The Impact of Supernovas on Stellar Mass: From Ejection to Cosmic Element Creation

What happens to the mass of a star during a supernova explosion?

During a supernova explosion, up to half the star’s mass is ejected into space in an explosive event. This mass ejection leaves the star with about 75% of its original mass, which is dispersed into the surrounding space. This process essentially wipes out the 'star' as we know it, leaving behind a dead core that could be either a neutron star or a black hole, depending on the star's mass.

What is a Supernova?

A supernova is a violent astronomical event that signifies the end of a star's life. It releases a tremendous amount of energy and expels a large portion of the star's material. Once this occurs, the original stellar entity no longer exists, replaced by a compact, dead core.

Elements and Supernovae

The remnants of supernovae play a crucial role in the formation of our solar system. The sun, moon, and planets we see today are essentially fragments of a star that had its life ended by a supernova. The dust from these remnants gradually drifts through space and eventually comes together under the force of gravity to form new celestial bodies. This process is particularly significant because many of the elements in our universe, such as those heavier than iron, are not created within the confines of a star. Instead, they are forged in the intense conditions of a supernova explosion.

Red Giants and Pre-Supernova Stages

Many stars transition into red giants as they age. This phase begins when the core of the star becomes so full of helium that it can no longer sustain hydrogen fusion. Consequently, the outer layers of the star begin to expand and cool, turning red. Red giants can be enormous, sometimes extending over a hundred times the diameter of our sun. Due to their enormous size, red giants can be significant in the ejection of material from a potential supernova.

However, not all stars destined for supernova explosions pass through the red giant phase. Some may directly transition to the supernova stage, bypassing the red giant stage altogether.

The Fusion and Ejection Process

The ultimate cause of a supernova is the fusion of elements within the star. This process continues until iron is formed. Iron has 30 protons, and it does not combine with other atoms. Adding pressure and heat to iron only serves to heat it further; it does not facilitate the creation of another element. As a result, no explosion can occur, and the star's outer layers are pushed outwards in a significant manner.

This process ultimately leads to the star's core collapsing and the outer layers being ejected into space. The leftover core can become either a neutron star or, if it is sufficiently massive, a black hole. The ejected material is enriched with heavy elements like gold, uranium, and europium, which cannot be synthesized within a star due to their higher atomic numbers.

A remarkable statement from Professor Adam Burrows highlights the unique role of supernovae in element creation: 'The products of the merger of two neutron stars would be gold, uranium, europium—some of the heaviest elements in nature.'

Thus, supernovae play a pivotal role not only in the ejection of stellar mass but also in the creation of the elements that make up our universe, from hydrogen and helium to the heavier elements that shape the Earth and sustain life.