Why does stellar nuclear fusion stop when iron is reached? How do heavier elements come into being than iron? These questions have been bothering scientists, so let's explore the mysteries together.
First, we need to understand the fundamentals of stellar nuclear fusion. The high-temperature, high-pressure environment inside the star brings the nuclei close to each other, and the internuclear forces cause them to come together to form heavier elements. In the process, the star releases a huge amount of energy, which is what we see as starlight. However, when the stellar nucleus fuses to iron, it suddenly stops. Why is that?
It turns out that the nucleus of iron has special properties. Its binding energy is the highest of all elements, which means that the structure of the iron nucleus is the most stable and it is not prone to fission or fusion reactions. Specifically, the fusion of elements before iron will release energy, and the elements heavier than iron will not release energy in order to fuse, but also need to absorb energy. So, we generally think that stars die after fusing to iron.
In other words, the iron nucleus is like a strong castle that is difficult to break. Therefore, when the stellar nucleus fuses to iron, the reaction stops.
But how do the heavy elements in the universe come about? This brings us to two extreme celestial phenomena: supernova explosions and neutron star collisions.
A supernova explosion is the final stage of a star's life cycle. When the iron nuclei inside the star accumulate to a certain extent, a violent explosion occurs, and the entire star disintegrates in an instant. In this process, an unimaginable amount of energy is produced enough for iron to continue to fuse, resulting in the formation of elements heavier than iron. This is what we see as a supernova explosion, which produces most of the heavy elements in the universe.
Another way to produce heavy elements is neutron star collisions. When two neutron stars collide with each other, an extreme physical reaction occurs inside them, producing a large number of neutrons. These neutrons combine with iron nuclei to form elements that are heavier than iron. This phenomenon was first observed by scientists in 2017, revealing another source of heavy elements in the universe.
In summary, stellar nuclei fuse to iron stop, because the binding energy of iron nuclei is extremely high, making it difficult for further fusion reactions to occur. Elements heavier than iron are created through two extreme celestial phenomena: supernova explosions and neutron star collisions. These discoveries not only give us an insight into the evolution of the universe, but also provide new clues for us to explore the mysteries of the universe.