Red Giant Stars and Their Characteristics

What happens when a star becomes a red giant?

When a star becomes a red giant, what are the changes that occur?

Answer:

A star becomes a red giant when it's out of nuclear fuel. In this phase, the star expands and cools, shifting its color to red. Option 4

Explanation:

When a star exhausts its nuclear fuel, it enters a phase called the red giant phase. During this stage, the star will expand and cool, which is option 4 in your list. This happens because the helium core of the star contracts, releasing energy that causes the outer layers of the star to expand. As the star expands, it cools, changing its color from white or yellow to red, hence the name red giant.