Question

Which type of fusion occurs in the red giant phase of the demise of a sunlike star?

a.helium to carbon
b.helium to hydrogen
c.hydrogen to helium
d.hydrogen to carbon

Answer 1

In the red giant phase of a sunlike star, the fusion of helium into carbon occurs through the triple-alpha process. The correct option is a.

Step-by-step explanation:

The type of fusion that occurs in the red giant phase of a sunlike star is the fusion of helium to carbon. During this phase, the core of the star becomes hot enough to enable the triple-alpha process, where three helium nuclei (alpha particles) are combined to form a carbon nucleus.

This process is crucial for the star's evolution, and it occurs after the star has exhausted the hydrogen in its core and has expanded to become a red giant.

The helium fusion provides a new energy source for the star, causing it to enter a brief period of stability before eventually evolving further, which could lead to the star shedding its outer layers and forming what is known as a planetary nebula. The correct option is a.

Answer 2

During the red giant phase of the demise of a sunlike star, the fusion process involves a.helium to carbon. (option a)

Step-by-step explanation:

In the red giant phase, a sunlike star has exhausted the hydrogen fuel in its core, leading to the contraction of the core and the expansion of the outer layers. As the core contracts and heats up, helium fusion becomes the dominant nuclear process. Helium nuclei (alpha particles) fuse to form heavier elements like carbon through a series of nuclear reactions. This fusion process releases energy, causing the outer layers of the star to expand and creating the characteristic red giant phase.

The primary fusion sequence during the red giant phase involves the triple-alpha process, where three helium nuclei combine to form carbon. This process is crucial for the evolution of stars, as it represents a transition from hydrogen-burning to helium-burning phases. The increased gravitational pressure in the contracting core allows helium to reach the temperatures necessary for fusion to carbon. The release of energy from these fusion reactions counteracts the gravitational forces, preventing further collapse and contributing to the expansion of the outer layers into a red giant.

Understanding the fusion processes in different phases of a star's life cycle is essential for comprehending stellar evolution. The red giant phase, marked by helium to carbon fusion, signifies a critical stage in the life cycle of a sunlike star, leading to its eventual transformation and, ultimately, its demise. (option a)