerating rate.
Cosmologists discovered dark energy by using Type Ia supernovas as cosmic
measuring devices. All Type Ia supernovas display approximately the same
brightness, so scientists could assess the distance of the exploding stars'
home galaxies accordingly. Nevertheless, these supernovas display a
variation of approximately 15 percent. "To really understand dark energy,
you have to nail this variation to about 1 percent," said Jordan, a Flash
Center Research Associate.
The density of white dwarf stars, from which Type Ia supernovas evolve, is
equally extreme. When stars the size of the sun reach the ends of their
lives, they have shed most of their mass and leave behind an inert core
about the size of the moon. "If one were able to scoop out a cubic
centimeter -- roughly a teaspoon -- of material from that white dwarf, it
would weigh a thousand metric tons," Fisher explained. "These are incredibly
dense objects."
Type Ia supernovas are believed to only occur in binary star systems, those
in which two stars orbit one another. When a binary white dwarf has
gravitationally pulled enough matter off its companion star, an explosion
ensues. "This takes place over hundreds of millions of years," Jordan said.
"As the white dwarf becomes more and more dense with matter compressing on
top of it, an ignition takes place in its core. This ignition burns through
the star and eventually leads to a huge explosion."
The Flash team conducts whole-star simulations on a supercomputer at
Lawrence Berkeley National Laboratory in California. At Argonne, the team
will perform a related set of simulations. "You can think of them as a
nuclear flame in a box' in a small chunk of the full white dwarf," Fisher
said.
In the simulations at Argonne, the team will analyze how burning occurs in
four possible scenarios that lead to Type Ia supernovas. Burning in a white
dwarf can occur as a deflagration or as a detonation.
"Imagine a pool of gasoline and throw a match on it. That kind of burning
across the pool of gasoline is a deflagration," Jordan said. "A detonation
is simply if you were to light a stick of dynamite and allow it to explode."
In the Flash Center scenario, deflagration starts off-center of the star's
core. The burning creates a hot bubble of less dense ash that pops out the
side due to buoyancy, like a piece of Styrofoam submerged in water. But
gravity holds the ash close to the surface of the white dwarf. "This
fast-moving ash stays confined to the surface, flows around the white dwarf
and collides on the opposite side of breakout," Jordan said. The collision
triggers a detonation that incinerates the star. There are, however, three
other scenarios to consider. "To understand how the simulations relate to
the actual supernovae, we have to do more than a thousand different
simulations this year to vary the parameters within the models to see how
the parameters affect the supernovae," Jordan said.
Related Video:
[Video 1:
http://www.ci.uchicago.edu/flashviz/gallery/main.php?g2_itemId=4252]
This animation shows a thermonuclear flame burning its way through a white
dwarf star. The flame produces hot ash, which buoyantly rises as the flame
burns. The ash breaks out of but remains gravitationally bound to the
surface of the star and collides at a point on the opposite side of the star
from the breakout location. The collision region is compressed and heated
from the converging ash flows and when the conditions there become extreme
enough a detonation is triggered. In the animation, green represents the
approximate surface of the star and the colors mark regions of high
temperature in the billions of degrees Kelvin. As the ash rises and breaks
out of the star, it decompresses and cools; however, the as the ash flows
over the surface the animation shows the collision region attaining very
high temperatures.
[Video 2:
http://www.ci.uchicago.edu/flashviz/gallery/main.php?g2_itemId=4827]
This animation shows a thermonuclear flame burning its way through a white
dwarf star. The flame produces hot ash, which buoyantly rises as the flame
burns. The ash breaks out of but remains gravitationally bound to the
surface of the star and collides at a point on the opposite side of the star
from the breakout location. The blue shows the approximate surface of the
star and the orange shows the interface between the star and the hot ash
produced by the flame.
Credit: DOE NNSA ASC/Alliance Flash Center at the University of Chicago.
IMAGE CAPTIONS:
[Image 1:
http://news.uchicago.edu/images/assets/080501.flashimage1-375.jpg (11KB)]
A snapshot of a three-dimensional simulation of a Type Ia supernova, shortly
after the nuclear flame bubble that initiates the Ia event is ignited
slightly off-center from the progenitor white dwarf star (shown here as a
light blue surface).
Credit: DOE NNSA ASC/Alliance Flash Center at the University of Chicago.
[Image 2:
http://news.uchicago.edu/images/assets/080501.flashimage2-375.jpg (28KB)]
A close-up, high-resolution image of the nuclear flame bubble shown in image
1. This image depicts the vorticity of the flow, demonstrating the complex,
turbulent hydrodynamical processes that govern the nuclear flame bubble
burning during this stage, close to bubble breakout.
Credit: DOE NNSA ASC/Alliance Flash Center at the University of Chicago.
[Image 3:
http://news.uchicago.edu/images/assets/080501.flashimage3-375.jpg (13KB)]
A snapshot of a Type Ia supernova simulation taken very shortly after the
moment of detonation. The energy released during the detonation is
equivalent to 1,027 hydrogen bombs, each equivalent to 100 megatons of TNT.)
Credit: DOE NNSA ASC/Alliance Flash Center at the University of Chicago.
University of Chicago
Chicago, Illinois
MEDIA CONTACT
Steve Koppes, 773-702-8366
May 1, 2008
Argonne supercomputer to simulate extreme physics of exploding stars
Robert Fisher and Cal Jordan are among a team of scientists who will expend
22 million computational hours during the next year on one of the world's
most powerful supercomputers, simulating an event that takes less than five
seconds.
Fisher and Jordan require such resources in their field of extreme science.
Their work at the University of Chicago's Center for Astrophysical
Thermonuclear Flashes explores how the laws of nature unfold in natural
phenomena at unimaginably extreme temperatures and pressures. The Blue
Gene/P supercomputer at Argonne National Laboratory will serve as one of
their primary tools for studying exploding stars.
"The Argonne Blue Gene/P supercomputer is one of the largest and fastest
supercomputers in the world," said Fisher, a Flash Center Research
Scientist. "It has massive computational resources that are not available on
smaller platforms elsewhere." Desktop computers typically contain only one
or two processors; Blue Gene/P has more than 160,000 processors. What a
desktop computer could accomplish in a thousand years, the Blue Gene/P
supercomputer can perform in three days. "It's a different scale of
computation. It's computation at the cutting edge of science," Fisher said.
Access to Blue Gene/P, housed at the Argonne Advanced Leadership Computing
Facility, was made possible by a time allocation from the U.S. Department of
Energy's Innovative and Novel Computational Impact on Theory and Experiment
program. The Flash Center was founded in 1997 with a grant from the National
Nuclear Security Administration's Office of Advanced Simulation and
Computing. The NNSA's Academic Strategic Alliance Program has sustained the
Flash Center with funding and computing resources throughout its history.
The support stems from the DOE's interest in the physics that take place at
extremes of concentrated energy, including exploding stars called
supernovas. The Flash Center will devote its computer allocation to studying
Type Ia supernovas, in which temperatures reach billions of degrees.
A better understanding of Type Ia supernovas is critical to solving the
mystery of dark energy, one of the grandest challenges facing today's
cosmologists. Dark energy is somehow causing the universe to expand at an
accelerating rate.
Cosmologists discovered dark energy by using Type Ia supernovas as cosmic
measuring devices. All Type Ia supernovas display approximately the same
brightness, so scientists could assess the distance of the exploding stars'
home galaxies accordingly. Nevertheless, these supernovas display a
variation of approximately 15 percent. "To really understand dark energy,
you have to nail this variation to about 1 percent," said Jordan, a Flash
Center Research Associate.
The density of white dwarf stars, from which Type Ia supernovas evolve, is
equally extreme. When stars the size of the sun reach the ends of their
lives, they have shed most of their mass and leave behind an inert core
about the size of the moon. "If one were able to scoop out a cubic
centimeter -- roughly a teaspoon -- of material from that white dwarf, it
would weigh a thousand metric tons," Fisher explained. "These are incredibly
dense objects."
Type Ia supernovas are believed to only occur in binary star systems, those
in which two stars orbit one another. When a binary white dwarf has
gravitationally pulled enough matter off its companion star, an explosion
ensues. "This takes place over hundreds of millions of years," Jordan said.
"As the white dwarf becomes more and more dense with matter compressing on
top of it, an ignition takes place in its core. This ignition burns through
the star and eventually leads to a huge explosion."
The Flash team conducts whole-star simulations on a supercomputer at
Lawrence Berkeley National Laboratory in California. At Argonne, the team
will perform a related set of simulations. "You can think of them as a
nuclear flame in a box' in a small chunk of the full white dwarf," Fisher
said.
In the simulations at Argonne, the team will analyze how burning occurs in
four possible scenarios that lead to Type Ia supernovas. Burning in a white
dwarf can occur as a deflagration or as a detonation.
"Imagine a pool of gasoline and throw a match on it. That kind of burning
across the pool of gasoline is a deflagration," Jordan said. "A detonation
is simply if you were to light a stick of dynamite and allow it to explode."
In the Flash Center scenario, deflagration starts off-center of the star's
core. The burning creates a hot bubble of less dense ash that pops out the
side due to buoyancy, like a piece of Styrofoam submerged in water. But
gravity holds the ash close to the surface of the white dwarf. "This
fast-moving ash stays confined to the surface, flows around the white dwarf
and collides on the opposite side of breakout," Jordan said. The collision
triggers a detonation that incinerates the star. There are, however, three
other scenarios to consider. "To understand how the simulations relate to
the actual supernovae, we have to do more than a thousand different
simulations this year to vary the parameters within the models to see how
the parameters affect the supernovae," Jordan said.
Related Video:
[Video 1:
http://www.ci.uchicago.edu/flashviz/gallery/main.php?g2_itemId=4252]
This animation shows a thermonuclear flame burning its way through a white
dwarf star. The flame produces hot ash, which buoyantly rises as the flame
burns. The ash breaks out of but remains gravitationally bound to the
surface of the star and collides at a point on the opposite side of the star
from the breakout location. The collision region is compressed and heated
from the converging ash flows and when the conditions there become extreme
enough a detonation is triggered. In the animation, green represents the
approximate surface of the star and the colors mark regions of high
temperature in the billions of degrees Kelvin. As the ash rises and breaks
out of the star, it decompresses and cools; however, the as the ash flows
over the surface the animation shows the collision region attaining very
high temperatures.
[Video 2:
http://www.ci.uchicago.edu/flashviz/gallery/main.php?g2_itemId=4827]
This animation shows a thermonuclear flame burning its way through a white
dwarf star. The flame produces hot ash, which buoyantly rises as the flame
burns. The ash breaks out of but remains gravitationally bound to the
surface of the star and collides at a point on the opposite side of the star
from the breakout location. The blue shows the approximate surface of the
star and the orange shows the interface between the star and the hot ash
produced by the flame.
Credit: DOE NNSA ASC/Alliance Flash Center at the University of Chicago.
IMAGE CAPTIONS:
[Image 1:
http://news.uchicago.edu/images/assets/080501.flashimage1-375.jpg (11KB)]
A snapshot of a three-dimensional simulation of a Type Ia supernova, shortly
after the nuclear flame bubble that initiates the Ia event is ignited
slightly off-center from the progenitor white dwarf star (shown here as a
light blue surface).
Credit: DOE NNSA ASC/Alliance Flash Center at the University of Chicago.
[Image 2:
http://news.uchicago.edu/images/assets/080501.flashimage2-375.jpg (28KB)]
A close-up, high-resolution image of the nuclear flame bubble shown in image
1. This image depicts the vorticity of the flow, demonstrating the complex,
turbulent hydrodynamical processes that govern the nuclear flame bubble
burning during this stage, close to bubble breakout.
Credit: DOE NNSA ASC/Alliance Flash Center at the University of Chicago.
[Image 3:
http://news.uchicago.edu/images/assets/080501.flashimage3-375.jpg (13KB)]
A snapshot of a Type Ia supernova simulation taken very shortly after the
moment of detonation. The energy released during the detonation is
equivalent to 1,027 hydrogen bombs, each equivalent to 100 megatons of TNT.)
Credit: DOE NNSA ASC/Alliance Flash Center at the University of Chicago.