7.16P Describe the evolution of stars of similar mass to the Sun through…

The idea

Stars of similar mass to the Sun form from a nebula, a cloud of gas and dust. Gravity pulls the material together, and the core becomes hot and dense enough for hydrogen fusion, producing a main-sequence star. When the hydrogen in the core is used up, the star expands and cools at its surface to become a red giant, fusing heavier elements. Later the outer layers are shed and the remaining core contracts to a white dwarf. In a multiple-choice question, choose the option that places these four stages in the correct order and matches each stage to its description: nebula, main-sequence star, red giant, white dwarf.

What earns the marks

• Places the nebula first as the cloud of gas and dust from which the star forms.
• Identifies the main-sequence star as the stage powered by hydrogen fusion in the core.
• Describes the red giant as the later stage when the star expands and cools at its surface after core hydrogen is used up.
• Identifies the white dwarf as the final stage in which the remaining core contracts after outer layers are shed.

Common mistakes and how to put them right

• Orders the stages wrongly, for example placing the red giant before the main-sequence star.

  Put it right by keeping nebula, main-sequence star, red giant, white dwarf in that order.

• Describes the white dwarf as a large hot star.

  Put it right by describing it as the small, dense remaining core.

• Omits the nebula stage.

  Put it right by starting the sequence with the gas and dust cloud.

Exam tips

• Check the option keeps all four named stages in the order nebula, main-sequence star, red giant, white dwarf.
• Match each stage to its key feature: gas and dust cloud, hydrogen fusion, expansion and cooling, then a small dense core.
• Reject options that add stages not listed, such as supernova or black hole, for a Sun-like star.