MSI PI Alexander Heger (Physics) and Ph.D. student Ke-Jung (Ken) Chen use MSI resources to study and model pulsational pair-instability supernovae. In this form of supernova, a massive star expells “shells” of matter on a time-scale of years. The shells interact and collide with each other, converting kinetic energy into visible light.
A recent issue of Nature included an article by Professor Heger explaining this phenomenon and discussing observations by Eran Ofek (Weizmann Institute of Science, Rehovot, Israel) and his colleagues of a massive star shortly before it went supernova. The article is accompanied by a dramatic simulation visualization of shell collisions produced by Mr. Chen.
The Heger group’s investigations into these pulsational pair-instability supernovae include the use of CASTRO, which is a three-dimensional adaptive mesh refinement code. Using Itasca, the researchers are able to create visualizations of the interaction of stellar materials. Other areas of study by this group include simulations of Type 1 X-ray bursts and numerical simulation of the first binary star in the universe, including radiation feedback and supernova simulation.
Mr. Chen was a Finalist in the 2010 MSI Research Exhibition poster competition and was the Grand Prize winner at the 2011 competition. MSI highlighted this research in the Spring 2011 MSI Research Bulletin. Professor Heger and his colleagues published another recent article concerning supernova explosions in December 2012 in the Astrophysical Journal (“New Two-Dimensional Models of Supernova Explosions by the Neutrino-Heating Mechanism: Evidence for Different Instability Regimes in Collapsing Stellar Cores,” Astrophysical Journal, 761(1): 72, DOI:10.1088/0004-637X/761/1/72 (2012)).
(Left): A simulation of a collision between two shells of matter ejected by a massive star in two subsequent pulsational pair-instability supernova eruptions, only years apart, just before the star dies. Displayed is a slice through the upper-right corner of the event. The radius of the shell that contains collision fragments (red knots) is about 500 times the Earth–Sun distance. The color coding represents gas density ranging from 10−11 to 10−16 grams per cubic centimeter, with red indicating the highest density and dark blue the lowest.
(Right): Close-up of fluid instabilities; these can grow to a large scale and destroy the “onion” structure of stars leading to the mixture of the ejecta.