UPSC Prelims 2009 Q44: Science & Technology – Space Technology & Astronomy
Who of the following scientists proved that the stars with mass less than 1·44 times the
mass of the Sun end up as White Dwarfs when they die ?
- (a) Edwin Hubble
- (b) S. Chandrashekhar
- (c) Stephen Hawking
- (d) Steven Weinberg
Answer: (b) S. Chandrashekhar
Explanation
Who proved the White Dwarf mass limit
A specific astrophysicist established the theoretical mass threshold determining a star's ultimate fate.
| Option | Verdict | Reason |
|---|---|---|
| (a) Edwin Hubble | Incorrect | Known for expanding universe observations, not this specific mass-limit theory |
| (b) S. Chandrashekhar | Correct | Subrahmanyan Chandrasekhar proved that stars with mass below 1.44 times the Sun's mass (the 'Chandrasekhar limit') end up as White Dwarfs |
| (c) Stephen Hawking | Incorrect | Known for black hole theoretical physics, not this specific limit |
| (d) Steven Weinberg | Incorrect | Known for particle physics/electroweak theory, not this specific astrophysical limit |
Chandrasekhar limit facts:
| Point | Detail |
|---|---|
| Discoverer | S. Chandrasekhar |
| Threshold | 1.44 solar masses |
| Below this mass | Star ends as a White Dwarf |
Answer: (b) S. Chandrashekhar.
Why each option is right or wrong
- (a) Incorrect. Edwin Hubble is known for unrelated cosmological observations.
- (b) CORRECT. S. Chandrasekhar established the mass limit (1.44 solar masses) for stars ending as White Dwarfs.
- (c) Incorrect. Stephen Hawking is known for black hole theory, not this specific limit.
- (d) Incorrect. Steven Weinberg is known for particle physics, unrelated to this astrophysical limit.
Key point
S. Chandrasekhar proved that stars with mass below 1.44 times the Sun's mass (the 'Chandrasekhar limit') end up as White Dwarfs when they die.
Remember
S. Chandrasekhar: proved stars below 1.44 solar masses end as White Dwarfs (the Chandrasekhar limit).
Common mistakes
- Confusing Chandrasekhar's stellar-mass-limit theory with unrelated astrophysicists' famous contributions (Hubble's expanding universe, Hawking's black holes).
- Not knowing the specific '1.44 solar masses' figure as the Chandrasekhar limit.
- Mixing up different physicists' specific areas of groundbreaking work.
Exam tip
Chandrasekhar limit = 1.44 solar masses, proved by S. Chandrasekhar, determining White Dwarf fate. A specific, named physics constant.
Sources
- S. Chandrasekhar — "The Maximum Mass of Ideal White Dwarfs", The Astrophysical Journal, vol. 74 (1931)
- Nobel Prize — The Nobel Prize in Physics 1983 (Subrahmanyan Chandrasekhar and William A. Fowler), press release