_____ describes the life cycle of a star.
Nuclear fusion
Nebular clouds
Stellar evolution
The big bang
life cycle involves evolution
The correct answer is "Stellar evolution."
To understand the life cycle of a star, we need to follow these steps:
1. Nebular clouds: Stars are formed from giant clouds of gas and dust called nebulae. Gravity causes the cloud to collapse inward, forming a spinning disk of material.
2. Nuclear fusion: As the material in the cloud becomes denser and hotter, nuclear fusion occurs at its core. This is when hydrogen atoms combine to form helium and release a tremendous amount of energy. This energy pushes against gravity and creates a balance, giving rise to a stable star.
3. Stellar evolution: After nuclear fusion starts, the star enters the main sequence phase, which is the stage where it spends most of its life. The duration of this phase depends on the star's mass.
Low-mass stars, like our Sun, gradually burn through their hydrogen fuel and eventually expand into red giants. The core collapses, creating a dense white dwarf surrounded by expelled outer layers, known as a planetary nebula.
Higher-mass stars, on the other hand, go through more complex stages. They can become red supergiants, and then undergo a supernova explosion, leaving behind a dense core known as a neutron star or a black hole.
4. The Big Bang: While the Big Bang is a significant event in the history of the universe, it is not specifically related to the life cycle of individual stars. The Big Bang theory explains the origin of the universe as a whole, whereas stellar evolution describes the various stages a star goes through during its lifetime.
So, the correct description of the life cycle of a star is "Stellar evolution."