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2013 Annual Science Report

Arizona State University Reporting  |  SEP 2012 – AUG 2013

Astrophysical Controls on the Elements of Life, Task 3: Model the Injection of Supernova Material Into Star-Forming Molecular Clouds

Project Summary

The goal of this task is to see if material ejected from a star that has exploded as a supernova can make its way into the gas as it is forming new solar systems. It has been expected that this material, because it is moving so fast (> 2000 km/s) when it hits the cold, dense molecular cloud in which stars are forming, would shock, heat up, and then “bounce” off of the cloud boundary.

4 Institutions
3 Teams
1 Publication
0 Field Sites
Field Sites

Project Progress

A major breakthrough was accomplished last year and described in last year’s report. This work was published in the Astrophysical Journal in September 2012, and was also presented at the March 2013, Lunar and Planetary Science Conference. We engaged in high-performance computing, using 500,000 CPU hours on the ASU Arizona Center for Advanced Computing Saguaro cluster, to calculate the fate of supernova ejecta, as they collide with molecular cloud gas in the same star-forming region. The numerical challenge is that penetration of supernova gas relies on rapidly cooling, fragmentation and contraction of the ejecta, involving a range of lengthscales. We overcame these challenges and showed that supernova gas can cool quickly enough to penetrate into the molecular cloud.

Stars can be contaminated with supernova material just as they are forming, at contamination levels consistent with isotopic and chemical evidence from meteorites. There is a high probability (> 10%) of this event happening to stars like the Sun. Further details are described in our 2012 report.

A figure is reproduced from the paper that was published describing this result (Refer to Figure 1).

Time Sequence (Top to Bottom) of How Supernova Material Can Be Injected Into a Molecular Cloud
Figure 1: Time sequence (from top to bottom) of how supernova material can be injected into a molecular cloud. (Left): Density of gas. Densities vary from the orange density 10˄-22˄ g cm˄-3˄ of the ionized gas near the massive star (which has just exploded as a supernova) up to the “blue” density 10˄-19˄ g cm˄-3˄ of the nearby molecular cloud (from which the massive star was born). The bullet of supernova material is ~ 0.003 pc in radius, much smaller than the parsecs scale of the computational domain. The bullet travels from left to right at initial speeds > 2000 km/s, penetrating into the molecular cloud, sending out lateral shock waves that expand the channel. The bullet is stopped after 10,000 yr at a depth of 0.5 pc. (Right): the same sequence, but showing the concentration of ejecta material. By 10,000 years the supernova material has been spread evenly along the channel, and is expected to mix thoroughly in the lateral direction due to (unmodeled) turbulence.

Publications

  • Pan, L., Desch, S. J., Scannapieco, E., & Timmes, F. X. (2012). MIXING OF CLUMPY SUPERNOVA EJECTA INTO MOLECULAR CLOUDS. The Astrophysical Journal, 756(1), 102. doi:10.1088/0004-637x/756/1/102