IP1: Dust formation and evolution in supernova ejecta and remnants

Cosmic dust is ubiquitous in our universe and plays a crucial role in the physics and chemistry of any environment that it pervades. In space, the formation of dust from the gas phase requires high gas temperatures and densities to nucleate and condense. Such conditions are found in circumstellar environments, like the winds of evolved stars or the ejecta of supernovae. Dust and a few molecules, namely CO and SiO, have been detected in the ejecta of Type II Supernovae some hundred days after explosion. But the observed dust masses are small, and fall short of the large dust masses necessary to explain the dust enrichment of primitive galaxies in the early universe. How much dust can a Type II supernova form? What is the nature of the dust synthesised after the explosion? How can the dust survive the harsh environment of the supernova remnant?

IP1 aims at answering these questions by studying the chemical processes triggering the formation of dust in Type II supernova explosion, and the impact of mixing on the dust chemical composition and mass yields. A novel approach based on chemical kinetics will be used to describe the molecular phase of the ejecta and the nucleation of dust grains from the gas phase. The condensation of dust will be studied using a Monte Carlo approach. Mixing of elements induced by Rayleigh-Taylor instabilities resulting from the post-explosion reverse shock has a profound impact on the chemistry. For example, the formation of molecules and the nucleation of dust grains are hampered in the oxygen-rich and the carbon-rich zones of the helium core by reaction with He ions. All those aspects will be considered to derive a clear picture of dust formation in these explosive events.

Once the interplay between the mixing resulting from the explosion and the dust formation mechanism will be well understood, and reliable dust chemical compositions and mass yields derived for various progenitor masses, the IP aims at studying the time evolution and reprocessing of dust in young supernova remnants such as Cas A. Supernova dust has been identified in meteorites, implying that the dust formed in supernova ejecta can somehow survive in the remnant and at later phases of dilution with the interstellar medium. The dust processing due to the reverse shock in the remnant will be investigated for a pre-shock molecular and dusty clump or filament and the chemistry of the post-reverse shock gas will be explored.

Collaborators at Universität Basel

Dr. Isabelle Cherchneff (IP leader)

Prof. F-K. Thielemann (co-IP leader)

Mr. Arkapraba Sarangi (PhD student)

Ms. Chiara Biscaro (PhD student)