New study found that Cosmic rays help Supernovae in bigger explosions

Topic: New study found that Cosmic rays help Supernovae in bigger explosions


The final stage of cataclysmic explosions of dying massive stars, called supernovae, could pack a six-times-large punch on surrounding interstellar gas with the help of cosmic rays, according to a new study led by researchers at the University of Oxford . The work will be presented today (July 19) by PhD student Francisco Rodriguez Monteiro at the Virtual National Astronomy Meeting (NAM 2021).

When supernovae explode, they emit light and billions of particles into space. While light can freely reach us, the particles are trapped in a spiral loop by the magnetic shockwave generated during the explosion. Passing back and forth through shock fronts, these particles are accelerated to nearly the speed of light and, upon escaping from a supernova, are thought to be the source of the mysterious form of radiation known as cosmic rays.

Because of their immense speed, cosmic rays experience strong relativistic effects, effectively losing less energy than regular matter and allowing them to travel great distances through the Milky Way. Along the way, they influence the energy and composition of the interstellar gas in its path and may play a key role in setting off the formation of new stars in dense pockets of gas. However, to date, the influence of cosmic rays in galaxy evolution is not well understood.

In the first high-resolution numerical study of its kind, the team ran simulations of the evolution of shock waves emanating from supernova explosions over several million years. They found that cosmic rays may play an important role in the final stages of a supernova’s evolution and have the potential to inject energy into the galactic gas around it.

Rodriguez Monteiro explains: “Initially, it is not known how the explosion evolved from the addition of cosmic rays. Nevertheless, when the supernova reaches a stage in which it accelerates more than the conversion of the supernova’s thermal energy into kinetic energy. We found that cosmic rays could give an additional push to the gas, making the final speed 4–6 times greater than previously predicted.”

The results suggest that the weak gas surrounding the interstellar medium, or the driven gas outflow into the sarco galactic medium, will be dramatically heavier than previously estimated.

Contrary to state-of-the-art theoretical arguments, simulations also suggest that the additional push provided by cosmic rays is more significant when massive stars explode in low-density environments. This could facilitate the formation of super-bubbles driven by successive generations of supernovae, sweeping gas through the interstellar medium and ejecting it from the galactic disk.

Rodriguez Monteiro says: “Our results are the first look at extraordinary new insights that cosmic rays will provide to our understanding of the complex nature of galaxy formation.”

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