September 17, 2001
DOE grant creates Center for Supernova Research based at UCSC
By Tim Stephens
Massive exploding stars called supernovae are among the most spectacular phenomena
in the universe. Astrophysicists, however, are still struggling to work out the mechanics
of these awesome explosions. A team of astrophysicists and computer scientists at
UCSC and three other institutions is now tackling the problem with support from a
$2 million, three-year grant from the Department of Energy (DOE).
The grant establishes a Center for Supernova Research headquartered at UCSC. Stanford
Woosley, professor and chair of astronomy and astrophysics, is principal investigator
and director of the new center. The other partner institutions are the University
of Arizona and the Los Alamos and Lawrence Livermore National Laboratories.
|This is a simulation of the density profile of a 1 solar mass main sequence star
(just like the sun) after shock wave passage from a Type Ia supernova (which "went
off" above the top of the image). The blue colors represent the density of the
"core" of the main sequence star, green is less dense material from the
envelope, yellow is material being stripped from the envelope, red is the background
density after the supernova shock has passed. Image: Lawrence
Livermore National Laboratory
"The goal is to build realistic numerical models of exploding stars, using the
fastest computers available to simulate the explosions," Woosley said.
The grant is funded by the DOE's new Scientific Discovery through Advanced Computing
(SciDAC) program, which aims to address complex scientific problems by taking advantage
of the extraordinary computing capabilities of terascale computers (computers capable
of doing trillions of calculations per second). The supernova researchers will be
using several powerful supercomputers, including those at the National Energy Research
Scientific Computing Center at Lawrence Berkeley National Laboratory and the Accelerated
Strategic Computing Initiative at Lawrence Livermore National Laboratory. The researchers
will also use a large "Beowulf" computing cluster to be built at UCSC this
"Almost all of modern physics comes to bear in a supernova explosion--radiation
transport, fluid dynamics, thermonuclear fusion, and so on," Woosley said. "We
know the basic equations, but putting all of that together to create a multidimensional
simulation of a supernova is something you can't do without a lot of computing power."
A supernova occurs when the core of a star collapses under the gravitational force
of its own mass. This can happen in a binary star system when mass is transferred
between two closely orbiting stars, resulting in what is known as a type 1 supernova.
The other basic type of supernova, type 2, occurs at the end of the lifetime of a
single massive star, when its nuclear fuel is exhausted.
A supernova explosion can be as bright as an entire galaxy, releasing immense amounts
of energy. The explosion also spews into space all of the chemical elements forged
by nuclear fusion reactions during the life of the star and some that are formed
during the explosion itself. These materials may then contribute to the formation
of new stars and planets. Thus, supernovae are ultimately responsible for the rich
array of elements that populate the periodic table.
In the past, researchers have been limited to modeling supernovae in one or two dimensions,
Woosley said. "But nature makes supernovae in three dimensions, and the explosions
are not perfect spheres," he said. "We see all sorts of clumpiness and
structure, so we want to build computer modeling capabilities commensurate with those
When the results of a computer simulation look like the observational data astronomers
gather from real supernovae, the modelers know they are on the right track. Realistic
models of supernovae can be powerful tools for understanding the evolution of stars
and the abundances of heavy elements. The models can also help researchers interpret
The DOE's SciDAC program is funding 51 projects this year in areas ranging from climate
modeling to high-energy physics. The Center for Supernova Research is one of two
SciDAC projects that will be investigating supernovae. The other supernova project
is led by Oak Ridge National Laboratory.