Element synthesis by supernova explosion
Do you know how the elements which constitute our bodies and our earth were synthesized? Many common elements around us, such as oxygen and iron, were synthesized by supernova explosions and scattered through the universe. A supernova explosion is observed as a star shining suddenly and brightly in the night sky. It is a huge explosion occurring when a star of some sort dies. The composition ratio of synthesized elements is determined by the nature of the original star which caused the supernova explosion. In other words, the ratio depends on the type of explosion, whether it was a huge explosion of a heavy star at the end of its life or a huge explosion of a binary system comprising light stars, arising from a specific condition. Accordingly, if we can discern the types and amounts of elements existing in the universe, we can begin to understand the types and numbers of supernova explosions that have occurred in the universe, in other words, what kind of stars have formed and died until now.
By focusing on the identification of the amounts of elements in high-temperature gases confined by gravity within a galaxy cluster or elliptical galaxy, we intend to investigate the formation history of the stars comprising various galaxies, as well as the history of element synthesis. Many stars, such as the sun, gather due to their own gravity to form a galaxy. Our own galaxy is called the galactic system. The Milky Way crossing the night sky is a lateral view of the system. An elliptical galaxy is a type of galaxy with an elliptical shape. An elliptical galaxy differs from a spiral galaxy such as our own galactic system not only in shape but in the nature of its stars too. A group of hundreds and thousands of galaxies brought together by their own gravity is called a galaxy cluster.
The amount of high-temperature gases is very large. In fact, most matter in the universe is not stars but high-temperature gases. For example, in a galaxy cluster, high-temperature gases fill the areas between galaxies, and the mass of these gases is several times that of the galaxies. The temperature of the gases is extremely high, between several to 100 million deg. C. Even in an elliptical galaxy, gases with several million deg. C are present, though their mass is about 1% of stars. The gases in an elliptical galaxy are those emitted from stars, so their elemental composition ratio is the same as that of the stars. Thus, in order to identify the amount of oxygen or iron synthesized by supernova explosions occurring in galaxies, it is essential to investigate the amounts of these elements contained in the gases.