Which stage in a massive star's life is characterized by an expanded, very bright outer envelope known as a red supergiant?

Which stage in a massive star's life is characterized by an expanded, very bright outer envelope known as a red supergiant?

• A. White dwarf
• B. Red supergiant
• C. Neutron star
• D. Black hole

Answer: (B)

Red supergiant describes a late life stage of massive stars when their outer layers expand into a gigantic, bright envelope. After the core runs out of hydrogen, it contracts and heats up, while the outer layers puff out and cool. The result is an enormous star with a cool surface, which gives it a reddish hue, but its vast size makes it extremely luminous. This expanded envelope is what makes the star appear so bright and large, as seen in famous examples like Betelgeuse. By contrast, white dwarfs are compact remnants of smaller stars, and neutron stars or black holes are dense, collapsed remnants without a large expanding envelope.

Red supergiant describes a late life stage of massive stars when their outer layers expand into a gigantic, bright envelope. After the core runs out of hydrogen, it contracts and heats up, while the outer layers puff out and cool. The result is an enormous star with a cool surface, which gives it a reddish hue, but its vast size makes it extremely luminous. This expanded envelope is what makes the star appear so bright and large, as seen in famous examples like Betelgeuse. By contrast, white dwarfs are compact remnants of smaller stars, and neutron stars or black holes are dense, collapsed remnants without a large expanding envelope.