Which stellar phase is characterized by expansion to roughly 0.5 to 3 times the Sun's size and fusion of hydrogen into helium, ultimately leading to a carbon-oxygen white dwarf?

Which stellar phase is characterized by expansion to roughly 0.5 to 3 times the Sun's size and fusion of hydrogen into helium, ultimately leading to a carbon-oxygen white dwarf?

• A. Giant phase
• B. Main sequence
• C. Red giant phase
• D. Planetary nebula

Answer: (B)

Hydrogen burning in the core marks the main sequence phase, the period when a star fuses hydrogen into helium and maintains a steady balance between gravity and pressure. Stars on the main sequence cover a range of sizes, roughly from half a solar radius up to a few solar radii, so expansion to about 0.5 to 3 times the Sun’s size fits the typical main-sequence width. This hydrogen-burning engine is what powers the star for a long, stable part of its life. After the hydrogen in the core runs out, a Sun-like star leaves this phase, becomes a red giant, and ultimately ejects its outer layers to reveal a carbon-oxygen white dwarf. So the described phase aligns with the main sequence, where hydrogen fusion in the core sets the star’s luminosity and size range, followed by evolution to a CO white dwarf.

Hydrogen burning in the core marks the main sequence phase, the period when a star fuses hydrogen into helium and maintains a steady balance between gravity and pressure. Stars on the main sequence cover a range of sizes, roughly from half a solar radius up to a few solar radii, so expansion to about 0.5 to 3 times the Sun’s size fits the typical main-sequence width. This hydrogen-burning engine is what powers the star for a long, stable part of its life. After the hydrogen in the core runs out, a Sun-like star leaves this phase, becomes a red giant, and ultimately ejects its outer layers to reveal a carbon-oxygen white dwarf. So the described phase aligns with the main sequence, where hydrogen fusion in the core sets the star’s luminosity and size range, followed by evolution to a CO white dwarf.