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?
Answer & explanation
Answer: (d) Statement-I is incorrect, but Statement-II is correct
A star's mass decides how fast it burns. Big, massive stars need very high rates of nuclear fusion in their cores to hold themselves up against their own gravity, so they use up their hydrogen in a few million years, while small dwarf stars burn slowly and can shine for billions or even trillions of years. So the fusion-rate statement is true, and the longer-life statement is the reverse of the truth.
- ✗ Statement-I Massive stars are short-lived: some last only a few million years, whereas low-mass red dwarfs can last trillions of years; the Sun will spend about 10 billion years on the main sequence.
- ✓ Statement-II More massive stars must fuse hydrogen at a much higher rate to generate the outward pressure that balances their stronger gravity, which also makes them hotter and brighter.
Remember · Bigger star → faster fusion → shorter life. Massive stars: millions of years, end as supernovae; red dwarfs: trillions of years. Sun: about 10 billion years on the main sequence.
Sources
- NASA Science: Stars ↗ “More massive stars must burn fuel at a higher rate to generate the energy that keeps them from collapsing under their own weight. Some low-mass stars will shine for trillions of years – longer than the universe has currently existed – while some massive stars will live for only a few million years.”
- NASA Imagine the Universe: Stars ↗ “Our sun will spend about 10 billion years on the main sequence. However, a more massive star uses its fuel faster, and may only be on the main sequence for millions of years.”
Question and answer: UPSC's official GS Paper I (2024, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). ·