UPSC Prelims 2002 Q27: Geography – Astronomy & Earth - Sun System
Which one of the following statements is correct with reference to our solar system?
- (a) The Earth is the densest of all the planets in our solar system
- (b) The predominant element in the composition of Earth is silicon
- (c) The Sun contains 75 % of the mass of the solar system
- (d) The diameter of the Sun is 190 times that of the Earth
Answer: (a) The Earth is the densest of all the planets in our solar system
Explanation
Statements about our solar system
| Statement | Verdict |
|---|---|
| Earth is the densest planet | True — about 5.51 g/cm³, the highest of all planets |
| The predominant element in Earth is silicon | False — iron is the most abundant element by mass (silicon is the commonest in the crust, after oxygen) |
| The Sun has 75% of the mass of the solar system | False — about 99.8 per cent |
| The Sun's diameter is 190 times Earth's | False — about 109 times |
The Earth, at about 5.5 g/cm³, is the densest planet of the solar system. The Sun contains almost all (99.8 per cent) of the mass and has a diameter about 109 times that of the Earth.
Answer: (a) The Earth is the densest of all the planets in our solar system.
Why each option is right or wrong
- (a) CORRECT. The Earth's mean density of 5.51 g/cm³ is the highest.
- (b) Incorrect. Iron is the most abundant element of the Earth as a whole.
- (c) Incorrect. The Sun has about 99.8 per cent of the mass, not 75.
- (d) Incorrect. The Sun's diameter is about 109 times the Earth's.
Key point
Sun: 99.8% of the system's mass, 109 Earth diameters, 1.3 million Earths by volume.
Remember
Earth is the densest planet; Sun diameter is 109 times Earth's.
Common mistakes
- Choosing silicon for the Earth as a whole; it is the crust that is silicon rich.
- Using 190 instead of 109 for the diameter ratio.
- Rounding the Sun's share down to 75%.
Exam tip
Eliminate the percentage and ratio claims, which are far from the real figures.
Sources
- NCERT Class VIII Science — Stars and the Solar System
- NASA — Sun Fact Sheet (Goddard Space Flight Center, Planetary Fact Sheets)