CHAPTER 09 · Read Cosmos
Stellar evolution and the origin of elements
Will the Sun also explode as a supernova?
Explore this chapter ↗Let's begin! The experience allows you to directly interact with the scenes and observation tools.
Different stars, different endings
Chapter 9 of the original book connects the life cycle of a star to the material origins of humanity. Gravity, internal pressure, and nuclear fusion all change the structure of the star, and the resulting consequences extend to the next generation.
A crucial distinction is mass. If we lump together stars like the Sun with much heavier stars into a single story of birth and explosion, we will misunderstand the process by which stars create matter.
OBSERVE · Start with evidence
Three pieces of evidence
- Stars like the Sun evolve into red giants, shedding their outer layers to become white dwarfs.
- Sufficiently massive stars can undergo core collapse and supernova explosions.
- The fate of remaining objects, such as neutron stars and black holes, also depends on specific conditions.
The life cycle of a star becoming our material
Commentary following stars and the origin of matter in chapter 9 of the original book. The stellar life cycles are representative paths; no single process explains all stars and all elements.
Why don't stars simply collapse?
While stars may seem like simply burning balls of gas, their structure is governed by the interplay of gravity and internal pressure. The energy produced by nuclear fusion is crucial for understanding a star's state.
When the fuel and internal conditions change, the star will not remain in its current state indefinitely. Follow the changes in its structure as it transitions from a bright, shining moment.
Questions to ConsiderWhat factors should be considered when explaining the evolution of a star?
The future of the Sun and the future of massive stars
Stars like the Sun can be explained as going through a red giant phase and ending as a white dwarf, leaving behind its outer layers. The image of all stars exploding as supernovae eliminates this difference.
For much more massive stars, there are paths that lead to core collapse and either a neutron star or a black hole. Remember that the final outcome depends on factors other than mass, so do not judge all stars based on a single threshold.
Questions to ConsiderWhat conclusions should be drawn from comparing the two stars?
The end of one star, the beginning of the next world
The matter emitted by a star is connected to the materials that form the next generation of stars and planets. This connection expands the question of the elements within the body to the history of the universe.
However, do not say that all elements were created in the same explosion of the same star. The origin of matter is a history of multiple processes, and it is also necessary to distinguish between obtaining matter and organizing life with that matter.
Questions to ConsiderWhat should be included in a sentence explaining the origin of the elements within the body?
Discoveries and their limits
This is a representative evolutionary pathway. Actual stellar evolution is also influenced by factors such as mass loss, composition, and interactions with binary companions. Modern observations of neutron star collisions are a post-Sagan addition.
Write a sentence that connects the life cycle of a star with the matter within the body, but does not explain everything with a single explosion.
Explore this chapter ↗Evidence and further reading
By tracing the evolution of stellar matter, we can reach the early universe. How can we verify the past, which no one has ever seen?