News Release
NC State Astrophysicists Receive Grant to Study Supernovae Mysteries
Media Contact(s)
Sally Ramey, College of Physical and Mathematical Sciences, (919) 513-0300
Oct. 4, 2007
FOR IMMEDIATE RELEASE
Three North Carolina State University astrophysicists have received a three-year, $585,900 grant from the National Science Foundation to investigate Type Ia supernovae, one of the two types of supernova explosions.
Recent findings from Drs. Stephen Reynolds, John Blondin, and Kazimierz Borkowski have raised questions about whether or not these phenomena should be used as standards for measuring distances in space.
Type Ia supernovae are thought to occur when a white dwarf star, the extremely dense remains of a low-mass star, happens to have a companion star close enough to drop material onto the white dwarf, raising its mass over a critical limit. The white dwarf then detonates like a gigantic thermonuclear bomb. About one-fifth of all supernovae are of this type, the rest involving single massive progenitor stars that run out of fuel. Both types of supernova are also heavy-element factories. Type Ia supernovae produce almost all the iron in the universe.
It was thought that since all Type Ia supernovae result from white dwarfs just barely over the critical mass, these explosions should be quite similar to one another, so they are regularly used as standards to measure distances to the galaxies in which they occur. They are also extremely bright, so they can be seen at enormous distances, and have been used to chart the expansion of the universe and the recently discovered surprising acceleration of the expansion.
But recent discoveries by the NC State researchers have shown that not all Type Ia supernovae are so similar after all. Reynolds and colleagues utilized the orbiting Chandra X-ray Observatory to study the remnant of Kepler's supernova of 1604, and determined that this Type Ia explosion may have had a progenitor star of much higher mass than is usual.
Borkowski led another X-ray study that found older remnants of Type Ia supernovae that also appear to be unusual. Most Type Ia explosions have not shown evidence of occurring in the midst of dense circumstellar gas, which is where Borkowski found Type Ia remnants.
The team has suggested reasons for the discrepancies they have found, and has proposed a series of studies to explore the nature of Type Ia supernovae.
The work will center on using high-performance computers to simulate the evolution of a white dwarf and its companion before the explosion, to study the explosion itself, and to predict the appearance of the supernova remnant hundreds and thousands of years after the explosion.
"Given the importance of these explosions for the origin of many chemical elements in the universe, and for studying its expansion, this project will address a very important problem in astrophysics," Reynolds said.
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