Research

The formation and evolution of primordial stars (the first stars) in the universe is a highly significant area of contemporary astrophysical research. The feedback of primordial stars affected the evolution of their surroundings, leading to the formation of the later stars and the first galaxies. To bring the point closer to home, most of the elements of the periodic table were synthesized inside those primordial stars through nuclear fusion. Thus, the first stars play a crucial role in our understanding of the evolution of the universe. However, their cosmic traces are so far away that they are hard to observe using even the world’s biggest telescopes. Current studies show that the first stars were very massive, with masses around hundreds of solar masses, and they would end their lives in very energetic explosions, called supernovae (SNe), shining as bright as the entire galaxy. Observing the first SNe provides an alternative way to study the first stars and the early universe.

During a SN explosion, fluid instabilities are generated because the star is in a hydro- dynamically unstable situation, which is like the effects of stirring a fire or blowing air into a hot grill. The resulting mixing of the supernova ejecta may be observable. Fluid instabilities occur in our daily life. For example, if you place heavy dyed water on top of lighter tap water, the interface is unstable, and the dyed water tends to sink into the tap water. The instabilities are the result of one fluid moving ”past” the other. Imagine viewing the mixing from a fixed point above the surface of the liquids. The movement cannot be well described from only one dimension, such as from some height above the bottom of the glass; different fluids and fluid motions could occur at the same height. Therefore, second or third dimensions, perpendicular to height, are required to describe and to simulate such instabilities. Before my work, the theoretical models for the first SNe were based on one-dimensional simulations. My PhD thesis was the pioneering work that studied the instabilities in the SNe of the first stars using two- and three-dimensional hydrodynamic simulations. The goal was to predict useful observational signatures for these events that can be utilized by current and forthcoming observatories.