Free Astronomy and Space MCQs with Answers

241. Which of the following is the largest planet?

• A. Neptune
• B. Jupiter
• C. Saturn
• D. Mars

Explanation: Jupiter is the largest planet in the solar system, both in diameter and mass. Saturn and Neptune are also giant planets but are smaller than Jupiter.

242. Which of the following planets has the smallest diameters_____?

• A. Mercury
• B. Marx
• C. Pluto
• D. Venus

Explanation: Mercury is the smallest of the eight officially recognised planets. Pluto is smaller, but it is classified as a dwarf planet rather than a planet, so Mercury is the intended answer.

243. Which of the following planets is fastest rotating planet?

• A. Mercury
• B. Marx
• C. Jupiter
• D. Venus

Explanation: Jupiter rotates once in about 10 hours, making it the fastest-rotating planet in the solar system. The option printed as “Marx” presumably refers to Mars, which rotates much more slowly.

244. Spring tides occur on new moon and full moon days because on these days_____________?

• A. Sun, moon and earth are in a straight line
• B. Sun and earth are at right angles
• C. Sun and moon are at right angles
• D. Earth and moon are at right angles

Explanation: During a new moon or full moon, the Sun, Moon, and Earth are nearly aligned, so their gravitational effects reinforce one another. This produces the unusually high spring tides.

245. Which on of the following planets orbits around the sun in a clockwise direction?

• A. Earth
• B. Mercury
• C. Jupiter
• D. Venus

Explanation: Venus rotates and orbits in the retrograde, or clockwise, sense when viewed from above the solar system's north pole. Earth, Mercury, and Jupiter orbit counterclockwise in that reference frame.

246. Which one of the following is not a unit of distance?

• A. Parsec
• B. Astronomical Unit
• C. Light Year
• D. Foot Candle

Explanation: A parsec, astronomical unit, and light-year are all units used to measure distance. A foot-candle measures illuminance, or light falling on a surface, not distance.

247. Constellations referred to as zodiac, are__________?

• A. Imaginary regions that encompass the path of the planets
• B. Signs of Roman gods
• C. A group of stars
• D. None of these

Explanation: The zodiac is the belt of sky along the ecliptic, the apparent path of the Sun and the approximate paths of the planets. Thus its constellations are treated as regions encompassing the planetary path, not merely any group of stars.

248. 'Black holes' refers to_______________?

• A. Holes occurring in heavenly bodies
• B. Bright spots on the sun
• C. Collapsing object of high density
• D. Collapsing object of low density

Explanation: A black hole forms when a very massive object collapses under gravity into an extremely dense region whose escape speed exceeds the speed of light. It is not a literal hole or a bright spot on the Sun.

249. The phases of the moon are partially the result of the____________?

• A. Changes in the shape of the moon
• B. Revolution of the moon around the earth
• C. Variations in the moon's gravitation
• D. Variations in the speed of rotation of the moon

Explanation: Moon phases result mainly from the Moon's revolution around Earth, which changes the portion of its sunlit half visible from Earth. The Moon does not change shape; its rotation is synchronised with its orbit.

250. What is the temperature at the center of the Sun?

• A. 6 million °C
• B. 10 million °C
• C. 15 million °C
• D. 20 million °C

Explanation: The Sun's core reaches about 15 million °C, allowing hydrogen nuclei to fuse into helium. The visible surface is far cooler, at roughly 5,500 °C, which is a common source of confusion.