Solar System — Set 1

Correct Answer: B. Sun

• **Sun** = the nearest star to Earth, at the center of our solar system. • **150 million km** — the average distance from Earth to the Sun (1 AU). • 💡 Wrong-option analysis: Proxima Centauri: nearest star to the solar system (not Earth); Alpha Centauri: a triple-star system 4.37 light-years away; Sirius: brightest star in the night sky but far from Earth.

Correct Answer: B. Venus

• **Venus** = called 'Morning Star' or 'Evening Star' because it appears brilliantly in the sky just before sunrise or after sunset. • **2nd planet** — Venus is the second planet from the Sun and the brightest natural object in the night sky after the Moon. • 💡 Wrong-option analysis: Mars: called 'Red Planet', not morning/evening star; Mercury: also near Sun but too faint; Jupiter: visible at night but not called morning/evening star.

Correct Answer: B. Mars and Jupiter

• **Asteroid Belt** = a region of space between Mars and Jupiter containing millions of rocky bodies called asteroids. • **2.2–3.2 AU** — the asteroid belt spans from 2.2 to 3.2 astronomical units from the Sun. • 💡 Wrong-option analysis: Earth and Mars: too close to the Sun, no belt there; Jupiter and Saturn: the region beyond Jupiter; Saturn and Uranus: outer solar system, no belt here.

Correct Answer: D. Saturn

• **Saturn** = famous for its extensive and complex ring system made mostly of ice particles and rocky debris. • **7 main rings** — Saturn has 7 named ring groups spanning up to 282,000 km from its center. • 💡 Wrong-option analysis: Uranus: has 13 rings but they are thin and dark; Neptune: has 5 faint rings; Jupiter: has a faint ring system discovered in 1979.

Correct Answer: B. Hydrogen

• **Hydrogen** = the primary gas in the Sun, constituting about 74% of its mass and serving as fuel for nuclear fusion. • **74% hydrogen, 24% helium** — these two elements make up nearly 98% of the Sun's total mass. • 💡 Wrong-option analysis: Oxygen: trace element in the Sun; Helium: second most abundant (24%) but not primary; Nitrogen: found in Earth's atmosphere, not primarily in the Sun.

Correct Answer: A. Mars

• **Mars** = known as the 'Red Planet' due to iron oxide (rust) on its surface giving it a reddish appearance. • **2 moons** — Mars has two small moons: Phobos and Deimos, which may be captured asteroids. • 💡 Wrong-option analysis: Saturn: known for its rings, not red color; Jupiter: has a Great Red Spot but is not called Red Planet; Venus: called Earth's twin, not Red Planet.

Correct Answer: D. Saturn

• **Titan** = the largest moon of Saturn and the only moon in the solar system with a dense atmosphere. • **2nd largest moon** — Titan is the second-largest moon in the solar system; Ganymede (Jupiter) is the largest. • 💡 Wrong-option analysis: Neptune: its largest moon is Triton; Uranus: its largest moon is Titania; Jupiter: its largest moon is Ganymede, not Titan.

Correct Answer: B. Jupiter

• **Jupiter** = the largest planet in the solar system, a gas giant with mass exceeding all other planets combined. • **2.5x combined mass** — Jupiter's mass is more than 2.5 times that of all other planets combined, and it has the famous Great Red Spot storm. • 💡 Wrong-option analysis: Uranus: 3rd largest by radius; Neptune: 4th largest; Saturn: 2nd largest, known for its ring system.

Correct Answer: A. 8 minutes 20 seconds

• **8 minutes 20 seconds** = the approximate time sunlight takes to travel from the Sun to Earth. • **300,000 km/s** — light travels at this speed, covering the 150 million km Earth-Sun distance in ~500 seconds. • 💡 Wrong-option analysis: 12 minutes: overestimate; 5 minutes: underestimate (would be for ~90 million km); 10 minutes: slightly too high for 150 million km.

Correct Answer: D. Venus

• **Venus** = rotates from East to West (retrograde rotation), meaning the Sun rises in the west and sets in the east on Venus. • **243 Earth days** — Venus takes 243 Earth days to complete one rotation, the slowest spin of any planet. • 💡 Wrong-option analysis: Jupiter: rotates West to East like most planets; Earth: standard West to East rotation; Mars: also rotates West to East.