Consider the following statements :
Statement-I :
Giant stars live much longer than dwarf stars.
Statement-II :
Compared to dwarf stars, giant stars have a greater rate of nuclear reactions.
Which one of the following is correct in respect of the above statements ?
Both Statement-I and Statement-II are correct and Statement-II explains Statement-I .
Both Statement-I and Statement-II are correct, but Statement-II does not explain Statement-I
Statement-I is correct, but Statement-II is incorrect
Statement-I is incorrect, but Statement-II is correct
Answer is Wrong!
Answer is Right!
This question was previously asked in
UPSC IAS – 2024
Statement-I: “Giant stars live much longer than dwarf stars.” This statement is incorrect. Giant stars, being more massive than dwarf stars (like our Sun, a G-type dwarf), have much stronger gravitational forces. This results in higher temperatures and pressures in their cores, which accelerates the rate of nuclear fusion. Although they have more fuel, they burn it at a vastly higher rate, leading to significantly shorter lifespans compared to dwarf stars. Dwarf stars, with their slower rate of fusion, can live for billions or even trillions of years.
Statement-II: “Compared to dwarf stars, giant stars have a greater rate of nuclear reactions.” This statement is correct. As explained above, the higher core temperatures and pressures in giant stars lead to a much higher rate of nuclear fusion reactions (converting hydrogen to helium) compared to dwarf stars. This high reaction rate is responsible for their high luminosity.
Statement I is incorrect, and Statement II is correct. Statement II actually explains *why* Statement I is incorrect (higher reaction rate leads to shorter lifespan). Therefore, Option D is the correct choice.